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Why haven't aliens visited us? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, I've got a question for you about aliens.
• 0:12
  Speaker 1: Did you meet some aliens? Can you introduce me? I'd
• 0:15
  Speaker 1: love to meet some aliens. Well, that's my question. Would
• 0:17
  Speaker 1: you believe me if I just told you that I
• 0:20
  Speaker 1: think there are aliens here on Earth? Well? Are you
• 0:23
  Speaker 1: joking or are you being serious? Well? I mean, would
• 0:25
  Speaker 1: I joke about science? Isn't that what this podcast? Is
• 0:28
  Speaker 1: you joking about science? Me? Now, I don't think I
• 0:34
  Speaker 1: joke about science. I think we are a jostle science. Well, um,
• 0:39
  Speaker 1: I think a question of that magnitude of that, you know,
• 0:43
  Speaker 1: historical importance, I'd need to see some evidence. Really, you
• 0:46
  Speaker 1: wouldn't trust me if I said, hey, I met an alien,
• 0:51
  Speaker 1: or I think I know who an alien is. Um,
• 0:53
  Speaker 1: I have a lot of confidence in you, but I
• 0:55
  Speaker 1: think you know, I need to see some evidence on
• 0:57
  Speaker 1: such a big claim and don't take it personally. You know,
• 1:00
  Speaker 1: I don't think I believe Stephen Hawking or Neil deGrasse Tyson,
• 1:03
  Speaker 1: or you know, anybody on a question of such magnitude. Actually,
• 1:06
  Speaker 1: those are the guys that I think are aliens. Okay,
• 1:10
  Speaker 1: now you have me convinced I am jorhe I'm the
• 1:29
  Speaker 1: creator of DHD Comics and a cartoonist. Hi, I'm Daniel.
• 1:32
  Speaker 1: I'm a particle physicist and probably not an alien. Probably
• 1:36
  Speaker 1: keep that in mind. Who can really say for sure?
• 1:39
  Speaker 1: And together we're the co authors of the book We
• 1:41
  Speaker 1: Have No Idea, A Guide to the Unknown Universe, and
• 1:44
  Speaker 1: the co host of this podcast, Daniel and Jorge Explained
• 1:47
  Speaker 1: the Universe, a production of I Heart Radio. That's right,
• 1:50
  Speaker 1: the podcast in which we take you on a journey
• 1:53
  Speaker 1: here and there and everywhere to wonder where is their life?
• 1:56
  Speaker 1: Who's thinking about the universe? Are we the only ones
• 2:00
  Speaker 1: asking our minds out into the vast reaches of empty space,
• 2:03
  Speaker 1: wondering who else is out there? Are we alone? Or
• 2:06
  Speaker 1: is there somebody else out there thinking about the universe?
• 2:09
  Speaker 1: I thought you were gonna launch into Doctor SEUs type
• 2:12
  Speaker 1: of Ryan there, But did Doctor So let's write a
• 2:15
  Speaker 1: book about aliens. Maybe he was the alien. Maybe that's
• 2:20
  Speaker 1: why his books are so good. Now this is the
• 2:22
  Speaker 1: podcast in which we tackle big questions with a Doctor
• 2:26
  Speaker 1: Seuss sort of mindset, explaining things in simple words. That's right.
• 2:29
  Speaker 1: All the places you'll go, all the places will take you. Oh,
• 2:33
  Speaker 1: the tentacles you'll meet on aliens who come and visit. Yeah,
• 2:38
  Speaker 1: we uh kind of This podcast is a lot about
• 2:41
  Speaker 1: our place in the universe, you know, right, And a
• 2:44
  Speaker 1: big question is are we alone? Are we the only
• 2:47
  Speaker 1: ones thinking and having existential crises and having podcasts in
• 2:54
  Speaker 1: this huge universe. It's an amazing question, and it's my
• 2:58
  Speaker 1: favorite type of question because does no matter what the
• 3:00
  Speaker 1: answer is, it's mind blowing, right, Like, Either we're totally
• 3:05
  Speaker 1: alone in the universe trillions and trillions of stars and
• 3:08
  Speaker 1: planets and we're the only thinking technological creatures. That's incredible.
• 3:13
  Speaker 1: What that means I don't know, but spiritually that's pretty important, right,
• 3:18
  Speaker 1: Or we're not and there are thinking aliens out there.
• 3:22
  Speaker 1: Life began on other planets, intelligence is possible in other areas, Like,
• 3:27
  Speaker 1: that's incredible, and what we could learn from those folks.
• 3:30
  Speaker 1: So either answer is incredible, and one day I hope
• 3:33
  Speaker 1: humanity will know the answer. They will know whether we
• 3:36
  Speaker 1: live in this universe where we're all alone or in
• 3:39
  Speaker 1: that universe where we have neighbors, and they're gonna look
• 3:42
  Speaker 1: back and wonder, like, Wow, what was it like to
• 3:44
  Speaker 1: live before we knew the answer to this really basic question. Yeah,
• 3:48
  Speaker 1: they might wonder how could you not know or how
• 3:50
  Speaker 1: could you not expect there to be other sentient life
• 3:53
  Speaker 1: out there? Yeah, it's incredible and so but here we
• 3:55
  Speaker 1: are living in the dark ages of human knowledge, right,
• 3:58
  Speaker 1: not knowing whether we are alone, and of course wondering.
• 4:02
  Speaker 1: And so that's the kind of question that we wanted
• 4:04
  Speaker 1: to ponder today. Are we alone in the universe? Yeah?
• 4:07
  Speaker 1: Could there be somebody else out there? What does physics
• 4:10
  Speaker 1: say about whether or not aliens could have come to visit?
