WEBVTT
0
00:00:00.000 --> 00:00:02.040
Andrew Dunkley: Hello again. Thanks for joining us on Space
1
00:00:02.040 --> 00:00:04.680
Nuts. This is a Q and A edition. My name is
2
00:00:04.680 --> 00:00:06.720
Andrew Dunkley. What's a Q and A edition?
3
00:00:06.720 --> 00:00:09.520
It's an edition where we get Q's and
4
00:00:09.520 --> 00:00:12.480
give you A's because you're so clever.
5
00:00:12.800 --> 00:00:14.360
Uh, something like that. Anyway, we're going
6
00:00:14.360 --> 00:00:16.160
to answer audience questions. That's what I'm
7
00:00:16.160 --> 00:00:17.600
getting at. We've got questions about
8
00:00:17.760 --> 00:00:20.000
redshift, We've got questions about dark
9
00:00:20.080 --> 00:00:20.720
photons.
10
00:00:20.720 --> 00:00:21.040
Professor Fred Watson: What?
11
00:00:21.700 --> 00:00:24.000
Andrew Dunkley: Uh, we've got questions about deep space
12
00:00:24.160 --> 00:00:26.960
astronomy and another one about the expansion
13
00:00:26.960 --> 00:00:29.120
of the universe. I think we talked about that
14
00:00:29.120 --> 00:00:31.440
last episode. Anyway, uh, we'll see if we can
15
00:00:31.440 --> 00:00:33.900
solve all of that on this episode of space
16
00:00:33.900 --> 00:00:35.660
nuts. 15 seconds.
17
00:00:35.660 --> 00:00:38.076
Professor Fred Watson: Guidance is internal. 10,
18
00:00:38.257 --> 00:00:41.020
9, ignition sequence. Star
19
00:00:41.180 --> 00:00:41.864
space nuts.
20
00:00:41.936 --> 00:00:43.304
Andrew Dunkley: 5, 4, 3, 2.
21
00:00:43.376 --> 00:00:43.664
Roger: 1.
22
00:00:43.736 --> 00:00:46.544
Professor Fred Watson: 2, 3, 4, 5, 5, 4, 3, 2,
23
00:00:46.616 --> 00:00:48.139
1. Space nuts.
24
00:00:48.220 --> 00:00:50.060
Andrew Dunkley: Astronauts report it feels good.
25
00:00:51.260 --> 00:00:54.220
And with us again to kind of
26
00:00:54.220 --> 00:00:56.740
try to maybe answer some of that is
27
00:00:56.740 --> 00:00:58.620
Professor Fred Watson Watson, astronomer at
28
00:00:58.620 --> 00:00:59.500
large. Hello, Fred Watson.
29
00:01:00.050 --> 00:01:02.890
Professor Fred Watson: Hello, Andrew. Um, kind of is probably the
30
00:01:02.890 --> 00:01:04.530
best description really, isn't it?
31
00:01:05.650 --> 00:01:08.400
Andrew Dunkley: Possibly so. Possibly so. Um,
32
00:01:08.530 --> 00:01:10.210
but you know, it's good to get questions.
33
00:01:10.210 --> 00:01:13.210
We've got a whole new batch, so, um, let's
34
00:01:13.210 --> 00:01:14.770
get stuck straight into it.
35
00:01:14.770 --> 00:01:17.760
Now. First question comes from, um. Uh,
36
00:01:18.290 --> 00:01:20.530
I love the way he always ends his questions.
37
00:01:20.530 --> 00:01:23.070
I'm not going to reveal anything, but, um,
38
00:01:23.070 --> 00:01:24.130
let's hear from Roger.
39
00:01:24.530 --> 00:01:27.510
Roger: Hey there, Space Nuts. This is Roger
40
00:01:27.510 --> 00:01:30.110
the truck driver. Tonight I'm in,
41
00:01:30.170 --> 00:01:33.070
uh, Rutland, Vermont. Got a
42
00:01:33.070 --> 00:01:35.230
question about the red shift of galaxies.
43
00:01:36.090 --> 00:01:38.910
Um, if the light that we're seeing from a far
44
00:01:38.910 --> 00:01:41.670
off galaxy is shifted to the red and it
45
00:01:41.670 --> 00:01:43.790
started out at a higher frequency,
46
00:01:44.350 --> 00:01:46.990
doesn't that mean energy's lost somewhere
47
00:01:46.990 --> 00:01:49.710
between here and there? And is that energy
48
00:01:49.790 --> 00:01:52.610
just transferred into space? And if it
49
00:01:52.610 --> 00:01:55.090
is, does that contribute to the
50
00:01:55.090 --> 00:01:57.410
expansion of space? And I'm not saying it's
51
00:01:57.410 --> 00:01:59.890
dark energy, but does it
52
00:01:59.890 --> 00:02:02.890
contribute to it or does that
53
00:02:02.890 --> 00:02:05.370
energy get dissipated in another way?
54
00:02:06.410 --> 00:02:08.730
All right. Always digging the show, guys.
55
00:02:08.730 --> 00:02:09.690
Keep on trucking.
56
00:02:11.370 --> 00:02:14.210
Andrew Dunkley: I love that. I love that. Uh, we've got
57
00:02:14.210 --> 00:02:15.890
train drivers that do that. Unfortunately,
58
00:02:15.890 --> 00:02:17.370
they do it at 3 o' clock in the morning.
59
00:02:18.730 --> 00:02:21.330
Although today he did it at 10 to 7. I was
60
00:02:21.330 --> 00:02:23.290
pretty annoyed. Pretty annoyed.
61
00:02:23.290 --> 00:02:25.250
Professor Fred Watson: This is, uh, the one going past your place?
62
00:02:25.250 --> 00:02:27.330
Andrew Dunkley: Yeah, behind our place there's a rail line.
63
00:02:27.330 --> 00:02:29.090
It doesn't get used a heck of a lot, but when
64
00:02:29.090 --> 00:02:30.040
it does, um.
65
00:02:30.490 --> 00:02:30.970
Eli: Yes?
66
00:02:31.050 --> 00:02:33.890
Andrew Dunkley: The glasses rattle. Uh, the ones on my face,
67
00:02:33.890 --> 00:02:36.250
I mean. Uh, thanks, Roger. Great question.
68
00:02:36.460 --> 00:02:39.450
Uh, so, um, yeah, the change
69
00:02:39.450 --> 00:02:42.040
in frequency with the, um,
70
00:02:43.130 --> 00:02:46.090
energy loss, um, where does the energy go and
71
00:02:46.090 --> 00:02:48.370
does it contribute to the expansion of the
72
00:02:48.370 --> 00:02:51.250
universe? And could it possibly be.
73
00:02:51.330 --> 00:02:53.090
Maybe, maybe not dark matter
74
00:02:54.130 --> 00:02:56.450
or dark energy or something?
75
00:02:56.450 --> 00:02:58.650
Professor Fred Watson: Yeah, yeah. Um, there's a lot.
76
00:02:58.650 --> 00:02:59.970
Andrew Dunkley: He packed a lot into that question.
77
00:03:00.050 --> 00:03:02.370
Professor Fred Watson: He did. And it's a great question too. Uh,
78
00:03:02.370 --> 00:03:04.290
and, you know, I mean, it's a,
79
00:03:04.690 --> 00:03:07.450
uh, project, um, Absolutely right. The
80
00:03:07.450 --> 00:03:10.050
conservation of energy. Uh, energy
81
00:03:10.130 --> 00:03:12.690
can't be created or destroyed. That's the
82
00:03:12.690 --> 00:03:15.490
fundamental rule. Its
83
00:03:15.570 --> 00:03:17.730
energy is always conserved.
84
00:03:18.890 --> 00:03:21.890
But, uh, the universe doesn't play
85
00:03:21.890 --> 00:03:23.530
by the ordinary rules.
86
00:03:24.790 --> 00:03:26.400
Uh, and, um,
87
00:03:28.810 --> 00:03:31.210
it's an interesting answer here.
88
00:03:31.550 --> 00:03:34.450
Um, and I have to say it's changed
89
00:03:34.450 --> 00:03:37.410
my view of what this, you know, what
90
00:03:37.410 --> 00:03:40.250
the answer to this problem was because,
91
00:03:40.410 --> 00:03:43.290
um, when we've been asked this before,
92
00:03:43.370 --> 00:03:45.130
we haven't been asked it for a long time.
93
00:03:46.280 --> 00:03:48.570
I just assumed that the energy, uh,
94
00:03:49.160 --> 00:03:51.800
basically was absorbed by the universe by
95
00:03:51.800 --> 00:03:54.680
space time, uh, and
96
00:03:55.000 --> 00:03:57.400
maybe contributed to the expansion.
97
00:03:57.480 --> 00:03:58.040
Although,
98
00:04:00.390 --> 00:04:02.800
uh, you can't have it both ways because it's
99
00:04:02.800 --> 00:04:05.640
the expansion that's causing the photon's
100
00:04:05.640 --> 00:04:08.350
energy to be lost. Uh,
101
00:04:08.600 --> 00:04:11.400
and just stepping back, exactly as
102
00:04:11.400 --> 00:04:13.640
Roger said, uh, you've got light going
103
00:04:13.640 --> 00:04:15.320
through the universe. It's,
104
00:04:15.670 --> 00:04:18.570
uh, its wavelength is being stretched by
105
00:04:18.570 --> 00:04:21.490
the expansion of the universe. Therefore the
106
00:04:21.490 --> 00:04:24.410
light is losing energy. Because the energy
107
00:04:24.410 --> 00:04:26.930
of a beam of light is all about the
108
00:04:26.930 --> 00:04:28.890
frequency of the light, in other words, or
109
00:04:28.890 --> 00:04:31.610
the wavelength. Putting it another way. So
110
00:04:31.770 --> 00:04:34.490
if you increase the wavelength, you lose
111
00:04:34.490 --> 00:04:37.280
energy. And that's, um,
112
00:04:37.610 --> 00:04:40.610
a given already. Uh, so what I
113
00:04:40.610 --> 00:04:42.330
used to say was, yes, it kind of goes into
114
00:04:42.330 --> 00:04:44.610
the universe. But I've done a bit more
115
00:04:44.610 --> 00:04:46.650
reading on this and I was wrong.
116
00:04:48.760 --> 00:04:51.750
Um, because when
117
00:04:51.750 --> 00:04:54.750
you apply general relativity to
118
00:04:54.750 --> 00:04:56.950
the universe as a whole, and that's the.
119
00:04:57.510 --> 00:04:59.190
As we've talked about, and we've talked about
120
00:04:59.190 --> 00:05:01.780
it at length in the last episode, it's, uh,
121
00:05:01.780 --> 00:05:04.510
the kind of fundamental rule that governs
122
00:05:04.510 --> 00:05:06.790
everything that we understand in the
123
00:05:06.790 --> 00:05:09.270
universe. Um, when you
124
00:05:09.510 --> 00:05:11.110
apply general relativity,
125
00:05:12.820 --> 00:05:12.860
Andrew Dunkley: uh,
126
00:05:12.870 --> 00:05:15.810
Professor Fred Watson: that conservation of energy
127
00:05:16.770 --> 00:05:19.730
that we expect to happen in the
128
00:05:19.730 --> 00:05:22.050
everyday world, it
129
00:05:22.290 --> 00:05:24.900
doesn't hold good. So energy, uh,
130
00:05:25.250 --> 00:05:27.690
is not conserved in an expanding
131
00:05:27.690 --> 00:05:30.690
universe. Uh, and so
132
00:05:31.250 --> 00:05:33.010
basically the energy
133
00:05:33.810 --> 00:05:36.730
simply disappears. It's
134
00:05:36.730 --> 00:05:39.450
just not there anymore because of the
135
00:05:39.450 --> 00:05:41.810
expansion of the universe. It's not causing
136
00:05:41.810 --> 00:05:43.490
the expansion of the universe. It's not
137
00:05:43.680 --> 00:05:45.800
create contributing to dark energy or dark
138
00:05:45.800 --> 00:05:48.640
matter, the energy loss, it just vanishes.
139
00:05:49.520 --> 00:05:51.520
Wow. So work that one out.
140
00:05:51.680 --> 00:05:52.400
Andrew Dunkley: I can't.
141
00:05:53.040 --> 00:05:54.240
Professor Fred Watson: No, I can't either.
142
00:05:56.470 --> 00:05:59.400
Um, I kind of really
143
00:05:59.400 --> 00:06:01.760
need to look at the equations on this.
144
00:06:02.330 --> 00:06:04.480
Andrew Dunkley: Um, don't show them to me. I mean,
145
00:06:06.400 --> 00:06:08.160
Professor Fred Watson: yeah, I'M not that keen on looking at them
146
00:06:08.160 --> 00:06:10.830
myself either. Too much else to do. But, uh,
147
00:06:11.190 --> 00:06:14.170
um, uh, but yes, that is
148
00:06:14.250 --> 00:06:16.410
the thinking on this.
149
00:06:17.030 --> 00:06:19.890
Uh, and I think the conservation
150
00:06:19.890 --> 00:06:22.430
rule does not work, uh,
151
00:06:24.890 --> 00:06:26.810
um, when it comes to
152
00:06:28.010 --> 00:06:29.850
the universe on a whole.
153
00:06:30.170 --> 00:06:30.570
Andrew Dunkley: Yeah.
154
00:06:30.570 --> 00:06:30.930
Professor Fred Watson: Wow.
155
00:06:30.930 --> 00:06:33.650
Andrew Dunkley: Gee, um, that's quite a
156
00:06:33.650 --> 00:06:35.370
revelation. Who figured that out?
157
00:06:37.160 --> 00:06:39.770
Professor Fred Watson: Uh, uh, it's on a number of
158
00:06:40.250 --> 00:06:43.130
different, uh, physics, uh, related websites.
159
00:06:43.990 --> 00:06:45.830
Andrew Dunkley: There's the reason no one knows about it
160
00:06:45.830 --> 00:06:47.830
because it's physics and
161
00:06:48.710 --> 00:06:50.070
who reads that stuff?
162
00:06:50.870 --> 00:06:53.790
Professor Fred Watson: Yeah, I think the relativistic bit of
163
00:06:53.790 --> 00:06:56.550
it, uh, comes from the fact
164
00:06:57.110 --> 00:07:00.030
that the energy of a particle,
165
00:07:00.030 --> 00:07:02.390
which is what we're talking about, it's an
166
00:07:02.390 --> 00:07:04.950
observer dependent quantity.
167
00:07:05.750 --> 00:07:08.430
And so that's why relativity plays a part in
168
00:07:08.430 --> 00:07:10.230
this because you're the observer
169
00:07:11.270 --> 00:07:13.640
and you're talking about something that's
170
00:07:13.640 --> 00:07:15.840
relative to another observer, that is the
171
00:07:15.840 --> 00:07:18.800
photon. Uh, and that's why you've got,
172
00:07:18.840 --> 00:07:21.680
uh, a relativistic
173
00:07:22.160 --> 00:07:23.120
access. Ah, to it.
