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Thank you very much, Steve, for this kind introduction and also explaining that this is not my day job.
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And there and I does the health warning.
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I am not a historian. All right. But what I want to do today is tell you a little bit, first of all,
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about the firm of Howard Grubb in Dublin and then tie that in with the measurements that were made in 1919.
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And you'll see some of the equipment from Rob's time that that proved to be very important for these particular measurements.
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So I need to set the whole thing in context and.
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That's it. That's it. So around the 1840s, 1850s in Ireland was a sort of golden era in astronomy.
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What probably a lot of people don't realise is that actually Ireland, up to about the 1870s or so,
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had not only the largest reflecting telescope in the world, that was the six foot, the so-called Avison of Parsons Town.
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It was the the biggest reflector in the world, but it also had the largest refractor in the world in a place called Marguerite Castle in Sligo.
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Now, of course, Ireland is not the best place when it comes to optical observing night.
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Neither is Oxford. But you know, this was pre jetting off to La Palma or Hawaii,
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etc. So it's understandable that they had to they had to based them at home, so to speak.
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So this golden era of astronomy in Ireland then gave rise to an actual industry building telescopes.
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And this man here, Thomas Grubb, was the first was the founder of the firm.
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He initially started off believing not his business was making billiard tables.
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And at that time, by the way, the billiard tables weren't slate billiard tables.
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They were actually metal that were fashioned into as flat as a tabletop as possible.
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But he started in that, but he had an interest in scientific instrumentation,
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and so he started building telescopes and microscopes, etc. But although he he made telescopes,
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for example, for the US Naval Observatory, a number of small telescopes around Europe,
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he realised that telescope making was not a very steady business.
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But you would get an order for a large telescope.
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The firm would be going for a few months working on that and then the mightn't be in order for quite some time.
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So he decided to go into another business which was actually making money or more precisely printing money.
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He got the post in the bank of the Bank of Ireland, produced its own notes, rather like the Bank of England does at that time.
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And he got the post with the recommendation of William Rowan Hamilton, noted mathematician and not sure you know,
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that letter of reference from mathematician today would get you a job in the Bank of England, for example.
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But maybe, maybe. But anyway, so that's how he got the job.
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And he essentially passed on the business to his son, Howard Groep and Howard started actually doing a degree in Trinity College.
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We actually never finished it, but he became very, very well known in instrument making circles and he made telescopes.
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And I'll just show you few examples in the next few minutes for for institutions all around the world, including Vienna, for Melbourne, etc.
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As I said, I'll show you some examples. But he also was involved with some telescopes in the states.
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For example, if any of you ever go to the Lick Observatory, you'll see there's a rising floor in the observatory,
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which was the solution for the problem of when you make a bigger and bigger refractor, of course.
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And if you're looking at something which is low down on the horizon or even in 30 degrees or whatever,
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then it gets very difficult for the observer to look through the eyepiece.
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So he came up with the idea of the rising floor.
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So hydraulically moving floor. And he also later in life, he was the person who developed the Marine periscope.
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So it's difficult to kind of realise it now.
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The inventor, by the way, of the modern submarine was a guy called Holland, John Holland, who was also from County Clare.
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But he Holland tried to get the the British Army interested in submarines and they weren't particularly interested.
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So he actually ended up over in the US.
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Where his first source of funding was the Fenian Brotherhood.
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Now I can imagine what what they intend to do with the first submarine,
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but they actually ran out of money and he eventually sold the idea to the US Navy
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and started building submarines and at which point British he got interested.
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But the first submarines actually went around blind.
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They had no periscope. They simply just went underwater, went a certain distance, hoping for the best, the particular direction.
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But then Grupp invented the periscope in particular for a submarine, and that was extremely challenging business at the time to do that.
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Anyway, at one point in his his firm, which is in a place called Rat Mines in Dublin, it had 400 people working on optics.
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Here's an actual picture of his firm in rat minds.
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This is with the opening of the new building. And you note the clear.
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Health and safety. Cognisance, right?
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Yes. And. Here's one of his famous telescopes, the great Melbourne Telescope.
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So Melbourne, after the Gold Rush, had a lot of money.
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This is back in sort of 1840 748, and they decided they were going to do the local government decided on a prestige
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project which was to build the largest telescope in the Southern Hemisphere.
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They had virtually no astronomers, by the way, but they decided to build the telescope anyway.
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So Hargrove was commissioned it making the telescope.
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And that was actually the last one.
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Major telescope using Speculum Mirror. So you built using glass mirror after that, people started using glass and parks, etcetera.
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And but that telescope, actually, there had been a number of reincarnations of that telescope.
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And it was used up to about, I think about 15 years ago for the Metro Project, you know,
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for searching for massive objects in the halo of our galaxy, which were causing gravitational deflection.
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Gravitational lensing. So and then of course, there was the fire of Mount Stromlo and that telescope was destroyed.
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But in fact, the Museum of Victoria is now in the process of restoring it.
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Here's another one of his telescopes. This is the the largest refractor on mainland in Europe and Vienna.
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And this was built also by Howard Grubb. And he built sort of half of the telescopes for the car to see.
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The car to see was, in fact, the first survey.
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I mean, we were talking about surveys last night, astronomical surveys.
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And so this the car to see you from around the 1890s and it ran for quite a number of years was actually the first survey of the sky.
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Obviously, it was a photographic survey and it involved a number of universities and observatories around the world,
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including the Vatican Observatory. So that's why over here you see a group of nuns.
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So back in 1895, 1900, they were actually doing the measurements on on plates.
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Now, take that into consideration during your next survey and this telescope,
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which maybe some of you might know because it was an Oxford at one point,
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the Ratcliff telescope, some grubby construct that had ended up, of course, in Pretoria.
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But it was initially in Oxford, and this was constructed by Hart Group.
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Anyway, so let's start with the dust to give you some background about Hargrove himself.
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But he was very not only an instrument maker, but he was very interested in astronomy itself.
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Back in the 1900s, he organised an expedition to Spain to observe the kips there.
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And this was an expedition that involved the Royal Irish Academy and the Royal Dublin Society.
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So they they they duly headed off to Spain, initially was told an enormous number of people were going to go.
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But then just around that period, there was problems with the Boer War, etc. and the net result of that was not so many people wanted to travel.
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So anyway, they headed off to Spain. As you can see here, you have a 10th of a point.
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Oh, there is one. I have one just here for.
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I've got one. Steve Yeah, no problem, sir. You should have taken this out right at the beginning.
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Yeah. So that's decided to die.
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This one. Oh, this one?
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Yeah. Okay, so let's see. Okay.
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So it works very well. Alright. So here is actually the group in the senior in in in Spain, the travelled there for the 1900s of clips.
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This is actually Hargrove himself.
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This is a guy called Charles Jasper Jolly who was director of Dun Cinque Observatory, which is actually part of my own institute.
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Now, this guy is his name is Wilson.
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He did a lot of work on the sun and some of you may have heard of Wilson.
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He was also made the first temperature measurement of the sun, and he came from a place near Dublin.
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And what I thought was very interesting about this picture is that clearly Wilson,
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W.E. Wilson thought, you know, he was going off to Spain and he would require his helmet.
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All right. The deepest, darkest Spain. So whereas this is Rupert.
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This is Rupert Grove, the son of Howard Grove.
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And he has the more the modern idea of what going to Spain involves, but with the sort of straw hat, etc.
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So you can see the cultural transition of the current man. So here you see them setting up the equipment for the 1900s eclipse.
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You can see Wilson there in the background. And but this is the particular instrument that I want to draw your attention to.
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So this is Jolie with the 24th photographic camera.
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So here you see where the photographic plate would have gone. And you can just about see it peering over the edge here.
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There was a see the start, which, of course, just takes the light from the sun.
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It turns as the sun moves, essentially. Or is half of the race because of the law of law of reflection.
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And so it then sends the light into this stationary tube, which has a lens at the front.
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And the image is produced back here. So, of course, what they were trying to do was image the corona of the sun and which they duly did.
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It was extremely, very good conditions. And this is actually an image from the 1900s eclipse,
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which is actually in the raw in our academy that use this for an inch lens, which was 20 foot focal length.
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And you can see here a number of prominences coming out of the sun.
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Now, this picture, by the way, several people have asked me, wow, I didn't realise they had colour photography in 1900.
