1
00:00:07,520 --> 00:00:10,640
Speaker 1: So, Daniel, you do a lot of cooking. What is

2
00:00:10,680 --> 00:00:13,560
Speaker 1: the biggest kitchen implement that you have?

3
00:00:15,320 --> 00:00:18,759
Speaker 2: Do We measure kitchen implements by size. Now is the

4
00:00:18,800 --> 00:00:20,320
Speaker 2: biggest one? The most important?

5
00:00:21,160 --> 00:00:24,000
Speaker 1: It is to me, I got one giant ladle and

6
00:00:24,040 --> 00:00:27,720
Speaker 1: that is the most important. What is let's talk about

7
00:00:27,760 --> 00:00:30,639
Speaker 1: sheer volume? What takes up the most space for you?

8
00:00:31,280 --> 00:00:34,680
Speaker 2: Well, actually, we went out and bought a huge soup pot.

9
00:00:34,960 --> 00:00:37,160
Speaker 2: Last time, we made soup for about one hundred people.

10
00:00:37,840 --> 00:00:40,840
Speaker 1: One hundred people for dinner. That's a lot.

11
00:00:41,720 --> 00:00:44,320
Speaker 2: Yeah. Well, you know, we were out celebrating solstice and

12
00:00:44,360 --> 00:00:46,480
Speaker 2: you got to go a little crazy on the solstice.

13
00:00:46,680 --> 00:00:48,559
Speaker 2: So we had one hundred people over for sit down

14
00:00:48,600 --> 00:00:50,160
Speaker 2: dinner and we made a lot of soup.

15
00:00:50,560 --> 00:00:54,279
Speaker 1: I would rather burn my kitchen down in a ritualistic

16
00:00:54,440 --> 00:01:00,240
Speaker 1: bonfire than do one hundred sets of dishes after that.

17
00:01:00,240 --> 00:01:02,800
Speaker 2: That sounds like a great way to celebrate the solstice. Actually,

18
00:01:02,920 --> 00:01:04,440
Speaker 2: kitchen bonfire.

19
00:01:04,080 --> 00:01:07,600
Speaker 1: Kitchen effigy. There we go, No more washing dishes.

20
00:01:07,680 --> 00:01:10,400
Speaker 2: Hooray, it's the solstice magic.

21
00:01:27,120 --> 00:01:27,320
Speaker 1: Hi.

22
00:01:27,400 --> 00:01:29,920
Speaker 2: I'm Daniel. I'm a particle physicist and a professor a

23
00:01:30,080 --> 00:01:33,000
Speaker 2: uc irvine and I'm not into astrology, but I do

24
00:01:33,080 --> 00:01:34,200
Speaker 2: love the Solstice.

25
00:01:34,560 --> 00:01:38,920
Speaker 1: I am Katie Golden. I host podcast on animal behavior

26
00:01:39,040 --> 00:01:45,640
Speaker 1: called Creature Feature, and I am super duper into Solstice

27
00:01:46,000 --> 00:01:53,960
Speaker 1: magics such as logs in the house and putting stones

28
00:01:54,080 --> 00:01:58,880
Speaker 1: up such that they make interesting shapes and the light

29
00:01:59,440 --> 00:02:02,160
Speaker 1: hits them in just such a way. M.

30
00:02:02,400 --> 00:02:04,040
Speaker 2: I see you're building Katie hinge.

31
00:02:04,280 --> 00:02:07,920
Speaker 1: Katie hinge. You know, Okay for the summer Solstice one,

32
00:02:07,960 --> 00:02:11,280
Speaker 1: I actually did talk about Britta Boyne, but I also

33
00:02:11,360 --> 00:02:15,119
Speaker 1: want to talk about how there's a wood hinge as

34
00:02:15,200 --> 00:02:19,200
Speaker 1: well as the stone hinge. And the word hinge it

35
00:02:19,480 --> 00:02:23,960
Speaker 1: actually comes from the idea of a thing hanging like

36
00:02:24,000 --> 00:02:28,200
Speaker 1: a hinge hanging. So stone hinge is like hanging rocks,

37
00:02:28,919 --> 00:02:34,000
Speaker 1: and wood hinge is another ancient people's way of creating

38
00:02:34,320 --> 00:02:39,240
Speaker 1: basically a annual sun dial, and that was made out

39
00:02:39,280 --> 00:02:40,600
Speaker 1: of wooden timber.

40
00:02:41,120 --> 00:02:43,000
Speaker 2: M I just always thought they were trying to hinge

41
00:02:43,040 --> 00:02:46,320
Speaker 2: their bets. I was thinking about starting a hinge.

42
00:02:46,040 --> 00:02:49,519
Speaker 1: Fund, you know, Oh my god, Well we do need

43
00:02:49,560 --> 00:02:52,359
Speaker 1: to teach Daniel about the difference between a hinge and

44
00:02:52,400 --> 00:02:55,079
Speaker 1: a hedge.

45
00:02:56,160 --> 00:02:57,560
Speaker 2: Well could you have a hedge hinge?

46
00:02:57,960 --> 00:03:01,120
Speaker 1: Uh? You know what, It's never been done as far

47
00:03:01,160 --> 00:03:04,120
Speaker 1: as I know in gardening science, but that never doesn't

48
00:03:04,160 --> 00:03:04,640
Speaker 1: mean never.

49
00:03:05,200 --> 00:03:07,160
Speaker 2: Well, okay, how about a biology one that a hedgehog

50
00:03:07,240 --> 00:03:09,000
Speaker 2: hinge hedgehog hinge.

51
00:03:09,240 --> 00:03:12,880
Speaker 1: Well, you know, maybe there's a hedgehog hinge for hedgehogs

52
00:03:12,880 --> 00:03:13,640
Speaker 1: looking for love.

53
00:03:15,000 --> 00:03:16,799
Speaker 2: All right, we'll hedge our bets until we get there.