174
00:07:24.000 --> 00:07:26.880
Andrew Dunkley: Wow. Okay. Um, great question,
175
00:07:26.960 --> 00:07:29.079
Roger. I'm not sure you were expecting that
176
00:07:29.079 --> 00:07:31.840
answer, but, uh, there it is. Uh, the energy
177
00:07:31.920 --> 00:07:34.240
just gone,
178
00:07:35.360 --> 00:07:38.360
goes, vanishes, ceases to
179
00:07:38.360 --> 00:07:40.320
exist. It's a dead poly.
180
00:07:41.680 --> 00:07:44.200
So anyway, um,
181
00:07:45.200 --> 00:07:47.470
no one got that joke. I was, um,
182
00:07:48.320 --> 00:07:50.480
doing a Monty Python skit for some reason.
183
00:07:50.640 --> 00:07:52.000
Professor Fred Watson: Yeah, you were. That's right.
184
00:07:53.360 --> 00:07:55.520
Look, I'm pursuing this in a little bit more
185
00:07:55.520 --> 00:07:58.360
detail and, uh, just trying to, you know, see
186
00:07:58.360 --> 00:08:00.800
whether we've got alternative. Alternative
187
00:08:00.960 --> 00:08:02.320
views of this.
188
00:08:02.560 --> 00:08:04.800
Andrew Dunkley: Well, generally speaking, you do get
189
00:08:04.800 --> 00:08:06.640
alternative views when it comes to this kind
190
00:08:06.640 --> 00:08:06.840
of stuff.
191
00:08:06.840 --> 00:08:09.710
Professor Fred Watson: That's right. Um, yes,
192
00:08:09.710 --> 00:08:10.070
so
193
00:08:12.310 --> 00:08:15.310
that's right. Uh, uh,
194
00:08:15.670 --> 00:08:18.310
I think the standard explanation today is
195
00:08:18.310 --> 00:08:21.270
that energy is not conserved.
196
00:08:21.670 --> 00:08:22.230
Okay.
197
00:08:23.030 --> 00:08:24.790
Andrew Dunkley: We'll leave it at that until somebody throws
198
00:08:24.790 --> 00:08:26.070
another spanner into the.
199
00:08:26.070 --> 00:08:27.550
Professor Fred Watson: Yeah, uh, we might be giving a different
200
00:08:27.550 --> 00:08:29.350
answer next week. It could be.
201
00:08:29.910 --> 00:08:31.870
Andrew Dunkley: Thanks, Roger. Great to hear from you. Toot,
202
00:08:31.870 --> 00:08:33.510
toot. Uh, we'll catch you next time.
203
00:08:33.830 --> 00:08:36.310
Our next question comes from
204
00:08:36.470 --> 00:08:39.110
Peter. He's from San Diego, California.
205
00:08:39.190 --> 00:08:40.940
While listening to another astrophysics
206
00:08:41.329 --> 00:08:43.409
podcast, I heard the term dark
207
00:08:43.809 --> 00:08:46.329
photon for the first time. Apparently this is
208
00:08:46.329 --> 00:08:48.929
a particle astrophysicists are, uh, seeking
209
00:08:49.009 --> 00:08:51.489
in order to explain dark matter and, or dark
210
00:08:51.489 --> 00:08:54.289
energy. Could you please elaborate on what a
211
00:08:54.289 --> 00:08:56.369
dark photon could be?
212
00:08:57.190 --> 00:08:59.689
Um, dad, joke for Andrew. A photon
213
00:08:59.689 --> 00:09:02.129
travels at the speed of light. Does that mean
214
00:09:02.129 --> 00:09:04.809
a dark photon travels at the speed of
215
00:09:04.809 --> 00:09:07.649
dark. I like that.
216
00:09:07.729 --> 00:09:09.740
That's good. Yeah, that's really good. Uh,
217
00:09:09.740 --> 00:09:12.089
keep up the great work, he says. Uh, thank
218
00:09:12.089 --> 00:09:12.689
you, Peter.
219
00:09:13.070 --> 00:09:13.590
Professor Fred Watson: All as well.
220
00:09:13.590 --> 00:09:15.630
Andrew Dunkley: In San Diego, California.
221
00:09:16.170 --> 00:09:18.310
Uh, have you ever heard of a dark photon,
222
00:09:18.310 --> 00:09:18.750
Fred Watson?
223
00:09:19.050 --> 00:09:21.710
Professor Fred Watson: Um, yes, I'VE probably got a few in this box
224
00:09:21.710 --> 00:09:24.710
here. The
225
00:09:24.710 --> 00:09:26.510
speed of dark. Just, just going back to that,
226
00:09:26.590 --> 00:09:29.550
that quip, uh, there was
227
00:09:29.550 --> 00:09:32.510
a storey I read, uh, probably
228
00:09:32.990 --> 00:09:35.790
a fortnight ago, uh, about
229
00:09:36.350 --> 00:09:38.510
exactly this. In that dark
230
00:09:39.310 --> 00:09:42.230
ness can move faster than the speed
231
00:09:42.230 --> 00:09:42.670
of light.
232
00:09:43.230 --> 00:09:43.630
Andrew Dunkley: No,
233
00:09:46.510 --> 00:09:49.070
Professor Fred Watson: but it's ah, an illusory darkness. It's when
234
00:09:49.070 --> 00:09:52.030
you've got um, light beams
235
00:09:52.510 --> 00:09:55.390
interfering with one another so that
236
00:09:55.390 --> 00:09:57.310
you've uh, interference
237
00:09:58.430 --> 00:10:00.750
light beams can cancel out. So if you've got
238
00:10:00.750 --> 00:10:03.110
two light waves and you add them up out of
239
00:10:03.110 --> 00:10:04.710
phase, they can cancel out and you get
240
00:10:04.710 --> 00:10:07.690
darkness. That's a well known principle
241
00:10:07.690 --> 00:10:09.770
of interferometry. I used to play with that
242
00:10:09.770 --> 00:10:12.210
when I was a student a lot. Uh,
243
00:10:12.490 --> 00:10:14.530
but there are certain circumstances that
244
00:10:14.530 --> 00:10:17.210
those patterns of darkness can actually
245
00:10:17.210 --> 00:10:19.530
exceed the speed of light
246
00:10:20.170 --> 00:10:22.170
because they're not actually real, they're
247
00:10:22.170 --> 00:10:24.650
not real entities. They're not a thing that's
248
00:10:24.650 --> 00:10:26.650
carrying any sort of information or energy.
249
00:10:26.650 --> 00:10:29.450
They're just patterns in an
250
00:10:29.450 --> 00:10:31.090
interference pattern. They're just dark
251
00:10:31.090 --> 00:10:32.930
patches in it. And I think under certain
252
00:10:32.930 --> 00:10:35.290
circumstances they could go faster than the
253
00:10:35.290 --> 00:10:38.150
speed of light. Darkness might
254
00:10:38.150 --> 00:10:41.070
be not quite as uh, you know, as twee as
255
00:10:41.070 --> 00:10:43.710
you thought it was. I guess so
256
00:10:43.710 --> 00:10:46.710
anyway, anyway, uh, that's not the
257
00:10:47.430 --> 00:10:49.950
question, uh, because dark photons are
258
00:10:49.950 --> 00:10:52.310
definitely something different and they're
259
00:10:52.390 --> 00:10:55.270
basically uh, hypothetical.
260
00:10:55.510 --> 00:10:58.230
They've been hypothesised by
261
00:10:58.310 --> 00:11:01.010
physicists and cosmologists as uh,
262
00:11:01.350 --> 00:11:03.350
being a uh, force carrier
263
00:11:04.350 --> 00:11:06.670
similar to the ordinary photon
264
00:11:07.150 --> 00:11:10.110
but related to dark
265
00:11:10.270 --> 00:11:13.070
matter. In other
266
00:11:13.070 --> 00:11:15.830
words, you might have. Sorry, somebody's
267
00:11:15.830 --> 00:11:17.910
trying to phone me. I'm just gonna kill that
268
00:11:17.910 --> 00:11:20.430
call. Yeah, um,
269
00:11:21.070 --> 00:11:21.790
that was me.
270
00:11:21.790 --> 00:11:23.790
Andrew Dunkley: That was me. No it wasn't.
271
00:11:26.910 --> 00:11:29.870
Professor Fred Watson: You know, they're part of the. There may be.
272
00:11:29.950 --> 00:11:32.430
When we discover finally what dark matter is,
273
00:11:33.310 --> 00:11:35.690
there may be a suite of
274
00:11:36.250 --> 00:11:39.210
dark particles which could include
275
00:11:39.210 --> 00:11:41.610
dark photons. That's the bottom line.
276
00:11:41.850 --> 00:11:42.220
Andrew Dunkley: Right?
277
00:11:42.220 --> 00:11:45.210
Professor Fred Watson: Um, and so you know we mentioned last
278
00:11:45.210 --> 00:11:48.210
week the, or in the last episode the uh, the
279
00:11:48.210 --> 00:11:50.810
Large Hadron Collider being upgraded to the
280
00:11:50.810 --> 00:11:53.580
High Luminosity Large Hadron Collider. Um,
281
00:11:53.850 --> 00:11:56.250
that's one of the things they'd be looking
282
00:11:56.250 --> 00:11:57.770
for, will be dark photons.
283
00:11:58.730 --> 00:11:59.290
Okay.
284
00:11:59.690 --> 00:12:02.030
Andrew Dunkley: You know, I tried to do
285
00:12:02.500 --> 00:12:04.950
um, an AI search for an
286
00:12:04.950 --> 00:12:06.650
explanation on it and um,
287
00:12:07.950 --> 00:12:10.060
it sort of gave me all this gobbledygook. But
288
00:12:10.060 --> 00:12:12.950
um, you know, what would a dark
289
00:12:12.950 --> 00:12:15.750
proton, a photon do? It says it would
290
00:12:15.750 --> 00:12:17.870
carry a force within the dark sector.
291
00:12:19.230 --> 00:12:21.710
We call that the government. It might allow
292
00:12:21.710 --> 00:12:23.710
dark matter particles to interact with each
293
00:12:23.710 --> 00:12:25.990
other and it could very weakly mix with
294
00:12:25.990 --> 00:12:28.670
normal photons, giving us a way to Detect it.
295
00:12:28.750 --> 00:12:31.580
And the reason they reckon that scientists
296
00:12:31.580 --> 00:12:34.300
care about this, as you said, could explain
297
00:12:34.300 --> 00:12:36.860
what dark matter is made of. So
298
00:12:36.940 --> 00:12:39.220
therefore solving some of those gaps in our
299
00:12:39.220 --> 00:12:40.860
current physics theories.
300
00:12:43.260 --> 00:12:45.340
That's why people are interested in this and
301
00:12:45.340 --> 00:12:47.340
that's why they're upgrading the Large Hadron
302
00:12:47.340 --> 00:12:50.060
Collider. And hopefully we will
303
00:12:50.620 --> 00:12:52.700
learn more in years to come.
304
00:12:54.540 --> 00:12:55.340
That's the hope.
305
00:12:55.740 --> 00:12:58.620
Professor Fred Watson: That's the hope, yeah. So we might be talking
306
00:12:58.620 --> 00:13:01.220
one day about dark photons, um, having been
307
00:13:01.220 --> 00:13:03.890
detected, which would be a coup
308
00:13:03.890 --> 00:13:05.410
for space newts.
309
00:13:05.730 --> 00:13:08.570
Andrew Dunkley: Yes, it will. Uh, but at this stage they
310
00:13:08.570 --> 00:13:11.170
are not proven. It's just a theory. So
311
00:13:11.330 --> 00:13:13.970
that's about as much as we know at this point
312
00:13:13.970 --> 00:13:16.770
in time. But, uh, very good question. Uh,
313
00:13:16.930 --> 00:13:19.290
and, uh, thank you, Peter, for sending it in.
314
00:13:19.290 --> 00:13:22.010
This is Space Nuts with Andrew Dunkley and
315
00:13:22.010 --> 00:13:23.890
Professor Fred Watson Watson.
316
00:13:26.530 --> 00:13:29.490
0G and I feel fine. Space Nuts.
317
00:13:29.720 --> 00:13:31.560
Okay, Fred Watson, we'll move straight on to
318
00:13:31.560 --> 00:13:33.720
our next question, which is, uh, another
319
00:13:33.720 --> 00:13:36.440
audio question from Eli.
320
00:13:36.760 --> 00:13:39.000
Eli: Hello, this is Eli from
321
00:13:39.800 --> 00:13:42.240
sunny Coachella Valley in
322
00:13:42.240 --> 00:13:45.240
California. I'm embarrassed to
323
00:13:45.240 --> 00:13:47.640
admit it, but I still can't get my head
324
00:13:47.640 --> 00:13:50.640
around deep space astronomy. I get that
325
00:13:50.640 --> 00:13:53.440
the light from, say, a distant galaxy is a
326
00:13:53.440 --> 00:13:56.250
billion years old, but why
327
00:13:56.250 --> 00:13:59.210
that particular point in its time? Is
328
00:13:59.210 --> 00:14:01.450
it just a matter of whatever light is hitting
329
00:14:01.450 --> 00:14:03.730
us is the time we get to see.
330
00:14:05.090 --> 00:14:06.850
But for really early light,
331
00:14:07.890 --> 00:14:10.610
the JWST, early universe stuff
332
00:14:10.610 --> 00:14:13.090
that's been travelling for 13 billion years
333
00:14:13.090 --> 00:14:15.570
and just hitting us now,
334
00:14:16.690 --> 00:14:18.610
are we looking for the light that hasn't
335
00:14:19.010 --> 00:14:21.810
passed us by or hasn't made it here yet,
336
00:14:22.170 --> 00:14:24.610
but is from that one precise
337
00:14:24.610 --> 00:14:25.850
location long ago?
338
00:14:27.450 --> 00:14:30.210
This stuff is so difficult to get my head
339
00:14:30.210 --> 00:14:33.050
around. Love the show and hope
340
00:14:33.050 --> 00:14:34.970
you guys can clear this up for me.
341
00:14:36.150 --> 00:14:38.590
Andrew Dunkley: Uh, no, we can't. We just thought we'd, um,
342
00:14:38.590 --> 00:14:41.370
put the question in there. Thanks,
343
00:14:41.370 --> 00:14:44.210
Eli. Uh, this is a deep, um, I'm, um.
344
00:14:44.370 --> 00:14:46.450
Not only in deep space astronomy terms, but
345
00:14:46.450 --> 00:14:48.090
it is a deep, deep topic.
346
00:14:48.750 --> 00:14:51.610
Um, I mean, when we look up into the sky
347
00:14:51.610 --> 00:14:53.690
at night and we see all those beautiful
348
00:14:53.830 --> 00:14:56.550
coloured dots, we are looking at history.
