1
00:00:08,160 --> 00:00:11,879
Speaker 1: Isaac Newton was very clearly a smart guy. He made

2
00:00:12,000 --> 00:00:15,800
Speaker 1: huge leaps and understanding of optics and gravity and calculus.

3
00:00:16,239 --> 00:00:19,239
Speaker 1: But one of the biggest mental steps he took was

4
00:00:19,280 --> 00:00:22,200
Speaker 1: applying the laws that we have down here on Earth

5
00:00:22,680 --> 00:00:27,000
Speaker 1: to what's going on up there in space. His biggest

6
00:00:27,120 --> 00:00:30,960
Speaker 1: idea was probably that there should only be one idea,

7
00:00:31,560 --> 00:00:35,800
Speaker 1: one set of physical laws, but that it should cover everything.

8
00:00:36,720 --> 00:00:40,320
Speaker 1: And here we sit on a tiny, isolated rocking space

9
00:00:40,800 --> 00:00:44,839
Speaker 1: trying to make rules that explain the whole universe, only

10
00:00:44,880 --> 00:00:47,400
Speaker 1: able to see a tiny little bit of it and

11
00:00:47,479 --> 00:00:51,080
Speaker 1: study with our hands and our tools an even smaller bit.

12
00:00:51,920 --> 00:00:55,040
Speaker 1: It's sort of like visiting the zoo and only seeing

13
00:00:55,080 --> 00:00:58,120
Speaker 1: the insect exhibit, but then making laws that are supposed

14
00:00:58,120 --> 00:01:02,320
Speaker 1: to describe how elephants and amphibian's work. So ask yourself,

15
00:01:02,640 --> 00:01:21,920
Speaker 1: how likely is it that our ideas are actually universal? Hi?

16
00:01:22,240 --> 00:01:25,200
Speaker 1: I'm Daniel. I'm a particle physicist, and I have an

17
00:01:25,240 --> 00:01:30,360
Speaker 1: infinite list of questions about our probably infinite universe. And

18
00:01:30,440 --> 00:01:34,280
Speaker 1: welcome to the podcast. Daniel and Jorge explain the universe

19
00:01:34,360 --> 00:01:37,560
Speaker 1: of production of My Heart Radio. We talk about things

20
00:01:37,600 --> 00:01:40,360
Speaker 1: happening far far away, and we talk about things happening

21
00:01:40,440 --> 00:01:43,480
Speaker 1: under your feet. We ask questions about the very beginning

22
00:01:43,520 --> 00:01:46,319
Speaker 1: of time, and we ask questions about the very nature

23
00:01:46,360 --> 00:01:49,440
Speaker 1: of time and the end of time. We ask questions

24
00:01:49,440 --> 00:01:53,360
Speaker 1: about the entire universe because we think that curiosity and

25
00:01:53,400 --> 00:01:57,720
Speaker 1: asking questions is universal. We think everybody out there has questions,

26
00:01:57,960 --> 00:02:01,280
Speaker 1: and everybody deserves to have their question is explored, if

27
00:02:01,360 --> 00:02:04,480
Speaker 1: not answered, because not every question has an answer to

28
00:02:04,560 --> 00:02:08,040
Speaker 1: it so far, but questions really are at the heart

29
00:02:08,120 --> 00:02:11,680
Speaker 1: of science, and that's why on today's program, while my

30
00:02:11,800 --> 00:02:15,240
Speaker 1: friend collaborator and co host Jorge can't be here today,

31
00:02:15,600 --> 00:02:18,400
Speaker 1: I'm gonna take the opportunity to gather up a bunch

32
00:02:18,440 --> 00:02:22,280
Speaker 1: of questions asked from listeners and try to answer them.

33
00:02:22,520 --> 00:02:25,760
Speaker 1: We're always asking people please send us your questions. If

34
00:02:25,760 --> 00:02:29,160
Speaker 1: there's something you don't understand about the universe, something you've

35
00:02:29,200 --> 00:02:32,200
Speaker 1: read and didn't quite follow, something you've thought through that

36
00:02:32,280 --> 00:02:34,840
Speaker 1: didn't quite make sense to you, please send it to

37
00:02:34,919 --> 00:02:38,560
Speaker 1: us because we cherish those questions. Those questions are our

38
00:02:38,680 --> 00:02:42,600
Speaker 1: opportunity to help people understand what we do and what

39
00:02:42,680 --> 00:02:46,200
Speaker 1: we don't know about the universe. And remember that everybody

40
00:02:46,240 --> 00:02:49,800
Speaker 1: out there who was asking questions is basically an armchair physicist.

41
00:02:50,200 --> 00:02:53,080
Speaker 1: If you are trying to wrap your mind around the universe,

42
00:02:53,080 --> 00:02:56,360
Speaker 1: you're trying to make one holistic sense of understanding of

43
00:02:56,400 --> 00:02:59,640
Speaker 1: how things work. If you've read something somewhere and you're

44
00:02:59,639 --> 00:03:01,639
Speaker 1: trying to make it agree with something else you used

45
00:03:01,680 --> 00:03:03,920
Speaker 1: to think, or something you read somewhere else, or something

46
00:03:03,960 --> 00:03:07,400
Speaker 1: your friend told you, that's doing physics. You're trying to

47
00:03:07,960 --> 00:03:11,560
Speaker 1: unify your understanding. You're saying, I need to have one

48
00:03:11,919 --> 00:03:17,799
Speaker 1: set of ideas that describes the entire universe that explains everything. Now,

49
00:03:17,840 --> 00:03:20,280
Speaker 1: of course, we don't know if it's possible to describe

50
00:03:20,280 --> 00:03:23,240
Speaker 1: the entire universities in one set of laws. We don't

51
00:03:23,240 --> 00:03:25,359
Speaker 1: know if it's possible for humans to do it, or

52
00:03:25,400 --> 00:03:29,720
Speaker 1: maybe take some super alien intelligence or some artificial intelligence

53
00:03:30,000 --> 00:03:33,520
Speaker 1: with super incredible powers. But that doesn't stop us from trying,

54
00:03:33,960 --> 00:03:36,960
Speaker 1: because it's our dream that we could encapsulate the entire

55
00:03:37,000 --> 00:03:40,920
Speaker 1: workings of the universe somehow inside the puny human mind.

56
00:03:41,440 --> 00:03:43,800
Speaker 1: So please, if we haven't answered a question that's in

57
00:03:43,880 --> 00:03:47,160
Speaker 1: your mind, send it to us two questions at Daniel

58
00:03:47,200 --> 00:03:50,440
Speaker 1: and Jorge dot com. We answer all of our emails

59
00:03:50,480 --> 00:03:53,760
Speaker 1: and sometimes we put those questions here on the podcast.

60
00:03:54,200 --> 00:03:56,119
Speaker 1: But If you don't like writing emails or you don't

61
00:03:56,120 --> 00:03:58,840
Speaker 1: want to engage with us on Twitter, we have other

62
00:03:58,920 --> 00:04:02,000
Speaker 1: ways to get your questions answered. You can check out

63
00:04:02,080 --> 00:04:05,680
Speaker 1: Daniel's public office hours, look at the website for the podcast,

64
00:04:05,800 --> 00:04:08,840
Speaker 1: or go to sites dot you see I dot E,

65
00:04:09,000 --> 00:04:12,120
Speaker 1: d U slash Daniel, you'll see a link. Therefore, when

66
00:04:12,240 --> 00:04:15,680
Speaker 1: Daniel has public office hours, he hangs out on Zoom

67
00:04:15,720 --> 00:04:18,960
Speaker 1: and answers questions about physics and life and the universe

68
00:04:19,040 --> 00:04:22,320
Speaker 1: and everything from people like you, people who have thought

69
00:04:22,320 --> 00:04:25,200
Speaker 1: about stuff and have a nagging little question that they

70
00:04:25,240 --> 00:04:27,880
Speaker 1: can't find the answer to using Google and they just

71
00:04:28,040 --> 00:04:30,880
Speaker 1: have to know how it works, all right, And today

72
00:04:30,960 --> 00:04:34,279
Speaker 1: on the podcast will be answering questions from listeners from

73
00:04:34,320 --> 00:04:37,800
Speaker 1: all over the world. Our first question comes to us

74
00:04:38,000 --> 00:04:42,440
Speaker 1: from Germany. I have a question concerning doc energy. Does

75
00:04:42,440 --> 00:04:46,440
Speaker 1: it violate the law of energy conservation? It seems to

76
00:04:46,480 --> 00:04:50,119
Speaker 1: come out of nothing and getting bigger and bigger. Thanks

77
00:04:50,160 --> 00:04:53,280
Speaker 1: a lot, all right, Thank you and Juras from Germany.

78
00:04:53,279 --> 00:04:55,520
Speaker 1: This is a beautiful example of what I was just

79
00:04:55,640 --> 00:04:59,200
Speaker 1: talking about about applying our ideas about how things work

80
00:04:59,240 --> 00:05:01,640
Speaker 1: in the universe and taking them to the extreme and

81
00:05:01,680 --> 00:05:06,200
Speaker 1: saying does this really work everywhere. Is this a universal law?

82
00:05:06,560 --> 00:05:08,240
Speaker 1: Is there some part of the universe that seemed to

83
00:05:08,279 --> 00:05:11,359
Speaker 1: break this rule which would make it not universal? And

84
00:05:11,400 --> 00:05:13,839
Speaker 1: one of the most fundamental things we thought we understood

85
00:05:13,880 --> 00:05:18,760
Speaker 1: about the universe was this idea of energy conservation. Of course,

86
00:05:18,800 --> 00:05:21,480
Speaker 1: a hundred years ago, we thought other things were conserved,

87
00:05:21,560 --> 00:05:24,880
Speaker 1: like mass. We thought that stuff was conserved, that you

88
00:05:24,880 --> 00:05:27,000
Speaker 1: could move it around, you could switch it up, you

89
00:05:27,040 --> 00:05:30,160
Speaker 1: could rearrange it like lego bricks, but you couldn't create

90
00:05:30,279 --> 00:05:33,719
Speaker 1: or destroy mass. Now, of course we know that's not true.

91
00:05:34,240 --> 00:05:36,720
Speaker 1: And the lesson we learned from that, from the lack

92
00:05:36,839 --> 00:05:40,240
Speaker 1: of mass conservation, is that mass is not a fundamental

93
00:05:40,320 --> 00:05:43,200
Speaker 1: element of the universe. It can be created, it can

94
00:05:43,200 --> 00:05:45,560
Speaker 1: be destroyed. You can have more mass, you can have

95
00:05:45,680 --> 00:05:48,840
Speaker 1: less mass. It's not something which we should consider sort

96
00:05:48,839 --> 00:05:52,480
Speaker 1: of on the list of fundamental descriptors of the universe.

97
00:05:52,680 --> 00:05:56,080
Speaker 1: And that's important because what we're doing with physics is

98
00:05:56,160 --> 00:05:59,920
Speaker 1: trying to drill down to the most fundamental, the simplest description,

99
00:06:00,279 --> 00:06:03,000
Speaker 1: Because we imagine if one day we are looking at

100
00:06:03,000 --> 00:06:05,720
Speaker 1: a list of the fundamental elements of the universe, of

101
00:06:05,800 --> 00:06:09,120
Speaker 1: things that define the universe and completely explain the universe

102
00:06:09,440 --> 00:06:12,680
Speaker 1: that we will somehow be revealing the nature of the universe.