• 4:14
  Speaker 1: So today on the podcast, we'll be tackling the question
• 4:22
  Speaker 1: why haven't aliens visited us or you know, at least
• 4:26
  Speaker 1: called U or d M, does or sent the text
• 4:30
  Speaker 1: message at least you know, let's you know what. Maybe
• 4:34
  Speaker 1: they're using Google Plus and they didn't realize they's been canceled.
• 4:38
  Speaker 1: That would be a t they were early adopters, but
• 4:41
  Speaker 1: it worked against them. Maybe Google, maybe people like Google
• 4:45
  Speaker 1: are the aliens and they tried. That's right, they tried.
• 4:48
  Speaker 1: That's right. And let's set some assumptions, right, because you
• 4:50
  Speaker 1: could talk about this question from lots of different angles.
• 4:53
  Speaker 1: But I think we should make two assumptions. One, let's
• 4:56
  Speaker 1: assume that there are aliens out there, right, I mean,
• 5:00
  Speaker 1: why why do we have to assume it? Well, um,
• 5:03
  Speaker 1: I don't know, Maybe I just prefer it. You know,
• 5:06
  Speaker 1: it's hard for me to imagine that we live in
• 5:07
  Speaker 1: the universe where we are the smartest things in the university.
• 5:11
  Speaker 1: You know, that's just difficult to accept. Well, I think
• 5:13
  Speaker 1: this is the core of the paradox, you know, the question,
• 5:17
  Speaker 1: you know, because you know, we hear a lot from scientists,
• 5:19
  Speaker 1: and you know, science people like Neolograsty Tyson and Stephen Hawking,
• 5:24
  Speaker 1: perhaps that you know, the universe is so big and
• 5:26
  Speaker 1: there's so many stars and so many galaxies out there
• 5:30
  Speaker 1: that there must be life out there. But I think,
• 5:33
  Speaker 1: you know, probably the everyday person listening to this might
• 5:36
  Speaker 1: be thinking, but you know, why haven't we heard from them?
• 5:39
  Speaker 1: You know, any kind of radio signal or probe or
• 5:43
  Speaker 1: a visit or a postcard something. Um, that's kind of
• 5:46
  Speaker 1: the paradox, right, It's like it it seems like we
• 5:48
  Speaker 1: should assume aliens exists, but why haven't we heard from them?
• 5:52
  Speaker 1: That's right, That's right. That's that's the other question. I
• 5:55
  Speaker 1: think the second assumption we should make is that we haven't. Right,
• 5:59
  Speaker 1: there's a lot of talk their people say they've seen
• 6:02
  Speaker 1: UFOs and maybe pilots see weird stuff over the ocean.
• 6:05
  Speaker 1: And there's this ridiculous documentary featuring Bubba Lazar and his
• 6:09
  Speaker 1: absurd claims about having worked in an alien you know,
• 6:13
  Speaker 1: technology re re engineering base. But he has absolutely no
• 6:18
  Speaker 1: evidence to back up any of these claims. That we
• 6:20
  Speaker 1: could dissect some of those claims, etcetera. But I think
• 6:23
  Speaker 1: it was in the Joe Rogan podcast to right, yeah exactly.
• 6:27
  Speaker 1: Netflix paid money for it. Joe Rogan had this guy on,
• 6:31
  Speaker 1: but the guy has absolutely no evidence to back up
• 6:33
  Speaker 1: any of his claims. So I think you can just
• 6:35
  Speaker 1: put him in the same category as lots of other
• 6:37
  Speaker 1: folks that have seen something weird, something they don't understand,
• 6:41
  Speaker 1: and are maybe not reliable eye witnesses. Right, Well, I
• 6:44
  Speaker 1: think this this is kind of the question is should
• 6:46
  Speaker 1: you just believe someone who says they saw aliens? Does
• 6:49
  Speaker 1: physics say it's impossible and therefore you should pay no
• 6:52
  Speaker 1: attention to them, or does physics say that it might
• 6:55
  Speaker 1: be possible, in which case you maybe should think about
• 6:58
  Speaker 1: it or look into it more. Aren't closely? That's right,
• 7:01
  Speaker 1: and that's the question we want to answer. Today's Is
• 7:04
  Speaker 1: there a physics reason to say aliens could not have
• 7:07
  Speaker 1: come visit. Right, does physics say it's possible for aliens
• 7:10
  Speaker 1: to have found us? Or does physics say it's impossible?
• 7:13
  Speaker 1: And then you can take your own skepticism if you
• 7:15
  Speaker 1: like to, to listen to Bob Lazar's claims or the
• 7:18
  Speaker 1: claims of anybody else who who says they've been abducted
• 7:21
  Speaker 1: by aliens, has been experimented on by aliens, etcetera. But
• 7:25
  Speaker 1: today we're going to focus on that question. Right, could
• 7:27
  Speaker 1: aliens have contacted us? Right? Because it could be that
• 7:30
  Speaker 1: it's impossible for aliens to have visited us or contact us, right,
• 7:34
  Speaker 1: I mean, the universe is so vast and d predictable
• 7:38
  Speaker 1: that we you know, it could be impossible for there
• 7:41
  Speaker 1: to be other life out there, and it could be
• 7:44
  Speaker 1: impossible for them to ever reach us or get to us. Right,
• 7:48
  Speaker 1: that's right, And you're just thinking about it momentarily, like
• 7:52
  Speaker 1: you know that space is vast, You know that space
• 7:54
  Speaker 1: is mostly empty. You know, even if it takes us
• 7:57
  Speaker 1: years to get even to the neighboring planet. Right, we've
• 8:00
  Speaker 1: got a rocket ship and wanted to fly to Mars.