349
00:14:56.950 --> 00:14:59.110
And it's variable history because some of
350
00:14:59.110 --> 00:15:01.950
it's 4.41 light years away and
351
00:15:01.950 --> 00:15:04.950
some of it's 400,000 light
352
00:15:04.950 --> 00:15:07.510
years away, some of it's further than that.
353
00:15:07.810 --> 00:15:09.750
Um, but then you've got the cosmic
354
00:15:10.230 --> 00:15:12.870
microwave background radiation, which is kind
355
00:15:12.870 --> 00:15:14.150
of a leftover of,
356
00:15:14.930 --> 00:15:17.910
um, what happened after the
357
00:15:17.910 --> 00:15:19.670
Big Bang and that,
358
00:15:20.820 --> 00:15:23.100
that's a different kettle of fish. And I can
359
00:15:23.100 --> 00:15:25.220
understand why you've got a headache. Eli,
360
00:15:25.620 --> 00:15:26.580
over to you, Fred Watson.
361
00:15:27.860 --> 00:15:30.860
Professor Fred Watson: Thanks. Um, so I
362
00:15:30.860 --> 00:15:32.580
guess uh, you know,
363
00:15:33.860 --> 00:15:36.180
I understand Eli's issue as well.
364
00:15:36.280 --> 00:15:36.980
Um,
365
00:15:38.980 --> 00:15:40.860
you've got to be in the right place at the
366
00:15:40.860 --> 00:15:43.060
right time to see a photon from a distant
367
00:15:43.060 --> 00:15:46.060
galaxy. But I guess the way
368
00:15:46.060 --> 00:15:48.020
to envisage this is if you think
369
00:15:48.970 --> 00:15:50.890
of the universe, um,
370
00:15:51.770 --> 00:15:54.450
and you've got to perhaps think of it as if
371
00:15:54.450 --> 00:15:55.770
you were looking at it from the outside,
372
00:15:55.770 --> 00:15:58.050
which we never can. But, uh, if you can think
373
00:15:58.050 --> 00:16:00.650
of it that way, then it's full of
374
00:16:01.210 --> 00:16:03.370
objects which are radiating light.
375
00:16:04.249 --> 00:16:06.930
Even in its infancy, when the universe was
376
00:16:06.930 --> 00:16:09.370
very young, the stuff in it was basically
377
00:16:09.610 --> 00:16:12.290
shining. Um, once we got past the Dark Ages,
378
00:16:12.290 --> 00:16:14.570
where no stars were shining, uh,
379
00:16:15.330 --> 00:16:18.010
um, and those are the galaxies that we now
380
00:16:18.010 --> 00:16:20.510
see. So they constantly radiate, creating
381
00:16:20.510 --> 00:16:23.470
light. And that's just like a river of
382
00:16:23.470 --> 00:16:26.470
light that's flowing down time,
383
00:16:26.470 --> 00:16:29.190
if I can put it that way. Uh, and
384
00:16:30.150 --> 00:16:33.030
a long time in the future it
385
00:16:33.030 --> 00:16:35.190
reaches us. But it's not just
386
00:16:36.070 --> 00:16:38.590
an individual photon or something that's
387
00:16:38.590 --> 00:16:41.150
reaching us. It's this stream of stuff that
388
00:16:41.150 --> 00:16:43.790
is being radiated throughout the
389
00:16:43.790 --> 00:16:46.230
universe by these galaxies. So we,
390
00:16:46.850 --> 00:16:49.760
um. And we pick it up. We
391
00:16:49.760 --> 00:16:52.520
pick it up sometimes exactly as you've said.
392
00:16:52.520 --> 00:16:54.480
Well, up to 10 billion years after it's been
393
00:16:54.800 --> 00:16:57.760
radiated. I think 12 billion years,
394
00:16:58.130 --> 00:17:00.480
uh, are the oldest or the earliest galaxies
395
00:17:00.480 --> 00:17:02.639
that we now see. We're looking back in time
396
00:17:02.639 --> 00:17:05.440
12 billion years and seeing them as they were
397
00:17:05.840 --> 00:17:08.360
perhaps a billion and a half years after the
398
00:17:08.360 --> 00:17:11.160
Big Bang. Um, and they are shining,
399
00:17:11.160 --> 00:17:13.320
they're radiating light, uh, in the early
400
00:17:13.320 --> 00:17:16.230
universe and down the track that reaches us
401
00:17:16.390 --> 00:17:18.390
because that light's going in all directions.
402
00:17:18.390 --> 00:17:20.310
So it wouldn't matter where in the universe
403
00:17:20.310 --> 00:17:22.710
we were, we would still see them.
404
00:17:23.510 --> 00:17:25.670
Uh, we'd just see them in a, you know, in a
405
00:17:25.670 --> 00:17:27.670
different position in the sky. If we're a
406
00:17:27.670 --> 00:17:30.589
long way from where we are now. Yeah, but,
407
00:17:30.589 --> 00:17:33.350
yeah, so I guess it's, you
408
00:17:33.350 --> 00:17:35.950
know, in a way, one way of thinking about
409
00:17:35.950 --> 00:17:38.910
this is if you imagine us on planet
410
00:17:38.910 --> 00:17:41.820
Earth here and imagine us being
411
00:17:41.820 --> 00:17:44.700
surrounded by a whole series of
412
00:17:44.700 --> 00:17:47.580
shells which, uh, we're at the centre
413
00:17:47.580 --> 00:17:49.340
of. And this is a bit like the crystalline
414
00:17:49.340 --> 00:17:51.820
spheres that people used to think, uh, the
415
00:17:51.820 --> 00:17:54.100
universe was made of. Uh, but
416
00:17:54.580 --> 00:17:57.340
these shells, uh, spherical shells,
417
00:17:57.340 --> 00:17:59.700
all centred on the Earth, but each one
418
00:18:00.020 --> 00:18:02.740
clicks over to a time
419
00:18:02.820 --> 00:18:05.660
further in the past, uh, because the
420
00:18:05.660 --> 00:18:08.660
light's coming to us from the whole cosmos,
421
00:18:08.660 --> 00:18:11.220
which is full of stuff. Uh, and that's why
422
00:18:11.220 --> 00:18:13.560
we, these shells sort of being
423
00:18:13.560 --> 00:18:16.140
illuminated in a way by the objects that, uh,
424
00:18:16.400 --> 00:18:18.680
radiated them at that time. Uh,
425
00:18:20.100 --> 00:18:22.880
um, that we see them because of
426
00:18:23.120 --> 00:18:25.520
the distance that they are away from us means
427
00:18:25.520 --> 00:18:28.520
that the light has taken that long to get to
428
00:18:28.520 --> 00:18:31.040
us, whether that helps or not. In fact, I
429
00:18:31.040 --> 00:18:33.040
think I've just confused it completely. But,
430
00:18:35.080 --> 00:18:36.560
Andrew Dunkley: um, I
431
00:18:38.570 --> 00:18:41.330
just doing a little experimental search here
432
00:18:41.330 --> 00:18:41.930
for a sec.
433
00:18:44.090 --> 00:18:46.970
What I agree
434
00:18:46.970 --> 00:18:49.690
with in terms of Eli's question and getting
435
00:18:49.690 --> 00:18:52.650
your head around it is, um, if
436
00:18:52.650 --> 00:18:54.730
Betelgeuse, or however you want to pronounce
437
00:18:54.730 --> 00:18:57.570
it, went supernova right now as we
438
00:18:57.570 --> 00:18:58.170
were speaking,
439
00:19:00.410 --> 00:19:02.010
we wouldn't see it for
440
00:19:03.700 --> 00:19:05.140
640 years.
441
00:19:05.780 --> 00:19:06.340
Roger: Yeah.
442
00:19:07.220 --> 00:19:09.700
Andrew Dunkley: So for it to have gone
443
00:19:09.700 --> 00:19:12.700
supernova in the past and us to witness
444
00:19:12.700 --> 00:19:14.420
it, it has to have happened
445
00:19:15.940 --> 00:19:18.660
pretty close to 640 years ago.
446
00:19:19.220 --> 00:19:20.260
Does that make sense?
447
00:19:20.420 --> 00:19:23.260
Professor Fred Watson: Yes. Um, so you could think of that in
448
00:19:23.260 --> 00:19:25.460
another way. Um, you know,
449
00:19:26.300 --> 00:19:29.060
um, anywhere between us and 640
450
00:19:29.060 --> 00:19:31.620
light years away, there could be this pulse
451
00:19:31.620 --> 00:19:33.540
of light that's on its way to us
452
00:19:34.260 --> 00:19:37.220
from Betelgeuse. Uh, it would spread
453
00:19:37.220 --> 00:19:39.940
out in a sphere, and as that sphere
454
00:19:39.940 --> 00:19:42.140
expanded, eventually it would wash over the
455
00:19:42.140 --> 00:19:44.980
Earth and we'd see it, um, and perhaps
456
00:19:44.980 --> 00:19:46.740
see it during the day as well, because it
457
00:19:46.740 --> 00:19:49.700
might get bright enough to do that. Uh, and
458
00:19:49.700 --> 00:19:51.220
I think that's a really good way of putting
459
00:19:51.220 --> 00:19:53.820
it, Andrew, because thinking, um, about the
460
00:19:53.820 --> 00:19:55.500
galaxies, they're just streaming light out
461
00:19:55.500 --> 00:19:58.300
all the time, but something like a, uh,
462
00:19:58.380 --> 00:20:01.140
supernova explosion, which gives a big pulse
463
00:20:01.140 --> 00:20:04.140
of light, um, that's perhaps easier to get
464
00:20:04.140 --> 00:20:06.180
your head around because that's. That's just
465
00:20:06.180 --> 00:20:08.940
gotta, um. It'll
466
00:20:08.940 --> 00:20:11.500
take whatever time is
467
00:20:11.500 --> 00:20:14.420
represented by the distance away. So 640
468
00:20:14.420 --> 00:20:17.260
light years away. It'll take 640 years
469
00:20:17.260 --> 00:20:19.340
to get here for that pulse to get here. But
470
00:20:19.340 --> 00:20:22.260
then it will sweep over us and we'll see the
471
00:20:22.260 --> 00:20:24.220
light. The light fading away.
472
00:20:24.460 --> 00:20:25.770
Andrew Dunkley: Yeah. And, um,
473
00:20:27.340 --> 00:20:29.500
the reason I chose that target is because
474
00:20:29.740 --> 00:20:32.500
there's a lot of conjecture about
475
00:20:32.500 --> 00:20:35.220
its future and the possibility that it's
476
00:20:35.220 --> 00:20:36.940
reaching that critical mass point.
477
00:20:37.480 --> 00:20:37.800
Professor Fred Watson: Yes.
478
00:20:38.190 --> 00:20:39.720
Andrew Dunkley: Um, but it could have already happened.
479
00:20:39.720 --> 00:20:41.240
That's the other thing.
480
00:20:42.040 --> 00:20:45.040
Professor Fred Watson: But that's something we can have no knowledge
481
00:20:45.040 --> 00:20:47.400
of. That's the key thing, because, um,
482
00:20:47.880 --> 00:20:50.360
we are limited by the speed of light. That's
483
00:20:50.440 --> 00:20:52.320
the thing that always limits our view of the
484
00:20:52.320 --> 00:20:52.760
universe.
485
00:20:52.760 --> 00:20:55.640
Andrew Dunkley: And just to confuse Eli a little bit more,
486
00:20:56.440 --> 00:20:59.040
there are, ah, probably things in the
487
00:20:59.040 --> 00:21:01.040
universe we will never witness because the
488
00:21:01.040 --> 00:21:04.000
light is just too far away to reach us in any
489
00:21:04.000 --> 00:21:05.960
reasonable amount of time. Even
490
00:21:06.910 --> 00:21:09.830
beyond the life of the Earth itself or
491
00:21:09.830 --> 00:21:12.180
our sun. Uh,
492
00:21:13.230 --> 00:21:15.750
there are things we will never, ever know
493
00:21:15.750 --> 00:21:16.030
about.
494
00:21:16.670 --> 00:21:17.310
Professor Fred Watson: Correct.
495
00:21:18.200 --> 00:21:21.040
Andrew Dunkley: Um, and that's where it just gives you, um,
496
00:21:22.430 --> 00:21:24.830
one of those Headaches that requires, uh, you
497
00:21:24.830 --> 00:21:27.630
to take paracetamol and ibuprofen at the same
498
00:21:27.630 --> 00:21:27.950
time.
499
00:21:32.100 --> 00:21:34.720
Um, deep, deep headaches. But Eli, great
500
00:21:34.720 --> 00:21:36.440
question. I'm not sure we solved your
501
00:21:36.440 --> 00:21:39.420
problem, but, um, anyway, uh,
502
00:21:40.800 --> 00:21:42.600
I try to explain this sort of stuff to my
503
00:21:42.600 --> 00:21:45.520
grandson, uh, and, uh, my granddaughters.
504
00:21:45.520 --> 00:21:48.280
And, you know, how do you
505
00:21:48.280 --> 00:21:50.160
explain time and distance
506
00:21:51.040 --> 00:21:53.970
to a young child? And, um,
507
00:21:53.970 --> 00:21:55.360
when you're trying to get through traffic,
508
00:21:57.200 --> 00:21:58.840
Professor Fred Watson: that might not be the best time to do it.
509
00:21:58.840 --> 00:22:00.720
Andrew Dunkley: Probably not, but they're very interested.
510
00:22:01.280 --> 00:22:03.240
Very interested. Thanks, Eli.
511
00:22:03.240 --> 00:22:03.840
Great question.
512
00:22:06.540 --> 00:22:09.180
Professor Fred Watson: The crew of Artemis 2 now bound for the moon,
513
00:22:09.420 --> 00:22:11.980
humanity's next great voyage begins.
514
00:22:12.620 --> 00:22:13.820
Space nuts.
515
00:22:14.140 --> 00:22:16.190
Andrew Dunkley: Our final question comes, uh,
516
00:22:16.780 --> 00:22:19.740
from Nova Scotia. It's from Ken.
517
00:22:19.910 --> 00:22:21.940
Uh, look, this is an old chestnut. We've,
518
00:22:21.940 --> 00:22:24.660
we've probably spoken about this many times,
519
00:22:24.660 --> 00:22:27.620
but it's always good to, um, to revisit. If
520
00:22:27.620 --> 00:22:30.340
the universe is expanding, what is it
521
00:22:30.340 --> 00:22:32.700
expanding into? And also,
522
00:22:33.330 --> 00:22:35.090
is the universe spherical?
523
00:22:36.770 --> 00:22:39.010
Professor Fred Watson: So, um, yes. What's it expanding into?
524
00:22:39.010 --> 00:22:41.130
Andrew Dunkley: Well, we don't know.