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They didn't. These this was coloured afterwards. Right.
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So just in case you're wondering that. But nevertheless, I think for 1900, you can see there is, you know, a very good quality.
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Actually what I did at one point. I mean, as I said, this this particular eclipse well, eclipse is normally visible over a very long track.
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And in this case, it was visible all the way from the US through places like Georgia, South Georgia, North Carolina to Spain, Portugal, Spain, etc.
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So there are quite a few records of this eclipse and here you see a little sort of prominences here.
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They're the same, more or less the same ones there in Spain. This is a couple of hours difference because it took time for the for the solar for
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for the track of the eclipse to move across the Atlantic from the US over to Europe.
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But you can see here that this is actually from the Smithsonian Archive.
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They had a station at North Carolina and a guy called Thomas Smiley, who is the photographer for the Smithsonian,
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actually recorded what's probably the first photograph of you recorded CME because you can see suddenly this,
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you know, the foot points here have developed into a major problems here, which has been injected into the corona.
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So we then kind of fast forwards a number of years.
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And as you know, and as Steve has already mentioned, towards the end of 1915,
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Einstein came up with this prediction that for the deflection of starlight when an eclipse occurs.
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And he predicted basically that, as you can see from here, the light of the of a star,
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which, of course, passes close to the sun, is bent, is altered in such a fashion.
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As you can see, I think from this diagram, the stars appear to move away from the sun itself compared to their normal position.
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So in the absence of the sun, and this is purely an effect of gravitational deflection.
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And he predicted the maximum amount will be 1.75 arcseconds and it scales with distance away from the sun so
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that to be the value would get for a star just at the surface of the sun or appearing to be at the surface.
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And of course, if you go to twice as far away, it's only half of that value.
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So that was the prediction in 1915.
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Now testing that prediction, there was there was a problem in trying to test the prediction, which is, of course, the First World War.
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And so it wasn't feasible to mount an eclipse expedition.
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So but back in 1917 then there was a this is a great title.
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So the Royal Astronomical Society and the Royal Society came together to form what was called a joint permanent eclipse committee.
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No, I still don't understand that title. No clips is permanent and hopefully no committee is permanent.
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So although I have my doubts in some cases, but anyway, they came together.
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They came up with this idea of an expedition, but they had a basic problem.
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And the basic problem was this that most of the Royal Society's Instrumentation and Royal
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Astronomical Society's instrumentation had been sent off to an eclipse in Russia in 1914.
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And then what happened was, of course, the First World War broke out, so they didn't get the equipment back.
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The astronomers got back, but the equipment was held up, of course, at the end of the war.
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Then you had the Bolshevik Revolution and they still didn't get their equipment back.
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In fact, they didn't get it back until the ninth, I think around 1925.
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So they were stuck and they asked to the Royal Irish Academy if they could assist by
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giving them some equipment from the Royal Irish Academy jus for previous eclipses.
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So there was actually a particular priest whose name was Courtney.
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Courtney. He was a stoney horse, which is in northern England, the school there.
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But he had associations with the Royal Academy and realised the potential of the equipment that had already been there.
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So they asked the Rowan Irish Academy for this equipment and that was duly of course a loan to them.
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So the idea behind the Eclipse expeditions was that there were actually two expeditions because chances were that maybe one of the,
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you know, might be cloudy. So the two sites that were chosen were kept off the west coast of Africa, but also a place called Sobral in Brazil.
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So those are the two sites and they're in the diagram.
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You can actually see the track of the eclipse itself.
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And it was regarded as an extremely favourable eclipse for measuring the deflection of starlight.
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Why? Because the sun was actually in a cluster behind each cluster, as you can see up here.
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We have used this one. You have.
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This is the tourist bowl. This is Aldebaran.
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This to be here. And this is the Hyades all all these stars here and up here at Hyades cluster.
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So there was a lot of stars. The sun was in a sort of perfect position because you could use a lot of these stars for reference purposes.
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And in particular, what I just want to point out is this star capital, which was the it's a double.
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It's a real double. It's not just an optical double. And capital was, you know, essentially the nearest star to the sun or nearest double star.
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So the idea was to use the sun, other stars in the hyades to make measurements of the gravitational deflection of stars.
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Normally, the sun isn't in such a such a good position from the point of view of getting bright stars.
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So the eclipse. The Eclipse parties went out at two sets of instrumentation, by the way, and that actually involved Oxford as well.
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It was a 13 inch crop lens fed by a 16 inch sealer start from Oxford, and that was the actual instrument used and kept.
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And it's so proud to use something very, very similar.
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A 13 inch crop lens as well, said by a six inch seedless tart from Greenwich.
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And in addition, the four inch lens that I mentioned earlier on from the 1900s are clips and an eight inch
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steel stuffed so that but the latter were essentially just the backup instrumentation.
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So this is the instrumentation they got from the Royal Arch Patent.
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The intention really was to make the, shall we say, the serious measurements using the 13 inch lenses and 16 inch sealed stones.
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And this particular man Andrew Crumlin was the leader of the expedition to so bravely was from County County Antrim.
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So he actually led the expedition out to Sobral and then Arthur Eddington led the one to.
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So that was fine. They actually went took them about a month.
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By the way, if you ever get a chance to read one of these papers about the Eclipse expeditions of the past to read more like travelogues,
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they describe the boats that they got the the how, you know, the local natives not necessarily in wonderful tone sometimes, by the way.
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But it is really worth reading just to see how how things have changed.
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So this is actually the so brown eclipse equipment. And in fact, the equipment over here, this is the the 16 inch seals.
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This is the 13 inch group lens. But this is the backup equipment.
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This is a four inch lens. And the agency to start.
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So just in case anything went wrong. And of course it did.
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Right. So that was Brazil.
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And the results from this World Cup is they got a few images, but unfortunately it was cloudy and so they didn't get an awful lot.
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So brown, the large scene was not suffered from sole reason because the sun was had been shining for a couple of days.
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So that was the downside of the beautiful weather that they had in Brazil.
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And as a result of that, the 16 and see the start produced distorted images.
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But the four inch lens. And the agency.
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The start actually produced the best results of the law, and in fact, were the results chosen by Addington in the end as the definitive answers.
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Right. And what they found was that affection for the limit of son.
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Because obviously they had to extrapolate it to, you know, using the one overall law of 1.98 plus or -0.18 arcseconds.
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And in fact, these plates were remeasured in 1979 by Harvey, and he got 1.9 plus or -0.11.
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So pretty much the same result, confirming that Eddington and Dyson had done their had done the proper job.
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And of course that's with more modern instrumentation at the time.
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And this is actually I literally did not have this up until about two days ago.
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Right. There's a there's a problem, which was that the 1919 eclipse plates from the Royal Greenwich Observatory went missing.
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All of them. Right. And this is actually from the clandestine border, the State Observatory in Heidelberg.
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Max Wolff was the director, Dan, at the time, and he was sent by Eddington a copy of one of the printed images.
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Right. So if you go on the Web and look for the 1919 eclipse and look for images of the eclipse, they're pretty lousy.
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And the reason is to just scans from old books. At the time, there are no proper scanned 19, 19 plates.
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Right. So we did come across this one.
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But in turn recently, it turns out that the The Greenwich Observer, while the Royal Greenwich Observatory at the Royal Observatory at Greenwich,
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which is now run by the Maritime Institute, apparently they held on to three plates,
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which hopefully now we'll be able to get in the next few weeks and get them scanned as well.
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But otherwise, the the the Royal Greenwich Observatory, the main set of Royal Greenwich Observatory plates, should now be in the Bodleian.
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But they're not. They're missing. And this is known by its that they're missing.
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But anyway, this is just to show you one of the print cap plates and these very faint stars here, very difficult to make measurements on.
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This is capital. Just to give you an idea of the quality of the plates from the time and this is, of course, the name of the sun.
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So as you can see, this is Dyson's paper and Edison's paper measuring the deflection of starlight.
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They give the value here. I gave you the error is wrong.
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1.94.
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But as you can see in summarising the results of the two expedition, the greatest weight must be awarded to those obtained by the four inch lenses.
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So brown and observations seem to stop. So that's.
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So that was actually the source of the measurements. I like this bit from the newspaper at the time.
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I think it's really good. Right.