103
00:06:12,920 --> 00:06:15,520
Speaker 1: So we don't want anything on that list which isn't fundamental.

104
00:06:15,839 --> 00:06:18,240
Speaker 1: You don't want that list to have like strings and

105
00:06:18,440 --> 00:06:21,280
Speaker 1: energy and then ice cream, right because ice cream can

106
00:06:21,320 --> 00:06:24,679
Speaker 1: be described by all the other elements already on the list.

107
00:06:24,920 --> 00:06:26,600
Speaker 1: So we want to strip it down to a sort

108
00:06:26,640 --> 00:06:30,000
Speaker 1: of most minimal set of rules, most minimal set of

109
00:06:30,040 --> 00:06:33,599
Speaker 1: things you need to describe the universe. Having left our

110
00:06:33,720 --> 00:06:36,719
Speaker 1: list of things that describe how the universe works tells

111
00:06:36,800 --> 00:06:39,719
Speaker 1: us something about what the universe isn't. It isn't a

112
00:06:39,760 --> 00:06:44,640
Speaker 1: place that cares so much about mass. However, energy seems

113
00:06:44,680 --> 00:06:48,120
Speaker 1: to have retained its exalted stature as a quantity which

114
00:06:48,240 --> 00:06:51,960
Speaker 1: is conserved. And you know what is energy conservation anyway.

115
00:06:52,160 --> 00:06:55,640
Speaker 1: Energy conservation is the statement that you can calculate this

116
00:06:55,720 --> 00:06:58,240
Speaker 1: thing about nature. You add up all the energy in

117
00:06:58,279 --> 00:07:00,919
Speaker 1: a system, all the ways that things can move or

118
00:07:00,960 --> 00:07:03,800
Speaker 1: wiggle or store energy, and then you let a bunch

119
00:07:03,800 --> 00:07:07,719
Speaker 1: of stuff happen. Things collide, things explode, things slash around, whatever,

120
00:07:08,240 --> 00:07:10,080
Speaker 1: and you add up all the energy again and it

121
00:07:10,120 --> 00:07:13,160
Speaker 1: should be the same. So it's sort of a statement

122
00:07:13,200 --> 00:07:16,040
Speaker 1: that energy is fundamental to the universe. You can move

123
00:07:16,080 --> 00:07:18,160
Speaker 1: it around, that you can change it from one thing

124
00:07:18,200 --> 00:07:20,640
Speaker 1: to another, but that you can't get rid of it,

125
00:07:20,680 --> 00:07:23,320
Speaker 1: that it's inherent, that it's fundamental, that it's a deep

126
00:07:23,560 --> 00:07:27,920
Speaker 1: part of what makes the universe the universe. So if

127
00:07:28,040 --> 00:07:31,320
Speaker 1: energy is not conserved, then that tells you what It

128
00:07:31,400 --> 00:07:34,679
Speaker 1: tells you that maybe energy isn't actually important to the universe.

129
00:07:35,040 --> 00:07:39,000
Speaker 1: Maybe energy isn't on that list of fundamental elements we

130
00:07:39,080 --> 00:07:42,720
Speaker 1: think are needed to define and describe the universe. So

131
00:07:42,800 --> 00:07:45,520
Speaker 1: Andreas is doing exactly what a physicists should be doing,

132
00:07:45,920 --> 00:07:50,160
Speaker 1: thinking about ways energy conservation might be violated. We know,

133
00:07:50,240 --> 00:07:53,240
Speaker 1: for example, that if you roll a boulder up a hill,

134
00:07:53,640 --> 00:07:56,400
Speaker 1: you're spending energy in your muscles, and that energy then

135
00:07:56,440 --> 00:08:00,040
Speaker 1: goes into the position of the boulder. It's gravitation in

136
00:08:00,120 --> 00:08:02,600
Speaker 1: a location is more distant from the Earth, And if

137
00:08:02,600 --> 00:08:04,240
Speaker 1: you let go of the boulder and run it back

138
00:08:04,280 --> 00:08:07,119
Speaker 1: down the hill, the energy goes from that potential energy

139
00:08:07,120 --> 00:08:10,200
Speaker 1: of the boulder into its motion, into its kinetic energy.

140
00:08:10,440 --> 00:08:13,880
Speaker 1: So we have lots of examples of where energy is conserved,

141
00:08:13,920 --> 00:08:17,000
Speaker 1: and people probably expect to hear that energy is conserved

142
00:08:17,040 --> 00:08:19,640
Speaker 1: everywhere in the universe and there's some way you can

143
00:08:19,680 --> 00:08:22,760
Speaker 1: do the calculation to figure out that energy is actually

144
00:08:22,760 --> 00:08:25,760
Speaker 1: conserved in the case of dark energy. So what is

145
00:08:25,800 --> 00:08:29,000
Speaker 1: he talking about. Remember that dark energy is not something

146
00:08:29,000 --> 00:08:33,680
Speaker 1: that's very well understood. It's not a theoretically well formulated idea.

147
00:08:34,040 --> 00:08:37,960
Speaker 1: It's more an observation. It's an observation that the universe

148
00:08:38,160 --> 00:08:42,480
Speaker 1: is expanding and that that expansion is accelerating. So we

149
00:08:42,559 --> 00:08:44,600
Speaker 1: look out into the universe and we see that the

150
00:08:44,720 --> 00:08:48,480
Speaker 1: universe is expanding, and not only are things moving away

151
00:08:48,520 --> 00:08:51,199
Speaker 1: from us, but the speed at which they're moving away

152
00:08:51,200 --> 00:08:54,719
Speaker 1: from us is increasing. You might expect the opposite to

153
00:08:54,720 --> 00:08:57,800
Speaker 1: be happening. In fact, physicists expected the opposite to be

154
00:08:57,840 --> 00:09:00,600
Speaker 1: happening for a long time, that things were moving away

155
00:09:00,600 --> 00:09:03,720
Speaker 1: from us, but that speed might be decreasing as gravity

156
00:09:03,840 --> 00:09:06,880
Speaker 1: very slowly pulls on things and tugs them back together.

157
00:09:07,280 --> 00:09:11,400
Speaker 1: After the Big Bang, what we actually found about years

158
00:09:11,400 --> 00:09:13,679
Speaker 1: ago now is that things are moving away from us

159
00:09:13,800 --> 00:09:16,840
Speaker 1: faster and faster, and we don't have an explanation for

160
00:09:17,000 --> 00:09:20,120
Speaker 1: why this is. All we have is the observation that

161
00:09:20,240 --> 00:09:24,160
Speaker 1: it is happening. There are a few sort of proto explanations.

162
00:09:24,160 --> 00:09:26,959
Speaker 1: There are ideas for what might describe it, but none

163
00:09:26,960 --> 00:09:30,000
Speaker 1: of those ideas really work so far. One of those

164
00:09:30,040 --> 00:09:33,719
Speaker 1: ideas is that there is energy in empty space, that

165
00:09:33,880 --> 00:09:37,360
Speaker 1: all of space has energy in it. For example, the

166
00:09:37,440 --> 00:09:40,920
Speaker 1: Higgs Boson field is a quantum field that's in all

167
00:09:40,960 --> 00:09:43,840
Speaker 1: of space, and even when it's at its most relaxed,

168
00:09:43,840 --> 00:09:47,400
Speaker 1: at its lowest level, it doesn't have zero energy in it.

169
00:09:47,840 --> 00:09:50,200
Speaker 1: That means that when you create a piece of space,

170
00:09:50,760 --> 00:09:54,160
Speaker 1: you're creating a Higgs Boson field that has energy in it.

171
00:09:54,559 --> 00:09:56,680
Speaker 1: And this is what Andreas is talking about. That dark

172
00:09:56,800 --> 00:10:01,040
Speaker 1: energy creates more space because it's not just moving things

173
00:10:01,160 --> 00:10:06,400
Speaker 1: through space. It's creating new space between galaxies. It's stretching

174
00:10:06,440 --> 00:10:09,560
Speaker 1: that space. It's making new space. And when you make

175
00:10:09,600 --> 00:10:13,400
Speaker 1: new space, it comes with new energy. So it seems

176
00:10:13,400 --> 00:10:17,400
Speaker 1: an awful law like dark energy is in fact violating

177
00:10:17,640 --> 00:10:21,480
Speaker 1: conservation of energy because as you make more space, you

178
00:10:21,520 --> 00:10:24,640
Speaker 1: are increasing the total volume of the universe. And if

179
00:10:24,679 --> 00:10:28,280
Speaker 1: every cubic meter of space has a certain energy, then

180
00:10:28,320 --> 00:10:31,320
Speaker 1: by increasing the volume of space, you're increasing the total

181
00:10:31,600 --> 00:10:35,559
Speaker 1: energy in the universe. How does that not violate conservation

182
00:10:35,679 --> 00:10:39,640
Speaker 1: of energy? Well, in fact it does, and as energy

183
00:10:39,720 --> 00:10:43,880
Speaker 1: conservation is not guaranteed in our universe, and this is

184
00:10:43,960 --> 00:10:47,680
Speaker 1: one example. As space expands, the energy increases because you

185
00:10:47,720 --> 00:10:51,600
Speaker 1: get more dark energy, which means overall more energy. There's

186
00:10:51,640 --> 00:10:55,440
Speaker 1: also another example, which is that energy can decrease when

187
00:10:55,480 --> 00:10:59,319
Speaker 1: space expands. If you have a photon flying through space,

188
00:10:59,440 --> 00:11:03,040
Speaker 1: for example, from the cosmic microwave background radiation, then what

189
00:11:03,160 --> 00:11:07,320
Speaker 1: happens when space expands. When space stretches, Well, that photon

190
00:11:07,520 --> 00:11:11,440
Speaker 1: gets red shifted. Its wavelength gets longer because space has

191
00:11:11,480 --> 00:11:15,320
Speaker 1: gotten stretched. Right, Imagine you draw a wiggle on a

192
00:11:15,360 --> 00:11:17,720
Speaker 1: sheet of paper and then you stretch that paper, the

193
00:11:17,800 --> 00:11:21,559
Speaker 1: wavelength gets longer. But for photons, the energy and the

194
00:11:21,600 --> 00:11:26,120
Speaker 1: wavelength are very closely connected. One defines the other. Higher

195
00:11:26,280 --> 00:11:29,400
Speaker 1: energy photons are those with shorter wavelengths, and so if

196
00:11:29,440 --> 00:11:32,839
Speaker 1: you stretch the wavelength of a photon, then you decrease

197
00:11:32,960 --> 00:11:37,160
Speaker 1: its energy. Where does that energy go. It doesn't go anywhere.