525
00:22:41.130 --> 00:22:43.250
Professor Fred Watson: And yes, that's.
526
00:22:43.650 --> 00:22:45.970
Yes. Uh, it's actually, we don't know. And
527
00:22:45.970 --> 00:22:48.930
maybe, maybe, maybe. So,
528
00:22:49.000 --> 00:22:51.570
um, the universe
529
00:22:52.210 --> 00:22:55.090
is everything that we can detect. That's
530
00:22:55.090 --> 00:22:56.850
the definition of the universe. Everything we
531
00:22:56.850 --> 00:22:59.490
can measure or detect. And that means,
532
00:23:00.370 --> 00:23:02.450
and we observe the expansion,
533
00:23:03.250 --> 00:23:06.210
but we don't know whether there's an edge
534
00:23:06.210 --> 00:23:08.050
to the universe. We don't know whether it's
535
00:23:08.050 --> 00:23:10.410
infinite. We don't know anything beyond the
536
00:23:10.410 --> 00:23:13.130
horizons that we see. And um, the most
537
00:23:13.130 --> 00:23:14.850
obvious one is the cosmic microwave
538
00:23:14.850 --> 00:23:16.900
background radiation, um,
539
00:23:17.730 --> 00:23:19.570
beyond which we can't see. But the universe
540
00:23:19.570 --> 00:23:21.570
almost certainly goes on beyond that,
541
00:23:22.130 --> 00:23:24.610
probably for a very long way, maybe very big.
542
00:23:24.930 --> 00:23:27.330
But we've got no knowledge of a boundary or
543
00:23:28.190 --> 00:23:30.510
any other medium that it might be expanding
544
00:23:30.510 --> 00:23:33.230
into. So, um,
545
00:23:33.610 --> 00:23:36.430
uh, one possibility is the idea of multiple
546
00:23:36.430 --> 00:23:38.830
universes. And they might
547
00:23:38.830 --> 00:23:40.990
exist maybe
548
00:23:41.630 --> 00:23:44.080
in a higher dimensional, uh,
549
00:23:45.390 --> 00:23:48.270
arena, if I can put it that way. You know,
550
00:23:48.750 --> 00:23:51.670
if you can, um, find that
551
00:23:51.670 --> 00:23:54.670
there are extra dimensions, we know the
552
00:23:54.830 --> 00:23:56.870
three dimensions of space and one of time.
553
00:23:56.870 --> 00:23:58.550
That's what we've got now.
554
00:23:59.830 --> 00:24:02.230
But, uh, if there are hidden
555
00:24:02.630 --> 00:24:04.870
extra dimensions, maybe they provide
556
00:24:05.830 --> 00:24:08.150
a venue for the universe to expand into.
557
00:24:08.970 --> 00:24:11.750
Uh, and there are various theories
558
00:24:11.750 --> 00:24:14.750
that accept that, um, M. M theory is one of
559
00:24:14.750 --> 00:24:17.710
them, where M is probably an abbreviation
560
00:24:17.710 --> 00:24:19.990
for membrane. The idea is that the universe
561
00:24:20.470 --> 00:24:22.590
can be collapsed onto a two dimensional
562
00:24:22.590 --> 00:24:24.390
membrane, and there are lots of these
563
00:24:24.390 --> 00:24:27.300
membranes in the kind
564
00:24:27.300 --> 00:24:29.580
of higher dimensional universe. But that's
565
00:24:29.580 --> 00:24:31.420
just conjecture and we've got no
566
00:24:32.060 --> 00:24:34.420
mechanism for proving that at the moment. The
567
00:24:34.420 --> 00:24:36.700
only thing we know with certainty with
568
00:24:36.700 --> 00:24:38.740
absolute certainty is that the universe is
569
00:24:38.740 --> 00:24:39.340
expanding.
570
00:24:39.500 --> 00:24:41.940
Andrew Dunkley: Yes. Uh, at an accelerating rate. Although
571
00:24:41.940 --> 00:24:43.900
the accelerating rate's not as accelerating
572
00:24:43.900 --> 00:24:45.580
as it once was. Possibly.
573
00:24:45.740 --> 00:24:46.380
Professor Fred Watson: Possibly.
574
00:24:46.530 --> 00:24:49.100
Andrew Dunkley: Um, yeah. There's three possible
575
00:24:49.980 --> 00:24:52.900
shapes of the universe. He asks if it's
576
00:24:52.900 --> 00:24:55.860
a sphere. Um, there's, uh, the flat
577
00:24:55.860 --> 00:24:58.470
universe theory. Do we have to go there? Uh,
578
00:24:58.470 --> 00:25:00.360
there's the closed universe
579
00:25:01.160 --> 00:25:04.080
theory, which is the positive curvature, so a
580
00:25:04.080 --> 00:25:06.960
sphere. Or the open universe theory,
581
00:25:06.960 --> 00:25:09.040
which is negative curvature. Huh. So it's
582
00:25:09.040 --> 00:25:11.800
more like the shape of a saddle. From what
583
00:25:11.800 --> 00:25:13.720
I'm reading, the most popular,
584
00:25:15.170 --> 00:25:17.800
uh, likelihood is the flat universe theory.
585
00:25:18.520 --> 00:25:21.080
Professor Fred Watson: But it's only flat in a Euclidean sense.
586
00:25:21.400 --> 00:25:23.960
It doesn't mean it's shaped like a
587
00:25:23.960 --> 00:25:26.920
tabletop. Uh, it means that parallel
588
00:25:26.920 --> 00:25:29.670
lines never meet. Basically, that's what we
589
00:25:29.670 --> 00:25:31.950
mean by flat. It's the shape of the geometry.
590
00:25:32.510 --> 00:25:35.030
Andrew Dunkley: And the other thing that they suggest is
591
00:25:35.030 --> 00:25:37.870
that, um, it can be flat and still
592
00:25:37.870 --> 00:25:39.790
expanding. As you said, uh, it might be
593
00:25:39.790 --> 00:25:42.510
infinite. We've talked about that before.
594
00:25:42.590 --> 00:25:45.230
And there is likely no centre and no edge.
595
00:25:46.190 --> 00:25:48.270
Professor Fred Watson: Correct. That's what we believe
596
00:25:49.070 --> 00:25:51.710
now, um, to its shape.
597
00:25:52.110 --> 00:25:54.920
So, uh, so
598
00:25:56.120 --> 00:25:58.720
basically, I think Ken's question is, is it
599
00:25:58.720 --> 00:26:00.920
spherical? And
600
00:26:01.480 --> 00:26:03.960
we don't know the answer to that. We know
601
00:26:03.960 --> 00:26:06.560
that the volume within which we can
602
00:26:06.560 --> 00:26:08.760
detect is spherical because
603
00:26:09.720 --> 00:26:12.360
the cosmic microwave background radiation
604
00:26:12.760 --> 00:26:15.160
forms an imaginary shell,
605
00:26:16.100 --> 00:26:19.080
uh, all around our galaxy. And it's
606
00:26:19.080 --> 00:26:21.440
the same distance in every direction. So in
607
00:26:21.440 --> 00:26:24.000
that regard, it's what we call isotropic, the
608
00:26:24.000 --> 00:26:26.870
same in all directions. Uh, and
609
00:26:26.870 --> 00:26:28.790
that's really the only thing we can
610
00:26:29.670 --> 00:26:32.350
lay it down to. But there are ideas that if
611
00:26:32.350 --> 00:26:34.270
you looked at the universe on a bigger scale
612
00:26:34.270 --> 00:26:36.390
than we could see, it wouldn't be. That it
613
00:26:36.390 --> 00:26:38.870
might be different in different directions.
614
00:26:39.820 --> 00:26:42.070
Um, and that, in fact, has been
615
00:26:42.390 --> 00:26:44.950
hypothesised as one of the sources of dark
616
00:26:44.950 --> 00:26:47.270
energy, that we're just seeing a local bit of
617
00:26:47.270 --> 00:26:49.400
the universe that's expanding, whose, uh,
618
00:26:49.750 --> 00:26:51.790
expansion is increasing, whereas somewhere
619
00:26:51.790 --> 00:26:54.750
else it might be slowing down
620
00:26:54.750 --> 00:26:56.800
the expansion of the universe. Um,
621
00:26:58.990 --> 00:27:00.190
Andrew Dunkley: yeah, sorry, go on.
622
00:27:00.350 --> 00:27:02.910
Professor Fred Watson: No, that would be a universe that's not
623
00:27:02.910 --> 00:27:04.550
isotropic. It's not the same in all
624
00:27:04.550 --> 00:27:06.810
directions, but we assume it's isotropic. So,
625
00:27:06.810 --> 00:27:09.190
uh, that's all we can do in our assumptions
626
00:27:09.190 --> 00:27:10.030
in cosmology.
627
00:27:10.190 --> 00:27:13.150
Andrew Dunkley: We just can't see beyond
628
00:27:13.310 --> 00:27:15.310
what we can see. Which sounds stupid, but
629
00:27:15.470 --> 00:27:18.190
that's the way the universe is. Um,
630
00:27:18.430 --> 00:27:20.630
we've got the known universe and then the
631
00:27:20.630 --> 00:27:20.990
rest of the.
632
00:27:21.940 --> 00:27:24.140
Professor Fred Watson: That's right, basically. And the rest might
633
00:27:24.140 --> 00:27:25.700
be a lot bigger than the known universe.
634
00:27:25.940 --> 00:27:27.440
Andrew Dunkley: Yeah, but we just don't know. Um,
635
00:27:29.060 --> 00:27:30.940
the only thing I thought of is, like, you
636
00:27:30.940 --> 00:27:32.820
look at Earth's atmosphere and as you go out,
637
00:27:32.820 --> 00:27:35.460
it fins. And so there's no defined
638
00:27:35.540 --> 00:27:38.260
line between space and
639
00:27:38.660 --> 00:27:41.180
the Earth proper. Could the
640
00:27:41.180 --> 00:27:43.060
universe be of the same ilk?
641
00:27:44.180 --> 00:27:47.060
Professor Fred Watson: Yes, but that would imply that space time
642
00:27:47.060 --> 00:27:49.700
just sort of keeps. Just keeps on going. It
643
00:27:49.700 --> 00:27:50.700
just might be empty.
644
00:27:51.400 --> 00:27:53.420
Uh, yeah,
645
00:27:53.880 --> 00:27:56.060
uh, we don't know.
646
00:27:56.220 --> 00:27:57.100
Andrew Dunkley: We don't know.
647
00:27:57.500 --> 00:27:59.500
Professor Fred Watson: Why are you asking us? We don't know.
648
00:28:02.580 --> 00:28:05.500
Andrew Dunkley: Uh, um, thank you, Ken. Uh, very
649
00:28:05.500 --> 00:28:07.460
thought provoking question and thanks for
650
00:28:07.460 --> 00:28:08.060
sending it in.
651
00:28:08.060 --> 00:28:10.100
If you have questions for us, please send
652
00:28:10.100 --> 00:28:11.980
them to us via our website,
653
00:28:12.060 --> 00:28:14.700
spacenutspodcast.com spacenuts
654
00:28:14.700 --> 00:28:16.980
IO there's a little button at the top called
655
00:28:16.980 --> 00:28:19.900
AMA M and that's what you click on to
656
00:28:20.200 --> 00:28:22.080
send us text and audio questions. If you've
657
00:28:22.080 --> 00:28:23.880
got a device with a microphone, you're all
658
00:28:23.880 --> 00:28:26.720
set. Uh, most smartphones and smart devices
659
00:28:26.720 --> 00:28:29.080
have that and you can send it to us
660
00:28:29.560 --> 00:28:31.520
in audio form. Don't forget to tell us who
661
00:28:31.520 --> 00:28:32.880
you are and where you're from. Or you can
662
00:28:32.880 --> 00:28:34.480
send us a text question. Just fill in the
663
00:28:34.480 --> 00:28:37.280
blanks. And while you're there, have a look
664
00:28:37.280 --> 00:28:39.080
around, visit the shop, get something from
665
00:28:39.400 --> 00:28:42.360
yourself. Um, you know, whatever you like.
666
00:28:42.920 --> 00:28:44.480
And we're done. Fred Watson, thank you so
667
00:28:44.480 --> 00:28:45.660
much. That was a tough one.
668
00:28:47.010 --> 00:28:50.010
Professor Fred Watson: Yeah, well, we, you know, uh, Space
669
00:28:50.010 --> 00:28:52.290
Nuts always probes the limits of knowledge.
670
00:28:52.290 --> 00:28:54.010
We. It does. Ah, that's what we.
671
00:28:54.010 --> 00:28:56.570
Andrew Dunkley: Unfortunately, I have such limited knowledge,
672
00:28:56.570 --> 00:28:58.650
I'm not very helpful. But I'm glad you're
673
00:28:58.650 --> 00:28:58.930
here.
674
00:28:59.250 --> 00:29:01.929
Professor Fred Watson: No, you are very helpful and, um, so are our
675
00:29:01.929 --> 00:29:04.170
listeners because they keep on probing, which
676
00:29:04.170 --> 00:29:04.450
is great.
677
00:29:04.450 --> 00:29:06.570
Andrew Dunkley: They do indeed. All right, Fred Watson,
678
00:29:06.570 --> 00:29:07.890
thanks very much. We'll catch you on the next
679
00:29:07.890 --> 00:29:08.370
episode.
680
00:29:08.690 --> 00:29:10.170
Professor Fred Watson: Sounds great. Thanks, Andrew.
681
00:29:10.170 --> 00:29:11.770
Andrew Dunkley: Professor Fred Watson Watson, astronomer at
682
00:29:11.770 --> 00:29:13.850
large. And thanks to Huw in the studio, who
683
00:29:13.850 --> 00:29:15.530
couldn't be with us today because he's been
684
00:29:15.530 --> 00:29:17.560
expanding at an accelerating rate. So he was.
685
00:29:17.710 --> 00:29:19.910
Enter the gym. And from me, Andrew Dunkley.
686
00:29:19.910 --> 00:29:21.550
Thanks for your company. We'll see you on the
687
00:29:21.550 --> 00:29:23.070
next episode of Space Nuts.
688
00:29:23.070 --> 00:29:23.710
Professor Fred Watson: Bye. Bye.
689
00:29:24.330 --> 00:29:27.110
Andrew Dunkley: Uh, you'll be listening to the Space Nuts
690
00:29:27.110 --> 00:29:30.070
podcast, available at
691
00:29:30.070 --> 00:29:32.030
Apple Podcasts, Spotify,
692
00:29:32.190 --> 00:29:34.950
iHeartRadio or your favourite podcast
693
00:29:34.950 --> 00:29:36.670
player. You can also stream on
694
00:29:36.670 --> 00:29:38.990
demand@bytes.comm this
695
00:29:38.990 --> 00:29:41.390
Professor Fred Watson: has been another quality podcast production
696
00:29:41.390 --> 00:29:42.910
from bytes.um.com.