54
00:03:16,800 --> 00:03:20,080
Speaker 2: But anyway, welcome to the podcast Daniel and Jorge Explain

55
00:03:20,120 --> 00:03:23,200
Speaker 2: the Universe, a production of iHeartRadio in which we do

56
00:03:23,240 --> 00:03:25,799
Speaker 2: not hedge our bets. We go all in on trying

57
00:03:25,840 --> 00:03:29,040
Speaker 2: to understand how the universe works and explain it all

58
00:03:29,080 --> 00:03:31,520
Speaker 2: to you. We tackle the biggest questions, from the very

59
00:03:31,600 --> 00:03:34,560
Speaker 2: nature of the universe to the smallest questions about quantum

60
00:03:34,560 --> 00:03:37,920
Speaker 2: particles and the fundamental nature of space and time and

61
00:03:38,240 --> 00:03:41,360
Speaker 2: everything in between, including how to get your hedgehogs out

62
00:03:41,400 --> 00:03:42,160
Speaker 2: of your hinge.

63
00:03:42,840 --> 00:03:46,280
Speaker 1: So there is a question I always get about hedgehogs,

64
00:03:46,320 --> 00:03:49,560
Speaker 1: and it is how do they reproduce? And my answer

65
00:03:49,720 --> 00:03:54,120
Speaker 1: is very carefully, that's a.

66
00:03:54,160 --> 00:03:59,600
Speaker 2: Very pointed answer, Katie. And people have questions about the universe.

67
00:03:59,600 --> 00:04:02,080
Speaker 2: They want about hedgehogs, they want about quantum particles, they

68
00:04:02,080 --> 00:04:05,080
Speaker 2: wonder about quantum hedgehogs, they wonder about hinges, and what

69
00:04:05,160 --> 00:04:08,200
Speaker 2: ancient people saw on them. They wonder what the solstice means,

70
00:04:08,280 --> 00:04:12,000
Speaker 2: and they wonder what's going on between us and distant stars.

71
00:04:12,440 --> 00:04:14,840
Speaker 2: And that's all part of doing physics. You don't have

72
00:04:14,920 --> 00:04:17,200
Speaker 2: to be a professional academic to be a physicist. You

73
00:04:17,240 --> 00:04:19,880
Speaker 2: just have to wonder about the nature of the universe

74
00:04:20,080 --> 00:04:23,280
Speaker 2: and then share that curiosity with everybody else, and we

75
00:04:23,360 --> 00:04:26,120
Speaker 2: hope you share it with us. If you have a

76
00:04:26,200 --> 00:04:28,640
Speaker 2: question about how the universe works, and you can find

77
00:04:28,640 --> 00:04:31,560
Speaker 2: an answer on Google or chat, GPT or your friendly

78
00:04:31,600 --> 00:04:35,000
Speaker 2: neighborhood physicists, please write to me to questions at Daniel

79
00:04:35,040 --> 00:04:38,279
Speaker 2: Andjorge dot com. We will answer it. Everybody gets an

80
00:04:38,320 --> 00:04:41,000
Speaker 2: answer in their inbox, and sometimes we take an answer

81
00:04:41,040 --> 00:04:44,080
Speaker 2: and put it right here on the podcast, also because

82
00:04:44,120 --> 00:04:45,920
Speaker 2: we've been missing you and we wanted to hear from

83
00:04:45,960 --> 00:04:46,359
Speaker 2: you again.

84
00:04:47,320 --> 00:04:51,320
Speaker 1: So ninety nine percent of a part of coul physicist's

85
00:04:51,400 --> 00:04:55,880
Speaker 1: job is asking the right questions, and one percent is

86
00:04:55,920 --> 00:04:57,120
Speaker 1: you know, math or whatever.

87
00:04:58,560 --> 00:05:00,000
Speaker 2: And there's also got to be rooting there for now.

88
00:05:00,279 --> 00:05:03,160
Speaker 1: Napping is crucial, right right, And like a little bit

89
00:05:03,200 --> 00:05:03,839
Speaker 1: of grant.

90
00:05:03,560 --> 00:05:08,960
Speaker 2: Writing occasionally, and so on today's episode, we'll be answering

91
00:05:14,240 --> 00:05:19,680
Speaker 2: listener questions. Winter Solstice Edition Happy holidays and New Year

92
00:05:19,720 --> 00:05:22,760
Speaker 2: and Solstice to everybody out there who celebrates whatever it

93
00:05:22,839 --> 00:05:25,560
Speaker 2: is you celebrate. Today, we're going to be celebrating my

94
00:05:25,720 --> 00:05:29,000
Speaker 2: answering a really fun question from a listener, a question

95
00:05:29,120 --> 00:05:32,080
Speaker 2: he thought of while he was in his backyard shed,

96
00:05:32,400 --> 00:05:37,040
Speaker 2: maybe building his own hinge. Here's the question from Alex.

97
00:05:37,880 --> 00:05:41,880
Speaker 3: Hi, guys, I was working in my backyard on my shed,

98
00:05:42,480 --> 00:05:45,880
Speaker 3: and I was using a metal crowbar to help out

99
00:05:46,240 --> 00:05:49,080
Speaker 3: one day when I just realized holding it how strong

100
00:05:49,080 --> 00:05:52,720
Speaker 3: it was. So my question that came to me was,

101
00:05:53,440 --> 00:05:57,720
Speaker 3: what is actually the longest physical possible crowbar made of

102
00:05:57,760 --> 00:06:05,600
Speaker 3: metal that that could exist in space? Is it possible

103
00:06:05,640 --> 00:06:09,320
Speaker 3: that you could build one? One could exist that's long

104
00:06:09,400 --> 00:06:12,880
Speaker 3: enough to stretch between stars, especially if you didn't have

105
00:06:12,880 --> 00:06:15,600
Speaker 3: to worry about adding to its length with unlimited supplies,

106
00:06:17,320 --> 00:06:19,720
Speaker 3: and if it was nowhere near any other gravitational objects.

107
00:06:20,440 --> 00:06:23,440
Speaker 3: What would the ramifications be of having it like a

108
00:06:23,480 --> 00:06:26,000
Speaker 3: crowbar where one end was light hours away from the other,

109
00:06:26,160 --> 00:06:29,120
Speaker 3: or even light years away from the other. It seems

110
00:06:29,120 --> 00:06:32,839
Speaker 3: a bit weird to travel light speed and not get

111
00:06:32,839 --> 00:06:35,320
Speaker 3: from one end to the other on one particular object.

112
00:06:36,480 --> 00:06:40,719
Speaker 1: Thank you, So you know I have a similar question.