198
00:11:37,200 --> 00:11:40,840
Speaker 1: It just goes away. So we have two examples of

199
00:11:40,920 --> 00:11:44,920
Speaker 1: the violation of the conservation of energy, both coming from

200
00:11:45,000 --> 00:11:48,439
Speaker 1: space expanding. And that's the clue as the clue that

201
00:11:48,480 --> 00:11:52,280
Speaker 1: tells us why energy might not be conserved, and most

202
00:11:52,320 --> 00:11:54,880
Speaker 1: of the conservation laws in physics, most of the things

203
00:11:54,920 --> 00:11:57,439
Speaker 1: that are conserved that are not changed when you let

204
00:11:57,440 --> 00:12:00,520
Speaker 1: things bang around and smash into each other come from

205
00:12:00,640 --> 00:12:04,280
Speaker 1: some kind of symmetry. This is very deep result in

206
00:12:04,320 --> 00:12:08,240
Speaker 1: physics called Noether's theorem from Emily Norther, who developed it

207
00:12:08,280 --> 00:12:11,120
Speaker 1: more than a hundred years ago, and she discovered that

208
00:12:11,240 --> 00:12:13,840
Speaker 1: every time you have a symmetry, like every time you

209
00:12:13,880 --> 00:12:16,640
Speaker 1: can take space and rotate it and still get the

210
00:12:16,679 --> 00:12:20,000
Speaker 1: same laws of physics, or move your coordinate system over

211
00:12:20,040 --> 00:12:23,120
Speaker 1: by ten kilometers and still expect the same law of physics,

212
00:12:23,200 --> 00:12:26,120
Speaker 1: or fast forward things by a hundred years and still

213
00:12:26,120 --> 00:12:28,600
Speaker 1: expect the same laws of physics. Every time you can

214
00:12:28,640 --> 00:12:32,280
Speaker 1: apply some sort of translation or rotation to the universe

215
00:12:32,679 --> 00:12:35,160
Speaker 1: and not see any change in the law of physics.

216
00:12:35,160 --> 00:12:38,520
Speaker 1: That's a symmetry, and every symmetry has some kind of

217
00:12:38,640 --> 00:12:42,240
Speaker 1: conservation law that comes from it. So, for example, the

218
00:12:42,280 --> 00:12:45,400
Speaker 1: fact that space is the same everywhere, that the laws

219
00:12:45,440 --> 00:12:48,240
Speaker 1: of physics apply here and somewhere else, that gives you

220
00:12:48,280 --> 00:12:51,120
Speaker 1: the law of conservation of momentum, and the fact that

221
00:12:51,160 --> 00:12:54,760
Speaker 1: you can rotate space, that there's no preferred direction, that

222
00:12:54,800 --> 00:12:57,920
Speaker 1: physics should work the same in every direction. That's why

223
00:12:57,960 --> 00:13:00,920
Speaker 1: we have conservation of angular moment them and it's the

224
00:13:00,920 --> 00:13:04,040
Speaker 1: symmetry of the universe with respect to time is what

225
00:13:04,160 --> 00:13:07,720
Speaker 1: gives us conservation of energy. The fact that it seems

226
00:13:07,720 --> 00:13:09,880
Speaker 1: like the universe should work the same now as it

227
00:13:09,920 --> 00:13:12,080
Speaker 1: does in a hundred years and a thousand years ago

228
00:13:12,840 --> 00:13:16,920
Speaker 1: is what gives us conservation of energy. But that only

229
00:13:17,000 --> 00:13:20,160
Speaker 1: works if we expect the same rules to apply now

230
00:13:20,320 --> 00:13:23,040
Speaker 1: and in a hundred years and in a thousand years.

231
00:13:23,080 --> 00:13:26,720
Speaker 1: That only works if space is essentially static, if it's

232
00:13:26,760 --> 00:13:29,760
Speaker 1: not changing, if space is the same now and in

233
00:13:29,800 --> 00:13:32,800
Speaker 1: a hundred years and a thousand years ago. But we

234
00:13:32,960 --> 00:13:36,880
Speaker 1: know that it's not because we know that space is expanding.

235
00:13:37,200 --> 00:13:39,760
Speaker 1: So conservation of energy is something we expect to apply

236
00:13:39,920 --> 00:13:43,800
Speaker 1: in a static universe where space is not changing. In

237
00:13:43,840 --> 00:13:48,280
Speaker 1: our universe, however, space is expanding, and it's expanding quite rapidly.

238
00:13:48,559 --> 00:13:51,720
Speaker 1: Expansion is not a small thing in our universe. Seventy

239
00:13:51,880 --> 00:13:55,320
Speaker 1: percent of the energy budget of the universe goes towards

240
00:13:55,320 --> 00:13:59,280
Speaker 1: the expansion of space time, so when space is expanding,

241
00:13:59,679 --> 00:14:02,760
Speaker 1: energy is not concerned. Now, we did a whole podcast

242
00:14:02,800 --> 00:14:05,720
Speaker 1: episode about this conservation of energy, and there is one

243
00:14:05,720 --> 00:14:08,319
Speaker 1: way that you can sort of rig up a calculation

244
00:14:08,679 --> 00:14:11,520
Speaker 1: in which you get negative energy from gravity that might

245
00:14:11,559 --> 00:14:15,000
Speaker 1: account for some of this, but most cosmologists think it's

246
00:14:15,000 --> 00:14:17,720
Speaker 1: sort of a band aid and theoretically doesn't hold together.

247
00:14:17,960 --> 00:14:19,920
Speaker 1: And you're interested in more details and not check on

248
00:14:19,960 --> 00:14:24,600
Speaker 1: our whole podcast episode about conservation of energy. But congrats

249
00:14:24,600 --> 00:14:27,640
Speaker 1: to you Andrea's for figuring this out, for applying your

250
00:14:27,760 --> 00:14:32,040
Speaker 1: understanding of physics to crazy scenarios far beyond your living

251
00:14:32,120 --> 00:14:35,240
Speaker 1: room and coming up with a contradiction. And those contradictions

252
00:14:35,240 --> 00:14:38,200
Speaker 1: are what leads to questions, and those questions are would

253
00:14:38,280 --> 00:14:42,120
Speaker 1: lead us to deeper understandings about the universe. So keep

254
00:14:42,160 --> 00:14:45,840
Speaker 1: asking questions. Thanks very much for sending that in. All right,

255
00:14:45,960 --> 00:14:48,360
Speaker 1: I have more questions from listeners I want to get

256
00:14:48,360 --> 00:15:04,880
Speaker 1: to but first let's take a quick break. All right,

257
00:15:04,960 --> 00:15:07,200
Speaker 1: we're back, and this is Daniel and I'm here today

258
00:15:07,200 --> 00:15:11,000
Speaker 1: on my own answering questions from listeners. I love when

259
00:15:11,000 --> 00:15:14,040
Speaker 1: people write to us. They send us amazing questions, things

260
00:15:14,080 --> 00:15:16,400
Speaker 1: that they have been thinking about the universe and that

261
00:15:16,480 --> 00:15:19,440
Speaker 1: they can't figure out via Google, and they don't happen

262
00:15:19,480 --> 00:15:22,200
Speaker 1: to know a physicists they can ask these questions of,

263
00:15:22,480 --> 00:15:24,600
Speaker 1: so they send them to us. And I have a

264
00:15:24,640 --> 00:15:28,080
Speaker 1: bit of an embarrassing backlog of questions from listeners that

265
00:15:28,160 --> 00:15:30,720
Speaker 1: I really want to get to, and so while Jorge

266
00:15:30,800 --> 00:15:33,040
Speaker 1: isn't here, I'm gonna plow through a bunch of these

267
00:15:33,080 --> 00:15:35,880
Speaker 1: and try to catch up to our backlog. So thanks

268
00:15:35,960 --> 00:15:38,680
Speaker 1: very much to everybody who's senting questions. Here's the next

269
00:15:38,720 --> 00:15:41,200
Speaker 1: question we're gonna answer today. Hey guys, this is Jeff

270
00:15:41,240 --> 00:15:44,800
Speaker 1: from Los Angeles. My question relates to the period of

271
00:15:44,880 --> 00:15:47,960
Speaker 1: inflation after the Big Bang. I know you said the

272
00:15:48,080 --> 00:15:51,120
Speaker 1: universe expanded by a factor of ten to the thirty

273
00:15:51,320 --> 00:15:53,040
Speaker 1: in the small amount of time of ten to the

274
00:15:53,080 --> 00:15:56,360
Speaker 1: minus thirty. How do you explain that if nothing can

275
00:15:56,400 --> 00:15:59,520
Speaker 1: travel faster than the speed of light. I also want

276
00:15:59,520 --> 00:16:02,720
Speaker 1: to know if the edges of the universe were expanding

277
00:16:02,760 --> 00:16:06,960
Speaker 1: at this crazy fast speed, and it was expanding through nothing,

278
00:16:07,440 --> 00:16:10,960
Speaker 1: then what's slowing it down? Why isn't the universe still

279
00:16:11,000 --> 00:16:14,560
Speaker 1: expanding at that crazy rate of inflation? I look forward

280
00:16:14,560 --> 00:16:16,600
Speaker 1: to the answer. Thanks a lot, all right, Jeff from

281
00:16:16,720 --> 00:16:19,880
Speaker 1: l A who's basically an amateur cosmologist. Thank you for

282
00:16:19,960 --> 00:16:22,880
Speaker 1: thinking deeply about the universe and for trying to reconcile

283
00:16:22,960 --> 00:16:25,560
Speaker 1: what you've heard about the early days of the universe

284
00:16:25,600 --> 00:16:28,960
Speaker 1: with what you understand about how the universe works. Again,

285
00:16:29,280 --> 00:16:33,080
Speaker 1: that's exactly what doing physics means, so let's get to it.

286
00:16:33,160 --> 00:16:36,000
Speaker 1: The first part of your question was if the universe

287
00:16:36,040 --> 00:16:39,360
Speaker 1: expanded by a factor ten to the thirty intended to

288
00:16:39,440 --> 00:16:43,280
Speaker 1: minus thirty questions, how is that possible? Given that we

289
00:16:43,320 --> 00:16:46,320
Speaker 1: know that there's a very hard limit on how fast

290
00:16:46,400 --> 00:16:49,840
Speaker 1: things can move through space, which is the speed of light.

291
00:16:50,040 --> 00:16:52,640
Speaker 1: It's a great question. Another way to think about this

292
00:16:52,720 --> 00:16:56,760
Speaker 1: question is how did the universe get so big? I mean,

293
00:16:56,760 --> 00:17:00,560
Speaker 1: the universe is about fourteen billion years old, but the

294
00:17:00,640 --> 00:17:04,600
Speaker 1: size of the observable universe, the distance to the furthest

295
00:17:04,680 --> 00:17:07,560
Speaker 1: things that we can see, you might expect to be

296
00:17:07,920 --> 00:17:11,040
Speaker 1: fourteen billion years times the speed of light, which would

297
00:17:11,040 --> 00:17:15,119
Speaker 1: be fourteen billion light years, but it's not. It's much

298
00:17:15,200 --> 00:17:17,919
Speaker 1: much further than that. We can see things that are

299
00:17:17,960 --> 00:17:22,040
Speaker 1: about forty five billion light years away, So the size

300
00:17:22,080 --> 00:17:26,119
Speaker 1: of the observable universe is about ninety billion light years wide.

301
00:17:26,520 --> 00:17:29,240
Speaker 1: How is that possible? How is it possible to see

302
00:17:29,280 --> 00:17:32,960
Speaker 1: things which are further away than the speed of light

303
00:17:33,160 --> 00:17:35,479
Speaker 1: times the age of the universe. How did that stuff

304
00:17:35,680 --> 00:17:39,040
Speaker 1: get there so far? How did the universe expand faster

305
00:17:39,160 --> 00:17:42,000
Speaker 1: than the speed of light. So it's a wonderful question.