0
00:00:00.000 --> 00:00:02.040
Andrew Dunkley: Hello again. Thanks for joining us on Space
1
00:00:02.040 --> 00:00:04.680
Nuts. This is a Q and A edition. My name is
2
00:00:04.680 --> 00:00:06.720
Andrew Dunkley. What's a Q and A edition?
3
00:00:06.720 --> 00:00:09.520
It's an edition where we get Q's and
4
00:00:09.520 --> 00:00:12.480
give you A's because you're so clever.
5
00:00:12.800 --> 00:00:14.360
Uh, something like that. Anyway, we're going
6
00:00:14.360 --> 00:00:16.160
to answer audience questions. That's what I'm
7
00:00:16.160 --> 00:00:17.600
getting at. We've got questions about
8
00:00:17.760 --> 00:00:20.000
redshift, We've got questions about dark
9
00:00:20.080 --> 00:00:20.720
photons.
10
00:00:20.720 --> 00:00:21.040
Professor Fred Watson: What?
11
00:00:21.700 --> 00:00:24.000
Andrew Dunkley: Uh, we've got questions about deep space
12
00:00:24.160 --> 00:00:26.960
astronomy and another one about the expansion
13
00:00:26.960 --> 00:00:29.120
of the universe. I think we talked about that
14
00:00:29.120 --> 00:00:31.440
last episode. Anyway, uh, we'll see if we can
15
00:00:31.440 --> 00:00:33.900
solve all of that on this episode of space
16
00:00:33.900 --> 00:00:35.660
nuts. 15 seconds.
17
00:00:35.660 --> 00:00:38.076
Professor Fred Watson: Guidance is internal. 10,
18
00:00:38.257 --> 00:00:41.020
9, ignition sequence. Star
19
00:00:41.180 --> 00:00:41.864
space nuts.
20
00:00:41.936 --> 00:00:43.304
Andrew Dunkley: 5, 4, 3, 2.
21
00:00:43.376 --> 00:00:43.664
Roger: 1.
22
00:00:43.736 --> 00:00:46.544
Professor Fred Watson: 2, 3, 4, 5, 5, 4, 3, 2,
23
00:00:46.616 --> 00:00:48.139
1. Space nuts.
24
00:00:48.220 --> 00:00:50.060
Andrew Dunkley: Astronauts report it feels good.
25
00:00:51.260 --> 00:00:54.220
And with us again to kind of
26
00:00:54.220 --> 00:00:56.740
try to maybe answer some of that is
27
00:00:56.740 --> 00:00:58.620
Professor Fred Watson Watson, astronomer at
28
00:00:58.620 --> 00:00:59.500
large. Hello, Fred Watson.
29
00:01:00.050 --> 00:01:02.890
Professor Fred Watson: Hello, Andrew. Um, kind of is probably the
30
00:01:02.890 --> 00:01:04.530
best description really, isn't it?
31
00:01:05.650 --> 00:01:08.400
Andrew Dunkley: Possibly so. Possibly so. Um,
32
00:01:08.530 --> 00:01:10.210
but you know, it's good to get questions.
33
00:01:10.210 --> 00:01:13.210
We've got a whole new batch, so, um, let's
34
00:01:13.210 --> 00:01:14.770
get stuck straight into it.
35
00:01:14.770 --> 00:01:17.760
Now. First question comes from, um. Uh,
36
00:01:18.290 --> 00:01:20.530
I love the way he always ends his questions.
37
00:01:20.530 --> 00:01:23.070
I'm not going to reveal anything, but, um,
38
00:01:23.070 --> 00:01:24.130
let's hear from Roger.
39
00:01:24.530 --> 00:01:27.510
Roger: Hey there, Space Nuts. This is Roger
40
00:01:27.510 --> 00:01:30.110
the truck driver. Tonight I'm in,
41
00:01:30.170 --> 00:01:33.070
uh, Rutland, Vermont. Got a
42
00:01:33.070 --> 00:01:35.230
question about the red shift of galaxies.
43
00:01:36.090 --> 00:01:38.910
Um, if the light that we're seeing from a far
44
00:01:38.910 --> 00:01:41.670
off galaxy is shifted to the red and it
45
00:01:41.670 --> 00:01:43.790
started out at a higher frequency,
46
00:01:44.350 --> 00:01:46.990
doesn't that mean energy's lost somewhere
47
00:01:46.990 --> 00:01:49.710
between here and there? And is that energy
48
00:01:49.790 --> 00:01:52.610
just transferred into space? And if it
49
00:01:52.610 --> 00:01:55.090
is, does that contribute to the
50
00:01:55.090 --> 00:01:57.410
expansion of space? And I'm not saying it's
51
00:01:57.410 --> 00:01:59.890
dark energy, but does it
52
00:01:59.890 --> 00:02:02.890
contribute to it or does that
53
00:02:02.890 --> 00:02:05.370
energy get dissipated in another way?
54
00:02:06.410 --> 00:02:08.730
All right. Always digging the show, guys.
55
00:02:08.730 --> 00:02:09.690
Keep on trucking.
56
00:02:11.370 --> 00:02:14.210
Andrew Dunkley: I love that. I love that. Uh, we've got
57
00:02:14.210 --> 00:02:15.890
train drivers that do that. Unfortunately,
58
00:02:15.890 --> 00:02:17.370
they do it at 3 o' clock in the morning.
59
00:02:18.730 --> 00:02:21.330
Although today he did it at 10 to 7. I was
60
00:02:21.330 --> 00:02:23.290
pretty annoyed. Pretty annoyed.
61
00:02:23.290 --> 00:02:25.250
Professor Fred Watson: This is, uh, the one going past your place?
62
00:02:25.250 --> 00:02:27.330
Andrew Dunkley: Yeah, behind our place there's a rail line.
63
00:02:27.330 --> 00:02:29.090
It doesn't get used a heck of a lot, but when
64
00:02:29.090 --> 00:02:30.040
it does, um.
65
00:02:30.490 --> 00:02:30.970
Eli: Yes?
66
00:02:31.050 --> 00:02:33.890
Andrew Dunkley: The glasses rattle. Uh, the ones on my face,
67
00:02:33.890 --> 00:02:36.250
I mean. Uh, thanks, Roger. Great question.
68
00:02:36.460 --> 00:02:39.450
Uh, so, um, yeah, the change
69
00:02:39.450 --> 00:02:42.040
in frequency with the, um,
70
00:02:43.130 --> 00:02:46.090
energy loss, um, where does the energy go and
71
00:02:46.090 --> 00:02:48.370
does it contribute to the expansion of the
72
00:02:48.370 --> 00:02:51.250
universe? And could it possibly be.
73
00:02:51.330 --> 00:02:53.090
Maybe, maybe not dark matter
74
00:02:54.130 --> 00:02:56.450
or dark energy or something?
75
00:02:56.450 --> 00:02:58.650
Professor Fred Watson: Yeah, yeah. Um, there's a lot.
76
00:02:58.650 --> 00:02:59.970
Andrew Dunkley: He packed a lot into that question.
77
00:03:00.050 --> 00:03:02.370
Professor Fred Watson: He did. And it's a great question too. Uh,
78
00:03:02.370 --> 00:03:04.290
and, you know, I mean, it's a,
79
00:03:04.690 --> 00:03:07.450
uh, project, um, Absolutely right. The
80
00:03:07.450 --> 00:03:10.050
conservation of energy. Uh, energy
81
00:03:10.130 --> 00:03:12.690
can't be created or destroyed. That's the
82
00:03:12.690 --> 00:03:15.490
fundamental rule. Its
83
00:03:15.570 --> 00:03:17.730
energy is always conserved.
84
00:03:18.890 --> 00:03:21.890
But, uh, the universe doesn't play
85
00:03:21.890 --> 00:03:23.530
by the ordinary rules.
86
00:03:24.790 --> 00:03:26.400
Uh, and, um,
87
00:03:28.810 --> 00:03:31.210
it's an interesting answer here.
88
00:03:31.550 --> 00:03:34.450
Um, and I have to say it's changed
89
00:03:34.450 --> 00:03:37.410
my view of what this, you know, what
90
00:03:37.410 --> 00:03:40.250
the answer to this problem was because,
91
00:03:40.410 --> 00:03:43.290
um, when we've been asked this before,
92
00:03:43.370 --> 00:03:45.130
we haven't been asked it for a long time.
93
00:03:46.280 --> 00:03:48.570
I just assumed that the energy, uh,
94
00:03:49.160 --> 00:03:51.800
basically was absorbed by the universe by
95
00:03:51.800 --> 00:03:54.680
space time, uh, and
96
00:03:55.000 --> 00:03:57.400
maybe contributed to the expansion.
97
00:03:57.480 --> 00:03:58.040
Although,
98
00:04:00.390 --> 00:04:02.800
uh, you can't have it both ways because it's
99
00:04:02.800 --> 00:04:05.640
the expansion that's causing the photon's
100
00:04:05.640 --> 00:04:08.350
energy to be lost. Uh,
101
00:04:08.600 --> 00:04:11.400
and just stepping back, exactly as
102
00:04:11.400 --> 00:04:13.640
Roger said, uh, you've got light going
103
00:04:13.640 --> 00:04:15.320
through the universe. It's,
104
00:04:15.670 --> 00:04:18.570
uh, its wavelength is being stretched by
105
00:04:18.570 --> 00:04:21.490
the expansion of the universe. Therefore the
106
00:04:21.490 --> 00:04:24.410
light is losing energy. Because the energy
107
00:04:24.410 --> 00:04:26.930
of a beam of light is all about the
108
00:04:26.930 --> 00:04:28.890
frequency of the light, in other words, or
109
00:04:28.890 --> 00:04:31.610
the wavelength. Putting it another way. So
110
00:04:31.770 --> 00:04:34.490
if you increase the wavelength, you lose
111
00:04:34.490 --> 00:04:37.280
energy. And that's, um,
112
00:04:37.610 --> 00:04:40.610
a given already. Uh, so what I
113
00:04:40.610 --> 00:04:42.330
used to say was, yes, it kind of goes into
114
00:04:42.330 --> 00:04:44.610
the universe. But I've done a bit more
115
00:04:44.610 --> 00:04:46.650
reading on this and I was wrong.
116
00:04:48.760 --> 00:04:51.750
Um, because when
117
00:04:51.750 --> 00:04:54.750
you apply general relativity to
118
00:04:54.750 --> 00:04:56.950
the universe as a whole, and that's the.
119
00:04:57.510 --> 00:04:59.190
As we've talked about, and we've talked about
120
00:04:59.190 --> 00:05:01.780
it at length in the last episode, it's, uh,
121
00:05:01.780 --> 00:05:04.510
the kind of fundamental rule that governs
122
00:05:04.510 --> 00:05:06.790
everything that we understand in the
123
00:05:06.790 --> 00:05:09.270
universe. Um, when you
124
00:05:09.510 --> 00:05:11.110
apply general relativity,
125
00:05:12.820 --> 00:05:12.860
Andrew Dunkley: uh,
126
00:05:12.870 --> 00:05:15.810
Professor Fred Watson: that conservation of energy
127
00:05:16.770 --> 00:05:19.730
that we expect to happen in the
128
00:05:19.730 --> 00:05:22.050
everyday world, it
129
00:05:22.290 --> 00:05:24.900
doesn't hold good. So energy, uh,
130
00:05:25.250 --> 00:05:27.690
is not conserved in an expanding
131
00:05:27.690 --> 00:05:30.690
universe. Uh, and so
132
00:05:31.250 --> 00:05:33.010
basically the energy
133
00:05:33.810 --> 00:05:36.730
simply disappears. It's
134
00:05:36.730 --> 00:05:39.450
just not there anymore because of the
135
00:05:39.450 --> 00:05:41.810
expansion of the universe. It's not causing
136
00:05:41.810 --> 00:05:43.490
the expansion of the universe. It's not
137
00:05:43.680 --> 00:05:45.800
create contributing to dark energy or dark
138
00:05:45.800 --> 00:05:48.640
matter, the energy loss, it just vanishes.
139
00:05:49.520 --> 00:05:51.520
Wow. So work that one out.
140
00:05:51.680 --> 00:05:52.400
Andrew Dunkley: I can't.
141
00:05:53.040 --> 00:05:54.240
Professor Fred Watson: No, I can't either.
142
00:05:56.470 --> 00:05:59.400
Um, I kind of really
143
00:05:59.400 --> 00:06:01.760
need to look at the equations on this.
144
00:06:02.330 --> 00:06:04.480
Andrew Dunkley: Um, don't show them to me. I mean,
145
00:06:06.400 --> 00:06:08.160
Professor Fred Watson: yeah, I'M not that keen on looking at them
146
00:06:08.160 --> 00:06:10.830
myself either. Too much else to do. But, uh,
147
00:06:11.190 --> 00:06:14.170
um, uh, but yes, that is
148
00:06:14.250 --> 00:06:16.410
the thinking on this.
149
00:06:17.030 --> 00:06:19.890
Uh, and I think the conservation
150
00:06:19.890 --> 00:06:22.430
rule does not work, uh,
151
00:06:24.890 --> 00:06:26.810
um, when it comes to
152
00:06:28.010 --> 00:06:29.850
the universe on a whole.
153
00:06:30.170 --> 00:06:30.570
Andrew Dunkley: Yeah.
154
00:06:30.570 --> 00:06:30.930
Professor Fred Watson: Wow.
155
00:06:30.930 --> 00:06:33.650
Andrew Dunkley: Gee, um, that's quite a
156
00:06:33.650 --> 00:06:35.370
revelation. Who figured that out?
157
00:06:37.160 --> 00:06:39.770
Professor Fred Watson: Uh, uh, it's on a number of
158
00:06:40.250 --> 00:06:43.130
different, uh, physics, uh, related websites.
159
00:06:43.990 --> 00:06:45.830
Andrew Dunkley: There's the reason no one knows about it
160
00:06:45.830 --> 00:06:47.830
because it's physics and
161
00:06:48.710 --> 00:06:50.070
who reads that stuff?
162
00:06:50.870 --> 00:06:53.790
Professor Fred Watson: Yeah, I think the relativistic bit of
163
00:06:53.790 --> 00:06:56.550
it, uh, comes from the fact
164
00:06:57.110 --> 00:07:00.030
that the energy of a particle,
165
00:07:00.030 --> 00:07:02.390
which is what we're talking about, it's an
166
00:07:02.390 --> 00:07:04.950
observer dependent quantity.
167
00:07:05.750 --> 00:07:08.430
And so that's why relativity plays a part in
168
00:07:08.430 --> 00:07:10.230
this because you're the observer
169
00:07:11.270 --> 00:07:13.640
and you're talking about something that's
170
00:07:13.640 --> 00:07:15.840
relative to another observer, that is the
171
00:07:15.840 --> 00:07:18.800
photon. Uh, and that's why you've got,
172
00:07:18.840 --> 00:07:21.680
uh, a relativistic
173
00:07:22.160 --> 00:07:23.120
access. Ah, to it.