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So this is they had Dyson and Eddington made the announcement that Einstein was correct at the Royal Society in November 1919.
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And I like this bit. The subject was a lively topic of conversation in the House of Commons yesterday.
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This is Joseph L'Amour for Cambridge University.
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On arriving at the lecture before the Royal Astronomical Society last evening said he he'd been
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besieged by inquiries as to whether Newton had been cast down and Cambridge done in Cambridge,
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a clearly being done in on this occasion.
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So, of course, Eddington became very famous on the front of Time magazine at the time and spent quite a bit of time with Einstein as well.
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And so that was fine. But there was the kind of rumour that this equipment had actually gone back to Ireland at some point.
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So I decided to follow up on this because I'd become interested in her brother and I was trying to trace where this equipment had gone.
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Anyway, long story short, through the archives in the Royal Society and in the Royal Astronomical Society,
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I basically and the Royal Lodge Academy basically found out that the equipment had been sent back to Ireland in 1947.
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At the foundation of my own institution. But the Institute found a way to prevent studies.
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Was well, the first section of it, which was theoretical physics, was opened up during the Second World War.
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And so people like Erwin Schrödinger ended up in Ireland.
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And because the President of Ireland's at the time realised there was a lot of scholars and
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fleeing the Nazis and he decided to set up the institute for them to come to during the war.
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Anyway, so I actually found and in turn the sea Lestat and the 20 foot lens buried.
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Well, in one case the instrument was buried in the basement amongst many other items in the observatory.
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Quite, quite a lot of stuff in empty territory. But in addition to see, the Star turned out to be in the garage of an X technician.
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And at some point it been sent off for him to do a bit of restoration work on it, you know.
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But anyway, we found it. It has.
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The nice thing about Grub equipment was that grub equipment has numbers on sort of boiler plate numbers.
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And fortunately, a well, grub grub, by the way, moved.
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After the First World War they moved to Newcastle and became persons who of course built telescopes.
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Up until the, up until the seventies persons when it closed,
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then they a lot of a lot of old stuff was being dumped and they had of the optics
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unit actually rescued some books from Dublin that were actually in a skip.
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And these were passed on to me because some retired.
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I was interested in Graham and turned out one of his books actually had Graham's numbers and where the instruments had been.
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So from the the number. Then I realised this was the actual seal of state and the lands had been used.
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And so brown, apart from the fact it was known the lens was 1946 inches focal length and you know, etc.
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So it was pretty, pretty definitive. Now hopefully that's the work.
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Okay. So this is the restored scene to start.
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So Madonna Observatory with the CAA in Clay did did a job on that.
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University College London restored the the Einstein hands to four inch lens.
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When I got this video from from the CAA a couple of weeks ago, I thought there was something wrong with my hard drive.
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And it turned out it was actually the noise of the governors and the see the stuff working for the first time in 37 years.
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So. So that's restored. It's now back in Dublin and in fact, we're kind of going to unveil is next week because we're celebrating,
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as Steve said, 100 years since Einstein before the general theory of relativity.
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So just to just to recap, it's this instrument here, which was the backup equipment which is now being found.
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So that was great and wonderful.
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But then that turned out to be a kind of twist to the story, which turned out to be very interesting.
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Because I realised something about the eclipses.
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So as a coastal thing you all know earth goes round the sun in 365 and a quarter days, more or less.
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Right. This is why we have the the leap year.
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And it means, for example, the solstice.
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The winter solstice. The summer solstice actually shifts over over time.
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And then, of course, you insert a leap year and then it brings it back.
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For example, in my the classic example I like Steve mentioned, I work a volt on some work in our view astronomy.
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And there's a site near Ireland called Newgrange which is actually aligned.
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It's a very long passage, but it was aligned with the winter solstice, but the winter solstice four or 5000 years ago,
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I mean, the carving dating of the scientists, 3200 or so B.C. And it's perfectly aligned for the for the winter solstice.
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And every winter solstice, you know, there's a small select party end up inside its main chamber to see the sun coming in.
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And I'm sort of wheeled up there on the 21st of December for this event.
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And, you know, there's some notable politicians or visiting dignitaries and whatever.
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But once every four years, actually on the 22nd that I'm told to keep my mouth shut.
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But then the following day, I really enjoy going up.
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And then there's some members of the public are allowed in. And I'd say this is the real solstice, not yesterday.
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Right. So you can see the pattern here.
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So basically, this is the this is of course, this is just the summer solstice, but it's the same thing applies.
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And what you have then is this oscillation, depending upon the leap year effect.
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Right. But in addition, as you also know, 365 and a quarter isn't quite right in Julian calendar.
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And there's another correction depending upon whether the first two digits of the century are divisible or not to be divisible by four.
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And so depending upon that, you either insert and and make them leap year or not, as the case may be.
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So that's why this particular pattern here. Okay, so that's fine.
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So you get this kind of drift. But what I realised was one eclipse, the 1900s eclipse that occurred in 28th May 1900 and the second eclipse,
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which was the one that was used in Sobral and and kept, was the 29th of May.
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Right. But one was in the morning.
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The other was in the afternoon. And one, you know, it was out of step as regards to be pure effect.
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So it turns out if you put them both into a planetarium program, for example, you'll see this.
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The top one is made of 28, 1900s eclipse.
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There's capital. All right.
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And that was the one in Spain that grob one looked at and reported.
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This is so brown. Eclipse made 29th. There's capital.
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Of course, it's upside down. Remember, Brazil is in the southern hemisphere, right?
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That's why. Otherwise, within one arc minute, the sun is in exactly the same place.
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It's just a coincidence. It's nothing to do, by the way, with Saracens, etc., during different serial cycles.
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It was just pure coincidence. So what we're saying is that the same equipment had been used to observe the same eclipse.
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Right. Essentially the same. The other advantage of 1900 clips, by the way, is, of course, the sun goes through cycles.
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The 11 year the 11 year cycles are more probably 22 year, but 11 year cycles in terms of criminal activity.
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And 1900 was less active than 1919.
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So there were advantages to 1900 versus 1919.
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So let's just sum it up. The sun was in exactly the same position.
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The sky, within a minute or two of our solar activity was lower in 1900 than it was in 1919.
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The same four inch lens and sills that was used to image the sun in the same part of the sky.
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Just coincidences.
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But it begs the obvious question why didn't anybody really think of doing using photography of historical data to try and measure this deflection?
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And there was a very good reason why people were doing photography.
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They were looking for a planet called Vulcan.
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Right. So, Vulkan, let me explain that.
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And I think many of you know, you know, the history of general relativity.
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There is an effect through, for example, the advancement of the perihelion of mercury.
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And the initial explanation for this, of course, we now know, of course, is just a general atavistic effect.
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But the initial explanation was in terms of a possible planet that was inside the orbit of Mercury and was therefore very,
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very difficult to see it even being given a name, Vulcan.
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And people started to search for Vulcan. Right.
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It's kind of ironic that the plates from the searching for Vulcan, which was purely erroneous due to the fans of the perihelion of Mercury,
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turns out to be of interest in terms of measuring the fraction of starlight.
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So that's the reason why they looked at it. And so then started looking at a number of plates from around the world from 1900.
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This is, for example, the shabu observatory's Oakland near San Francisco.
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And there's, as you can see, their capital 1900.
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Almost identical position as the 1919 model. Okay.
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But there are similar plates, Miller says, in Lake Observatory.
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There's a set in the Royal Observatory in Edinburgh as well.
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Okay. And so they all had gone off to observe this 1900s eclipse.
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But there was a suggestion to use historical plates.
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And the first person to suggest it was this man here on the left, Irwin Freundlich, or Irwin Finley Freundlich,
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as he sometimes called because he had a Scottish mother and a German German father, and he was a friend of Einstein's.
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And so back in around 1914, just before the war broke out, Einstein had predicted the deflection of starlight,
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a sort of first approximation, which we now call a sort of Newtonian approximation.
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It turns out, of course, to be wrong by a factor of two.
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But Freundlich had suggested using historical material to do this deflection of starlight measurement.
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Now, Freundlich had a couple of problems. One was he wasn't really a very practical observer.
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He was more of a theoretician. The second thing was that Struve, who was director, didn't believe in Einstein at all.
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I knew it. No, no comment. And so basically, he was not supported in this pursuit.