113
00:06:40,839 --> 00:06:44,080
Speaker 1: But once I just saw a crow bar on the ground,

114
00:06:44,440 --> 00:06:47,560
Speaker 1: I think there were some people working on something like

115
00:06:47,600 --> 00:06:51,240
Speaker 1: a manhole or something sort of nearby. But also I

116
00:06:51,320 --> 00:06:54,840
Speaker 1: wondered if the world operates by video game rules, which is,

117
00:06:55,000 --> 00:06:57,599
Speaker 1: if you find a crowbar, is that yours now? Do

118
00:06:57,680 --> 00:06:59,560
Speaker 1: you pick it up and put it in your inventory?

119
00:06:59,680 --> 00:07:01,039
Speaker 1: Or is that that's still stealing?

120
00:07:02,040 --> 00:07:04,479
Speaker 2: I don't know. Maybe the world operates by checkof rules.

121
00:07:04,520 --> 00:07:06,920
Speaker 2: If you find a crowbar in act one, then you're

122
00:07:06,920 --> 00:07:08,839
Speaker 2: gonna have about to break into something with it in

123
00:07:08,880 --> 00:07:09,520
Speaker 2: Act three.

124
00:07:10,000 --> 00:07:11,960
Speaker 1: I mean that is just video game rules.

125
00:07:12,000 --> 00:07:16,680
Speaker 2: Also exactly exactly. I used to play like King's Quest

126
00:07:16,760 --> 00:07:18,680
Speaker 2: back in the day, and every time you found like

127
00:07:18,720 --> 00:07:20,400
Speaker 2: a weird magic rap mushroom, you put it in your

128
00:07:20,400 --> 00:07:22,200
Speaker 2: back pocket because you knew you were gonna need it

129
00:07:22,240 --> 00:07:24,000
Speaker 2: to solve some puzzle later on.

130
00:07:24,520 --> 00:07:27,240
Speaker 1: Get ye bucket. You're gonna need that bucket for the

131
00:07:27,360 --> 00:07:29,280
Speaker 1: dragon at the end of the game.

132
00:07:29,480 --> 00:07:31,920
Speaker 2: Exactly, and you can't go back, so get the bucket now.

133
00:07:32,480 --> 00:07:35,080
Speaker 2: And Alex is wondering about like the practical limits of

134
00:07:35,160 --> 00:07:38,160
Speaker 2: how big we could build something like, could you build

135
00:07:38,160 --> 00:07:40,600
Speaker 2: a crowbar that's long enough that you can use it

136
00:07:40,680 --> 00:07:44,119
Speaker 2: to like poke people on other planets that that's pretty crazy,

137
00:07:44,160 --> 00:07:44,760
Speaker 2: thought Alex.

138
00:07:45,720 --> 00:07:49,160
Speaker 1: It's interesting, right, because sure you could have like a

139
00:07:49,280 --> 00:07:52,520
Speaker 1: large object, but the bigger it gets. Like, there's a

140
00:07:52,520 --> 00:07:55,120
Speaker 1: lot of questions here, right, we need to know about

141
00:07:55,800 --> 00:07:59,400
Speaker 1: a what are crowbars made out of? Steel? Iron?

142
00:08:00,040 --> 00:08:00,320
Speaker 2: Feeling?

143
00:08:00,960 --> 00:08:04,000
Speaker 1: Steal? And so it's like, I guess a lot of

144
00:08:04,040 --> 00:08:08,800
Speaker 1: it is basically the strength, like the steal, you know,

145
00:08:08,840 --> 00:08:11,720
Speaker 1: the the what steals made out of? How that would work?

146
00:08:12,680 --> 00:08:16,760
Speaker 1: But also you know how even if it's made out

147
00:08:16,800 --> 00:08:19,720
Speaker 1: of any material, right, Like let's say crowbar made out

148
00:08:19,760 --> 00:08:24,400
Speaker 1: of whatever material, the strongest, hardest material you could get, Like,

149
00:08:24,640 --> 00:08:28,080
Speaker 1: is there a limit to the size of physical objects

150
00:08:28,080 --> 00:08:30,960
Speaker 1: in the universe before some wacky starts happening?

151
00:08:31,800 --> 00:08:34,600
Speaker 2: Yeah, this is really fun, And there's a really important

152
00:08:34,679 --> 00:08:38,560
Speaker 2: lesson here about how we do physics anyway, because an

153
00:08:38,559 --> 00:08:41,839
Speaker 2: important sort of often implicit step that we don't talk

154
00:08:41,880 --> 00:08:45,520
Speaker 2: about when we do physics is building a simplified model

155
00:08:45,760 --> 00:08:48,760
Speaker 2: of the universe. Like you want to answer a physics question,

156
00:08:48,920 --> 00:08:51,720
Speaker 2: you know, like a piano is falling from a window.

157
00:08:52,160 --> 00:08:53,920
Speaker 2: Is it going to squish that little doggie?

158
00:08:54,360 --> 00:08:55,520
Speaker 1: No?

159
00:08:55,559 --> 00:08:58,280
Speaker 2: Oh no, hopefully answer is no. But to answer that

160
00:08:58,320 --> 00:09:01,720
Speaker 2: physics question, which you have to do is simplify at first.

161
00:09:01,760 --> 00:09:03,440
Speaker 2: Because you don't care about a lot of the details.

162
00:09:03,440 --> 00:09:05,360
Speaker 2: You don't care about the color of the piano, you

163
00:09:05,400 --> 00:09:08,679
Speaker 2: can probably ignore the crosswinds. You build a simplified model

164
00:09:08,679 --> 00:09:11,079
Speaker 2: that just contains the information necessary to.

165
00:09:11,040 --> 00:09:13,839
Speaker 1: Answer the question, like the breed of the dog for.