174
00:07:24.000 --> 00:07:26.880
Andrew Dunkley: Wow. Okay. Um, great question,
175
00:07:26.960 --> 00:07:29.079
Roger. I'm not sure you were expecting that
176
00:07:29.079 --> 00:07:31.840
answer, but, uh, there it is. Uh, the energy
177
00:07:31.920 --> 00:07:34.240
just gone,
178
00:07:35.360 --> 00:07:38.360
goes, vanishes, ceases to
179
00:07:38.360 --> 00:07:40.320
exist. It's a dead poly.
180
00:07:41.680 --> 00:07:44.200
So anyway, um,
181
00:07:45.200 --> 00:07:47.470
no one got that joke. I was, um,
182
00:07:48.320 --> 00:07:50.480
doing a Monty Python skit for some reason.
183
00:07:50.640 --> 00:07:52.000
Professor Fred Watson: Yeah, you were. That's right.
184
00:07:53.360 --> 00:07:55.520
Look, I'm pursuing this in a little bit more
185
00:07:55.520 --> 00:07:58.360
detail and, uh, just trying to, you know, see
186
00:07:58.360 --> 00:08:00.800
whether we've got alternative. Alternative
187
00:08:00.960 --> 00:08:02.320
views of this.
188
00:08:02.560 --> 00:08:04.800
Andrew Dunkley: Well, generally speaking, you do get
189
00:08:04.800 --> 00:08:06.640
alternative views when it comes to this kind
190
00:08:06.640 --> 00:08:06.840
of stuff.
191
00:08:06.840 --> 00:08:09.710
Professor Fred Watson: That's right. Um, yes,
192
00:08:09.710 --> 00:08:10.070
so
193
00:08:12.310 --> 00:08:15.310
that's right. Uh, uh,
194
00:08:15.670 --> 00:08:18.310
I think the standard explanation today is
195
00:08:18.310 --> 00:08:21.270
that energy is not conserved.
196
00:08:21.670 --> 00:08:22.230
Okay.
197
00:08:23.030 --> 00:08:24.790
Andrew Dunkley: We'll leave it at that until somebody throws
198
00:08:24.790 --> 00:08:26.070
another spanner into the.
199
00:08:26.070 --> 00:08:27.550
Professor Fred Watson: Yeah, uh, we might be giving a different
200
00:08:27.550 --> 00:08:29.350
answer next week. It could be.
201
00:08:29.910 --> 00:08:31.870
Andrew Dunkley: Thanks, Roger. Great to hear from you. Toot,
202
00:08:31.870 --> 00:08:33.510
toot. Uh, we'll catch you next time.
203
00:08:33.830 --> 00:08:36.310
Our next question comes from
204
00:08:36.470 --> 00:08:39.110
Peter. He's from San Diego, California.
205
00:08:39.190 --> 00:08:40.940
While listening to another astrophysics
206
00:08:41.329 --> 00:08:43.409
podcast, I heard the term dark
207
00:08:43.809 --> 00:08:46.329
photon for the first time. Apparently this is
208
00:08:46.329 --> 00:08:48.929
a particle astrophysicists are, uh, seeking
209
00:08:49.009 --> 00:08:51.489
in order to explain dark matter and, or dark
210
00:08:51.489 --> 00:08:54.289
energy. Could you please elaborate on what a
211
00:08:54.289 --> 00:08:56.369
dark photon could be?
212
00:08:57.190 --> 00:08:59.689
Um, dad, joke for Andrew. A photon
213
00:08:59.689 --> 00:09:02.129
travels at the speed of light. Does that mean
214
00:09:02.129 --> 00:09:04.809
a dark photon travels at the speed of
215
00:09:04.809 --> 00:09:07.649
dark. I like that.
216
00:09:07.729 --> 00:09:09.740
That's good. Yeah, that's really good. Uh,
217
00:09:09.740 --> 00:09:12.089
keep up the great work, he says. Uh, thank
218
00:09:12.089 --> 00:09:12.689
you, Peter.
219
00:09:13.070 --> 00:09:13.590
Professor Fred Watson: All as well.
220
00:09:13.590 --> 00:09:15.630
Andrew Dunkley: In San Diego, California.
221
00:09:16.170 --> 00:09:18.310
Uh, have you ever heard of a dark photon,
222
00:09:18.310 --> 00:09:18.750
Fred Watson?
223
00:09:19.050 --> 00:09:21.710
Professor Fred Watson: Um, yes, I'VE probably got a few in this box
224
00:09:21.710 --> 00:09:24.710
here. The
225
00:09:24.710 --> 00:09:26.510
speed of dark. Just, just going back to that,
226
00:09:26.590 --> 00:09:29.550
that quip, uh, there was
227
00:09:29.550 --> 00:09:32.510
a storey I read, uh, probably
228
00:09:32.990 --> 00:09:35.790
a fortnight ago, uh, about
229
00:09:36.350 --> 00:09:38.510
exactly this. In that dark
230
00:09:39.310 --> 00:09:42.230
ness can move faster than the speed
231
00:09:42.230 --> 00:09:42.670
of light.
232
00:09:43.230 --> 00:09:43.630
Andrew Dunkley: No,
233
00:09:46.510 --> 00:09:49.070
Professor Fred Watson: but it's ah, an illusory darkness. It's when
234
00:09:49.070 --> 00:09:52.030
you've got um, light beams
235
00:09:52.510 --> 00:09:55.390
interfering with one another so that
236
00:09:55.390 --> 00:09:57.310
you've uh, interference
237
00:09:58.430 --> 00:10:00.750
light beams can cancel out. So if you've got
238
00:10:00.750 --> 00:10:03.110
two light waves and you add them up out of
239
00:10:03.110 --> 00:10:04.710
phase, they can cancel out and you get
240
00:10:04.710 --> 00:10:07.690
darkness. That's a well known principle
241
00:10:07.690 --> 00:10:09.770
of interferometry. I used to play with that
242
00:10:09.770 --> 00:10:12.210
when I was a student a lot. Uh,
243
00:10:12.490 --> 00:10:14.530
but there are certain circumstances that
244
00:10:14.530 --> 00:10:17.210
those patterns of darkness can actually
245
00:10:17.210 --> 00:10:19.530
exceed the speed of light
246
00:10:20.170 --> 00:10:22.170
because they're not actually real, they're
247
00:10:22.170 --> 00:10:24.650
not real entities. They're not a thing that's
248
00:10:24.650 --> 00:10:26.650
carrying any sort of information or energy.
249
00:10:26.650 --> 00:10:29.450
They're just patterns in an
250
00:10:29.450 --> 00:10:31.090
interference pattern. They're just dark
251
00:10:31.090 --> 00:10:32.930
patches in it. And I think under certain
252
00:10:32.930 --> 00:10:35.290
circumstances they could go faster than the
253
00:10:35.290 --> 00:10:38.150
speed of light. Darkness might
254
00:10:38.150 --> 00:10:41.070
be not quite as uh, you know, as twee as
255
00:10:41.070 --> 00:10:43.710
you thought it was. I guess so
256
00:10:43.710 --> 00:10:46.710
anyway, anyway, uh, that's not the
257
00:10:47.430 --> 00:10:49.950
question, uh, because dark photons are
258
00:10:49.950 --> 00:10:52.310
definitely something different and they're
259
00:10:52.390 --> 00:10:55.270
basically uh, hypothetical.
260
00:10:55.510 --> 00:10:58.230
They've been hypothesised by
261
00:10:58.310 --> 00:11:01.010
physicists and cosmologists as uh,
262
00:11:01.350 --> 00:11:03.350
being a uh, force carrier
263
00:11:04.350 --> 00:11:06.670
similar to the ordinary photon
264
00:11:07.150 --> 00:11:10.110
but related to dark
265
00:11:10.270 --> 00:11:13.070
matter. In other
266
00:11:13.070 --> 00:11:15.830
words, you might have. Sorry, somebody's
267
00:11:15.830 --> 00:11:17.910
trying to phone me. I'm just gonna kill that
268
00:11:17.910 --> 00:11:20.430
call. Yeah, um,
269
00:11:21.070 --> 00:11:21.790
that was me.
270
00:11:21.790 --> 00:11:23.790
Andrew Dunkley: That was me. No it wasn't.
271
00:11:26.910 --> 00:11:29.870
Professor Fred Watson: You know, they're part of the. There may be.
272
00:11:29.950 --> 00:11:32.430
When we discover finally what dark matter is,
273
00:11:33.310 --> 00:11:35.690
there may be a suite of
274
00:11:36.250 --> 00:11:39.210
dark particles which could include
275
00:11:39.210 --> 00:11:41.610
dark photons. That's the bottom line.
276
00:11:41.850 --> 00:11:42.220
Andrew Dunkley: Right?
277
00:11:42.220 --> 00:11:45.210
Professor Fred Watson: Um, and so you know we mentioned last
278
00:11:45.210 --> 00:11:48.210
week the, or in the last episode the uh, the
279
00:11:48.210 --> 00:11:50.810
Large Hadron Collider being upgraded to the
280
00:11:50.810 --> 00:11:53.580
High Luminosity Large Hadron Collider. Um,
281
00:11:53.850 --> 00:11:56.250
that's one of the things they'd be looking
282
00:11:56.250 --> 00:11:57.770
for, will be dark photons.
283
00:11:58.730 --> 00:11:59.290
Okay.
284
00:11:59.690 --> 00:12:02.030
Andrew Dunkley: You know, I tried to do
285
00:12:02.500 --> 00:12:04.950
um, an AI search for an
286
00:12:04.950 --> 00:12:06.650
explanation on it and um,
287
00:12:07.950 --> 00:12:10.060
it sort of gave me all this gobbledygook. But
288
00:12:10.060 --> 00:12:12.950
um, you know, what would a dark
289
00:12:12.950 --> 00:12:15.750
proton, a photon do? It says it would
290
00:12:15.750 --> 00:12:17.870
carry a force within the dark sector.
291
00:12:19.230 --> 00:12:21.710
We call that the government. It might allow
292
00:12:21.710 --> 00:12:23.710
dark matter particles to interact with each
293
00:12:23.710 --> 00:12:25.990
other and it could very weakly mix with
294
00:12:25.990 --> 00:12:28.670
normal photons, giving us a way to Detect it.
295
00:12:28.750 --> 00:12:31.580
And the reason they reckon that scientists
296
00:12:31.580 --> 00:12:34.300
care about this, as you said, could explain
297
00:12:34.300 --> 00:12:36.860
what dark matter is made of. So
298
00:12:36.940 --> 00:12:39.220
therefore solving some of those gaps in our
299
00:12:39.220 --> 00:12:40.860
current physics theories.
300
00:12:43.260 --> 00:12:45.340
That's why people are interested in this and
301
00:12:45.340 --> 00:12:47.340
that's why they're upgrading the Large Hadron
302
00:12:47.340 --> 00:12:50.060
Collider. And hopefully we will
303
00:12:50.620 --> 00:12:52.700
learn more in years to come.
304
00:12:54.540 --> 00:12:55.340
That's the hope.
305
00:12:55.740 --> 00:12:58.620
Professor Fred Watson: That's the hope, yeah. So we might be talking
306
00:12:58.620 --> 00:13:01.220
one day about dark photons, um, having been
307
00:13:01.220 --> 00:13:03.890
detected, which would be a coup
308
00:13:03.890 --> 00:13:05.410
for space newts.
309
00:13:05.730 --> 00:13:08.570
Andrew Dunkley: Yes, it will. Uh, but at this stage they
310
00:13:08.570 --> 00:13:11.170
are not proven. It's just a theory. So
311
00:13:11.330 --> 00:13:13.970
that's about as much as we know at this point
312
00:13:13.970 --> 00:13:16.770
in time. But, uh, very good question. Uh,
313
00:13:16.930 --> 00:13:19.290
and, uh, thank you, Peter, for sending it in.
314
00:13:19.290 --> 00:13:22.010
This is Space Nuts with Andrew Dunkley and
315
00:13:22.010 --> 00:13:23.890
Professor Fred Watson Watson.
316
00:13:26.530 --> 00:13:29.490
0G and I feel fine. Space Nuts.
317
00:13:29.720 --> 00:13:31.560
Okay, Fred Watson, we'll move straight on to
318
00:13:31.560 --> 00:13:33.720
our next question, which is, uh, another
319
00:13:33.720 --> 00:13:36.440
audio question from Eli.
320
00:13:36.760 --> 00:13:39.000
Eli: Hello, this is Eli from
321
00:13:39.800 --> 00:13:42.240
sunny Coachella Valley in
322
00:13:42.240 --> 00:13:45.240
California. I'm embarrassed to
323
00:13:45.240 --> 00:13:47.640
admit it, but I still can't get my head
324
00:13:47.640 --> 00:13:50.640
around deep space astronomy. I get that
325
00:13:50.640 --> 00:13:53.440
the light from, say, a distant galaxy is a
326
00:13:53.440 --> 00:13:56.250
billion years old, but why
327
00:13:56.250 --> 00:13:59.210
that particular point in its time? Is
328
00:13:59.210 --> 00:14:01.450
it just a matter of whatever light is hitting
329
00:14:01.450 --> 00:14:03.730
us is the time we get to see.
330
00:14:05.090 --> 00:14:06.850
But for really early light,
331
00:14:07.890 --> 00:14:10.610
the JWST, early universe stuff
332
00:14:10.610 --> 00:14:13.090
that's been travelling for 13 billion years
333
00:14:13.090 --> 00:14:15.570
and just hitting us now,
334
00:14:16.690 --> 00:14:18.610
are we looking for the light that hasn't
335
00:14:19.010 --> 00:14:21.810
passed us by or hasn't made it here yet,
336
00:14:22.170 --> 00:14:24.610
but is from that one precise
337
00:14:24.610 --> 00:14:25.850
location long ago?
338
00:14:27.450 --> 00:14:30.210
This stuff is so difficult to get my head
339
00:14:30.210 --> 00:14:33.050
around. Love the show and hope
340
00:14:33.050 --> 00:14:34.970
you guys can clear this up for me.
341
00:14:36.150 --> 00:14:38.590
Andrew Dunkley: Uh, no, we can't. We just thought we'd, um,
342
00:14:38.590 --> 00:14:41.370
put the question in there. Thanks,
343
00:14:41.370 --> 00:14:44.210
Eli. Uh, this is a deep, um, I'm, um.
344
00:14:44.370 --> 00:14:46.450
Not only in deep space astronomy terms, but
345
00:14:46.450 --> 00:14:48.090
it is a deep, deep topic.
346
00:14:48.750 --> 00:14:51.610
Um, I mean, when we look up into the sky
347
00:14:51.610 --> 00:14:53.690
at night and we see all those beautiful
348
00:14:53.830 --> 00:14:56.550
coloured dots, we are looking at history.