• 8:02
  Speaker 1: That would take years, and so to get to a
• 8:04
  Speaker 1: nearby star or do you get to you know, several
• 8:07
  Speaker 1: to explore a space of stars that's a significant fraction
• 8:10
  Speaker 1: of the galaxy. How long would that take? Is that possible?
• 8:13
  Speaker 1: Is the galaxy just too big to explore? That's the
• 8:16
  Speaker 1: kind of question we want to dig into today. Right,
• 8:20
  Speaker 1: So this is a question probably a lot of people
• 8:22
  Speaker 1: maybe think about at least in the back of their
• 8:25
  Speaker 1: minds or entertainedly. You know, everyone has seen the Avengers movies.
• 8:30
  Speaker 1: They're they're aliens there in Star Wars. In the Avengers
• 8:35
  Speaker 1: movies that like, some of the aliens look like raccoons,
• 8:38
  Speaker 1: which is that would be weird? Raccoons are like the
• 8:41
  Speaker 1: central race of the the universe. Wait wait, hold on,
• 8:46
  Speaker 1: are you saying we have been visited by aliens and
• 8:48
  Speaker 1: they are eating our garbage? Maybe it's a delicacy for them.
• 8:52
  Speaker 1: It's like a tourism. That would be a win win, right,
• 8:56
  Speaker 1: we meet aliens, we learned about the physics of the university,
• 9:00
  Speaker 1: and we find somebody to finally accept our recycling. Perfect.
• 9:05
  Speaker 1: We just have to put up with their pooping in
• 9:07
  Speaker 1: your yard or something. And what if they're trash is
• 9:11
  Speaker 1: something we love? Right? Like they poop out gold bars
• 9:15
  Speaker 1: or something chocolate. Well, would you eat a chocolate bar
• 9:19
  Speaker 1: and alien pooped out? Or well you sort of do, right,
• 9:22
  Speaker 1: I mean chocolate, cocoa beans are are fermented, right, so
• 9:27
  Speaker 1: you're sort of eating a kind of the poop there
• 9:30
  Speaker 1: of bacteria. Right, chocolate is fermented. What I think? I
• 9:34
  Speaker 1: think they ferment that they ferment cocoa beans like they
• 9:37
  Speaker 1: harvest them and then they lead them on the sun.
• 9:39
  Speaker 1: They rot a little and then they I could, I could,
• 9:42
  Speaker 1: I could be saying physically impossible things. Well, um, I
• 9:46
  Speaker 1: don't know about whether cocoa is fermented, but you're right,
• 9:49
  Speaker 1: we do consume a lot of products that are fermented,
• 9:53
  Speaker 1: which is basically the byproduct of microbial metabolism. So we
• 9:56
  Speaker 1: have cheese and bread and beer. We're definitely building up
• 10:00
  Speaker 1: my cribial poop all the time, and some of it's delicious. Yeah,
• 10:04
  Speaker 1: until he's totally not derailed this conversation. But back to aliens,
• 10:10
  Speaker 1: Back to aliens, Back to aliens exactly. And so I
• 10:13
  Speaker 1: was wondering what do people think about the possibility, like,
• 10:17
  Speaker 1: you know, not just aliens, but like could we explore
• 10:19
  Speaker 1: the galaxy? Say we are the aliens? Right, if we
• 10:22
  Speaker 1: had a sufficient technology, could we explore the galaxy? How
• 10:25
  Speaker 1: would people do it? So I walked around campus that
• 10:27
  Speaker 1: you see Irvine, and I asked people that question, not
• 10:29
  Speaker 1: do you think aliens have visited us? But what do
• 10:32
  Speaker 1: you think is the best way to explore the whole galaxy?
• 10:35
  Speaker 1: To think about it for a second, if you were
• 10:37
  Speaker 1: in charge of NASA and or humanity, how would you
• 10:41
  Speaker 1: direct people to explore the universe? That's right, you have
• 10:45
  Speaker 1: an unlimited budget and unlimited time. What's the best way
• 10:48
  Speaker 1: to fait to visit every solar system and figure out
• 10:51
  Speaker 1: if there are aliens there? To find the raccoon home planet?
• 10:54
  Speaker 1: That's right? If you had an unlimited amount of raccoon
• 10:57
  Speaker 1: gold poop, what would you do? Here's what people had
• 11:02
  Speaker 1: to say, vonouma probes? Where's that? Uh? So it's the
• 11:07
  Speaker 1: idea by voneuman and by self replicating your robot. So
• 11:10
  Speaker 1: they sent them out in all directions, and then they
• 11:13
  Speaker 1: have the blueprint to replicate themselves using raw materials to
• 11:17
  Speaker 1: find and then send out other probes. So you keep
• 11:19
  Speaker 1: expanding in the swear you can cover the galaxy probably
• 11:23
  Speaker 1: and uh the under tousing years or so, and since
• 11:26
  Speaker 1: we had like two mc swear right, so that would
• 11:29
  Speaker 1: be the I remember someone told me that would be
• 11:31
  Speaker 1: the best way to do that through a telescope because
• 11:35
  Speaker 1: they'll probably be impossible, right, since it's just so far away.
• 11:38
  Speaker 1: I don't know how physically we would be able to
• 11:39
  Speaker 1: do that, so just by viewing it through satellites or
• 11:43
  Speaker 1: trying to get a really big telescope pretty much, well,
• 11:48
  Speaker 1: I need to certainly I'm trying to visit them via
• 11:52
  Speaker 1: telescope or other means. Well, I mean you need a rocket.
• 11:57
  Speaker 1: I don't know, jeez, that would take a long time.