166
00:09:13,840 --> 00:09:16,360
Speaker 2: Example, Yeah we don't care, I mean we care, but

167
00:09:16,440 --> 00:09:19,320
Speaker 2: doesn't change the answer. And so the trick there is

168
00:09:19,360 --> 00:09:21,240
Speaker 2: to make a model that's simple enough that you can

169
00:09:21,280 --> 00:09:23,560
Speaker 2: actually answer it because you've included all the details of

170
00:09:23,559 --> 00:09:27,800
Speaker 2: all the quantum particles and be intractable, but is sophisticated

171
00:09:27,920 --> 00:09:30,920
Speaker 2: enough that it still provides a realistic answer. That's the

172
00:09:30,960 --> 00:09:34,280
Speaker 2: sweet spot for doing physics. And the interesting thing is

173
00:09:34,320 --> 00:09:36,959
Speaker 2: that that's a different model in every scenario. You can

174
00:09:37,040 --> 00:09:39,360
Speaker 2: ignore the winds in this case, but if you're solving

175
00:09:39,400 --> 00:09:41,360
Speaker 2: a different problem like what's going to happen to this

176
00:09:41,440 --> 00:09:44,280
Speaker 2: leaf and a tornado, you can't ignore the winds. So

177
00:09:44,320 --> 00:09:46,079
Speaker 2: every time you solve a physics problem, you need to

178
00:09:46,120 --> 00:09:49,640
Speaker 2: ask yourself, am I including the right assumptions or the

179
00:09:49,640 --> 00:09:52,480
Speaker 2: assumptions I'm making going to ruin it? And so I

180
00:09:52,600 --> 00:09:55,079
Speaker 2: run into this all the time with these very long

181
00:09:55,200 --> 00:09:57,439
Speaker 2: space rods. Al It turns out Alex is not the

182
00:09:57,520 --> 00:10:00,199
Speaker 2: only person to think about really long rods. It comes

183
00:10:00,280 --> 00:10:02,720
Speaker 2: up a lot because people have this idea that a

184
00:10:02,880 --> 00:10:06,240
Speaker 2: rod is sort of like infinitely rigid. Like if I'm

185
00:10:06,320 --> 00:10:08,520
Speaker 2: across the room from you and I have a dowel

186
00:10:08,600 --> 00:10:11,280
Speaker 2: like a wooden stick, if I push it, then you're

187
00:10:11,320 --> 00:10:13,240
Speaker 2: gonna feel me pushing it. You're holding the other end,

188
00:10:13,240 --> 00:10:15,520
Speaker 2: you're gonna feel it. And people imagine that sort of

189
00:10:15,520 --> 00:10:18,200
Speaker 2: happens instantaneously, that if I push on the stick on

190
00:10:18,200 --> 00:10:21,240
Speaker 2: one side, you feel it instantly. And that's mostly true,

191
00:10:21,280 --> 00:10:23,280
Speaker 2: and for basically every problem you're going to solve here

192
00:10:23,320 --> 00:10:26,959
Speaker 2: on Earth, that's basically the case, because the information travels

193
00:10:27,080 --> 00:10:29,760
Speaker 2: very very fast. But then people wonder, all right, what

194
00:10:29,800 --> 00:10:31,640
Speaker 2: if I take a rod and I build it so

195
00:10:31,679 --> 00:10:34,960
Speaker 2: it's like four light years long, and I stretch it

196
00:10:35,000 --> 00:10:37,880
Speaker 2: from here to Alpha Centauri and some alien is holding

197
00:10:37,880 --> 00:10:41,040
Speaker 2: the other side. Can I tap on my side and

198
00:10:41,200 --> 00:10:43,520
Speaker 2: use that to communicate faster than the speed of light.

199
00:10:43,600 --> 00:10:46,680
Speaker 2: That's a very common question I get, And the answer

200
00:10:46,720 --> 00:10:50,120
Speaker 2: is obviously no. You can't break special relativity with a

201
00:10:50,360 --> 00:10:52,160
Speaker 2: dowel that's four light years long.

202
00:10:52,520 --> 00:10:54,160
Speaker 1: Even dowels have their limits.

203
00:10:54,160 --> 00:10:57,040
Speaker 2: I guess, yeah, and the reason is that you've broken

204
00:10:57,080 --> 00:11:00,800
Speaker 2: the assumptions. Down here on Earth, it works to a boom. Yeah,

205
00:11:00,840 --> 00:11:03,480
Speaker 2: the information travels instantly. That when you push one side

206
00:11:03,480 --> 00:11:06,320
Speaker 2: of the dowel, the other side moves instantly. But that

207
00:11:06,360 --> 00:11:09,880
Speaker 2: doesn't work anymore when the dowel's really really long, because

208
00:11:09,920 --> 00:11:13,000
Speaker 2: the time it takes now matters, because a dowel, even

209
00:11:13,040 --> 00:11:16,720
Speaker 2: here on Earth, doesn't transmit information instantly. What happens when

210
00:11:16,760 --> 00:11:19,200
Speaker 2: you push on one side of the dowel is that

211
00:11:19,240 --> 00:11:21,840
Speaker 2: you don't immediately move the other side. You push on

212
00:11:21,840 --> 00:11:24,760
Speaker 2: one side, and it moves the layer of molecules that

213
00:11:24,800 --> 00:11:27,160
Speaker 2: are next to the edge, which you mean the next layer,

214
00:11:27,200 --> 00:11:29,320
Speaker 2: which moved the next layer, which moved the next layer.

215
00:11:29,679 --> 00:11:32,280
Speaker 2: Because a dowel is not infinitely rigid, it's like a

216
00:11:32,360 --> 00:11:34,840
Speaker 2: very stiff version of a tube of water or like

217
00:11:34,880 --> 00:11:37,480
Speaker 2: a string. You're pushing on it and there's a wave

218
00:11:37,600 --> 00:11:41,160
Speaker 2: of information that travels down the dowel. So here on Earth,

219
00:11:41,200 --> 00:11:42,679
Speaker 2: you push on one side of the dowel, the other

220
00:11:42,760 --> 00:11:46,520
Speaker 2: side moves very shortly afterwards, but not instantly. It takes

221
00:11:46,559 --> 00:11:50,160
Speaker 2: time for that information and move down the dowel. Now,

222
00:11:50,120 --> 00:11:52,280
Speaker 2: when your Dowel is four light years long. That time

223
00:11:52,360 --> 00:11:54,880
Speaker 2: is no longer something you can ignore. It plays a

224
00:11:54,880 --> 00:11:57,920
Speaker 2: big part in how long it takes for the information

225
00:11:57,960 --> 00:12:00,600
Speaker 2: to get there. And if you ignore that, you're violating

226
00:12:00,600 --> 00:12:03,600
Speaker 2: special relativity. And it seems like you could send information

227
00:12:03,640 --> 00:12:05,600
Speaker 2: to the stars faster than the speed of light, which

228
00:12:05,640 --> 00:12:06,600
Speaker 2: of course you can't.