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He did try and go off to the 1914 eclipse and make measurements for that in Russia,
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not in the same science as the Royal Society and Royal Astronomical Society.
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And he ended up being interned, I think, somewhere around Serbia on the way to the eclipse.
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So anyway, he got out, but he he rose, in fact, to a number of observatories around the world, including Lech and the Royal Greenwich Observatory.
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To Dyson. This man here on the right, Curtis, tried to measure some historical plates.
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And then there was also an eclipse in 1917 in the US, and he actually did some work on that, but he was regarded as being well.
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Wallace Campbell, who is director of Lick, taught Curtis was a bit sloppy, by the way.
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Curtis. Some of you may have heard of the M 87 jet, so he was the guy who discovered the 87 jet.
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Photographically, he had no idea what it was, of course, at the time in the Aegean connection, but he actually discovered the jet from 87.
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So and the other complication then was that the U.S. entered the war around that time, and Curtis decided to go off the air with the U.S. military.
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So his work wasn't really completed and it wasn't done very, very well.
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Now, Dyson. As I said, Freundlich suggested to Dyson back in 1914 not to use historical material.
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I only know that because letters that are in the Lake Observatory Archive, where Freundlich writes to Campbell and says,
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I've contacted, you know, Dyson and suggested using historical material, but and that that he promised me help.
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Now, of course, when the war broke out, maybe things were a bit different at that point.
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Anyway, he never did. There's no correspondence in the audio corresponding to this.
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Then Dyson in 1917.
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Actually starts getting actively interested in measuring your general activity.
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Deflection Starlight and he prints in the monthly notices of the Royal Astronomical Society, a two page paper.
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Page one is measurements. Some historical measurements that he made on some plates from Tunisia that were in the audio archive.
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Page two I'm page one, by the way. He says, Oh, this method will clearly work.
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Right. You can see they're in black and white to page pages. This method will clearly work.
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But unfortunately, I can only measure two stars on this plate.
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So obviously that's not no good for measuring the reflections starlight.
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But the astral graphs will, will, will do the job.
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And then on page two. There is this eclipse coming up on the 29th of May 1919.
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We have to mount an expedition to to to measure Dr. Einstein's effect.
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And that's it. He shows a sort of diagram of where the stars will be in 1919 and nothing more.
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Just the two pages. So that's actually the diagram where he's made the his initial measurements.
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But then in the process of looking into this, I realised that.
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Dyson. Only honey had three sets of plates to look at from the astronauts.
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From eclipses. It ones from, as I mentioned here from Tunisia.
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That's the one he actually measured, measured on this two page paper.
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He had the plates from Sumatra, which wasn't very good in 1901.
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And then, to my surprise, I discovered he'd been at the 1900s of kids in Portugal.
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Right. So we had those sets of plates as well. And so he was at a place called over in Portugal that would have got the eclipse first as the
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eclipse crossed the Atlantic before Rob and his party would have gotten the eclipse in Spain.
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And here's the actually pictures of the party from the Bodleian Library, which was of course,
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then it was the Royal Greenwich Observatory's Library, which has been moved recently to the Bodleian.
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So this is the party in Portugal preparing for the eclipse.
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This man here is Kristie, who is the Astronomer Royal at the time.
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And his next in command was actually.
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And then I looked at the bottles and plates and there's.
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Capital is the limit to some here.
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So you can see the. Capital there.
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Now, these plates have only got a couple of stars on them,
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so it may not have been possible for Dyson to have done it any better than perhaps the ones from S-max.
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Maybe a bit better because there are two or three other stars.
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But he could have used the eclipse planes from Central Observatory, Greenwich or Lake or whatever at the time.
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Now. Why didn't he? I don't know. Well, to 100% accuracy, but I have my suspicions.
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I think it's the best way of putting it. So the problem was World War One.
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Eddington was a conscientious objector. He said he would go to prison first before serving in the army.
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The British army. 1916,
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conscription had been introduced and in the UK actually it was also one of the contributing factors to the revolution
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in Ireland in 1916 was the fact that it looked like Britain was going to enforce conscription in Ireland.
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So by 1917, Edington was in an awful lot of trouble in terms of defending himself from not going to the war and.
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Dyson and Eddington went to Cambridge together.
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In 1918. Eddington reached a stage where Eddington had to go in front of a military tribunal.
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To explain why he was not serving in the Army. He said what he had to do.
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And this was also it was the supporting letters from from Dyson that you would have to go off and observe the eclipse to test Einstein's
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theory of relativity and that it was crucial that he go and that there would not be another eclipse like this for a thousand years.
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No, I have checked. And yes, he actually was right, apart from I think to what there was one, which is just off the Falkland Islands.
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00:47:26,610 --> 00:47:31,020
In the 1930s where the hides were recovered.
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00:47:32,600 --> 00:47:36,200
Right. But that would have been at sea. So, yes, we will allow not one.
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00:47:36,350 --> 00:47:39,230
And in fact, yes, there's about a thousand years to the next one.
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Now you have to believe he never looked back 17 years, or it didn't cross Dyson's mind to look back 17 years.
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I just don't believe that. But, you know, that's so open to interpretation, right?
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00:48:00,860 --> 00:48:11,270
So anyway, Dyson insisted I don't and would have to lead this expedition, even though he was a theorist, by the way, in his first year in Cambridge.
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00:48:11,480 --> 00:48:17,750
If you read the stories about Eddington, he caused disaster in the first year lapse,
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and they suggest that you go off and do theory, which was a good idea.
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But then you have to ask yourself why? Okay.
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00:48:26,600 --> 00:48:34,330
So of course, he had a clear interest in general relativity. But, you know, Andrew Cromwell and who was an observer, was sent off for, you know, so.
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00:48:34,340 --> 00:48:39,420
BROWN Why didn't you pick somebody else from there or do you write?
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Andrew comment and by the way, never put his name to the paper. I don't know why I'm so.
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Anyway, Eddington went off to to observe the eclipse.
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And of course the results were published.
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And as I said, the results favoured Einstein's theory. So despite the fact that Dyson had these three sets of plates he picked.
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The worst, really one of the worst ones of the three.
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00:49:10,220 --> 00:49:13,630
Well, you know, it was kind of cloudy, so not much you could do with that. Right.
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And I still have no idea why, apart from the fact that I what I suggest was he realised from the 1900s eclipse.
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Plates and the you know, the fact that he made measurements on that, that the technique would work.
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And that may have also inspired them to realise about the 1919 eclipse.
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In the whole sort of trying to sort out the problem with Eddington as well.
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So there was always a claim, by the way, by Chandrasekhar that the only reason why Eddington was went to this eclipse was simply to avoid war.
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And a lot of people thought, well, because this was a well known dispute between Chandrasekhar and Eddington,
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that maybe it was a touch of sour grapes over all of this.
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But that may well have been something in this. So okay.
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So just to summarise, the actual equipment which had been used and proved crucial in the 1919 eclipse measurements has been found, has been restored.
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That's quite timely with next week being 100 years since Einstein proposed his general theory of relativity.
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The quip by a quirk of just a fluke chance.
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It turns out that same equipment had been used to observe an identical eclipse.
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19 years before us. And it does look like Dyson, I suppose to kind interpretation of this.
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Dyson probably realised that he would muddy the waters.
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If he'd had talked about an identical eclipse which had occurred.
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00:51:05,630 --> 00:51:10,250
You know, 19 years beforehand that would not have served Eddington's case.
431
00:51:10,400 --> 00:51:13,400
Certainly he did not. Or he was extremely stupid.
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00:51:13,610 --> 00:51:18,260
Right. So we've actually I mean,
433
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we've had a look at some of these plates to understand virtue and height in Heidelberg
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now is gathering all these plates together from different parts of the world.
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And we're going to remeasure them. And actually what our intention is that we make them available online for students of physics in 2016 to
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00:51:36,620 --> 00:51:43,340
actually measure the deflection of starlight from themselves with the 1900 plates and the 1919 plates,
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hopefully the ones in the audio are still alive. Okay, so thank you very much.
00:00:07,920 --> 00:00:14,010
Thank you very much, Steve, for this kind introduction and also explaining that this is not my day job.
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And there and I does the health warning.
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I am not a historian. All right. But what I want to do today is tell you a little bit, first of all,
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about the firm of Howard Grubb in Dublin and then tie that in with the measurements that were made in 1919.