306
00:17:42,280 --> 00:17:45,160
Speaker 1: And the key concept you need to know to understand

307
00:17:45,200 --> 00:17:48,960
Speaker 1: this is that there's a difference between moving through space

308
00:17:49,480 --> 00:17:53,320
Speaker 1: and expansion of space. So moving through space is the

309
00:17:53,400 --> 00:17:55,840
Speaker 1: kind of thing you're familiar with. You move through space

310
00:17:55,920 --> 00:17:58,040
Speaker 1: every day. When you get out of your bed and

311
00:17:58,080 --> 00:17:59,680
Speaker 1: you go for a glass of water in the middle

312
00:17:59,680 --> 00:18:02,359
Speaker 1: of the night, you are moving through space. When you

313
00:18:02,400 --> 00:18:04,800
Speaker 1: throw a baseball really really fast. When you get on

314
00:18:04,840 --> 00:18:07,440
Speaker 1: your spaceship and you try to travel to a nearby star,

315
00:18:07,840 --> 00:18:10,040
Speaker 1: you are moving through space. When you turn on your

316
00:18:10,040 --> 00:18:12,679
Speaker 1: flashlight and you shine it at the moon, you are

317
00:18:12,720 --> 00:18:16,200
Speaker 1: sending photons through space to the moon. And there is

318
00:18:16,240 --> 00:18:19,120
Speaker 1: in fact a very hard limit on the speed at

319
00:18:19,160 --> 00:18:22,560
Speaker 1: which things can move through space, and that's the speed

320
00:18:22,560 --> 00:18:25,640
Speaker 1: of light. In a vacuum. Nothing, no information at all,

321
00:18:25,720 --> 00:18:29,080
Speaker 1: can move through space faster than the speed of light.

322
00:18:29,359 --> 00:18:33,480
Speaker 1: That includes neutrinos, that includes everything, that includes quantum information.

323
00:18:33,760 --> 00:18:36,840
Speaker 1: It's a very tough rule, and breaking it when undermine

324
00:18:36,880 --> 00:18:40,639
Speaker 1: special relativity, which we're pretty sure as an accurate description

325
00:18:40,720 --> 00:18:44,200
Speaker 1: of space time in our universe. All right, So that's

326
00:18:44,240 --> 00:18:49,240
Speaker 1: moving through space, but that's different from the expansion of space.

327
00:18:49,359 --> 00:18:53,880
Speaker 1: The expansion of space means stretching space itself. So imagine,

328
00:18:53,920 --> 00:18:56,840
Speaker 1: for example, you are one meter apart from your friend.

329
00:18:57,119 --> 00:18:59,040
Speaker 1: You have a meter stick, and you measure exactly how

330
00:18:59,080 --> 00:19:01,400
Speaker 1: far apart you are. You could take a step back.

331
00:19:01,760 --> 00:19:04,800
Speaker 1: That would be moving through space. But you could also

332
00:19:05,200 --> 00:19:08,840
Speaker 1: expand the space between you. You could take the very

333
00:19:09,000 --> 00:19:12,359
Speaker 1: universe and stretch it so that now you guys are

334
00:19:12,440 --> 00:19:18,440
Speaker 1: two meters apart without having moved through space at all. Right, Remember,

335
00:19:18,520 --> 00:19:21,520
Speaker 1: space is not just the backdrop on which things happen.

336
00:19:21,880 --> 00:19:23,920
Speaker 1: It's not the stage on which the acts of the

337
00:19:24,000 --> 00:19:28,480
Speaker 1: universe are played out on. It's a dynamical thing. It's stretchy,

338
00:19:28,760 --> 00:19:32,359
Speaker 1: it's like goo. It responds to the presence of mass

339
00:19:32,359 --> 00:19:36,959
Speaker 1: and energy. It bends, it twists, it can expand, and

340
00:19:37,040 --> 00:19:40,120
Speaker 1: it tells things how to move. So space is really

341
00:19:40,240 --> 00:19:43,159
Speaker 1: part of the universe. It's not just like some fuzzy

342
00:19:43,320 --> 00:19:47,040
Speaker 1: abstract concept, some set of glowing axes in our mind

343
00:19:47,080 --> 00:19:49,960
Speaker 1: that we just impose on the universe to try to

344
00:19:50,000 --> 00:19:52,399
Speaker 1: make sense of it. Space really can do a bunch

345
00:19:52,400 --> 00:19:55,160
Speaker 1: of weird things. You already know this because you know

346
00:19:55,520 --> 00:19:58,239
Speaker 1: that gravity is not just a force. It's actually the

347
00:19:58,320 --> 00:20:01,879
Speaker 1: curving of space. Right, The reason that the Earth goes

348
00:20:01,920 --> 00:20:04,800
Speaker 1: around the Sun is not because gravity is a force

349
00:20:04,840 --> 00:20:07,480
Speaker 1: which is tugging on it, but because the presence of

350
00:20:07,520 --> 00:20:11,200
Speaker 1: the Sun changes the shape of space in its vicinity,

351
00:20:11,480 --> 00:20:14,040
Speaker 1: so that an object moving in a straight up inertial

352
00:20:14,080 --> 00:20:17,400
Speaker 1: path will move in a circle around the Sun. That's

353
00:20:17,440 --> 00:20:21,560
Speaker 1: because space can bend and twist, changing the relative distances

354
00:20:21,640 --> 00:20:25,119
Speaker 1: between things. So, for example, a photon a beam of

355
00:20:25,240 --> 00:20:28,520
Speaker 1: light always takes the shortest path between two things, But

356
00:20:28,600 --> 00:20:31,639
Speaker 1: the shortest path between two things isn't always what you

357
00:20:31,760 --> 00:20:34,320
Speaker 1: imagine to be a straight line, because the shape of

358
00:20:34,359 --> 00:20:37,560
Speaker 1: space can be complicated between two points. The same way

359
00:20:37,560 --> 00:20:39,840
Speaker 1: an airplane going from l A to London takes the

360
00:20:39,880 --> 00:20:42,639
Speaker 1: Great Circle route right, which seems like a curve, is

361
00:20:42,680 --> 00:20:46,960
Speaker 1: actually the shortest distance between two places on a curved surface,

362
00:20:47,240 --> 00:20:50,359
Speaker 1: which is why gravity can influence even things that don't

363
00:20:50,400 --> 00:20:53,639
Speaker 1: have mass. All right, So that tells us that space

364
00:20:53,680 --> 00:20:56,679
Speaker 1: can do things, and it can stretch, and it can expand,

365
00:20:57,320 --> 00:21:00,520
Speaker 1: and so that's exactly what happened in the very early universe.

366
00:21:00,800 --> 00:21:04,320
Speaker 1: It wasn't an explosion like a tiny dot of stuff

367
00:21:04,520 --> 00:21:07,679
Speaker 1: and then everything exploded out from the center. Instead, it

368
00:21:07,760 --> 00:21:12,160
Speaker 1: was an expansion of space itself. Huge amounts of new

369
00:21:12,280 --> 00:21:17,359
Speaker 1: space were made everywhere all over the universe simultaneously. So

370
00:21:17,480 --> 00:21:19,720
Speaker 1: that doesn't make it easier to understand the fact. It

371
00:21:19,760 --> 00:21:22,960
Speaker 1: makes it even more buying boggling that this happened, That

372
00:21:23,040 --> 00:21:25,919
Speaker 1: every unit of space was blown up by a factor

373
00:21:25,960 --> 00:21:29,760
Speaker 1: of ten to the thirty intend to the minus thirty seconds.

374
00:21:30,000 --> 00:21:32,479
Speaker 1: It's an incredible moment in the history of the universe.

375
00:21:32,560 --> 00:21:35,640
Speaker 1: It's an incredible idea to even have in your mind.

376
00:21:36,160 --> 00:21:39,720
Speaker 1: Imagine coming up with this Bonker's notion and then realizing

377
00:21:39,760 --> 00:21:42,719
Speaker 1: that actually it's the story that makes the most sense

378
00:21:42,880 --> 00:21:45,080
Speaker 1: in the universe. And you might ask, well, how do

379
00:21:45,160 --> 00:21:48,040
Speaker 1: we know. How do we know that the universe expanded

380
00:21:48,119 --> 00:21:50,919
Speaker 1: in this way, that it didn't just explode from a

381
00:21:50,920 --> 00:21:54,760
Speaker 1: tiny dot and spread out through the universe. Well, answer

382
00:21:54,880 --> 00:21:57,720
Speaker 1: number one is that it would be impossible. As you say,

383
00:21:57,760 --> 00:22:00,600
Speaker 1: it's not possible for things to travel that are in

384
00:22:00,640 --> 00:22:04,119
Speaker 1: that short distance because of the limitation of the speed

385
00:22:04,160 --> 00:22:07,159
Speaker 1: of light. It's against the rules. The only way to

386
00:22:07,240 --> 00:22:09,800
Speaker 1: get things that far apart in that short amount of

387
00:22:09,840 --> 00:22:13,720
Speaker 1: time is to create space between them, is to expand

388
00:22:13,800 --> 00:22:17,840
Speaker 1: the space between everything. But it's more than that, because

389
00:22:17,880 --> 00:22:22,840
Speaker 1: Explosions and expansion look different. Explosions are like a bomb.

390
00:22:23,119 --> 00:22:26,359
Speaker 1: You push everything out from one central location and send

391
00:22:26,359 --> 00:22:29,160
Speaker 1: it flying in every direction. And if there is an explosion,

392
00:22:29,400 --> 00:22:31,879
Speaker 1: you could look at the direction things are flying and

393
00:22:31,920 --> 00:22:34,640
Speaker 1: you could track them backwards, and you could point back

394
00:22:34,680 --> 00:22:37,480
Speaker 1: to the center. Right. If you come upon an explosion,

395
00:22:37,760 --> 00:22:39,480
Speaker 1: you can look at the path of the debris and

396
00:22:39,520 --> 00:22:42,640
Speaker 1: you can figure out where the bomb was. That's not

397
00:22:42,760 --> 00:22:45,960
Speaker 1: true for an expansion, and expansion is more like a

398
00:22:46,000 --> 00:22:48,879
Speaker 1: loaf of bread rising in the oven, where everything is

399
00:22:48,920 --> 00:22:53,040
Speaker 1: growing at every point simultaneously, assuming you're not a terrible baker, right,

400
00:22:53,359 --> 00:22:55,919
Speaker 1: and that your loaf is expanding smoothly. And that's what

401
00:22:56,000 --> 00:22:58,439
Speaker 1: we see when we look out into the universe. We

402
00:22:58,480 --> 00:23:01,680
Speaker 1: see these galaxies and they are rushing away from us.

403
00:23:01,960 --> 00:23:03,880
Speaker 1: They are moving away from us, and they're moving away

404
00:23:03,880 --> 00:23:07,719
Speaker 1: from us faster and faster every year. So either we

405
00:23:07,800 --> 00:23:10,879
Speaker 1: are at the exact center of the universe by some

406
00:23:11,040 --> 00:23:15,639
Speaker 1: incredible cosmic coincidence there was an explosion and we happen

407
00:23:15,720 --> 00:23:18,719
Speaker 1: to be right at the center of it, or it

408
00:23:18,760 --> 00:23:21,600
Speaker 1: looks this way because it's an expansion, and it would

409
00:23:21,680 --> 00:23:24,520
Speaker 1: look this way at any point in the universe. See.