229
00:12:06,960 --> 00:12:10,160
Speaker 1: This is actually the same problem from a biological perspective

230
00:12:10,160 --> 00:12:13,720
Speaker 1: of having like a giant brain, right, could you have

231
00:12:14,360 --> 00:12:20,480
Speaker 1: an enormous brain that could like communicate instantly, right, like

232
00:12:20,559 --> 00:12:24,720
Speaker 1: some galaxy sized brain. And the problem is that the

233
00:12:24,760 --> 00:12:26,880
Speaker 1: way our brains work in the same way that you

234
00:12:26,920 --> 00:12:29,560
Speaker 1: talked about, how like the molecules have to push on

235
00:12:29,600 --> 00:12:32,400
Speaker 1: the other molecules, Like our brain is all physics based.

236
00:12:32,480 --> 00:12:35,640
Speaker 1: Our whole bodies are basically a big rub Goldberg machine

237
00:12:35,880 --> 00:12:41,240
Speaker 1: of molecules bonking into other molecules, which creates things like thought.

238
00:12:41,840 --> 00:12:45,000
Speaker 1: And so if you have a say, a giant enough brain,

239
00:12:45,440 --> 00:12:48,520
Speaker 1: the time it would take to like have a single

240
00:12:48,600 --> 00:12:53,400
Speaker 1: thought would be incredibly slow. So the bigger the brain,

241
00:12:53,880 --> 00:12:57,080
Speaker 1: the more galaxy size the brain, actually the slower it

242
00:12:57,120 --> 00:12:58,280
Speaker 1: would take to have it.

243
00:12:58,400 --> 00:13:01,800
Speaker 2: Not yeah, exactly. And so if you're ignoring that, when

244
00:13:01,800 --> 00:13:03,560
Speaker 2: you're just thinking about a small brain. You can no

245
00:13:03,640 --> 00:13:06,520
Speaker 2: longer ignore that in a large brain. So the lesson is,

246
00:13:06,559 --> 00:13:08,600
Speaker 2: when you're doing physics, you have to always think about

247
00:13:08,679 --> 00:13:11,760
Speaker 2: what are the assumptions we're making and are those assumptions

248
00:13:11,800 --> 00:13:14,640
Speaker 2: still valid for this scenario. In the case of the

249
00:13:14,760 --> 00:13:18,959
Speaker 2: like five light year long rod, if you assume instantaneous

250
00:13:19,000 --> 00:13:21,240
Speaker 2: motion from one side to the other, then you're assuming

251
00:13:21,280 --> 00:13:24,320
Speaker 2: special relativity is broken. So you can't then go and say, oh, look,

252
00:13:24,360 --> 00:13:26,599
Speaker 2: this rod breaks special relativity. Well, you assume to it

253
00:13:26,760 --> 00:13:29,400
Speaker 2: is broken, and that's why you broke it. And so

254
00:13:29,640 --> 00:13:32,520
Speaker 2: there's a lot of unpacking of those assumptions in these questions.

255
00:13:33,080 --> 00:13:35,000
Speaker 2: But Alex's question is a little bit different. He's not

256
00:13:35,040 --> 00:13:37,360
Speaker 2: trying to communicate with aliens. He's just trying to build

257
00:13:37,360 --> 00:13:39,760
Speaker 2: a really long rod, and he's wondering, like how big

258
00:13:39,840 --> 00:13:42,400
Speaker 2: could you make it? Anyway? And I think that's exactly

259
00:13:42,440 --> 00:13:44,920
Speaker 2: what he's digging into, like what would break down? What

260
00:13:45,000 --> 00:13:48,400
Speaker 2: assumptions we make about building long rods would break down

261
00:13:48,400 --> 00:13:50,200
Speaker 2: if we try to make one that's like a light

262
00:13:50,280 --> 00:13:52,480
Speaker 2: year long, Which is a really cool question.

263
00:13:52,400 --> 00:13:55,200
Speaker 1: Yeah, because I mean there's a lot of things that

264
00:13:55,520 --> 00:13:57,800
Speaker 1: we could say, like on Earth, right, Like, we could

265
00:13:57,880 --> 00:14:00,200
Speaker 1: try to build a really long crow bar and at

266
00:14:00,200 --> 00:14:03,319
Speaker 1: a certain point it could collapse under its own weight.

267
00:14:03,600 --> 00:14:07,600
Speaker 1: But if something's in space, we'd have to figure out

268
00:14:07,640 --> 00:14:11,640
Speaker 1: what kinds of forces or how gravity would be acting

269
00:14:11,800 --> 00:14:15,440
Speaker 1: on something in a way that's different from Earth, right, Like, yes,

270
00:14:15,720 --> 00:14:18,280
Speaker 1: you can. You know, it's like have you ever you

271
00:14:18,280 --> 00:14:21,920
Speaker 1: know whiteboard pins? Like you create a big old lightsaber

272
00:14:21,960 --> 00:14:25,240
Speaker 1: out of whiteboard pins and at a certain point there's

273
00:14:25,320 --> 00:14:29,840
Speaker 1: too many and it collapses. But that's all using Earth physics.

274
00:14:29,880 --> 00:14:35,120
Speaker 1: So you could make a much longer whiteboard pin lightsaber

275
00:14:35,520 --> 00:14:39,280
Speaker 1: out in space because gravity is not impacting it in

276
00:14:39,320 --> 00:14:41,040
Speaker 1: the same way that it is on Earth. But then

277
00:14:41,080 --> 00:14:44,920
Speaker 1: once you get big enough, right with this pin dowel

278
00:14:45,080 --> 00:14:49,440
Speaker 1: or iron crowbar or whatever it is, something's happening. And

279
00:14:49,480 --> 00:14:52,040
Speaker 1: this is where I would like you to talk.

280
00:14:52,680 --> 00:14:56,800
Speaker 2: Yeah, exactly. So let's take this question out into deep space.