• 12:00
  Speaker 1: I would assume that that would be like years and
• 12:03
  Speaker 1: years and years. If there's a means of some kind
• 12:09
  Speaker 1: of fassion that might travel, it would be feasible. Otherwise,
• 12:13
  Speaker 1: I feel like the it would just be near impossible
• 12:17
  Speaker 1: to do that within a lifetime. All right, So what
• 12:19
  Speaker 1: do you think of people's answers? Uh? They all sound
• 12:22
  Speaker 1: pretty pretty reasonable to me. I mean, somebody said you
• 12:25
  Speaker 1: could use empty square or two empty square? Was that?
• 12:29
  Speaker 1: Is that a typo or a smire? Is that a
• 12:32
  Speaker 1: new theory? No? No, No, that's like you know, maybe
• 12:34
  Speaker 1: mc squared is not enough. So we've got to upgrade
• 12:38
  Speaker 1: physics squared. I'm gonna wait for five MC squared to
• 12:42
  Speaker 1: come out before I get my new physics. Do you
• 12:45
  Speaker 1: do you have to upgrade? Do you have to? Um?
• 12:47
  Speaker 1: You get new icons on your phone and everything. Yeah, exactly.
• 12:51
  Speaker 1: Every time a new theory of physics comes out, I
• 12:52
  Speaker 1: have to get a new physics phone. It's because otherwise
• 12:55
  Speaker 1: it went is too slow. No, there's some good ideas here.
• 12:58
  Speaker 1: I mean some people said, like the just use telescopes, right,
• 13:01
  Speaker 1: why do you have to go to every planet? And
• 13:03
  Speaker 1: that was really intriguing. Um, And I guess it's true
• 13:06
  Speaker 1: that if you had really powerful telescopes, if you could
• 13:09
  Speaker 1: really image things like across the galaxy and the one
• 13:13
  Speaker 1: way to do it. But you know, you can't see
• 13:15
  Speaker 1: the other side of the galaxy because the center of
• 13:17
  Speaker 1: the galaxy is in the way right. You can see
• 13:20
  Speaker 1: the nearby stars, you can see the rest of the
• 13:22
  Speaker 1: arm that we're on in the Milky Way, you can
• 13:24
  Speaker 1: see the next arm over, but the center of the
• 13:27
  Speaker 1: galaxy is blocking us from the other side. Right. It's
• 13:30
  Speaker 1: like we're on one side of Manhattan and you want
• 13:32
  Speaker 1: to look to see a little town on the other
• 13:34
  Speaker 1: side of Manhattan. You're just not gonna be able to
• 13:35
  Speaker 1: see anything I see. You're I think that the idea is,
• 13:39
  Speaker 1: why should I go over to my neighbors and shake
• 13:42
  Speaker 1: their hands to welcome them to the neighborhood when I
• 13:44
  Speaker 1: could choose spy on them with a telescope? Is kind
• 13:47
  Speaker 1: of That's right, exactly exactly and uh, And it's true
• 13:52
  Speaker 1: that we're developing more and more impressive telescopes and we
• 13:55
  Speaker 1: will soon be able to image planets around other stars,
• 13:59
  Speaker 1: which will be an in audible moment in the history
• 14:01
  Speaker 1: of exploration. I mean, we can see black holes, right,
• 14:04
  Speaker 1: and we have seen planets around other stars, right, like
• 14:07
  Speaker 1: little blips. Right. We've detected their presence because of their
• 14:10
  Speaker 1: gravitational effects and because they dim the light. But imaging
• 14:14
  Speaker 1: those planets directly, like seeing the photons that come from
• 14:16
  Speaker 1: those planets, so we can tell or is there a
• 14:18
  Speaker 1: cloudy atmosphere or is there blue water under it? You
• 14:21
  Speaker 1: know that kind of stuff where we're not quite there
• 14:23
  Speaker 1: yet though, though that's going to come soon. But even still,
• 14:26
  Speaker 1: even if you had incredible telescopes, there's a limit because
• 14:29
  Speaker 1: you just can't see the rest of the galaxy from here,
• 14:31
  Speaker 1: because the center of the galaxy is such a crazy blob.
• 14:34
  Speaker 1: There's a black hole there, the zillions of stars, this
• 14:37
  Speaker 1: gas and dust. So if you really wanted to be thorough,
• 14:39
  Speaker 1: telescopes are not going to get you all the way
• 14:41
  Speaker 1: around the galaxy. Well. Also, would it be satisfying, you know,
• 14:46
  Speaker 1: just to to see other alien filications, but not talk
• 14:51
  Speaker 1: to them and or exchange information with them? Would that
• 14:54
  Speaker 1: be satisfying? Not for me? I mean if we used
• 14:57
  Speaker 1: our telescopes and found an exoplanet that was fairly nearby,
• 15:00
  Speaker 1: you know, tens of light years or something, and we
• 15:03
  Speaker 1: saw aliens there, Oh my gosh, we'd have to send something.
• 15:06
  Speaker 1: We'd have to send a delegation because otherwise the conversation
• 15:09
  Speaker 1: would take forever. I mean, say it's twenty light years away, right,
• 15:13
  Speaker 1: then every step of the conversation is forty years, right
• 15:16
  Speaker 1: they say, huh, Let me say what you say? Huh,
• 15:20
  Speaker 1: that's sixty years gone by, you know. Um, So that
• 15:23
  Speaker 1: would be crazy. That would be a pretty slow If
• 15:26
  Speaker 1: you looked in out your window and you saw your
• 15:28
  Speaker 1: neighbors were having a huge raccoon party, you can go
• 15:30
  Speaker 1: over and knock on the doorway. No, I would send
• 15:32
  Speaker 1: him a letter and wait thirty three years, like, hey,
• 15:36
  Speaker 1: look they have a chocolate fountain at that party, let's
• 15:38
  Speaker 1: go over there. Um. But I think you know that
• 15:43
  Speaker 1: with the takeaways that there are a lot of ways
• 15:45
  Speaker 1: that we could explore the galaxy out there, right, We
• 15:48
  Speaker 1: could be seeing things out there, or sending signals or
• 15:52
  Speaker 1: sending probes, or getting on ships and taking off and
• 15:55
  Speaker 1: sending humans out there. And so if you flip it around,
• 15:59
  Speaker 1: the question is kind to like have other aliens done that?