410
00:23:24,520 --> 00:23:27,280
Speaker 1: The way an expansion looks is that it always looks

411
00:23:27,320 --> 00:23:29,600
Speaker 1: like you're at the center of it. No matter where

412
00:23:29,640 --> 00:23:31,280
Speaker 1: you are in a loaf of bread, if you look

413
00:23:31,320 --> 00:23:34,680
Speaker 1: around you, everything is growing away from you. Imagine putting

414
00:23:34,720 --> 00:23:36,760
Speaker 1: a bunch of chocolate chips into your loaf of bread

415
00:23:37,040 --> 00:23:40,240
Speaker 1: and tracking their emotion everywhere inside the loaf of bread,

416
00:23:40,280 --> 00:23:42,840
Speaker 1: of course, except for the crust. You would see this

417
00:23:43,000 --> 00:23:46,119
Speaker 1: chocolate chips moving away from you. So that's what we see.

418
00:23:46,400 --> 00:23:49,480
Speaker 1: We see that the universe is expanding, not that it's

419
00:23:49,520 --> 00:23:52,639
Speaker 1: exploding out from a tiny dot. And this expansion is

420
00:23:52,680 --> 00:23:55,159
Speaker 1: actually really important to sort of the state of the

421
00:23:55,280 --> 00:23:58,639
Speaker 1: universe as we know it, because when the universe began,

422
00:23:58,720 --> 00:24:02,760
Speaker 1: we think it began very very smooth, like totally homogeneous.

423
00:24:02,880 --> 00:24:06,119
Speaker 1: Everywhere was exactly like everywhere else. And why wouldn't it

424
00:24:06,160 --> 00:24:08,719
Speaker 1: be right when the universe is created, Why would you

425
00:24:08,760 --> 00:24:11,720
Speaker 1: have one spot that's like denser than another spot. The

426
00:24:11,800 --> 00:24:15,240
Speaker 1: problem is, however, a universe like that that's created perfectly smoothly,

427
00:24:15,760 --> 00:24:19,600
Speaker 1: nothing very interesting ever happens in that universe. There's nothing

428
00:24:19,680 --> 00:24:22,439
Speaker 1: for gravity to do in that universe because there's no

429
00:24:22,520 --> 00:24:25,600
Speaker 1: spots that are heavier or denser than anything else, which

430
00:24:25,640 --> 00:24:28,040
Speaker 1: is what gravity needs to sort of like seed the

431
00:24:28,119 --> 00:24:32,280
Speaker 1: structure to start coalescing things together into stars and planets

432
00:24:32,280 --> 00:24:35,240
Speaker 1: and galaxies and all that good stuff. So how did

433
00:24:35,240 --> 00:24:38,560
Speaker 1: the universe get any structure? Well, it was perfectly smooth,

434
00:24:38,680 --> 00:24:41,400
Speaker 1: except down to the quantum level. Of the quantum level,

435
00:24:41,520 --> 00:24:45,040
Speaker 1: there are always random fluctuations. Every point in the universe

436
00:24:45,080 --> 00:24:48,479
Speaker 1: gets a different random fluctuation, so you get these really

437
00:24:48,560 --> 00:24:52,600
Speaker 1: super duper tiny little variations in the density of the

438
00:24:52,680 --> 00:24:56,480
Speaker 1: universe due to quantum mechanics, and then inflation steps in.

439
00:24:56,480 --> 00:25:00,600
Speaker 1: Inflation takes those tiny little quantum fluctuations and it blows

440
00:25:00,600 --> 00:25:03,800
Speaker 1: them up to the macroscopic scale, makes things which were

441
00:25:04,040 --> 00:25:09,600
Speaker 1: invisibly small somehow suddenly now huge. Right, takes a meter

442
00:25:09,800 --> 00:25:11,879
Speaker 1: stick sized thing and it blows it up to a

443
00:25:11,960 --> 00:25:15,320
Speaker 1: trillion light years. It takes something which was sub atomic

444
00:25:15,520 --> 00:25:18,800
Speaker 1: and it makes it macroscopic. So now those random quantum

445
00:25:18,800 --> 00:25:21,800
Speaker 1: fluctuations are not small. They're pretty big, and they're big

446
00:25:21,920 --> 00:25:25,439
Speaker 1: enough to see the structure of the universe. So the

447
00:25:25,520 --> 00:25:28,240
Speaker 1: reason that we have a galaxy over here and then

448
00:25:28,240 --> 00:25:31,040
Speaker 1: over there it's empty space is because of a random

449
00:25:31,160 --> 00:25:35,400
Speaker 1: quantum fluctuation in the very early universe, which was expanded

450
00:25:35,480 --> 00:25:38,560
Speaker 1: out into something macroscopic that see to the structure of

451
00:25:38,600 --> 00:25:42,080
Speaker 1: that galaxy and allow gravity to pull stuff together to

452
00:25:42,200 --> 00:25:44,920
Speaker 1: make something interesting, to make me and to make you,

453
00:25:45,240 --> 00:25:48,000
Speaker 1: and to make the sun that warms our toes. Now,

454
00:25:48,040 --> 00:25:50,480
Speaker 1: the second part of Jeff's awesome question is that if

455
00:25:50,520 --> 00:25:53,840
Speaker 1: the edges of the universe were expanding through nothing, what's

456
00:25:53,880 --> 00:25:57,000
Speaker 1: slowing it down? Why isn't it still expanding at that

457
00:25:57,080 --> 00:26:00,520
Speaker 1: crazy rate? So lots of really good angles on the question.

458
00:26:00,800 --> 00:26:02,800
Speaker 1: First of all, we don't know if there is an

459
00:26:02,920 --> 00:26:05,200
Speaker 1: edge to the universe. I think in his mind Jeff

460
00:26:05,280 --> 00:26:08,080
Speaker 1: might be imagining an explosion, an explosion which has a

461
00:26:08,119 --> 00:26:11,400
Speaker 1: wavefront which is moving through the universe and then slowing down.

462
00:26:11,480 --> 00:26:13,440
Speaker 1: But we don't know that there was an edge. We

463
00:26:13,480 --> 00:26:15,840
Speaker 1: don't know if there is an edge. I think the

464
00:26:15,880 --> 00:26:18,440
Speaker 1: cleanest way to think about these things is to think

465
00:26:18,480 --> 00:26:21,639
Speaker 1: that the universe is infinite. We don't know that's true,

466
00:26:21,920 --> 00:26:24,600
Speaker 1: but it seems somehow more natural to have an infinite

467
00:26:24,680 --> 00:26:27,680
Speaker 1: universe than to have an edge. And then you can grapple.

468
00:26:27,760 --> 00:26:30,160
Speaker 1: Instead of thinking about the whole universe, just think about

469
00:26:30,200 --> 00:26:32,040
Speaker 1: a chunk of it and think about sort of the

470
00:26:32,080 --> 00:26:34,800
Speaker 1: density of that part of the universe. So I imagine

471
00:26:34,840 --> 00:26:38,720
Speaker 1: the whole universe created infinite at its birth as a

472
00:26:38,880 --> 00:26:43,400
Speaker 1: very very dense place, and then expanded suddenly, very rapidly,

473
00:26:43,720 --> 00:26:47,040
Speaker 1: using inflation. So there's no edge there. Everything is moving

474
00:26:47,080 --> 00:26:51,399
Speaker 1: away from everything else. He also asks, if there's no edge,

475
00:26:51,480 --> 00:26:55,000
Speaker 1: what's slowing it down? Why isn't it still expanding at

476
00:26:55,040 --> 00:26:58,520
Speaker 1: that crazy rate? Awesome question. I wish I knew the answer.

477
00:26:58,680 --> 00:27:01,400
Speaker 1: There was this incredible moment of inflation in the very

478
00:27:01,400 --> 00:27:04,680
Speaker 1: early universe, this rapid expansion in a very short amount

479
00:27:04,720 --> 00:27:07,399
Speaker 1: of time. We don't know what caused it. We have

480
00:27:07,520 --> 00:27:11,199
Speaker 1: ideas about ideas were sort of proto ideas for what

481
00:27:11,359 --> 00:27:14,439
Speaker 1: might have caused it, crazy particles and field called the

482
00:27:14,440 --> 00:27:17,920
Speaker 1: infloton field, but those are sort of placeholders to have ideas.

483
00:27:17,960 --> 00:27:20,880
Speaker 1: We don't really have any well worked out, super well

484
00:27:20,920 --> 00:27:25,560
Speaker 1: formulated ideas that actually come together mathematically to explain inflation.

485
00:27:26,040 --> 00:27:28,080
Speaker 1: So because we don't know what started it and what

486
00:27:28,200 --> 00:27:30,879
Speaker 1: sustained it, we also don't know why it stopped. We

487
00:27:30,960 --> 00:27:33,520
Speaker 1: just know that it started and we know that it stopped,

488
00:27:33,560 --> 00:27:36,320
Speaker 1: but the expansion itself has not stopped. It was very

489
00:27:36,400 --> 00:27:38,320
Speaker 1: rapid in the very beginning, and then it was very

490
00:27:38,359 --> 00:27:41,280
Speaker 1: slow for a while, but about five billion years ago

491
00:27:41,440 --> 00:27:44,520
Speaker 1: it started to pick up again. Dark energy took over

492
00:27:44,800 --> 00:27:47,800
Speaker 1: and it started to accelerate the expansion of the universe

493
00:27:47,960 --> 00:27:51,439
Speaker 1: once again. And this expansion is very similar to what

494
00:27:51,560 --> 00:27:54,280
Speaker 1: happened in the inflationary period of the universe. It's not

495
00:27:54,440 --> 00:27:57,480
Speaker 1: nearly as rapid, but the sort of stretching of space

496
00:27:57,600 --> 00:28:00,639
Speaker 1: is the same concept. We don't know if there's a

497
00:28:00,680 --> 00:28:04,800
Speaker 1: relationship between the mechanism or the reason for why space

498
00:28:04,880 --> 00:28:07,919
Speaker 1: is expanding now and why space expanded in the very beginning.

499
00:28:08,160 --> 00:28:11,399
Speaker 1: We're pretty clueless about what dark energy is. Again. We

500
00:28:11,440 --> 00:28:14,000
Speaker 1: have a few basic ideas for what might explain it,

501
00:28:14,200 --> 00:28:16,959
Speaker 1: but none of them hold together mathematically, so most of

502
00:28:16,960 --> 00:28:19,640
Speaker 1: this is just an observation. We see that this happened,

503
00:28:19,840 --> 00:28:23,520
Speaker 1: we can't explain why. So it is still expanding at

504
00:28:23,520 --> 00:28:26,439
Speaker 1: a crazy rate, not as crazy, but we don't know

505
00:28:26,520 --> 00:28:29,520
Speaker 1: the answer to the question why the universe stopped inflating

506
00:28:29,640 --> 00:28:33,440
Speaker 1: and why it's not inflating at that crazy rate today. So, Jeff,

507
00:28:33,440 --> 00:28:36,040
Speaker 1: the answer to your question is that the universe expanded

508
00:28:36,080 --> 00:28:39,160
Speaker 1: so rapidly, not by things moving through space, but by

509
00:28:39,240 --> 00:28:43,080
Speaker 1: expanding the nature of space itself, by creating new space

510
00:28:43,120 --> 00:28:46,280
Speaker 1: between stuff and why did that stop. We don't know

511
00:28:46,360 --> 00:28:50,160
Speaker 1: why inflation itself stopped, but the expansion has not stopped.