281
00:14:57,280 --> 00:14:59,160
Speaker 2: And the first thing the wonder is like, well, what's

282
00:14:59,200 --> 00:15:02,080
Speaker 2: the biggest thing we built in space so far? And

283
00:15:02,120 --> 00:15:04,560
Speaker 2: that's the International Space Station. It's not that impressively long,

284
00:15:04,600 --> 00:15:07,600
Speaker 2: it's about thirty six meters long, but you know, it's

285
00:15:07,600 --> 00:15:10,120
Speaker 2: not very far out in space, and they're not trying

286
00:15:10,120 --> 00:15:13,040
Speaker 2: to build something super duper long. I think the longest

287
00:15:13,080 --> 00:15:15,120
Speaker 2: thing that's ever actually been in space, it's more like

288
00:15:15,120 --> 00:15:18,160
Speaker 2: a kilometer. They build a space tether, which is like

289
00:15:18,200 --> 00:15:21,560
Speaker 2: a really long wire that you dangle from a spaceship

290
00:15:21,600 --> 00:15:24,560
Speaker 2: to try to like generate electrical current or to learn

291
00:15:24,600 --> 00:15:28,640
Speaker 2: to steer using mechnetic fields. So like a kilometer long,

292
00:15:28,640 --> 00:15:31,240
Speaker 2: it's the biggest thing that we've ever put into space.

293
00:15:31,760 --> 00:15:34,120
Speaker 2: But again that's also just the near Earth orbit. So

294
00:15:34,360 --> 00:15:37,040
Speaker 2: let's go deeper out into space and try to build

295
00:15:37,040 --> 00:15:40,640
Speaker 2: something that's really long and think about the forces involved.

296
00:15:40,680 --> 00:15:43,520
Speaker 2: Like when you build a rod at a steel or

297
00:15:43,560 --> 00:15:46,160
Speaker 2: even a dowel out of wood or whatever, how are

298
00:15:46,160 --> 00:15:48,680
Speaker 2: you actually building that thing. Usually we ignore it and

299
00:15:48,720 --> 00:15:51,280
Speaker 2: just say, oh, it's some smooth, continuous substance. But if

300
00:15:51,280 --> 00:15:54,800
Speaker 2: you zoom in, the reason it takes time to propagate

301
00:15:54,800 --> 00:15:57,720
Speaker 2: information along it is the same thing that's holding it together,

302
00:15:57,760 --> 00:16:00,720
Speaker 2: which is the forces between those molecules. All of these

303
00:16:00,760 --> 00:16:03,200
Speaker 2: objects in the end are like a mesh of modules.

304
00:16:03,280 --> 00:16:05,360
Speaker 2: Yet you have these little bits of matter tied together

305
00:16:05,480 --> 00:16:09,280
Speaker 2: by forces to build something larger, and it's those forces

306
00:16:09,320 --> 00:16:12,760
Speaker 2: that transmit the information also limit how big something can

307
00:16:12,880 --> 00:16:16,120
Speaker 2: get right and so out into deep space. What is

308
00:16:16,160 --> 00:16:19,000
Speaker 2: the thing that's limiting us. Well, those forces can work.

309
00:16:19,000 --> 00:16:22,720
Speaker 2: They can tie something together basically infinitely. There's no limitation there.

310
00:16:22,720 --> 00:16:25,040
Speaker 2: You can just keep adding layers and layers and layers

311
00:16:25,040 --> 00:16:27,160
Speaker 2: to your rod. The thing that's going to keep you

312
00:16:27,160 --> 00:16:30,480
Speaker 2: from building that rod light years long or infinitely long

313
00:16:30,560 --> 00:16:33,920
Speaker 2: in the end, are going to be the gravitational effects,

314
00:16:33,960 --> 00:16:37,160
Speaker 2: residual as they are, and the nature of space and

315
00:16:37,200 --> 00:16:40,720
Speaker 2: time itself. But let's first talk about the gravitational effects.

316
00:16:40,920 --> 00:16:44,440
Speaker 2: So one effect are tidal forces. So you say, well,

317
00:16:44,480 --> 00:16:47,640
Speaker 2: let's be out between the stars. AX is actually talking

318
00:16:47,640 --> 00:16:49,760
Speaker 2: about something which stretches between the stars. You have like

319
00:16:49,840 --> 00:16:51,840
Speaker 2: one end at one star and the other end at

320
00:16:51,880 --> 00:16:54,440
Speaker 2: another star. And if you have something that's like five

321
00:16:54,520 --> 00:16:56,800
Speaker 2: light years long, you can't have it that far away

322
00:16:56,800 --> 00:16:59,160
Speaker 2: from stars because it's going to be big enough. There's

323
00:16:59,160 --> 00:17:02,440
Speaker 2: always going to be some star nearby. And remember that

324
00:17:02,520 --> 00:17:04,679
Speaker 2: gravity does more than just pull on things. It can

325
00:17:04,720 --> 00:17:07,919
Speaker 2: actually pull things apart. These are called tidal forces. And

326
00:17:07,960 --> 00:17:11,160
Speaker 2: for example, if you're near a black hole, then your

327
00:17:11,280 --> 00:17:14,000
Speaker 2: head can have a different gravitational tug on it than

328
00:17:14,040 --> 00:17:17,000
Speaker 2: your feet, and that can effectively tear you apart. Like,

329
00:17:17,040 --> 00:17:19,080
Speaker 2: if the black hole is pulling on your feet harder

330
00:17:19,119 --> 00:17:21,080
Speaker 2: than it's pulling on your head because your feet are

331
00:17:21,119 --> 00:17:23,520
Speaker 2: a little bit closer, then it's going to pull you

332
00:17:23,560 --> 00:17:26,560
Speaker 2: apart because its gravity is really really strong. But if

333
00:17:26,560 --> 00:17:30,160
Speaker 2: you're really really long, then you don't need strong gravity

334
00:17:30,200 --> 00:17:32,200
Speaker 2: to have tidal forces. Because if one end of this

335
00:17:32,320 --> 00:17:34,960
Speaker 2: rod is closer to the star then the other end,

336
00:17:35,240 --> 00:17:37,680
Speaker 2: and the rod is really really long, it's going to

337
00:17:37,720 --> 00:17:40,960
Speaker 2: be a very large difference in the gravitational force from

338
00:17:40,960 --> 00:17:42,320
Speaker 2: one end of the rod to the other, and that

339
00:17:42,400 --> 00:17:44,679
Speaker 2: star is going to tear it apart. Even if the

340
00:17:44,680 --> 00:17:47,959
Speaker 2: star doesn't have really powerful gravity like black holes, the

341
00:17:47,960 --> 00:17:51,600
Speaker 2: sheer length of the rod makes the title forces very significant.