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And you'll see some of the equipment from Rob's time that that proved to be very important for these particular measurements.
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So I need to set the whole thing in context and.
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That's it. That's it. So around the 1840s, 1850s in Ireland was a sort of golden era in astronomy.
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What probably a lot of people don't realise is that actually Ireland, up to about the 1870s or so,
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had not only the largest reflecting telescope in the world, that was the six foot, the so-called Avison of Parsons Town.
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It was the the biggest reflector in the world, but it also had the largest refractor in the world in a place called Marguerite Castle in Sligo.
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Now, of course, Ireland is not the best place when it comes to optical observing night.
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Neither is Oxford. But you know, this was pre jetting off to La Palma or Hawaii,
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etc. So it's understandable that they had to they had to based them at home, so to speak.
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So this golden era of astronomy in Ireland then gave rise to an actual industry building telescopes.
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And this man here, Thomas Grubb, was the first was the founder of the firm.
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He initially started off believing not his business was making billiard tables.
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And at that time, by the way, the billiard tables weren't slate billiard tables.
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They were actually metal that were fashioned into as flat as a tabletop as possible.
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But he started in that, but he had an interest in scientific instrumentation,
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and so he started building telescopes and microscopes, etc. But although he he made telescopes,
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for example, for the US Naval Observatory, a number of small telescopes around Europe,
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he realised that telescope making was not a very steady business.
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But you would get an order for a large telescope.
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The firm would be going for a few months working on that and then the mightn't be in order for quite some time.
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So he decided to go into another business which was actually making money or more precisely printing money.
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He got the post in the bank of the Bank of Ireland, produced its own notes, rather like the Bank of England does at that time.
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And he got the post with the recommendation of William Rowan Hamilton, noted mathematician and not sure you know,
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that letter of reference from mathematician today would get you a job in the Bank of England, for example.
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But maybe, maybe. But anyway, so that's how he got the job.
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And he essentially passed on the business to his son, Howard Groep and Howard started actually doing a degree in Trinity College.
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We actually never finished it, but he became very, very well known in instrument making circles and he made telescopes.
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And I'll just show you few examples in the next few minutes for for institutions all around the world, including Vienna, for Melbourne, etc.
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As I said, I'll show you some examples. But he also was involved with some telescopes in the states.
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For example, if any of you ever go to the Lick Observatory, you'll see there's a rising floor in the observatory,
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which was the solution for the problem of when you make a bigger and bigger refractor, of course.
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And if you're looking at something which is low down on the horizon or even in 30 degrees or whatever,
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then it gets very difficult for the observer to look through the eyepiece.
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So he came up with the idea of the rising floor.
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So hydraulically moving floor. And he also later in life, he was the person who developed the Marine periscope.
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So it's difficult to kind of realise it now.
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The inventor, by the way, of the modern submarine was a guy called Holland, John Holland, who was also from County Clare.
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But he Holland tried to get the the British Army interested in submarines and they weren't particularly interested.
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So he actually ended up over in the US.
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Where his first source of funding was the Fenian Brotherhood.
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Now I can imagine what what they intend to do with the first submarine,
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but they actually ran out of money and he eventually sold the idea to the US Navy
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and started building submarines and at which point British he got interested.
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But the first submarines actually went around blind.
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They had no periscope. They simply just went underwater, went a certain distance, hoping for the best, the particular direction.
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But then Grupp invented the periscope in particular for a submarine, and that was extremely challenging business at the time to do that.
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Anyway, at one point in his his firm, which is in a place called Rat Mines in Dublin, it had 400 people working on optics.
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Here's an actual picture of his firm in rat minds.
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This is with the opening of the new building. And you note the clear.
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Health and safety. Cognisance, right?
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Yes. And. Here's one of his famous telescopes, the great Melbourne Telescope.
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So Melbourne, after the Gold Rush, had a lot of money.
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This is back in sort of 1840 748, and they decided they were going to do the local government decided on a prestige
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project which was to build the largest telescope in the Southern Hemisphere.
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They had virtually no astronomers, by the way, but they decided to build the telescope anyway.
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So Hargrove was commissioned it making the telescope.
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And that was actually the last one.
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Major telescope using Speculum Mirror. So you built using glass mirror after that, people started using glass and parks, etcetera.
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And but that telescope, actually, there had been a number of reincarnations of that telescope.
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And it was used up to about, I think about 15 years ago for the Metro Project, you know,
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for searching for massive objects in the halo of our galaxy, which were causing gravitational deflection.
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Gravitational lensing. So and then of course, there was the fire of Mount Stromlo and that telescope was destroyed.
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But in fact, the Museum of Victoria is now in the process of restoring it.
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Here's another one of his telescopes. This is the the largest refractor on mainland in Europe and Vienna.
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And this was built also by Howard Grubb. And he built sort of half of the telescopes for the car to see.
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The car to see was, in fact, the first survey.
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I mean, we were talking about surveys last night, astronomical surveys.
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And so this the car to see you from around the 1890s and it ran for quite a number of years was actually the first survey of the sky.
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Obviously, it was a photographic survey and it involved a number of universities and observatories around the world,
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including the Vatican Observatory. So that's why over here you see a group of nuns.
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So back in 1895, 1900, they were actually doing the measurements on on plates.
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Now, take that into consideration during your next survey and this telescope,
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which maybe some of you might know because it was an Oxford at one point,
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the Ratcliff telescope, some grubby construct that had ended up, of course, in Pretoria.
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But it was initially in Oxford, and this was constructed by Hart Group.
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Anyway, so let's start with the dust to give you some background about Hargrove himself.
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But he was very not only an instrument maker, but he was very interested in astronomy itself.
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Back in the 1900s, he organised an expedition to Spain to observe the kips there.
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And this was an expedition that involved the Royal Irish Academy and the Royal Dublin Society.
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So they they they duly headed off to Spain, initially was told an enormous number of people were going to go.
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But then just around that period, there was problems with the Boer War, etc. and the net result of that was not so many people wanted to travel.
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So anyway, they headed off to Spain. As you can see here, you have a 10th of a point.
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Oh, there is one. I have one just here for.
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I've got one. Steve Yeah, no problem, sir. You should have taken this out right at the beginning.
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Yeah. So that's decided to die.
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This one. Oh, this one?
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Yeah. Okay, so let's see. Okay.
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So it works very well. Alright. So here is actually the group in the senior in in in Spain, the travelled there for the 1900s of clips.
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This is actually Hargrove himself.
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This is a guy called Charles Jasper Jolly who was director of Dun Cinque Observatory, which is actually part of my own institute.
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Now, this guy is his name is Wilson.
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He did a lot of work on the sun and some of you may have heard of Wilson.
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He was also made the first temperature measurement of the sun, and he came from a place near Dublin.
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And what I thought was very interesting about this picture is that clearly Wilson,
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W.E. Wilson thought, you know, he was going off to Spain and he would require his helmet.
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All right. The deepest, darkest Spain. So whereas this is Rupert.
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This is Rupert Grove, the son of Howard Grove.
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And he has the more the modern idea of what going to Spain involves, but with the sort of straw hat, etc.
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So you can see the cultural transition of the current man. So here you see them setting up the equipment for the 1900s eclipse.
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You can see Wilson there in the background. And but this is the particular instrument that I want to draw your attention to.
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So this is Jolie with the 24th photographic camera.
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So here you see where the photographic plate would have gone. And you can just about see it peering over the edge here.
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There was a see the start, which, of course, just takes the light from the sun.
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It turns as the sun moves, essentially. Or is half of the race because of the law of law of reflection.
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And so it then sends the light into this stationary tube, which has a lens at the front.
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And the image is produced back here. So, of course, what they were trying to do was image the corona of the sun and which they duly did.
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It was extremely, very good conditions. And this is actually an image from the 1900s eclipse,
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which is actually in the raw in our academy that use this for an inch lens, which was 20 foot focal length.
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And you can see here a number of prominences coming out of the sun.
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Now, this picture, by the way, several people have asked me, wow, I didn't realise they had colour photography in 1900.
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They didn't. These this was coloured afterwards. Right.
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So just in case you're wondering that. But nevertheless, I think for 1900, you can see there is, you know, a very good quality.
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Actually what I did at one point. I mean, as I said, this this particular eclipse well, eclipse is normally visible over a very long track.