512
00:28:50,200 --> 00:28:53,320
Speaker 1: The universe is still expanding, and it's expanding faster and

513
00:28:53,360 --> 00:28:57,240
Speaker 1: faster every day. All right, Thanks for that super awesome question.

514
00:28:57,280 --> 00:28:59,360
Speaker 1: I love all of these ideas. I have one more

515
00:28:59,440 --> 00:29:01,720
Speaker 1: question I'm an get to today, but first let's take

516
00:29:01,920 --> 00:29:17,720
Speaker 1: another quick break. Okay, we're back and this is Daniel

517
00:29:17,760 --> 00:29:20,840
Speaker 1: and I'm answering questions about the nature of the universe

518
00:29:20,880 --> 00:29:24,760
Speaker 1: and how it expanded and whether it violates conservation of energy.

519
00:29:25,360 --> 00:29:28,720
Speaker 1: And our next question is a tiny bit more concrete. Hi,

520
00:29:28,880 --> 00:29:33,640
Speaker 1: Daniel and JOI I'm Tristan from Melbourne, Australia. Congratulations on

521
00:29:33,680 --> 00:29:37,760
Speaker 1: the awesome podcast. My question is about spice dust. We

522
00:29:37,840 --> 00:29:40,280
Speaker 1: hear about it all the time, but what exactly is

523
00:29:40,560 --> 00:29:44,640
Speaker 1: spice dust? Is it tiny gas molecules or really minute

524
00:29:44,720 --> 00:29:48,000
Speaker 1: dust particles like here on Earth or is spice dust

525
00:29:48,120 --> 00:29:51,120
Speaker 1: just a relative term? And they'm all like basketball sized

526
00:29:51,200 --> 00:29:54,120
Speaker 1: or cast sized or bigger? All right, Thanks very much

527
00:29:54,160 --> 00:29:57,760
Speaker 1: for that fun question. This is actually a surprisingly fascinating

528
00:29:57,840 --> 00:30:00,720
Speaker 1: topic when you think about do you think it's like

529
00:30:00,920 --> 00:30:02,960
Speaker 1: dirt and something you want to get rid of. It's

530
00:30:02,960 --> 00:30:05,520
Speaker 1: an annoyance. It gets in your way. If you zoom

531
00:30:05,520 --> 00:30:07,240
Speaker 1: in on it, you discover that, like a lot of

532
00:30:07,280 --> 00:30:10,080
Speaker 1: the dust in your house is actually left over dried

533
00:30:10,160 --> 00:30:12,600
Speaker 1: bits of human skin that makes you want to throw

534
00:30:12,680 --> 00:30:15,720
Speaker 1: up a little bit. So space dust is sort of similar.

535
00:30:15,760 --> 00:30:18,440
Speaker 1: For a long time, people thought space dust was just

536
00:30:18,520 --> 00:30:21,760
Speaker 1: like an annoyance. It was this stuff floating in space

537
00:30:21,800 --> 00:30:24,360
Speaker 1: which like blocked your view. I mean, if you look

538
00:30:24,400 --> 00:30:27,880
Speaker 1: out into space, it's incredible how far we can see.

539
00:30:28,320 --> 00:30:30,840
Speaker 1: You're standing on the top of a rock in space

540
00:30:30,840 --> 00:30:33,840
Speaker 1: and you're peering out in your eyeballs are absorbing photons

541
00:30:33,880 --> 00:30:37,560
Speaker 1: that have traveled billions of light years, mostly unimpeded to

542
00:30:37,600 --> 00:30:40,840
Speaker 1: get to you. It's incredible that space is as clear

543
00:30:40,960 --> 00:30:43,720
Speaker 1: as it is, so we shouldn't be complaining. We have

544
00:30:43,800 --> 00:30:46,560
Speaker 1: the best view in the universe. The kind of things

545
00:30:46,600 --> 00:30:50,080
Speaker 1: we see with hubble are just eye dropping the gorgeous.

546
00:30:50,120 --> 00:30:53,920
Speaker 1: But sometimes there are things that are obscured by space dust.

547
00:30:54,160 --> 00:30:56,320
Speaker 1: If you look at the center of the galaxy, for example,

548
00:30:56,320 --> 00:30:58,800
Speaker 1: they're huge clouds of dust to make it harder to

549
00:30:58,800 --> 00:31:01,480
Speaker 1: see what's going on there. And for a long time

550
00:31:01,520 --> 00:31:06,000
Speaker 1: astronomers treated space dust that way, like an annoyance, like, oh,

551
00:31:06,040 --> 00:31:08,960
Speaker 1: these things are shrouded in dust, so we can't see

552
00:31:09,000 --> 00:31:11,920
Speaker 1: them what's going on inside there? And if you're like me,

553
00:31:12,040 --> 00:31:15,720
Speaker 1: your curiosity is only heightened when something is hidden, something

554
00:31:15,800 --> 00:31:19,080
Speaker 1: is behind a veil, like things inside a black hole.

555
00:31:19,360 --> 00:31:22,240
Speaker 1: It just makes me want to know even more what's there.

556
00:31:22,560 --> 00:31:25,120
Speaker 1: So for a long time space dust was treated that way.

557
00:31:25,200 --> 00:31:27,440
Speaker 1: It's just something that gets in our way, something to

558
00:31:27,480 --> 00:31:31,040
Speaker 1: be annoyed about. However, now we see that space dust

559
00:31:31,120 --> 00:31:33,840
Speaker 1: is just sort of part of the dynamics of space,

560
00:31:33,960 --> 00:31:38,160
Speaker 1: part of the astrophysical soup that's constantly churning, making new

561
00:31:38,240 --> 00:31:41,000
Speaker 1: stars and all their crazy things, and it can actually

562
00:31:41,040 --> 00:31:44,640
Speaker 1: help us understand the structure of the galaxies and how

563
00:31:44,680 --> 00:31:47,920
Speaker 1: things work. For example, we can see space dust. It

564
00:31:47,960 --> 00:31:51,720
Speaker 1: doesn't just blocklight, it actually gives off its own light.

565
00:31:52,240 --> 00:31:54,959
Speaker 1: This is something I think is not widely enough understood

566
00:31:55,240 --> 00:31:59,600
Speaker 1: that everything in the universe glows. Everything in the universe

567
00:31:59,600 --> 00:32:02,480
Speaker 1: that's made that of our kind of stuff atoms, that's

568
00:32:02,480 --> 00:32:05,840
Speaker 1: only five of the universe, but all that stuff glows,

569
00:32:06,160 --> 00:32:09,520
Speaker 1: and it glows based on its temperature. The hotter you are,

570
00:32:09,800 --> 00:32:12,880
Speaker 1: the more energetic photons you give off, which is why.

571
00:32:12,920 --> 00:32:15,440
Speaker 1: For example, if you heat up metal, it starts to

572
00:32:15,480 --> 00:32:19,440
Speaker 1: glow and it glows at different frequencies, different colors as

573
00:32:19,480 --> 00:32:23,480
Speaker 1: it gets hotter. Everything is actually like that. Even you glow,

574
00:32:23,840 --> 00:32:26,840
Speaker 1: and if you put on infrared goggles then you can

575
00:32:26,880 --> 00:32:29,920
Speaker 1: see your body heat because of your temperature. But it's

576
00:32:29,960 --> 00:32:33,280
Speaker 1: not just living things. Even rocks glow, even if they're

577
00:32:33,400 --> 00:32:37,520
Speaker 1: very very cold. They glow at some wavelength. And space

578
00:32:37,600 --> 00:32:40,680
Speaker 1: dust is out there and it glows as well, so

579
00:32:40,760 --> 00:32:43,000
Speaker 1: you can see it. It's not giving off visible light.

580
00:32:43,200 --> 00:32:45,920
Speaker 1: But if you have a special camera like night vision

581
00:32:46,000 --> 00:32:49,800
Speaker 1: goggles for the universe and what we call an infrared telescope,

582
00:32:49,880 --> 00:32:51,840
Speaker 1: then you can see it. And if you point an

583
00:32:51,840 --> 00:32:55,880
Speaker 1: infrared telescope, for example, at the Andromeda galaxy, you can

584
00:32:55,920 --> 00:33:00,160
Speaker 1: see where in Andromeda there is this space dust. The

585
00:33:00,200 --> 00:33:04,200
Speaker 1: space does glows at different frequencies than the stars. The

586
00:33:04,280 --> 00:33:06,640
Speaker 1: stars admitted visible light and you can see them. That's

587
00:33:06,680 --> 00:33:09,080
Speaker 1: super fascinating. But then if you turn on your night

588
00:33:09,200 --> 00:33:12,600
Speaker 1: vision goggles for space, you can see the other stuff,

589
00:33:12,640 --> 00:33:16,240
Speaker 1: the colder stuff, which is glowing at longer wavelengths in

590
00:33:16,320 --> 00:33:19,400
Speaker 1: the infrared, and you can see it totally differently, and

591
00:33:19,480 --> 00:33:23,000
Speaker 1: Dromeda looks different in the infrared, you can see where

592
00:33:23,040 --> 00:33:26,160
Speaker 1: the space dust is, and that helps us understand like

593
00:33:26,440 --> 00:33:29,120
Speaker 1: how did and Drameda form, what's going on over there,

594
00:33:29,320 --> 00:33:31,800
Speaker 1: what are the dynamics, what things are moving against the

595
00:33:31,840 --> 00:33:34,920
Speaker 1: other stuff. So these days space dust isn't just like

596
00:33:34,960 --> 00:33:37,560
Speaker 1: an annoyance. It isn't just a cloud that gets in

597
00:33:37,600 --> 00:33:40,880
Speaker 1: your way. It's another thing out there that we can study.

598
00:33:41,120 --> 00:33:42,760
Speaker 1: And it turns out that there's a lot of different

599
00:33:42,840 --> 00:33:46,680
Speaker 1: kinds of space dust. Most generally, what is space dust.