• 16:02
  Speaker 1: Or or why haven't they done that? Yeah? Exactly why
• 16:05
  Speaker 1: haven't they done that? Because again, we're assuming we have
• 16:07
  Speaker 1: not been visited by secretive aliens that have taken over
• 16:10
  Speaker 1: the government and are infiltrating the highest levels of power.
• 16:15
  Speaker 1: Who we are assuming that nobody has come to visit,
• 16:17
  Speaker 1: And so then the question is why not? Right, if
• 16:19
  Speaker 1: the life, if the galaxy is teeming with life, why
• 16:22
  Speaker 1: have we not been visited or contacted? So I thought
• 16:25
  Speaker 1: that the first question might be like, well, you know,
• 16:28
  Speaker 1: why would they come here? You know, so what if
• 16:32
  Speaker 1: they know that we're here? What if they hear one
• 16:34
  Speaker 1: of our messages? Because you know, we've been broadcasting television
• 16:37
  Speaker 1: and radio for decades and decades, so it's possible, even
• 16:41
  Speaker 1: without intentionally trying to contact the aliens, that we've made
• 16:44
  Speaker 1: our presence known. It's kind of like, why would they
• 16:47
  Speaker 1: even come to Earth at all? Out of all the
• 16:49
  Speaker 1: billions of planets, why would they come to ours? Besides
• 16:53
  Speaker 1: the excellent trash that we have, really five star trash here,
• 17:00
  Speaker 1: I'm sure in the Michelin Guide to the Galaxy, Earth
• 17:03
  Speaker 1: ranks very high in the quality of our garbage. But yeah, exactly.
• 17:07
  Speaker 1: And so I thought, well, there is one way we've
• 17:09
  Speaker 1: made ourselves known, and that's through these messages to television
• 17:12
  Speaker 1: or radio broadcasts. So I thought, well, let's do a
• 17:14
  Speaker 1: little calculation, like is there time for those messages to
• 17:18
  Speaker 1: have gone out into the galaxy been received by aliens,
• 17:23
  Speaker 1: and have them have a chance to come back and visit?
• 17:25
  Speaker 1: Like should we have expected to be visited because of
• 17:29
  Speaker 1: the radio and TV broadcast that we've been sending out
• 17:31
  Speaker 1: inadvertently into space, right? Or when can we expect people
• 17:34
  Speaker 1: to hear our our nineteen fifties television right? That's right, exactly.
• 17:41
  Speaker 1: And you know some of us have sent messages into
• 17:43
  Speaker 1: space specifically, right, Like we used the air CBO radio
• 17:46
  Speaker 1: telescope to send a message back in response to the
• 17:49
  Speaker 1: wild signal that we got in in seventy seven. That's
• 17:52
  Speaker 1: very sporadic. Mostly we've just been broadcasting random stuff and
• 17:56
  Speaker 1: that just sends goes out into into interstellar space. So
• 18:00
  Speaker 1: if you had a really fine telescope, you might pick
• 18:01
  Speaker 1: it up, but of course physics limits us. Right those
• 18:05
  Speaker 1: messages have not penetrated the whole galaxy. We've only been
• 18:08
  Speaker 1: broadcasting for you know, maybe a hundred years, and so
• 18:12
  Speaker 1: you imagine a sphere that's just a hundred light years
• 18:15
  Speaker 1: around centered to the Earth. That's a tiny, tiny fraction
• 18:19
  Speaker 1: of the galaxy, which you remember is a hundred thousand
• 18:22
  Speaker 1: light years across to our radius of influence right now,
• 18:27
  Speaker 1: is pretty small. Like the idea that an alien heard
• 18:31
  Speaker 1: us and then came to visit us and we haven't
• 18:33
  Speaker 1: noticed it seems unlikely because who there's nobody could have
• 18:37
  Speaker 1: heard our message yet so far. Well, that was the
• 18:40
  Speaker 1: question I had, is how many how many planets are
• 18:43
  Speaker 1: there out there that could have heard our message and
• 18:45
  Speaker 1: had a chance to build a ship and come visit us.
• 18:48
  Speaker 1: So I did a little bit of calculation, and I said, well,
• 18:52
  Speaker 1: what if you know, how fast could they get here?
• 18:54
  Speaker 1: Let's not assume that they have faster than light travel, right,
• 18:56
  Speaker 1: Let's use physics. So assume that they traveled like half
• 18:59
  Speaker 1: this beat of light, which seems pretty reasonable, which is
• 19:02
  Speaker 1: pretty fast. That's still pretty fast, right, Yeah, that's pretty
• 19:05
  Speaker 1: that's pretty zippy. So then if we have a hundred
• 19:07
  Speaker 1: years since we broadcast the first message, then sort of
• 19:11
  Speaker 1: the outer shell that's fear would actually be like thirty
• 19:14
  Speaker 1: three light years away, right, people a hundred light years away.