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And in this case, it was visible all the way from the US through places like Georgia, South Georgia, North Carolina to Spain, Portugal, Spain, etc.
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So there are quite a few records of this eclipse and here you see a little sort of prominences here.
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They're the same, more or less the same ones there in Spain. This is a couple of hours difference because it took time for the for the solar for
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for the track of the eclipse to move across the Atlantic from the US over to Europe.
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But you can see here that this is actually from the Smithsonian Archive.
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They had a station at North Carolina and a guy called Thomas Smiley, who is the photographer for the Smithsonian,
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actually recorded what's probably the first photograph of you recorded CME because you can see suddenly this,
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you know, the foot points here have developed into a major problems here, which has been injected into the corona.
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So we then kind of fast forwards a number of years.
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And as you know, and as Steve has already mentioned, towards the end of 1915,
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Einstein came up with this prediction that for the deflection of starlight when an eclipse occurs.
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And he predicted basically that, as you can see from here, the light of the of a star,
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which, of course, passes close to the sun, is bent, is altered in such a fashion.
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As you can see, I think from this diagram, the stars appear to move away from the sun itself compared to their normal position.
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So in the absence of the sun, and this is purely an effect of gravitational deflection.
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And he predicted the maximum amount will be 1.75 arcseconds and it scales with distance away from the sun so
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that to be the value would get for a star just at the surface of the sun or appearing to be at the surface.
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And of course, if you go to twice as far away, it's only half of that value.
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So that was the prediction in 1915.
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Now testing that prediction, there was there was a problem in trying to test the prediction, which is, of course, the First World War.
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And so it wasn't feasible to mount an eclipse expedition.
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So but back in 1917 then there was a this is a great title.
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So the Royal Astronomical Society and the Royal Society came together to form what was called a joint permanent eclipse committee.
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No, I still don't understand that title. No clips is permanent and hopefully no committee is permanent.
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So although I have my doubts in some cases, but anyway, they came together.
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They came up with this idea of an expedition, but they had a basic problem.
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And the basic problem was this that most of the Royal Society's Instrumentation and Royal
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Astronomical Society's instrumentation had been sent off to an eclipse in Russia in 1914.
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And then what happened was, of course, the First World War broke out, so they didn't get the equipment back.
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The astronomers got back, but the equipment was held up, of course, at the end of the war.
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Then you had the Bolshevik Revolution and they still didn't get their equipment back.
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In fact, they didn't get it back until the ninth, I think around 1925.
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So they were stuck and they asked to the Royal Irish Academy if they could assist by
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giving them some equipment from the Royal Irish Academy jus for previous eclipses.
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So there was actually a particular priest whose name was Courtney.
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Courtney. He was a stoney horse, which is in northern England, the school there.
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But he had associations with the Royal Academy and realised the potential of the equipment that had already been there.
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So they asked the Rowan Irish Academy for this equipment and that was duly of course a loan to them.
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So the idea behind the Eclipse expeditions was that there were actually two expeditions because chances were that maybe one of the,
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you know, might be cloudy. So the two sites that were chosen were kept off the west coast of Africa, but also a place called Sobral in Brazil.
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So those are the two sites and they're in the diagram.
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You can actually see the track of the eclipse itself.
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And it was regarded as an extremely favourable eclipse for measuring the deflection of starlight.
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Why? Because the sun was actually in a cluster behind each cluster, as you can see up here.
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We have used this one. You have.
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This is the tourist bowl. This is Aldebaran.
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This to be here. And this is the Hyades all all these stars here and up here at Hyades cluster.
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So there was a lot of stars. The sun was in a sort of perfect position because you could use a lot of these stars for reference purposes.
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And in particular, what I just want to point out is this star capital, which was the it's a double.
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It's a real double. It's not just an optical double. And capital was, you know, essentially the nearest star to the sun or nearest double star.
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So the idea was to use the sun, other stars in the hyades to make measurements of the gravitational deflection of stars.
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Normally, the sun isn't in such a such a good position from the point of view of getting bright stars.
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So the eclipse. The Eclipse parties went out at two sets of instrumentation, by the way, and that actually involved Oxford as well.
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It was a 13 inch crop lens fed by a 16 inch sealer start from Oxford, and that was the actual instrument used and kept.
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And it's so proud to use something very, very similar.
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A 13 inch crop lens as well, said by a six inch seedless tart from Greenwich.
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And in addition, the four inch lens that I mentioned earlier on from the 1900s are clips and an eight inch
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steel stuffed so that but the latter were essentially just the backup instrumentation.
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So this is the instrumentation they got from the Royal Arch Patent.
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The intention really was to make the, shall we say, the serious measurements using the 13 inch lenses and 16 inch sealed stones.
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And this particular man Andrew Crumlin was the leader of the expedition to so bravely was from County County Antrim.
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So he actually led the expedition out to Sobral and then Arthur Eddington led the one to.
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So that was fine. They actually went took them about a month.
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By the way, if you ever get a chance to read one of these papers about the Eclipse expeditions of the past to read more like travelogues,
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they describe the boats that they got the the how, you know, the local natives not necessarily in wonderful tone sometimes, by the way.
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But it is really worth reading just to see how how things have changed.
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So this is actually the so brown eclipse equipment. And in fact, the equipment over here, this is the the 16 inch seals.
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This is the 13 inch group lens. But this is the backup equipment.
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This is a four inch lens. And the agency to start.
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So just in case anything went wrong. And of course it did.
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Right. So that was Brazil.
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And the results from this World Cup is they got a few images, but unfortunately it was cloudy and so they didn't get an awful lot.
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So brown, the large scene was not suffered from sole reason because the sun was had been shining for a couple of days.
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So that was the downside of the beautiful weather that they had in Brazil.
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And as a result of that, the 16 and see the start produced distorted images.
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But the four inch lens. And the agency.
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The start actually produced the best results of the law, and in fact, were the results chosen by Addington in the end as the definitive answers.
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Right. And what they found was that affection for the limit of son.
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Because obviously they had to extrapolate it to, you know, using the one overall law of 1.98 plus or -0.18 arcseconds.
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And in fact, these plates were remeasured in 1979 by Harvey, and he got 1.9 plus or -0.11.
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So pretty much the same result, confirming that Eddington and Dyson had done their had done the proper job.
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And of course that's with more modern instrumentation at the time.
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And this is actually I literally did not have this up until about two days ago.
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Right. There's a there's a problem, which was that the 1919 eclipse plates from the Royal Greenwich Observatory went missing.
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All of them. Right. And this is actually from the clandestine border, the State Observatory in Heidelberg.
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Max Wolff was the director, Dan, at the time, and he was sent by Eddington a copy of one of the printed images.
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Right. So if you go on the Web and look for the 1919 eclipse and look for images of the eclipse, they're pretty lousy.
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And the reason is to just scans from old books. At the time, there are no proper scanned 19, 19 plates.
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Right. So we did come across this one.
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But in turn recently, it turns out that the The Greenwich Observer, while the Royal Greenwich Observatory at the Royal Observatory at Greenwich,
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which is now run by the Maritime Institute, apparently they held on to three plates,
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which hopefully now we'll be able to get in the next few weeks and get them scanned as well.
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But otherwise, the the the Royal Greenwich Observatory, the main set of Royal Greenwich Observatory plates, should now be in the Bodleian.
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But they're not. They're missing. And this is known by its that they're missing.
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But anyway, this is just to show you one of the print cap plates and these very faint stars here, very difficult to make measurements on.
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This is capital. Just to give you an idea of the quality of the plates from the time and this is, of course, the name of the sun.
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So as you can see, this is Dyson's paper and Edison's paper measuring the deflection of starlight.
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They give the value here. I gave you the error is wrong.
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1.94.
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But as you can see in summarising the results of the two expedition, the greatest weight must be awarded to those obtained by the four inch lenses.
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So brown and observations seem to stop. So that's.
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So that was actually the source of the measurements. I like this bit from the newspaper at the time.
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I think it's really good. Right.
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So this is they had Dyson and Eddington made the announcement that Einstein was correct at the Royal Society in November 1919.
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And I like this bit. The subject was a lively topic of conversation in the House of Commons yesterday.
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This is Joseph L'Amour for Cambridge University.