600
00:33:46,760 --> 00:33:50,040
Speaker 1: It's basically anything that's out there in space that's very,

601
00:33:50,120 --> 00:33:53,440
Speaker 1: very small, right, So you wouldn't call Earth a big

602
00:33:53,480 --> 00:33:56,440
Speaker 1: speck of space dust. This is one of those arbitrary

603
00:33:56,560 --> 00:34:00,920
Speaker 1: categorizations in astronomy and astrophysics. Space does is basically anything

604
00:34:00,920 --> 00:34:03,840
Speaker 1: that's out there that's smaller than like a millimeter, and

605
00:34:03,880 --> 00:34:05,560
Speaker 1: it can go down all the way to like a

606
00:34:05,600 --> 00:34:09,000
Speaker 1: few molecules, but the upper edge is generally agreed to

607
00:34:09,080 --> 00:34:11,880
Speaker 1: be like a millimeter or half a millimeter, maybe a

608
00:34:11,920 --> 00:34:15,399
Speaker 1: tenth of a millimeter. Anything that size or smaller that's

609
00:34:15,400 --> 00:34:18,440
Speaker 1: floating out in space, we call it space dust. Bigger

610
00:34:18,480 --> 00:34:21,360
Speaker 1: than that, like a basketball or car sized thing, we

611
00:34:21,400 --> 00:34:24,279
Speaker 1: would call that an asteroid. Or a comet, or even

612
00:34:24,320 --> 00:34:26,799
Speaker 1: a proto planet or a moon or right a sun

613
00:34:27,160 --> 00:34:30,120
Speaker 1: if it gets big enough. So there's this whole spectrum

614
00:34:30,160 --> 00:34:33,239
Speaker 1: of sizes of stuff in space and things on the

615
00:34:33,280 --> 00:34:37,080
Speaker 1: smaller edge we call space and dust. And you might wonder, like, well,

616
00:34:37,080 --> 00:34:40,359
Speaker 1: why is there space dust? After all, you have these

617
00:34:40,440 --> 00:34:43,360
Speaker 1: huge clouds of things formed after the Big Bang, and

618
00:34:43,440 --> 00:34:46,520
Speaker 1: some of it gathered together to make stars, and some

619
00:34:46,680 --> 00:34:49,560
Speaker 1: of it gathered together to make planets, but not everything

620
00:34:49,640 --> 00:34:53,400
Speaker 1: instantly gets clean together. Right. Gravity is very patient, but

621
00:34:53,480 --> 00:34:56,960
Speaker 1: it's also very very weak, And the gravity on very

622
00:34:57,080 --> 00:35:01,160
Speaker 1: small objects, tiny little specks of up floating out in space,

623
00:35:01,760 --> 00:35:04,520
Speaker 1: is very weak. And other things I'm much more powerful.

624
00:35:04,920 --> 00:35:07,880
Speaker 1: One thing that prevents gravity from gathering stuff together is

625
00:35:08,200 --> 00:35:11,880
Speaker 1: angular momentum. If something is moving in a circle around

626
00:35:11,920 --> 00:35:15,120
Speaker 1: something with gravity, then it doesn't necessarily fall in the

627
00:35:15,200 --> 00:35:18,239
Speaker 1: same way the Earth orbits the Sun without falling in,

628
00:35:18,360 --> 00:35:21,319
Speaker 1: even though there is gravity tugging on the Earth from

629
00:35:21,320 --> 00:35:24,440
Speaker 1: the Sun. The reason we don't fall in immediately is

630
00:35:24,480 --> 00:35:26,920
Speaker 1: because we're moving in a circle. The same reason the

631
00:35:26,920 --> 00:35:30,400
Speaker 1: whole galaxy doesn't collapse into the central black hole is

632
00:35:30,480 --> 00:35:33,839
Speaker 1: because of angular momentum. That's just one example and so

633
00:35:33,920 --> 00:35:37,719
Speaker 1: that keeps some space dust from collapsing into larger objects,

634
00:35:38,040 --> 00:35:39,680
Speaker 1: and so you end up with this whole spectrum of

635
00:35:39,719 --> 00:35:42,280
Speaker 1: really dense stuff that's sort of cleared out the space

636
00:35:42,320 --> 00:35:45,520
Speaker 1: around them than a whole distribution of smaller bits, which

637
00:35:45,560 --> 00:35:48,760
Speaker 1: we call space dust. And we can study this stuff.

638
00:35:49,040 --> 00:35:52,759
Speaker 1: NASA actually sends planes up into the high atmosphere to

639
00:35:52,840 --> 00:35:56,120
Speaker 1: gather space dust and these big collectors under the wings

640
00:35:56,280 --> 00:35:58,640
Speaker 1: to pull it together and say like, well, what's in there.

641
00:35:59,040 --> 00:36:01,719
Speaker 1: And actually there's a huge amount of space dust out there.

642
00:36:01,880 --> 00:36:04,960
Speaker 1: It's not very rare. The Earth is traveling through a

643
00:36:05,000 --> 00:36:09,480
Speaker 1: cloud of this stuff is like one particle per million

644
00:36:09,560 --> 00:36:12,960
Speaker 1: cubic meters, but there's a lot of cubic meters out there,

645
00:36:13,280 --> 00:36:15,400
Speaker 1: and there's a lot of square meters on the surface

646
00:36:15,440 --> 00:36:17,879
Speaker 1: of the Earth, and so a lot of space dust

647
00:36:17,920 --> 00:36:21,160
Speaker 1: actually falls onto the Earth every year. Some of the

648
00:36:21,200 --> 00:36:23,719
Speaker 1: stuff that's lying around your house might be dead bits

649
00:36:23,719 --> 00:36:26,320
Speaker 1: of skin, but some of it might be space dust,

650
00:36:26,760 --> 00:36:30,560
Speaker 1: because there are thousands of tons of space dust that

651
00:36:30,719 --> 00:36:33,680
Speaker 1: reached the surface of the Earth every year. Yeah. I

652
00:36:33,800 --> 00:36:35,640
Speaker 1: just about fell out of my chair when I read

653
00:36:35,680 --> 00:36:39,280
Speaker 1: that tidbit that fact thousands of tons of the stuff

654
00:36:39,560 --> 00:36:42,000
Speaker 1: if you could like sweep up all the space dust

655
00:36:42,239 --> 00:36:44,600
Speaker 1: that hits the Earth and make a pile of it,

656
00:36:44,600 --> 00:36:48,240
Speaker 1: it would be a huge, huge mountain of space dust,

657
00:36:48,560 --> 00:36:51,200
Speaker 1: all right. So then what is this stuff? Right? What

658
00:36:51,360 --> 00:36:53,480
Speaker 1: is this stuff that's out there, that's floating through the

659
00:36:53,560 --> 00:36:57,520
Speaker 1: universe that didn't get gathered together into planets and rocks

660
00:36:57,560 --> 00:37:00,480
Speaker 1: and other kinds of stuff. Well, it's a big mix, right.

661
00:37:00,520 --> 00:37:03,759
Speaker 1: It's basically a big soup of leftover stuff either from

662
00:37:03,800 --> 00:37:07,000
Speaker 1: the very early universe that never got gathered together into

663
00:37:07,040 --> 00:37:09,840
Speaker 1: something else, or that has had a chance to be

664
00:37:10,320 --> 00:37:12,640
Speaker 1: part of a star or a planet and then got

665
00:37:12,680 --> 00:37:16,360
Speaker 1: blown into little smithereens. So one category of stuff is

666
00:37:16,640 --> 00:37:20,520
Speaker 1: star dust. Star dust are little pellets made on the

667
00:37:20,560 --> 00:37:24,360
Speaker 1: outside of stars, a little grains, for example, of oxygen

668
00:37:24,520 --> 00:37:27,719
Speaker 1: or carbon rich elements that are floating out near the

669
00:37:27,760 --> 00:37:30,640
Speaker 1: outside of stars, and that gets blown out away from

670
00:37:30,640 --> 00:37:33,280
Speaker 1: the star and so they get frozen into these little pellets.

671
00:37:33,480 --> 00:37:35,759
Speaker 1: Remember that in the first population of stars, we had

672
00:37:35,800 --> 00:37:39,840
Speaker 1: only hydrogen, but those hydrogen stars burned helium, and in

673
00:37:39,960 --> 00:37:43,080
Speaker 1: later generations of stars fuse that helium into heavier and

674
00:37:43,080 --> 00:37:46,480
Speaker 1: heavier stuff. So stars are the engines to make these

675
00:37:46,520 --> 00:37:50,040
Speaker 1: heavier elements, and eventually they can gather together. A lot

676
00:37:50,080 --> 00:37:52,560
Speaker 1: of this we call it ash because it's the product

677
00:37:52,600 --> 00:37:55,000
Speaker 1: of fusion. A lot of it falls to the center

678
00:37:55,040 --> 00:37:57,319
Speaker 1: of the star, makes a denser and denser core, which

679
00:37:57,320 --> 00:38:00,600
Speaker 1: eventually leaves the star to collapse, not all of it,

680
00:38:00,800 --> 00:38:03,160
Speaker 1: so if it gets blown out into the outer edges

681
00:38:03,200 --> 00:38:05,640
Speaker 1: of the star, and then it can get pushed even

682
00:38:05,680 --> 00:38:08,800
Speaker 1: further out and float out into space. So these little

683
00:38:08,840 --> 00:38:12,960
Speaker 1: grains of stuff produced inside stars, this is called star dust,

684
00:38:13,320 --> 00:38:15,360
Speaker 1: and this is floating out there, and a good amount

685
00:38:15,360 --> 00:38:18,320
Speaker 1: of the space dust are actually these kinds of grains,

686
00:38:18,840 --> 00:38:21,200
Speaker 1: and a lot of them came together to form our

687
00:38:21,320 --> 00:38:24,239
Speaker 1: star and our planet. So a lot of what makes

688
00:38:24,320 --> 00:38:27,720
Speaker 1: me and you and the Sun are actually these bits

689
00:38:27,760 --> 00:38:30,920
Speaker 1: of other stars. Now, of course, inside the Earth and

690
00:38:30,920 --> 00:38:33,480
Speaker 1: inside the Sun, they've all been melted down to their

691
00:38:33,480 --> 00:38:36,560
Speaker 1: basic elements and maybe even fused into other stuff. But

692
00:38:36,719 --> 00:38:39,360
Speaker 1: space dust hasn't. It's frozen. It's like a little time

693
00:38:39,440 --> 00:38:42,080
Speaker 1: capsule that tells you where it came from. And if

694
00:38:42,120 --> 00:38:44,640
Speaker 1: you can capture one of these grains of star dust,

695
00:38:44,680 --> 00:38:47,280
Speaker 1: and you can look at the relative fractions of stuff,

696
00:38:47,320 --> 00:38:50,120
Speaker 1: like how much iron is there, how much carbon is there?

697
00:38:50,320 --> 00:38:52,400
Speaker 1: Then you can get an idea from what kind of

698
00:38:52,480 --> 00:38:55,800
Speaker 1: star came from. You can read like it's ancient history

699
00:38:56,120 --> 00:38:59,319
Speaker 1: just by looking at what's inside of it. So each

700
00:38:59,360 --> 00:39:01,520
Speaker 1: of these is like a little time capsule that tells

701
00:39:01,600 --> 00:39:04,680
Speaker 1: us what happened. And these events are billions of years old.