349
00:14:56.950 --> 00:14:59.110
And it's variable history because some of
350
00:14:59.110 --> 00:15:01.950
it's 4.41 light years away and
351
00:15:01.950 --> 00:15:04.950
some of it's 400,000 light
352
00:15:04.950 --> 00:15:07.510
years away, some of it's further than that.
353
00:15:07.810 --> 00:15:09.750
Um, but then you've got the cosmic
354
00:15:10.230 --> 00:15:12.870
microwave background radiation, which is kind
355
00:15:12.870 --> 00:15:14.150
of a leftover of,
356
00:15:14.930 --> 00:15:17.910
um, what happened after the
357
00:15:17.910 --> 00:15:19.670
Big Bang and that,
358
00:15:20.820 --> 00:15:23.100
that's a different kettle of fish. And I can
359
00:15:23.100 --> 00:15:25.220
understand why you've got a headache. Eli,
360
00:15:25.620 --> 00:15:26.580
over to you, Fred Watson.
361
00:15:27.860 --> 00:15:30.860
Professor Fred Watson: Thanks. Um, so I
362
00:15:30.860 --> 00:15:32.580
guess uh, you know,
363
00:15:33.860 --> 00:15:36.180
I understand Eli's issue as well.
364
00:15:36.280 --> 00:15:36.980
Um,
365
00:15:38.980 --> 00:15:40.860
you've got to be in the right place at the
366
00:15:40.860 --> 00:15:43.060
right time to see a photon from a distant
367
00:15:43.060 --> 00:15:46.060
galaxy. But I guess the way
368
00:15:46.060 --> 00:15:48.020
to envisage this is if you think
369
00:15:48.970 --> 00:15:50.890
of the universe, um,
370
00:15:51.770 --> 00:15:54.450
and you've got to perhaps think of it as if
371
00:15:54.450 --> 00:15:55.770
you were looking at it from the outside,
372
00:15:55.770 --> 00:15:58.050
which we never can. But, uh, if you can think
373
00:15:58.050 --> 00:16:00.650
of it that way, then it's full of
374
00:16:01.210 --> 00:16:03.370
objects which are radiating light.
375
00:16:04.249 --> 00:16:06.930
Even in its infancy, when the universe was
376
00:16:06.930 --> 00:16:09.370
very young, the stuff in it was basically
377
00:16:09.610 --> 00:16:12.290
shining. Um, once we got past the Dark Ages,
378
00:16:12.290 --> 00:16:14.570
where no stars were shining, uh,
379
00:16:15.330 --> 00:16:18.010
um, and those are the galaxies that we now
380
00:16:18.010 --> 00:16:20.510
see. So they constantly radiate, creating
381
00:16:20.510 --> 00:16:23.470
light. And that's just like a river of
382
00:16:23.470 --> 00:16:26.470
light that's flowing down time,
383
00:16:26.470 --> 00:16:29.190
if I can put it that way. Uh, and
384
00:16:30.150 --> 00:16:33.030
a long time in the future it
385
00:16:33.030 --> 00:16:35.190
reaches us. But it's not just
386
00:16:36.070 --> 00:16:38.590
an individual photon or something that's
387
00:16:38.590 --> 00:16:41.150
reaching us. It's this stream of stuff that
388
00:16:41.150 --> 00:16:43.790
is being radiated throughout the
389
00:16:43.790 --> 00:16:46.230
universe by these galaxies. So we,
390
00:16:46.850 --> 00:16:49.760
um. And we pick it up. We
391
00:16:49.760 --> 00:16:52.520
pick it up sometimes exactly as you've said.
392
00:16:52.520 --> 00:16:54.480
Well, up to 10 billion years after it's been
393
00:16:54.800 --> 00:16:57.760
radiated. I think 12 billion years,
394
00:16:58.130 --> 00:17:00.480
uh, are the oldest or the earliest galaxies
395
00:17:00.480 --> 00:17:02.639
that we now see. We're looking back in time
396
00:17:02.639 --> 00:17:05.440
12 billion years and seeing them as they were
397
00:17:05.840 --> 00:17:08.360
perhaps a billion and a half years after the
398
00:17:08.360 --> 00:17:11.160
Big Bang. Um, and they are shining,
399
00:17:11.160 --> 00:17:13.320
they're radiating light, uh, in the early
400
00:17:13.320 --> 00:17:16.230
universe and down the track that reaches us
401
00:17:16.390 --> 00:17:18.390
because that light's going in all directions.
402
00:17:18.390 --> 00:17:20.310
So it wouldn't matter where in the universe
403
00:17:20.310 --> 00:17:22.710
we were, we would still see them.
404
00:17:23.510 --> 00:17:25.670
Uh, we'd just see them in a, you know, in a
405
00:17:25.670 --> 00:17:27.670
different position in the sky. If we're a
406
00:17:27.670 --> 00:17:30.589
long way from where we are now. Yeah, but,
407
00:17:30.589 --> 00:17:33.350
yeah, so I guess it's, you
408
00:17:33.350 --> 00:17:35.950
know, in a way, one way of thinking about
409
00:17:35.950 --> 00:17:38.910
this is if you imagine us on planet
410
00:17:38.910 --> 00:17:41.820
Earth here and imagine us being
411
00:17:41.820 --> 00:17:44.700
surrounded by a whole series of
412
00:17:44.700 --> 00:17:47.580
shells which, uh, we're at the centre
413
00:17:47.580 --> 00:17:49.340
of. And this is a bit like the crystalline
414
00:17:49.340 --> 00:17:51.820
spheres that people used to think, uh, the
415
00:17:51.820 --> 00:17:54.100
universe was made of. Uh, but
416
00:17:54.580 --> 00:17:57.340
these shells, uh, spherical shells,
417
00:17:57.340 --> 00:17:59.700
all centred on the Earth, but each one
418
00:18:00.020 --> 00:18:02.740
clicks over to a time
419
00:18:02.820 --> 00:18:05.660
further in the past, uh, because the
420
00:18:05.660 --> 00:18:08.660
light's coming to us from the whole cosmos,
421
00:18:08.660 --> 00:18:11.220
which is full of stuff. Uh, and that's why
422
00:18:11.220 --> 00:18:13.560
we, these shells sort of being
423
00:18:13.560 --> 00:18:16.140
illuminated in a way by the objects that, uh,
424
00:18:16.400 --> 00:18:18.680
radiated them at that time. Uh,
425
00:18:20.100 --> 00:18:22.880
um, that we see them because of
426
00:18:23.120 --> 00:18:25.520
the distance that they are away from us means
427
00:18:25.520 --> 00:18:28.520
that the light has taken that long to get to
428
00:18:28.520 --> 00:18:31.040
us, whether that helps or not. In fact, I
429
00:18:31.040 --> 00:18:33.040
think I've just confused it completely. But,
430
00:18:35.080 --> 00:18:36.560
Andrew Dunkley: um, I
431
00:18:38.570 --> 00:18:41.330
just doing a little experimental search here
432
00:18:41.330 --> 00:18:41.930
for a sec.
433
00:18:44.090 --> 00:18:46.970
What I agree
434
00:18:46.970 --> 00:18:49.690
with in terms of Eli's question and getting
435
00:18:49.690 --> 00:18:52.650
your head around it is, um, if
436
00:18:52.650 --> 00:18:54.730
Betelgeuse, or however you want to pronounce
437
00:18:54.730 --> 00:18:57.570
it, went supernova right now as we
438
00:18:57.570 --> 00:18:58.170
were speaking,
439
00:19:00.410 --> 00:19:02.010
we wouldn't see it for
440
00:19:03.700 --> 00:19:05.140
640 years.
441
00:19:05.780 --> 00:19:06.340
Roger: Yeah.
442
00:19:07.220 --> 00:19:09.700
Andrew Dunkley: So for it to have gone
443
00:19:09.700 --> 00:19:12.700
supernova in the past and us to witness
444
00:19:12.700 --> 00:19:14.420
it, it has to have happened
445
00:19:15.940 --> 00:19:18.660
pretty close to 640 years ago.
446
00:19:19.220 --> 00:19:20.260
Does that make sense?
447
00:19:20.420 --> 00:19:23.260
Professor Fred Watson: Yes. Um, so you could think of that in
448
00:19:23.260 --> 00:19:25.460
another way. Um, you know,
449
00:19:26.300 --> 00:19:29.060
um, anywhere between us and 640
450
00:19:29.060 --> 00:19:31.620
light years away, there could be this pulse
451
00:19:31.620 --> 00:19:33.540
of light that's on its way to us
452
00:19:34.260 --> 00:19:37.220
from Betelgeuse. Uh, it would spread
453
00:19:37.220 --> 00:19:39.940
out in a sphere, and as that sphere
454
00:19:39.940 --> 00:19:42.140
expanded, eventually it would wash over the
455
00:19:42.140 --> 00:19:44.980
Earth and we'd see it, um, and perhaps
456
00:19:44.980 --> 00:19:46.740
see it during the day as well, because it
457
00:19:46.740 --> 00:19:49.700
might get bright enough to do that. Uh, and
458
00:19:49.700 --> 00:19:51.220
I think that's a really good way of putting
459
00:19:51.220 --> 00:19:53.820
it, Andrew, because thinking, um, about the
460
00:19:53.820 --> 00:19:55.500
galaxies, they're just streaming light out
461
00:19:55.500 --> 00:19:58.300
all the time, but something like a, uh,
462
00:19:58.380 --> 00:20:01.140
supernova explosion, which gives a big pulse
463
00:20:01.140 --> 00:20:04.140
of light, um, that's perhaps easier to get
464
00:20:04.140 --> 00:20:06.180
your head around because that's. That's just
465
00:20:06.180 --> 00:20:08.940
gotta, um. It'll
466
00:20:08.940 --> 00:20:11.500
take whatever time is
467
00:20:11.500 --> 00:20:14.420
represented by the distance away. So 640
468
00:20:14.420 --> 00:20:17.260
light years away. It'll take 640 years
469
00:20:17.260 --> 00:20:19.340
to get here for that pulse to get here. But
470
00:20:19.340 --> 00:20:22.260
then it will sweep over us and we'll see the
471
00:20:22.260 --> 00:20:24.220
light. The light fading away.
472
00:20:24.460 --> 00:20:25.770
Andrew Dunkley: Yeah. And, um,
473
00:20:27.340 --> 00:20:29.500
the reason I chose that target is because
474
00:20:29.740 --> 00:20:32.500
there's a lot of conjecture about
475
00:20:32.500 --> 00:20:35.220
its future and the possibility that it's
476
00:20:35.220 --> 00:20:36.940
reaching that critical mass point.
477
00:20:37.480 --> 00:20:37.800
Professor Fred Watson: Yes.
478
00:20:38.190 --> 00:20:39.720
Andrew Dunkley: Um, but it could have already happened.
479
00:20:39.720 --> 00:20:41.240
That's the other thing.
480
00:20:42.040 --> 00:20:45.040
Professor Fred Watson: But that's something we can have no knowledge
481
00:20:45.040 --> 00:20:47.400
of. That's the key thing, because, um,
482
00:20:47.880 --> 00:20:50.360
we are limited by the speed of light. That's
483
00:20:50.440 --> 00:20:52.320
the thing that always limits our view of the
484
00:20:52.320 --> 00:20:52.760
universe.
485
00:20:52.760 --> 00:20:55.640
Andrew Dunkley: And just to confuse Eli a little bit more,
486
00:20:56.440 --> 00:20:59.040
there are, ah, probably things in the
487
00:20:59.040 --> 00:21:01.040
universe we will never witness because the
488
00:21:01.040 --> 00:21:04.000
light is just too far away to reach us in any
489
00:21:04.000 --> 00:21:05.960
reasonable amount of time. Even
490
00:21:06.910 --> 00:21:09.830
beyond the life of the Earth itself or
491
00:21:09.830 --> 00:21:12.180
our sun. Uh,
492
00:21:13.230 --> 00:21:15.750
there are things we will never, ever know
493
00:21:15.750 --> 00:21:16.030
about.
494
00:21:16.670 --> 00:21:17.310
Professor Fred Watson: Correct.
495
00:21:18.200 --> 00:21:21.040
Andrew Dunkley: Um, and that's where it just gives you, um,
496
00:21:22.430 --> 00:21:24.830
one of those Headaches that requires, uh, you
497
00:21:24.830 --> 00:21:27.630
to take paracetamol and ibuprofen at the same
498
00:21:27.630 --> 00:21:27.950
time.
499
00:21:32.100 --> 00:21:34.720
Um, deep, deep headaches. But Eli, great
500
00:21:34.720 --> 00:21:36.440
question. I'm not sure we solved your
501
00:21:36.440 --> 00:21:39.420
problem, but, um, anyway, uh,
502
00:21:40.800 --> 00:21:42.600
I try to explain this sort of stuff to my
503
00:21:42.600 --> 00:21:45.520
grandson, uh, and, uh, my granddaughters.
504
00:21:45.520 --> 00:21:48.280
And, you know, how do you
505
00:21:48.280 --> 00:21:50.160
explain time and distance
506
00:21:51.040 --> 00:21:53.970
to a young child? And, um,
507
00:21:53.970 --> 00:21:55.360
when you're trying to get through traffic,
508
00:21:57.200 --> 00:21:58.840
Professor Fred Watson: that might not be the best time to do it.
509
00:21:58.840 --> 00:22:00.720
Andrew Dunkley: Probably not, but they're very interested.
510
00:22:01.280 --> 00:22:03.240
Very interested. Thanks, Eli.
511
00:22:03.240 --> 00:22:03.840
Great question.
512
00:22:06.540 --> 00:22:09.180
Professor Fred Watson: The crew of Artemis 2 now bound for the moon,
513
00:22:09.420 --> 00:22:11.980
humanity's next great voyage begins.
514
00:22:12.620 --> 00:22:13.820
Space nuts.
515
00:22:14.140 --> 00:22:16.190
Andrew Dunkley: Our final question comes, uh,
516
00:22:16.780 --> 00:22:19.740
from Nova Scotia. It's from Ken.
517
00:22:19.910 --> 00:22:21.940
Uh, look, this is an old chestnut. We've,
518
00:22:21.940 --> 00:22:24.660
we've probably spoken about this many times,
519
00:22:24.660 --> 00:22:27.620
but it's always good to, um, to revisit. If
520
00:22:27.620 --> 00:22:30.340
the universe is expanding, what is it
521
00:22:30.340 --> 00:22:32.700
expanding into? And also,
522
00:22:33.330 --> 00:22:35.090
is the universe spherical?
523
00:22:36.770 --> 00:22:39.010
Professor Fred Watson: So, um, yes. What's it expanding into?
524
00:22:39.010 --> 00:22:41.130
Andrew Dunkley: Well, we don't know.
525
00:22:41.130 --> 00:22:43.250
Professor Fred Watson: And yes, that's.