342
00:17:51,720 --> 00:17:56,320
Speaker 1: I see. So you can't span a dell from one

343
00:17:56,359 --> 00:17:59,160
Speaker 1: start to the other because of the same title forces

344
00:17:59,240 --> 00:18:04,640
Speaker 1: that spaghettifies you in a black hole. But what if

345
00:18:04,680 --> 00:18:08,720
Speaker 1: you took away the stars? Right? Like, could you get

346
00:18:08,760 --> 00:18:14,040
Speaker 1: a like infinity rod if you took away stars and

347
00:18:14,200 --> 00:18:18,160
Speaker 1: just had it existing on its own in space without

348
00:18:18,280 --> 00:18:19,040
Speaker 1: hitting anything?

349
00:18:19,520 --> 00:18:21,680
Speaker 2: Yeah? Right, So get rid of the other gravity, and

350
00:18:21,800 --> 00:18:23,800
Speaker 2: you still have the issue of the gravity of the

351
00:18:23,920 --> 00:18:28,000
Speaker 2: rod itself. Right, You can't build an infinitely massive rod,

352
00:18:28,040 --> 00:18:30,120
Speaker 2: because eventually that thing is going to have its own

353
00:18:30,240 --> 00:18:34,199
Speaker 2: self gravity, that it's going to collapse into a black hole. Like,

354
00:18:34,240 --> 00:18:36,720
Speaker 2: you can't just make a blob of metal and keep

355
00:18:36,760 --> 00:18:38,800
Speaker 2: adding blobs of metal to it and make it as

356
00:18:38,840 --> 00:18:41,440
Speaker 2: big as you want, because it's going to start collapsing.

357
00:18:41,640 --> 00:18:44,240
Speaker 2: This already happens for things like planets, like the Earth

358
00:18:44,320 --> 00:18:47,280
Speaker 2: is about the largest rocky planet you can make. You

359
00:18:47,320 --> 00:18:49,159
Speaker 2: can add more rock to it, but that's going to

360
00:18:49,200 --> 00:18:51,560
Speaker 2: mean more gravity, and it's just going to compress the

361
00:18:51,640 --> 00:18:54,560
Speaker 2: Earth further. So as you add more mass to the Earth,

362
00:18:54,600 --> 00:18:57,600
Speaker 2: it doesn't get any bigger, it just gets denser. And

363
00:18:57,680 --> 00:19:00,239
Speaker 2: eventually you keep adding mass, you're going to end up

364
00:19:00,240 --> 00:19:02,800
Speaker 2: with a black hole. And so there is a limit

365
00:19:02,880 --> 00:19:05,760
Speaker 2: to how large and how massive you can make something

366
00:19:06,040 --> 00:19:09,000
Speaker 2: before it collapses into a black hole. So something self

367
00:19:09,040 --> 00:19:12,280
Speaker 2: gravity will also limit how large you can make an

368
00:19:12,320 --> 00:19:15,160
Speaker 2: object out of practical stuff like steel or wood.

369
00:19:15,359 --> 00:19:19,119
Speaker 1: Okay, so what about a really thin rod. Now stay

370
00:19:19,160 --> 00:19:22,320
Speaker 1: with me. What if you have a rod that is

371
00:19:22,440 --> 00:19:26,840
Speaker 1: like one atom per unit, right, is like one atom thick,

372
00:19:27,080 --> 00:19:30,880
Speaker 1: and then you just stack a bunch of atoms into

373
00:19:30,920 --> 00:19:37,160
Speaker 1: this very long rod, would that still be something that

374
00:19:37,359 --> 00:19:40,840
Speaker 1: would at a certain point start to collapse in on

375
00:19:40,920 --> 00:19:44,560
Speaker 1: itself because of gravity, or am I already breaking some

376
00:19:44,680 --> 00:19:47,600
Speaker 1: laws of physics by trying to create a one atom

377
00:19:49,040 --> 00:19:50,160
Speaker 1: diameter rod.

378
00:19:50,760 --> 00:19:53,520
Speaker 2: Now you could probably make a carbon nanofiber. Eventually it's

379
00:19:53,560 --> 00:19:55,920
Speaker 2: like one atom thick and super duper long. I don't

380
00:19:55,920 --> 00:19:58,239
Speaker 2: think it's a technical problem there, But what you're going

381
00:19:58,280 --> 00:20:00,199
Speaker 2: to run into is a problem with a knee. You're

382
00:20:00,240 --> 00:20:02,879
Speaker 2: a space and time, and if you can get rid

383
00:20:02,880 --> 00:20:05,439
Speaker 2: of gravity then nearby stars and effectively get rid of

384
00:20:05,440 --> 00:20:08,200
Speaker 2: the self gravity by making this thing really really lightweight,

385
00:20:08,720 --> 00:20:12,320
Speaker 2: you're going to run into dark energy. So in short distances,

386
00:20:12,880 --> 00:20:14,560
Speaker 2: like the size of our Solar system of the size

387
00:20:14,560 --> 00:20:17,800
Speaker 2: of our galaxy, the dominant force is gravity. It holds

388
00:20:17,800 --> 00:20:20,520
Speaker 2: things together, it shapes things, it determines the nature of

389
00:20:20,560 --> 00:20:24,399
Speaker 2: our universe. But over very large distances, gravity gets weaker. Right,

390
00:20:24,480 --> 00:20:26,960
Speaker 2: the further you are away from something, the weaker it's

391
00:20:26,960 --> 00:20:30,480
Speaker 2: gravity is. And at those distances something else takes over,

392
00:20:30,520 --> 00:20:34,280
Speaker 2: which is dark energy, meaning the expansion of the universe itself.