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On arriving at the lecture before the Royal Astronomical Society last evening said he he'd been
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besieged by inquiries as to whether Newton had been cast down and Cambridge done in Cambridge,
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a clearly being done in on this occasion.
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So, of course, Eddington became very famous on the front of Time magazine at the time and spent quite a bit of time with Einstein as well.
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And so that was fine. But there was the kind of rumour that this equipment had actually gone back to Ireland at some point.
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So I decided to follow up on this because I'd become interested in her brother and I was trying to trace where this equipment had gone.
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Anyway, long story short, through the archives in the Royal Society and in the Royal Astronomical Society,
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I basically and the Royal Lodge Academy basically found out that the equipment had been sent back to Ireland in 1947.
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At the foundation of my own institution. But the Institute found a way to prevent studies.
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Was well, the first section of it, which was theoretical physics, was opened up during the Second World War.
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And so people like Erwin Schrödinger ended up in Ireland.
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And because the President of Ireland's at the time realised there was a lot of scholars and
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fleeing the Nazis and he decided to set up the institute for them to come to during the war.
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Anyway, so I actually found and in turn the sea Lestat and the 20 foot lens buried.
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Well, in one case the instrument was buried in the basement amongst many other items in the observatory.
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Quite, quite a lot of stuff in empty territory. But in addition to see, the Star turned out to be in the garage of an X technician.
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And at some point it been sent off for him to do a bit of restoration work on it, you know.
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But anyway, we found it. It has.
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The nice thing about Grub equipment was that grub equipment has numbers on sort of boiler plate numbers.
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And fortunately, a well, grub grub, by the way, moved.
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After the First World War they moved to Newcastle and became persons who of course built telescopes.
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Up until the, up until the seventies persons when it closed,
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then they a lot of a lot of old stuff was being dumped and they had of the optics
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unit actually rescued some books from Dublin that were actually in a skip.
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And these were passed on to me because some retired.
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I was interested in Graham and turned out one of his books actually had Graham's numbers and where the instruments had been.
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So from the the number. Then I realised this was the actual seal of state and the lands had been used.
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And so brown, apart from the fact it was known the lens was 1946 inches focal length and you know, etc.
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So it was pretty, pretty definitive. Now hopefully that's the work.
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Okay. So this is the restored scene to start.
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So Madonna Observatory with the CAA in Clay did did a job on that.
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University College London restored the the Einstein hands to four inch lens.
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When I got this video from from the CAA a couple of weeks ago, I thought there was something wrong with my hard drive.
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And it turned out it was actually the noise of the governors and the see the stuff working for the first time in 37 years.
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So. So that's restored. It's now back in Dublin and in fact, we're kind of going to unveil is next week because we're celebrating,
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as Steve said, 100 years since Einstein before the general theory of relativity.
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So just to just to recap, it's this instrument here, which was the backup equipment which is now being found.
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So that was great and wonderful.
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But then that turned out to be a kind of twist to the story, which turned out to be very interesting.
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Because I realised something about the eclipses.
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So as a coastal thing you all know earth goes round the sun in 365 and a quarter days, more or less.
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Right. This is why we have the the leap year.
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And it means, for example, the solstice.
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The winter solstice. The summer solstice actually shifts over over time.
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And then, of course, you insert a leap year and then it brings it back.
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For example, in my the classic example I like Steve mentioned, I work a volt on some work in our view astronomy.
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And there's a site near Ireland called Newgrange which is actually aligned.
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It's a very long passage, but it was aligned with the winter solstice, but the winter solstice four or 5000 years ago,
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I mean, the carving dating of the scientists, 3200 or so B.C. And it's perfectly aligned for the for the winter solstice.
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And every winter solstice, you know, there's a small select party end up inside its main chamber to see the sun coming in.
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And I'm sort of wheeled up there on the 21st of December for this event.
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And, you know, there's some notable politicians or visiting dignitaries and whatever.
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But once every four years, actually on the 22nd that I'm told to keep my mouth shut.
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But then the following day, I really enjoy going up.
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And then there's some members of the public are allowed in. And I'd say this is the real solstice, not yesterday.
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Right. So you can see the pattern here.
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So basically, this is the this is of course, this is just the summer solstice, but it's the same thing applies.
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And what you have then is this oscillation, depending upon the leap year effect.
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Right. But in addition, as you also know, 365 and a quarter isn't quite right in Julian calendar.
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And there's another correction depending upon whether the first two digits of the century are divisible or not to be divisible by four.
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And so depending upon that, you either insert and and make them leap year or not, as the case may be.
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So that's why this particular pattern here. Okay, so that's fine.
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So you get this kind of drift. But what I realised was one eclipse, the 1900s eclipse that occurred in 28th May 1900 and the second eclipse,
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which was the one that was used in Sobral and and kept, was the 29th of May.
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Right. But one was in the morning.
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The other was in the afternoon. And one, you know, it was out of step as regards to be pure effect.
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So it turns out if you put them both into a planetarium program, for example, you'll see this.
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The top one is made of 28, 1900s eclipse.
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There's capital. All right.
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And that was the one in Spain that grob one looked at and reported.
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This is so brown. Eclipse made 29th. There's capital.
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Of course, it's upside down. Remember, Brazil is in the southern hemisphere, right?
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That's why. Otherwise, within one arc minute, the sun is in exactly the same place.
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It's just a coincidence. It's nothing to do, by the way, with Saracens, etc., during different serial cycles.
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It was just pure coincidence. So what we're saying is that the same equipment had been used to observe the same eclipse.
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Right. Essentially the same. The other advantage of 1900 clips, by the way, is, of course, the sun goes through cycles.
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The 11 year the 11 year cycles are more probably 22 year, but 11 year cycles in terms of criminal activity.
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And 1900 was less active than 1919.
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So there were advantages to 1900 versus 1919.
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So let's just sum it up. The sun was in exactly the same position.
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The sky, within a minute or two of our solar activity was lower in 1900 than it was in 1919.
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The same four inch lens and sills that was used to image the sun in the same part of the sky.
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Just coincidences.
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But it begs the obvious question why didn't anybody really think of doing using photography of historical data to try and measure this deflection?
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And there was a very good reason why people were doing photography.
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They were looking for a planet called Vulcan.
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Right. So, Vulkan, let me explain that.
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And I think many of you know, you know, the history of general relativity.
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There is an effect through, for example, the advancement of the perihelion of mercury.
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And the initial explanation for this, of course, we now know, of course, is just a general atavistic effect.
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But the initial explanation was in terms of a possible planet that was inside the orbit of Mercury and was therefore very,
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very difficult to see it even being given a name, Vulcan.
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And people started to search for Vulcan. Right.
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It's kind of ironic that the plates from the searching for Vulcan, which was purely erroneous due to the fans of the perihelion of Mercury,
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turns out to be of interest in terms of measuring the fraction of starlight.
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So that's the reason why they looked at it. And so then started looking at a number of plates from around the world from 1900.
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This is, for example, the shabu observatory's Oakland near San Francisco.
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And there's, as you can see, their capital 1900.
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Almost identical position as the 1919 model. Okay.
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But there are similar plates, Miller says, in Lake Observatory.
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There's a set in the Royal Observatory in Edinburgh as well.
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Okay. And so they all had gone off to observe this 1900s eclipse.
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But there was a suggestion to use historical plates.
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And the first person to suggest it was this man here on the left, Irwin Freundlich, or Irwin Finley Freundlich,
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as he sometimes called because he had a Scottish mother and a German German father, and he was a friend of Einstein's.
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And so back in around 1914, just before the war broke out, Einstein had predicted the deflection of starlight,
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a sort of first approximation, which we now call a sort of Newtonian approximation.
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It turns out, of course, to be wrong by a factor of two.
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But Freundlich had suggested using historical material to do this deflection of starlight measurement.
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Now, Freundlich had a couple of problems. One was he wasn't really a very practical observer.
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He was more of a theoretician. The second thing was that Struve, who was director, didn't believe in Einstein at all.
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I knew it. No, no comment. And so basically, he was not supported in this pursuit.
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He did try and go off to the 1914 eclipse and make measurements for that in Russia,
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not in the same science as the Royal Society and Royal Astronomical Society.
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And he ended up being interned, I think, somewhere around Serbia on the way to the eclipse.
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So anyway, he got out, but he he rose, in fact, to a number of observatories around the world, including Lech and the Royal Greenwich Observatory.