702
00:39:05,000 --> 00:39:07,759
Speaker 1: You know the star dusk grains that helped form our sun,

703
00:39:08,160 --> 00:39:10,520
Speaker 1: well that was five billion years ago, So they were

704
00:39:10,560 --> 00:39:14,000
Speaker 1: produced more than five billion years ago, and they're still

705
00:39:14,000 --> 00:39:17,960
Speaker 1: floating around. Some of them coalesced into like micro meteorites,

706
00:39:18,160 --> 00:39:21,360
Speaker 1: but they don't necessarily lose their elemental structure. They just

707
00:39:21,400 --> 00:39:23,560
Speaker 1: sort of got like get stuck together like a big

708
00:39:23,600 --> 00:39:26,520
Speaker 1: pile of rice grains. And so if you're careful, you

709
00:39:26,560 --> 00:39:29,200
Speaker 1: can tear them apart and look at the individual grains

710
00:39:29,239 --> 00:39:33,160
Speaker 1: and still study these little time capsule from other stars. Now,

711
00:39:33,239 --> 00:39:35,279
Speaker 1: sometimes you look at these space dust capsules and you

712
00:39:35,320 --> 00:39:38,880
Speaker 1: see something really strange, and people actually predicted that you

713
00:39:38,880 --> 00:39:43,760
Speaker 1: would see this. You see things produced in supernovas. Supernovas, remember,

714
00:39:43,760 --> 00:39:47,960
Speaker 1: are these very special occasions. When it starts, gravity overcomes

715
00:39:47,960 --> 00:39:51,520
Speaker 1: its pressure and it collapses very very rapidly, this implosion,

716
00:39:51,560 --> 00:39:54,840
Speaker 1: which then leads to an explosion where it throws crazy

717
00:39:54,920 --> 00:39:59,000
Speaker 1: stuff through space. Well, in those moments of implosion are

718
00:39:59,080 --> 00:40:02,359
Speaker 1: intense moments of fusion, and these are situations that allow

719
00:40:02,440 --> 00:40:04,880
Speaker 1: for the creation of other kinds of elements and different

720
00:40:04,920 --> 00:40:07,440
Speaker 1: mixtures of elements than what you would expect from the

721
00:40:07,480 --> 00:40:10,960
Speaker 1: normal production you get in a star. And sometimes these

722
00:40:11,000 --> 00:40:13,880
Speaker 1: things get thrown out during the supernova and they're like

723
00:40:13,920 --> 00:40:16,680
Speaker 1: little time capsules, a little like samples from what's going

724
00:40:16,760 --> 00:40:21,399
Speaker 1: on deep inside is supernova. So these supernova grains are

725
00:40:21,440 --> 00:40:25,440
Speaker 1: super awesome vines because they're not created nearly as often,

726
00:40:25,600 --> 00:40:28,600
Speaker 1: and they're this little time capsule from this incredible moment

727
00:40:28,840 --> 00:40:32,000
Speaker 1: during one of the most violent acts in our universe,

728
00:40:32,120 --> 00:40:34,520
Speaker 1: so they're super fun. And then a lot of the

729
00:40:34,520 --> 00:40:37,880
Speaker 1: other space dust is just floating tiny rocks. Basically. Some

730
00:40:38,040 --> 00:40:41,000
Speaker 1: of them are carbonaceous, you know, other ones have iron

731
00:40:41,080 --> 00:40:43,399
Speaker 1: or sulfur or nickel. Some of them are silicates, which

732
00:40:43,440 --> 00:40:46,200
Speaker 1: means they're basically bits of sand, and they have all

733
00:40:46,200 --> 00:40:49,280
Speaker 1: sorts of irregular shapes, you know, just like any random rocks.

734
00:40:49,280 --> 00:40:52,000
Speaker 1: Some of them are kind of fluffy, loose amalgams. Some

735
00:40:52,080 --> 00:40:55,040
Speaker 1: of them are very compact. Some of them accumulate little

736
00:40:55,120 --> 00:40:57,239
Speaker 1: layers of ice around them, so you might expect them

737
00:40:57,239 --> 00:41:00,840
Speaker 1: to be like super mini comets, and and the sizes

738
00:41:00,840 --> 00:41:02,799
Speaker 1: of them differ. Right, they go all the way down

739
00:41:02,840 --> 00:41:05,759
Speaker 1: from the tiny, tiny little grains up to you know,

740
00:41:05,880 --> 00:41:08,800
Speaker 1: less than a millimeter or so. And this is important

741
00:41:08,840 --> 00:41:12,200
Speaker 1: because the size determines how you can see them. Like

742
00:41:12,320 --> 00:41:16,279
Speaker 1: pretty big grains actually reflect light, so if the sun

743
00:41:16,560 --> 00:41:18,920
Speaker 1: is behind you, you could see them the way you

744
00:41:18,960 --> 00:41:21,839
Speaker 1: see the moon, like comes from the sun bounces off

745
00:41:21,880 --> 00:41:23,919
Speaker 1: of them and then back to you. But if they're

746
00:41:23,920 --> 00:41:26,400
Speaker 1: really really small, then they don't reflect light. They just

747
00:41:26,400 --> 00:41:29,560
Speaker 1: sort of deflected a little bit, which means it's only

748
00:41:29,600 --> 00:41:32,439
Speaker 1: easy to see them if the light is behind them.

749
00:41:32,480 --> 00:41:34,759
Speaker 1: They have to be back lit, and this is why,

750
00:41:34,800 --> 00:41:38,400
Speaker 1: for example, we didn't really know that Jupiter had rings

751
00:41:38,520 --> 00:41:41,680
Speaker 1: and had rings made of dust until we got cameras

752
00:41:41,680 --> 00:41:45,200
Speaker 1: out past Jupiter and you could look back and you

753
00:41:45,239 --> 00:41:48,480
Speaker 1: could see those rings of dust back lit by the

754
00:41:48,520 --> 00:41:51,239
Speaker 1: sun because they only deflect the light a little bit.

755
00:41:51,960 --> 00:41:54,640
Speaker 1: So it's important how big they are, and it's also

756
00:41:54,719 --> 00:41:57,279
Speaker 1: important their shape. We think this space dust is not

757
00:41:57,400 --> 00:42:01,000
Speaker 1: just around the Solar System, and not just in the galaxy,

758
00:42:01,080 --> 00:42:05,080
Speaker 1: but also between the galaxies. It's basically spread out everywhere,

759
00:42:05,440 --> 00:42:09,560
Speaker 1: and it's actually really valuable because these grains are not spheres.

760
00:42:09,600 --> 00:42:12,319
Speaker 1: They're like weird, all blong shapes. So what they do

761
00:42:12,360 --> 00:42:14,920
Speaker 1: is they tend to align with magnetic fields. They're like

762
00:42:15,360 --> 00:42:18,000
Speaker 1: tiny little needles and they tend to line up with

763
00:42:18,040 --> 00:42:21,680
Speaker 1: magnetic fields. And people have been studying magnetic fields through space,

764
00:42:21,719 --> 00:42:24,880
Speaker 1: wondering like, is their magnetic fields all through the galaxy?

765
00:42:25,120 --> 00:42:29,160
Speaker 1: Are there magnetic fields between galaxies? Are there magnetic fields

766
00:42:29,160 --> 00:42:32,160
Speaker 1: in deep space that were created during the Big Bang?

767
00:42:32,600 --> 00:42:35,120
Speaker 1: This is called the primordial magnetic field. We have a

768
00:42:35,160 --> 00:42:38,080
Speaker 1: whole podcast episode about it. If you listen to that.

769
00:42:38,120 --> 00:42:41,440
Speaker 1: What you learn is that these dust grains line up

770
00:42:41,480 --> 00:42:44,680
Speaker 1: with magnetic fields, which is important because it changes how

771
00:42:44,800 --> 00:42:47,640
Speaker 1: light moves through it because these dust greens are now polarized,

772
00:42:48,120 --> 00:42:50,640
Speaker 1: and so we can use space duft to sort of

773
00:42:51,080 --> 00:42:55,640
Speaker 1: track the magnetic fields in otherwise empty portions of space,

774
00:42:56,160 --> 00:42:59,400
Speaker 1: sort of like sprinkling magnetic filings on a sheet to

775
00:42:59,480 --> 00:43:02,480
Speaker 1: see if the the magnetic field there. It's actually good

776
00:43:02,520 --> 00:43:04,920
Speaker 1: that space dust is sort of everywhere, because if space

777
00:43:05,000 --> 00:43:07,759
Speaker 1: was truly empty, it would be much much harder to

778
00:43:07,840 --> 00:43:11,080
Speaker 1: study it. Alright, So I hope that answers your question,

779
00:43:11,200 --> 00:43:14,440
Speaker 1: what is space dust? It's tiny little grains of stuff,

780
00:43:14,640 --> 00:43:17,920
Speaker 1: some of them created within stars, some within supernovas, some

781
00:43:18,000 --> 00:43:20,760
Speaker 1: of them aligning with magnetic meals to tell us where

782
00:43:20,760 --> 00:43:23,280
Speaker 1: things are. We don't know what their future is. Maybe

783
00:43:23,320 --> 00:43:25,520
Speaker 1: one day some of them will gather together to make

784
00:43:25,560 --> 00:43:28,160
Speaker 1: a new star, a new planet, even a new race

785
00:43:28,200 --> 00:43:31,840
Speaker 1: of intelligent aliens that make a podcast even better than ours.

786
00:43:32,200 --> 00:43:34,919
Speaker 1: All right, so thank you very much everybody who's sent

787
00:43:35,000 --> 00:43:37,319
Speaker 1: in questions, and thanks also to those of you who

788
00:43:37,400 --> 00:43:40,480
Speaker 1: have sent in listener questions audio and not yet had

789
00:43:40,480 --> 00:43:43,359
Speaker 1: your questions answer. I promise we will get through our

790
00:43:43,400 --> 00:43:47,160
Speaker 1: backlog and we will answer all of your questions, because

791
00:43:47,239 --> 00:43:49,720
Speaker 1: I think that everybody out there should be asking questions

792
00:43:49,760 --> 00:43:52,959
Speaker 1: about the universe, should be tapped into their innate curiosity.

793
00:43:53,400 --> 00:43:56,800
Speaker 1: Discovering how the world works. Asking these questions and knowing

794
00:43:56,840 --> 00:43:59,960
Speaker 1: that there's an answer is one of the most satisfying experience.

795
00:44:00,160 --> 00:44:02,640
Speaker 1: Is it tells you that maybe the human mind is

796
00:44:02,719 --> 00:44:05,600
Speaker 1: capable of gaining not a full understanding, but at least

797
00:44:05,600 --> 00:44:09,359
Speaker 1: a foothold into our universe of ignorance, cracking that open

798
00:44:09,400 --> 00:44:12,120
Speaker 1: a little bit and revealing a tiny slice of how

799
00:44:12,200 --> 00:44:15,000
Speaker 1: the universe works. It's certainly we're doing, even if it

800
00:44:15,040 --> 00:44:19,440
Speaker 1: doesn't immediately lead to applications and better lasers and pants

801
00:44:19,480 --> 00:44:22,120
Speaker 1: with better zippers and stuff like that. I view the

802
00:44:22,160 --> 00:44:24,400
Speaker 1: deep exploration of the nature in the universe to be

803
00:44:24,480 --> 00:44:27,400
Speaker 1: on par with the creation of art. It's part of

804
00:44:27,400 --> 00:44:31,040
Speaker 1: what makes life worth living. So thanks everyone for lending

805
00:44:31,120 --> 00:44:34,120
Speaker 1: us your questions and your curiosity. It's been a wonderful ride,

806
00:44:34,440 --> 00:44:37,600
Speaker 1: and tune in next time for more questions from listeners.

807
00:44:45,440 --> 00:44:48,240
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain

808
00:44:48,320 --> 00:44:51,239
Speaker 1: the Universe is a production of I Heart Radio or

809
00:44:51,320 --> 00:44:54,239
Speaker 1: more podcast from my Heart Radio. Visit the I Heart

810
00:44:54,360 --> 00:44:57,960
Speaker 1: Radio Apple Apple Podcasts, or wherever you listen to your

811
00:44:58,000 --> 00:45:03,000
Speaker 1: favorite shows.