• 19:17
  Speaker 1: They're just now getting the messages we sent a hundred
• 19:20
  Speaker 1: years ago, so we could expect to see them in
• 19:22
  Speaker 1: two are the ones thirty three light years away? They
• 19:26
  Speaker 1: got the message sixty six years ago, so in principle,
• 19:30
  Speaker 1: they could have gotten on a ship, immediately pointed it
• 19:33
  Speaker 1: in our direction, been traveling a half the speed of
• 19:36
  Speaker 1: light for sixty six years, and arrived today, right, meaning
• 19:38
  Speaker 1: like they were ready to go. They had the car
• 19:42
  Speaker 1: warmed up in the garage, spaceship warmed up. They're like, oh,
• 19:45
  Speaker 1: we gotta let's go. That's right. Maybe they have like
• 19:48
  Speaker 1: a trash crisis on their planet. They're like, we desperately
• 19:51
  Speaker 1: need more trash. And then you know, they hear our
• 19:53
  Speaker 1: message and they're like, ah ha, this is what we
• 19:55
  Speaker 1: were waiting for. And then they just head out to
• 19:58
  Speaker 1: do a trash more like this. Think fan, that guy's
• 20:00
  Speaker 1: super hilarious. Let's go meet him. Yeah, exactly. And so
• 20:06
  Speaker 1: that's sort of the sphere of possibility. Anybody within thirty
• 20:09
  Speaker 1: three light years could have heard our messages and had time,
• 20:13
  Speaker 1: you know, given some assumptions that they have the technology,
• 20:16
  Speaker 1: that they're interested, etcetera, to come and visit us. So
• 20:19
  Speaker 1: then that seems kind of small. Thirty three light years,
• 20:21
  Speaker 1: it does seem kind of small, I mean compared to
• 20:23
  Speaker 1: the galaxy. But so then I thought, well, how many
• 20:26
  Speaker 1: how many planets are there out there? And so I
• 20:28
  Speaker 1: actually looked up how many stars there are within a
• 20:32
  Speaker 1: certain number of light years and it did a calculation,
• 20:34
  Speaker 1: and what did you find. It turns out that there's
• 20:36
  Speaker 1: a few hundred stars within that sphere, right, and we
• 20:40
  Speaker 1: know that about twenty of stars have an earth like planet.
• 20:45
  Speaker 1: Now that depends exactly on the kind of star. But
• 20:47
  Speaker 1: let's be generous, so ballparking, you know, And this is
• 20:50
  Speaker 1: what we do in physics. We're just like trying to
• 20:52
  Speaker 1: get the answer to within the factor of five. Again,
• 20:55
  Speaker 1: precision physics right there. Well, you know, decision six out
• 21:01
  Speaker 1: of a quarters plus or minus seven ten dollars. Here's
• 21:06
  Speaker 1: two dollars. That's pretty enough. Did you say it was
• 21:11
  Speaker 1: gonna cost ten billion oops to cost a hundred billions? Sorry? No.
• 21:14
  Speaker 1: In physics we do this a lot. We say, well,
• 21:16
  Speaker 1: we don't know. This is a really hard problem. We
• 21:18
  Speaker 1: don't know the answer precisely. Can we get a rough
• 21:21
  Speaker 1: estimate of it? You know, can we figure out, you know,
• 21:23
  Speaker 1: to within a factor of two or five ish roughly
• 21:25
  Speaker 1: with the back of the envelope and back of the
• 21:28
  Speaker 1: envelope exactly and so approximately fifty is the answer we
• 21:32
  Speaker 1: expected to be about fifty Earth like planets in that
• 21:36
  Speaker 1: sphere where our messages have had time to arrive and
• 21:40
  Speaker 1: there's been time for them to turn around and come
• 21:42
  Speaker 1: visit us. Interesting, fifty seems that it's a reasonable number,
• 21:45
  Speaker 1: isn't it like if you had fifty earths, you know,
• 21:49
  Speaker 1: surely some of them might have people on them and listening.
• 21:54
  Speaker 1: That's exactly the question. We don't know. We don't know
• 21:57
  Speaker 1: what fraction of earthlike planets have life on them? Is it?
• 22:02
  Speaker 1: Is it one in fifty, is it one in fifty trillion?
• 22:04
  Speaker 1: Or is it one over infinity right as an only Earth.
• 22:08
  Speaker 1: And so the fascinating thing about doing these measurements is
• 22:11
  Speaker 1: that we've learned something. We know it's not right because
• 22:15
  Speaker 1: there are fifty planets out there that have received our
• 22:17
  Speaker 1: messages and had time to come, and they haven't. So
• 22:21
  Speaker 1: that means that the rate at which earthlike planets have
• 22:25
  Speaker 1: intelligent technological aliens that are interested in visiting us is
• 22:30
  Speaker 1: less than one in fifty. Say that again, what's that's
• 22:32
  Speaker 1: the disc There are fifty planets out there that have
• 22:35
  Speaker 1: received our messages. Fifty earthlike planets have received our messages
• 22:39
  Speaker 1: and none of them have come to visit us. So
• 22:41
  Speaker 1: that means that the rate at which earthlike planets have
• 22:44
  Speaker 1: technological aliens that are interested in visiting us and willing
• 22:48
  Speaker 1: to take the trip is less than one in fifty.