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To Dyson. This man here on the right, Curtis, tried to measure some historical plates.
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And then there was also an eclipse in 1917 in the US, and he actually did some work on that, but he was regarded as being well.
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Wallace Campbell, who is director of Lick, taught Curtis was a bit sloppy, by the way.
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Curtis. Some of you may have heard of the M 87 jet, so he was the guy who discovered the 87 jet.
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Photographically, he had no idea what it was, of course, at the time in the Aegean connection, but he actually discovered the jet from 87.
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So and the other complication then was that the U.S. entered the war around that time, and Curtis decided to go off the air with the U.S. military.
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So his work wasn't really completed and it wasn't done very, very well.
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Now, Dyson. As I said, Freundlich suggested to Dyson back in 1914 not to use historical material.
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I only know that because letters that are in the Lake Observatory Archive, where Freundlich writes to Campbell and says,
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I've contacted, you know, Dyson and suggested using historical material, but and that that he promised me help.
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Now, of course, when the war broke out, maybe things were a bit different at that point.
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Anyway, he never did. There's no correspondence in the audio corresponding to this.
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Then Dyson in 1917.
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Actually starts getting actively interested in measuring your general activity.
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Deflection Starlight and he prints in the monthly notices of the Royal Astronomical Society, a two page paper.
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Page one is measurements. Some historical measurements that he made on some plates from Tunisia that were in the audio archive.
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Page two I'm page one, by the way. He says, Oh, this method will clearly work.
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Right. You can see they're in black and white to page pages. This method will clearly work.
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But unfortunately, I can only measure two stars on this plate.
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So obviously that's not no good for measuring the reflections starlight.
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But the astral graphs will, will, will do the job.
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And then on page two. There is this eclipse coming up on the 29th of May 1919.
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We have to mount an expedition to to to measure Dr. Einstein's effect.
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And that's it. He shows a sort of diagram of where the stars will be in 1919 and nothing more.
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Just the two pages. So that's actually the diagram where he's made the his initial measurements.
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But then in the process of looking into this, I realised that.
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Dyson. Only honey had three sets of plates to look at from the astronauts.
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From eclipses. It ones from, as I mentioned here from Tunisia.
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That's the one he actually measured, measured on this two page paper.
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He had the plates from Sumatra, which wasn't very good in 1901.
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And then, to my surprise, I discovered he'd been at the 1900s of kids in Portugal.
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Right. So we had those sets of plates as well. And so he was at a place called over in Portugal that would have got the eclipse first as the
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eclipse crossed the Atlantic before Rob and his party would have gotten the eclipse in Spain.
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And here's the actually pictures of the party from the Bodleian Library, which was of course,
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then it was the Royal Greenwich Observatory's Library, which has been moved recently to the Bodleian.
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So this is the party in Portugal preparing for the eclipse.
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This man here is Kristie, who is the Astronomer Royal at the time.
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And his next in command was actually.
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And then I looked at the bottles and plates and there's.
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Capital is the limit to some here.
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So you can see the. Capital there.
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Now, these plates have only got a couple of stars on them,
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so it may not have been possible for Dyson to have done it any better than perhaps the ones from S-max.
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Maybe a bit better because there are two or three other stars.
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But he could have used the eclipse planes from Central Observatory, Greenwich or Lake or whatever at the time.
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Now. Why didn't he? I don't know. Well, to 100% accuracy, but I have my suspicions.
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I think it's the best way of putting it. So the problem was World War One.
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Eddington was a conscientious objector. He said he would go to prison first before serving in the army.
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The British army. 1916,
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conscription had been introduced and in the UK actually it was also one of the contributing factors to the revolution
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in Ireland in 1916 was the fact that it looked like Britain was going to enforce conscription in Ireland.
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So by 1917, Edington was in an awful lot of trouble in terms of defending himself from not going to the war and.
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Dyson and Eddington went to Cambridge together.
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In 1918. Eddington reached a stage where Eddington had to go in front of a military tribunal.
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To explain why he was not serving in the Army. He said what he had to do.
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And this was also it was the supporting letters from from Dyson that you would have to go off and observe the eclipse to test Einstein's
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theory of relativity and that it was crucial that he go and that there would not be another eclipse like this for a thousand years.
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No, I have checked. And yes, he actually was right, apart from I think to what there was one, which is just off the Falkland Islands.
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In the 1930s where the hides were recovered.
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00:47:32,600 --> 00:47:36,200
Right. But that would have been at sea. So, yes, we will allow not one.
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And in fact, yes, there's about a thousand years to the next one.
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Now you have to believe he never looked back 17 years, or it didn't cross Dyson's mind to look back 17 years.
402
00:47:54,380 --> 00:47:59,340
I just don't believe that. But, you know, that's so open to interpretation, right?
403
00:48:00,860 --> 00:48:11,270
So anyway, Dyson insisted I don't and would have to lead this expedition, even though he was a theorist, by the way, in his first year in Cambridge.
404
00:48:11,480 --> 00:48:17,750
If you read the stories about Eddington, he caused disaster in the first year lapse,
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and they suggest that you go off and do theory, which was a good idea.
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But then you have to ask yourself why? Okay.
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So of course, he had a clear interest in general relativity. But, you know, Andrew Cromwell and who was an observer, was sent off for, you know, so.
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BROWN Why didn't you pick somebody else from there or do you write?
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Andrew comment and by the way, never put his name to the paper. I don't know why I'm so.
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Anyway, Eddington went off to to observe the eclipse.
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And of course the results were published.
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And as I said, the results favoured Einstein's theory. So despite the fact that Dyson had these three sets of plates he picked.
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The worst, really one of the worst ones of the three.
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00:49:10,220 --> 00:49:13,630
Well, you know, it was kind of cloudy, so not much you could do with that. Right.
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And I still have no idea why, apart from the fact that I what I suggest was he realised from the 1900s eclipse.
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Plates and the you know, the fact that he made measurements on that, that the technique would work.
417
00:49:34,470 --> 00:49:38,580
And that may have also inspired them to realise about the 1919 eclipse.
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00:49:40,120 --> 00:49:44,800
In the whole sort of trying to sort out the problem with Eddington as well.
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00:49:46,590 --> 00:49:55,110
So there was always a claim, by the way, by Chandrasekhar that the only reason why Eddington was went to this eclipse was simply to avoid war.
420
00:49:55,620 --> 00:50:00,959
And a lot of people thought, well, because this was a well known dispute between Chandrasekhar and Eddington,
421
00:50:00,960 --> 00:50:04,680
that maybe it was a touch of sour grapes over all of this.
422
00:50:05,250 --> 00:50:11,940
But that may well have been something in this. So okay.
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00:50:11,940 --> 00:50:23,370
So just to summarise, the actual equipment which had been used and proved crucial in the 1919 eclipse measurements has been found, has been restored.
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That's quite timely with next week being 100 years since Einstein proposed his general theory of relativity.
425
00:50:32,370 --> 00:50:37,170
The quip by a quirk of just a fluke chance.
426
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It turns out that same equipment had been used to observe an identical eclipse.
427
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19 years before us. And it does look like Dyson, I suppose to kind interpretation of this.
428
00:50:54,630 --> 00:50:58,620
Dyson probably realised that he would muddy the waters.
429
00:50:59,820 --> 00:51:04,140
If he'd had talked about an identical eclipse which had occurred.
430
00:51:05,630 --> 00:51:10,250
You know, 19 years beforehand that would not have served Eddington's case.
431
00:51:10,400 --> 00:51:13,400
Certainly he did not. Or he was extremely stupid.
432
00:51:13,610 --> 00:51:18,260
Right. So we've actually I mean,
433
00:51:18,530 --> 00:51:22,280
we've had a look at some of these plates to understand virtue and height in Heidelberg
434
00:51:22,280 --> 00:51:25,940
now is gathering all these plates together from different parts of the world.
435
00:51:26,450 --> 00:51:36,290
And we're going to remeasure them. And actually what our intention is that we make them available online for students of physics in 2016 to
436
00:51:36,620 --> 00:51:43,340
actually measure the deflection of starlight from themselves with the 1900 plates and the 1919 plates,
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00:51:43,640 --> 00:51:47,840
hopefully the ones in the audio are still alive. Okay, so thank you very much.