526
00:22:43.650 --> 00:22:45.970
Yes. Uh, it's actually, we don't know. And
527
00:22:45.970 --> 00:22:48.930
maybe, maybe, maybe. So,
528
00:22:49.000 --> 00:22:51.570
um, the universe
529
00:22:52.210 --> 00:22:55.090
is everything that we can detect. That's
530
00:22:55.090 --> 00:22:56.850
the definition of the universe. Everything we
531
00:22:56.850 --> 00:22:59.490
can measure or detect. And that means,
532
00:23:00.370 --> 00:23:02.450
and we observe the expansion,
533
00:23:03.250 --> 00:23:06.210
but we don't know whether there's an edge
534
00:23:06.210 --> 00:23:08.050
to the universe. We don't know whether it's
535
00:23:08.050 --> 00:23:10.410
infinite. We don't know anything beyond the
536
00:23:10.410 --> 00:23:13.130
horizons that we see. And um, the most
537
00:23:13.130 --> 00:23:14.850
obvious one is the cosmic microwave
538
00:23:14.850 --> 00:23:16.900
background radiation, um,
539
00:23:17.730 --> 00:23:19.570
beyond which we can't see. But the universe
540
00:23:19.570 --> 00:23:21.570
almost certainly goes on beyond that,
541
00:23:22.130 --> 00:23:24.610
probably for a very long way, maybe very big.
542
00:23:24.930 --> 00:23:27.330
But we've got no knowledge of a boundary or
543
00:23:28.190 --> 00:23:30.510
any other medium that it might be expanding
544
00:23:30.510 --> 00:23:33.230
into. So, um,
545
00:23:33.610 --> 00:23:36.430
uh, one possibility is the idea of multiple
546
00:23:36.430 --> 00:23:38.830
universes. And they might
547
00:23:38.830 --> 00:23:40.990
exist maybe
548
00:23:41.630 --> 00:23:44.080
in a higher dimensional, uh,
549
00:23:45.390 --> 00:23:48.270
arena, if I can put it that way. You know,
550
00:23:48.750 --> 00:23:51.670
if you can, um, find that
551
00:23:51.670 --> 00:23:54.670
there are extra dimensions, we know the
552
00:23:54.830 --> 00:23:56.870
three dimensions of space and one of time.
553
00:23:56.870 --> 00:23:58.550
That's what we've got now.
554
00:23:59.830 --> 00:24:02.230
But, uh, if there are hidden
555
00:24:02.630 --> 00:24:04.870
extra dimensions, maybe they provide
556
00:24:05.830 --> 00:24:08.150
a venue for the universe to expand into.
557
00:24:08.970 --> 00:24:11.750
Uh, and there are various theories
558
00:24:11.750 --> 00:24:14.750
that accept that, um, M. M theory is one of
559
00:24:14.750 --> 00:24:17.710
them, where M is probably an abbreviation
560
00:24:17.710 --> 00:24:19.990
for membrane. The idea is that the universe
561
00:24:20.470 --> 00:24:22.590
can be collapsed onto a two dimensional
562
00:24:22.590 --> 00:24:24.390
membrane, and there are lots of these
563
00:24:24.390 --> 00:24:27.300
membranes in the kind
564
00:24:27.300 --> 00:24:29.580
of higher dimensional universe. But that's
565
00:24:29.580 --> 00:24:31.420
just conjecture and we've got no
566
00:24:32.060 --> 00:24:34.420
mechanism for proving that at the moment. The
567
00:24:34.420 --> 00:24:36.700
only thing we know with certainty with
568
00:24:36.700 --> 00:24:38.740
absolute certainty is that the universe is
569
00:24:38.740 --> 00:24:39.340
expanding.
570
00:24:39.500 --> 00:24:41.940
Andrew Dunkley: Yes. Uh, at an accelerating rate. Although
571
00:24:41.940 --> 00:24:43.900
the accelerating rate's not as accelerating
572
00:24:43.900 --> 00:24:45.580
as it once was. Possibly.
573
00:24:45.740 --> 00:24:46.380
Professor Fred Watson: Possibly.
574
00:24:46.530 --> 00:24:49.100
Andrew Dunkley: Um, yeah. There's three possible
575
00:24:49.980 --> 00:24:52.900
shapes of the universe. He asks if it's
576
00:24:52.900 --> 00:24:55.860
a sphere. Um, there's, uh, the flat
577
00:24:55.860 --> 00:24:58.470
universe theory. Do we have to go there? Uh,
578
00:24:58.470 --> 00:25:00.360
there's the closed universe
579
00:25:01.160 --> 00:25:04.080
theory, which is the positive curvature, so a
580
00:25:04.080 --> 00:25:06.960
sphere. Or the open universe theory,
581
00:25:06.960 --> 00:25:09.040
which is negative curvature. Huh. So it's
582
00:25:09.040 --> 00:25:11.800
more like the shape of a saddle. From what
583
00:25:11.800 --> 00:25:13.720
I'm reading, the most popular,
584
00:25:15.170 --> 00:25:17.800
uh, likelihood is the flat universe theory.
585
00:25:18.520 --> 00:25:21.080
Professor Fred Watson: But it's only flat in a Euclidean sense.
586
00:25:21.400 --> 00:25:23.960
It doesn't mean it's shaped like a
587
00:25:23.960 --> 00:25:26.920
tabletop. Uh, it means that parallel
588
00:25:26.920 --> 00:25:29.670
lines never meet. Basically, that's what we
589
00:25:29.670 --> 00:25:31.950
mean by flat. It's the shape of the geometry.
590
00:25:32.510 --> 00:25:35.030
Andrew Dunkley: And the other thing that they suggest is
591
00:25:35.030 --> 00:25:37.870
that, um, it can be flat and still
592
00:25:37.870 --> 00:25:39.790
expanding. As you said, uh, it might be
593
00:25:39.790 --> 00:25:42.510
infinite. We've talked about that before.
594
00:25:42.590 --> 00:25:45.230
And there is likely no centre and no edge.
595
00:25:46.190 --> 00:25:48.270
Professor Fred Watson: Correct. That's what we believe
596
00:25:49.070 --> 00:25:51.710
now, um, to its shape.
597
00:25:52.110 --> 00:25:54.920
So, uh, so
598
00:25:56.120 --> 00:25:58.720
basically, I think Ken's question is, is it
599
00:25:58.720 --> 00:26:00.920
spherical? And
600
00:26:01.480 --> 00:26:03.960
we don't know the answer to that. We know
601
00:26:03.960 --> 00:26:06.560
that the volume within which we can
602
00:26:06.560 --> 00:26:08.760
detect is spherical because
603
00:26:09.720 --> 00:26:12.360
the cosmic microwave background radiation
604
00:26:12.760 --> 00:26:15.160
forms an imaginary shell,
605
00:26:16.100 --> 00:26:19.080
uh, all around our galaxy. And it's
606
00:26:19.080 --> 00:26:21.440
the same distance in every direction. So in
607
00:26:21.440 --> 00:26:24.000
that regard, it's what we call isotropic, the
608
00:26:24.000 --> 00:26:26.870
same in all directions. Uh, and
609
00:26:26.870 --> 00:26:28.790
that's really the only thing we can
610
00:26:29.670 --> 00:26:32.350
lay it down to. But there are ideas that if
611
00:26:32.350 --> 00:26:34.270
you looked at the universe on a bigger scale
612
00:26:34.270 --> 00:26:36.390
than we could see, it wouldn't be. That it
613
00:26:36.390 --> 00:26:38.870
might be different in different directions.
614
00:26:39.820 --> 00:26:42.070
Um, and that, in fact, has been
615
00:26:42.390 --> 00:26:44.950
hypothesised as one of the sources of dark
616
00:26:44.950 --> 00:26:47.270
energy, that we're just seeing a local bit of
617
00:26:47.270 --> 00:26:49.400
the universe that's expanding, whose, uh,
618
00:26:49.750 --> 00:26:51.790
expansion is increasing, whereas somewhere
619
00:26:51.790 --> 00:26:54.750
else it might be slowing down
620
00:26:54.750 --> 00:26:56.800
the expansion of the universe. Um,
621
00:26:58.990 --> 00:27:00.190
Andrew Dunkley: yeah, sorry, go on.
622
00:27:00.350 --> 00:27:02.910
Professor Fred Watson: No, that would be a universe that's not
623
00:27:02.910 --> 00:27:04.550
isotropic. It's not the same in all
624
00:27:04.550 --> 00:27:06.810
directions, but we assume it's isotropic. So,
625
00:27:06.810 --> 00:27:09.190
uh, that's all we can do in our assumptions
626
00:27:09.190 --> 00:27:10.030
in cosmology.
627
00:27:10.190 --> 00:27:13.150
Andrew Dunkley: We just can't see beyond
628
00:27:13.310 --> 00:27:15.310
what we can see. Which sounds stupid, but
629
00:27:15.470 --> 00:27:18.190
that's the way the universe is. Um,
630
00:27:18.430 --> 00:27:20.630
we've got the known universe and then the
631
00:27:20.630 --> 00:27:20.990
rest of the.
632
00:27:21.940 --> 00:27:24.140
Professor Fred Watson: That's right, basically. And the rest might
633
00:27:24.140 --> 00:27:25.700
be a lot bigger than the known universe.
634
00:27:25.940 --> 00:27:27.440
Andrew Dunkley: Yeah, but we just don't know. Um,
635
00:27:29.060 --> 00:27:30.940
the only thing I thought of is, like, you
636
00:27:30.940 --> 00:27:32.820
look at Earth's atmosphere and as you go out,
637
00:27:32.820 --> 00:27:35.460
it fins. And so there's no defined
638
00:27:35.540 --> 00:27:38.260
line between space and
639
00:27:38.660 --> 00:27:41.180
the Earth proper. Could the
640
00:27:41.180 --> 00:27:43.060
universe be of the same ilk?
641
00:27:44.180 --> 00:27:47.060
Professor Fred Watson: Yes, but that would imply that space time
642
00:27:47.060 --> 00:27:49.700
just sort of keeps. Just keeps on going. It
643
00:27:49.700 --> 00:27:50.700
just might be empty.
644
00:27:51.400 --> 00:27:53.420
Uh, yeah,
645
00:27:53.880 --> 00:27:56.060
uh, we don't know.
646
00:27:56.220 --> 00:27:57.100
Andrew Dunkley: We don't know.
647
00:27:57.500 --> 00:27:59.500
Professor Fred Watson: Why are you asking us? We don't know.
648
00:28:02.580 --> 00:28:05.500
Andrew Dunkley: Uh, um, thank you, Ken. Uh, very
649
00:28:05.500 --> 00:28:07.460
thought provoking question and thanks for
650
00:28:07.460 --> 00:28:08.060
sending it in.
651
00:28:08.060 --> 00:28:10.100
If you have questions for us, please send
652
00:28:10.100 --> 00:28:11.980
them to us via our website,
653
00:28:12.060 --> 00:28:14.700
spacenutspodcast.com spacenuts
654
00:28:14.700 --> 00:28:16.980
IO there's a little button at the top called
655
00:28:16.980 --> 00:28:19.900
AMA M and that's what you click on to
656
00:28:20.200 --> 00:28:22.080
send us text and audio questions. If you've
657
00:28:22.080 --> 00:28:23.880
got a device with a microphone, you're all
658
00:28:23.880 --> 00:28:26.720
set. Uh, most smartphones and smart devices
659
00:28:26.720 --> 00:28:29.080
have that and you can send it to us
660
00:28:29.560 --> 00:28:31.520
in audio form. Don't forget to tell us who
661
00:28:31.520 --> 00:28:32.880
you are and where you're from. Or you can
662
00:28:32.880 --> 00:28:34.480
send us a text question. Just fill in the
663
00:28:34.480 --> 00:28:37.280
blanks. And while you're there, have a look
664
00:28:37.280 --> 00:28:39.080
around, visit the shop, get something from
665
00:28:39.400 --> 00:28:42.360
yourself. Um, you know, whatever you like.
666
00:28:42.920 --> 00:28:44.480
And we're done. Fred Watson, thank you so
667
00:28:44.480 --> 00:28:45.660
much. That was a tough one.
668
00:28:47.010 --> 00:28:50.010
Professor Fred Watson: Yeah, well, we, you know, uh, Space
669
00:28:50.010 --> 00:28:52.290
Nuts always probes the limits of knowledge.
670
00:28:52.290 --> 00:28:54.010
We. It does. Ah, that's what we.
671
00:28:54.010 --> 00:28:56.570
Andrew Dunkley: Unfortunately, I have such limited knowledge,
672
00:28:56.570 --> 00:28:58.650
I'm not very helpful. But I'm glad you're
673
00:28:58.650 --> 00:28:58.930
here.
674
00:28:59.250 --> 00:29:01.929
Professor Fred Watson: No, you are very helpful and, um, so are our
675
00:29:01.929 --> 00:29:04.170
listeners because they keep on probing, which
676
00:29:04.170 --> 00:29:04.450
is great.
677
00:29:04.450 --> 00:29:06.570
Andrew Dunkley: They do indeed. All right, Fred Watson,
678
00:29:06.570 --> 00:29:07.890
thanks very much. We'll catch you on the next
679
00:29:07.890 --> 00:29:08.370
episode.
680
00:29:08.690 --> 00:29:10.170
Professor Fred Watson: Sounds great. Thanks, Andrew.
681
00:29:10.170 --> 00:29:11.770
Andrew Dunkley: Professor Fred Watson Watson, astronomer at
682
00:29:11.770 --> 00:29:13.850
large. And thanks to Huw in the studio, who
683
00:29:13.850 --> 00:29:15.530
couldn't be with us today because he's been
684
00:29:15.530 --> 00:29:17.560
expanding at an accelerating rate. So he was.
685
00:29:17.710 --> 00:29:19.910
Enter the gym. And from me, Andrew Dunkley.
686
00:29:19.910 --> 00:29:21.550
Thanks for your company. We'll see you on the
687
00:29:21.550 --> 00:29:23.070
next episode of Space Nuts.
688
00:29:23.070 --> 00:29:23.710
Professor Fred Watson: Bye. Bye.
689
00:29:24.330 --> 00:29:27.110
Andrew Dunkley: Uh, you'll be listening to the Space Nuts
690
00:29:27.110 --> 00:29:30.070
podcast, available at
691
00:29:30.070 --> 00:29:32.030
Apple Podcasts, Spotify,
692
00:29:32.190 --> 00:29:34.950
iHeartRadio or your favourite podcast
693
00:29:34.950 --> 00:29:36.670
player. You can also stream on
694
00:29:36.670 --> 00:29:38.990
demand@bytes.comm this
695
00:29:38.990 --> 00:29:41.390
Professor Fred Watson: has been another quality podcast production
696
00:29:41.390 --> 00:29:42.910
from bytes.um.com.