• 22:51
  Speaker 1: That's assuming that someone would get the signal, jump on
• 22:53
  Speaker 1: a rocket ship and come over. Yeah, exactly right. So
• 22:56
  Speaker 1: with all those assumptions, the answers is, you know, less
• 22:59
  Speaker 1: than one in fifty, and so that starts to answer
• 23:01
  Speaker 1: the question, right, We know it's not a percent. We
• 23:03
  Speaker 1: know that not every earthlike planet out there has technological
• 23:06
  Speaker 1: aliens desperate to visit us. Oh, I see, you're flipping
• 23:09
  Speaker 1: it around a little bit, right, You're you're using these
• 23:11
  Speaker 1: back of the envelope calculations to say, you know, if
• 23:16
  Speaker 1: we are going to get visited by aliens, that means
• 23:18
  Speaker 1: that they jumped on a ship when they heard us
• 23:19
  Speaker 1: and came to look for us. And so if we
• 23:21
  Speaker 1: haven't already, that means that probably none of these fifty
• 23:25
  Speaker 1: planets have such a civilization. Exactly, if if every single
• 23:29
  Speaker 1: earthlike planet out there had trash eating raccoons desperate to
• 23:33
  Speaker 1: visit us, then they would have come because there's been
• 23:36
  Speaker 1: time for them to do it. So because we haven't
• 23:39
  Speaker 1: been visited, therefore, not every earthlike planet is filled with
• 23:43
  Speaker 1: technologically advanced trash eating raccoons or other animals. Yeah, so
• 23:52
  Speaker 1: other similar aliens. And you know, there's there's a sequence
• 23:55
  Speaker 1: of assumptions built into their. Right, they have to be technological,
• 23:58
  Speaker 1: they have to use radio, they have to be interested, right,
• 24:03
  Speaker 1: they have to be willing all these things. But we
• 24:05
  Speaker 1: have learned something, right, we have learned something about what
• 24:09
  Speaker 1: aliens are not out there? Right, No, I see, So
• 24:12
  Speaker 1: we're ruling out sort of a class of aliens based
• 24:15
  Speaker 1: on what hasn't happened yet, that's right, that's right exactly, Okay,
• 24:19
  Speaker 1: And every year that number gets smaller, right, because every
• 24:22
  Speaker 1: year our radioways go out further, and every year that
• 24:27
  Speaker 1: means there are Every year that we don't have aliens
• 24:30
  Speaker 1: visitors means that it's less likely that there are aliens
• 24:33
  Speaker 1: like that exactly every year we don't get visited. If
• 24:36
  Speaker 1: next year they arrived, then boom, the number goes up.
• 24:42
  Speaker 1: Every year that we that that our sphere of influence
• 24:46
  Speaker 1: expands without being contacted, then we know we we have
• 24:50
  Speaker 1: a better and lower estimate of the rate at which
• 24:53
  Speaker 1: there are again technological, intelligent aliens interested in willing to
• 24:59
  Speaker 1: come and visit it. That are answering in any of
• 25:01
  Speaker 1: those assumptions, right, It could be that all those planets
• 25:04
  Speaker 1: have aliens, but they're not intelligent, or they're intelligent but
• 25:06
  Speaker 1: they're not technological, or they're intelligent and technological but they're
• 25:10
  Speaker 1: snobs and they're just not interested in coming to visit us, right, right.
• 25:12
  Speaker 1: Or sometimes you know, people have like forty seven thousand
• 25:15
  Speaker 1: emails in their inbox and they just can't wait, are
• 25:17
  Speaker 1: we talking about aliens? Now? We're talking about you I'm
• 25:20
  Speaker 1: just saying, sometimes it happens, you know, it's it's a
• 25:23
  Speaker 1: totally human thing too. Well, what I like is that
• 25:25
  Speaker 1: you're already empathizing with the aliens. You know, you're reaching out,
• 25:28
  Speaker 1: you're saying, I get you, I understand, I have a
• 25:31
  Speaker 1: I have a full inbox too. That's right, that's right anyway.
• 25:35
  Speaker 1: So that's the sort of scenario if they hear our messages.
• 25:39
  Speaker 1: But what if they don't, you know, like, yeah, they
• 25:42
  Speaker 1: doesn't have to be that they hear our messages. It
• 25:44
  Speaker 1: could be that they're like Star Trek, they're just out
• 25:47
  Speaker 1: there exploring, you know, they don't have to necessarily know
• 25:49
  Speaker 1: we're here to stumble across us. All right, Let's get
• 25:52
  Speaker 1: into another type of alien, which might find is just randomly. Right,
• 25:56
  Speaker 1: that's what you're saying. They're just out out and about
• 25:59
  Speaker 1: and they find it. So what are the likely what's
• 26:01
  Speaker 1: the likelihood that they'll stumble upon us like Columbus stumbled
• 26:04
  Speaker 1: upon the Native Americans, which is a great scenario for us. Yeah,
• 26:11
  Speaker 1: well for lots of reasons because of how well that
• 26:14
  Speaker 1: went for the Native Americans. But also if they arrive
• 26:17
  Speaker 1: and they happen to look just like us, then that
• 26:19
  Speaker 1: would be quite interesting. All right, let's get into that,
• 26:21
  Speaker 1: but first let's take a quick break. All right, we're
• 26:36
  Speaker 1: talking about aliens and how likely they are to have
• 26:39
  Speaker 1: visited us. So now we're exploring this scenario of what
• 26:43
  Speaker 1: are the chances that aliens have could have or could
• 26:46
  Speaker 1: stumble upon us. Meaning they're out and about exploring the
• 26:49
  Speaker 1: galaxy and they're like, oh, hey, here's a planet with
• 26:52
  Speaker 1: some cute little um water bags that move around and
• 26:56
  Speaker 1: have podcasts exactly, and there's sort of too compe heating
• 27:00
  Speaker 1: things going on from the physics point of view. On
• 27:02
  Speaker 1: one hand, the galaxy is huge. It's a hundred thousand