393
00:20:34,840 --> 00:20:38,440
Speaker 2: Remember that everywhere in the universe is expanding. Take any

394
00:20:38,600 --> 00:20:41,639
Speaker 2: arbitrary chunk of space as time goes on, that space

395
00:20:41,720 --> 00:20:45,119
Speaker 2: is getting larger. It's making new space. So between the

396
00:20:45,160 --> 00:20:48,080
Speaker 2: Earth and the Sun, for example, new space is being made,

397
00:20:48,240 --> 00:20:50,719
Speaker 2: but the gravity of the Earth and the Sun overpowers it.

398
00:20:51,040 --> 00:20:54,720
Speaker 2: Between our galaxy and the neighboring galaxy, new space is

399
00:20:54,760 --> 00:20:58,199
Speaker 2: being made, but again the gravity overpowers it. But eventually,

400
00:20:58,480 --> 00:21:02,920
Speaker 2: between clusters of galonyes, dark energy becomes more powerful because

401
00:21:02,960 --> 00:21:05,480
Speaker 2: you have more of these cubes of space and each

402
00:21:05,520 --> 00:21:08,680
Speaker 2: one is expanding, so that adds up and gravity gets

403
00:21:08,760 --> 00:21:12,719
Speaker 2: very very weak. So take Alex's super duper long, infinitely

404
00:21:12,800 --> 00:21:15,760
Speaker 2: thin rod. Eventually it's going to be so long that

405
00:21:15,880 --> 00:21:18,600
Speaker 2: dark energy is going to tear it apart. It's going

406
00:21:18,640 --> 00:21:21,959
Speaker 2: to be creating new space between those atoms faster than

407
00:21:21,960 --> 00:21:25,359
Speaker 2: those atoms can recover and bind themselves together. So you

408
00:21:25,400 --> 00:21:27,959
Speaker 2: can get spaghettified by space and time.

409
00:21:28,240 --> 00:21:33,200
Speaker 1: All right, So we cannot make an infinity rod. Unfortunately,

410
00:21:33,760 --> 00:21:37,480
Speaker 1: do we know, like how big something can get before

411
00:21:37,960 --> 00:21:42,640
Speaker 1: the expansion of the universe starts to break it apart.

412
00:21:42,920 --> 00:21:45,840
Speaker 2: It's gonna be really really big. And remember that nearby

413
00:21:45,960 --> 00:21:49,480
Speaker 2: galaxies are millions of light years away, and dark energy

414
00:21:49,520 --> 00:21:54,439
Speaker 2: only really dominates between clusters of galaxies, So we're talking

415
00:21:54,640 --> 00:21:57,840
Speaker 2: hundreds of millions of light years. So if you can

416
00:21:57,920 --> 00:22:01,680
Speaker 2: overcome the gravity of nearby stars and overcome tidal forces

417
00:22:01,680 --> 00:22:05,399
Speaker 2: completely and overcome collapsing due to self gravity, then you

418
00:22:05,440 --> 00:22:08,080
Speaker 2: could still build something that's like hundreds of millions of

419
00:22:08,119 --> 00:22:10,280
Speaker 2: light years long. So that's pretty good.

420
00:22:10,720 --> 00:22:13,880
Speaker 1: You know what. That sounds great. I'm going to write

421
00:22:13,880 --> 00:22:18,359
Speaker 1: a grant for UH to get started building on the

422
00:22:18,520 --> 00:22:20,880
Speaker 1: biggest spaghetti that one.

423
00:22:20,720 --> 00:22:23,680
Speaker 2: Could make, exact spaghetti simo.

424
00:22:24,280 --> 00:22:27,439
Speaker 1: Yeah. I bet Italy's government would fun that.

425
00:22:27,480 --> 00:22:30,960
Speaker 2: It's going to write yes in honor of the winter solstice.

426
00:22:31,040 --> 00:22:34,120
Speaker 2: I think that's a great idea. All right, Well, thank

427
00:22:34,160 --> 00:22:37,639
Speaker 2: you very much Alex for thinking big and wondering about

428
00:22:37,840 --> 00:22:40,760
Speaker 2: how far we can push our concepts of distance and

429
00:22:40,800 --> 00:22:44,640
Speaker 2: structure and space and time. Really fun way to explore

430
00:22:44,760 --> 00:22:47,600
Speaker 2: all of those different factors, and really appreciate everybody out

431
00:22:47,640 --> 00:22:50,119
Speaker 2: there who's thinking about the universe and wondering about it,

432
00:22:50,200 --> 00:22:52,800
Speaker 2: and who's brave enough to write into their favorite Internet

433
00:22:52,800 --> 00:22:55,399
Speaker 2: physicists to look for some answers. If you'd like to

434
00:22:55,400 --> 00:22:57,600
Speaker 2: see my email in your inbox, write to me two

435
00:22:57,720 --> 00:23:00,680
Speaker 2: questions at Daniel and Jorge dot com. I'd sure love

436
00:23:00,760 --> 00:23:03,399
Speaker 2: to hear from you. Thanks very much, Katie for pushing

437
00:23:03,440 --> 00:23:05,840
Speaker 2: the boundaries of space and time and humor today.

438
00:23:06,280 --> 00:23:10,440
Speaker 1: And thank you for signing on to my petition for

439
00:23:10,760 --> 00:23:12,760
Speaker 1: universe's longest spaghetti.

440
00:23:14,000 --> 00:23:17,159
Speaker 2: Funded funded funded. All right, Thanks everyone for listening, and

441
00:23:17,200 --> 00:23:24,960
Speaker 2: tune in next time for more science and curiosity. Come

442
00:23:25,000 --> 00:23:27,760
Speaker 2: find us on social media, where we answer questions and

443
00:23:27,960 --> 00:23:32,119
Speaker 2: post videos. We're on Twitter, disc Org, Instant, and now TikTok.

444
00:23:32,800 --> 00:23:35,600
Speaker 2: Thanks for listening, and remember that Daniel and Jorge Explain

445
00:23:35,680 --> 00:23:39,680
Speaker 2: the Universe is a production of iHeartRadio. For more podcasts

446
00:23:39,680 --> 00:23:44,360
Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever

447
00:23:44,400 --> 00:23:46,119
Speaker 2: you listen to your favorite shows.