• 27:06
  Speaker 1: light years across. It has billions and billions of stars,
• 27:09
  Speaker 1: so it seems sort of unimaginable to be able to
• 27:12
  Speaker 1: explore it to check every solar system. Right. On the
• 27:15
  Speaker 1: other hand, the galaxy is very old. So even though
• 27:18
  Speaker 1: the speed of light limits how fast you can zoom
• 27:20
  Speaker 1: between stars, there's a lot of time. You know, our
• 27:23
  Speaker 1: galaxy is almost as old as the universe, right, So
• 27:28
  Speaker 1: you're saying that we should take the time to mension
• 27:31
  Speaker 1: into account to not just how big space is, but
• 27:35
  Speaker 1: how old it is. Also makes it more what you're saying,
• 27:37
  Speaker 1: it makes it more likely that we'll get visited. Yeah, exactly,
• 27:40
  Speaker 1: because there's been a lot of time. So the galaxy
• 27:43
  Speaker 1: has been around for you know, more than ten billion
• 27:46
  Speaker 1: years um, though our planets only existed for you know,
• 27:49
  Speaker 1: four and a half billion. But even just take a
• 27:51
  Speaker 1: few billion years, like, that's a lot of time to
• 27:53
  Speaker 1: explore the galaxy. The galaxy is a hundred thousand light
• 27:56
  Speaker 1: years across, but it's been around for billions of years,
• 27:59
  Speaker 1: So even though you have the speed of light, it's
• 28:01
  Speaker 1: not actually that impossible to explore the entire galaxy. So
• 28:04
  Speaker 1: I thought, well, what if you have an alien ship
• 28:07
  Speaker 1: and you wanted to do that, and you wanted to
• 28:09
  Speaker 1: go from star to star and explore every single solar
• 28:12
  Speaker 1: system in the galaxy? How long would that take? How
• 28:15
  Speaker 1: long would it take for you to check off all
• 28:17
  Speaker 1: the boxes? Like if you're an alien and you have O,
• 28:19
  Speaker 1: C D, how long and you wanted to visit every
• 28:21
  Speaker 1: single star because you're you're like an intense tourist, how
• 28:24
  Speaker 1: long would it take? Care that's right, you have the
• 28:28
  Speaker 1: ultimate bucket lift, and yeah, how long would that take?
• 28:34
  Speaker 1: And and then I thought, well, let's not visit every
• 28:36
  Speaker 1: single star. Maybe these folks are out hunting four aliens,
• 28:40
  Speaker 1: so let's have them only visit stars that have Earth
• 28:43
  Speaker 1: like planets. So that cuts it down by a factor
• 28:44
  Speaker 1: of five. So now you have fifty billion stars in
• 28:49
  Speaker 1: the Milky Way to visit. That's the fraction we think
• 28:51
  Speaker 1: have Earth like Oh I see, they would only you
• 28:54
  Speaker 1: would only pick stars you think might have life on him. Yeah, exactly,
• 28:59
  Speaker 1: because we're interested being contacted by aliens that we can
• 29:02
  Speaker 1: talk to and learn physics from, and you know, share
• 29:06
  Speaker 1: the experience of being alive in this universe, and so
• 29:09
  Speaker 1: you could be totally wide open to lots of different
• 29:11
  Speaker 1: kinds of life. And I'm a huge fan of that.
• 29:14
  Speaker 1: I imagining like life in the core of stars whatever.
• 29:17
  Speaker 1: But you know, life that we can talk to and
• 29:19
  Speaker 1: interact with and have a chance to be technologically similar
• 29:21
  Speaker 1: to probably gonna come from earthlike planets. Okay, so how
• 29:24
  Speaker 1: long would it take us? Yeah, how long would it take? Well, Um,
• 29:27
  Speaker 1: the average distance between earthlike planets is about ten or
• 29:31
  Speaker 1: eleven light years, right, the average distance between stars is
• 29:34
  Speaker 1: about four ish light years, But there are not every
• 29:37
  Speaker 1: star as an earthlike planet, so it's about ten or
• 29:39
  Speaker 1: eleven light years between earthlike planets, and so again, assuming
• 29:43
  Speaker 1: you can travel at half the speed of light, it
• 29:45
  Speaker 1: takes you know, something like five years to go from
• 29:48
  Speaker 1: one to the other. Oh, I see, And that's assuming
• 29:52
  Speaker 1: that you sort of search efficiently, right, Like you have
• 29:56
  Speaker 1: a pretty good path to get them all. Yeah, exactly,
• 29:59
  Speaker 1: you start from one center and you sort of spiral outwards,
• 30:02
  Speaker 1: and you know, there's some additional geometrical complications there because
• 30:06
  Speaker 1: but but there are path to explore the galaxy where
• 30:08
  Speaker 1: you don't have to do a lot of backtracking, and
• 30:11
  Speaker 1: even if you do, that's not a huge factor, you know.
• 30:13
  Speaker 1: And again that's a factor to maybe and we're just
• 30:15
  Speaker 1: interested in sort of generally getting this answer right. And
• 30:18
  Speaker 1: so of course you're gonna get ended with a big number. Right.
• 30:21
  Speaker 1: You've got fifty billion solar systems with Earth like planets.
• 30:24
  Speaker 1: Each one takes twenty years to visit, and so you know,
• 30:28
  Speaker 1: you're talking trillions of years just in our galaxy, just
• 30:31
  Speaker 1: for our galaxy. And you know, you might imagine aliens
• 30:34
  Speaker 1: and other galaxies, but the distance between galaxies is ginormous
• 30:39
  Speaker 1: compared to the size of the galaxy, and so that's
• 30:42
  Speaker 1: you know, basically totally impractical without worms. That's why I's
• 30:45
  Speaker 1: focusing on just our galaxies. So a single ship would take,
• 30:48
  Speaker 1: you know, order trillions of years to explore the galaxy,
• 30:51
  Speaker 1: assuming you meaning like if you're in Captain Picard on
• 30:55
  Speaker 1: the starship Enterprise and you wanted to explore every possible
• 31:01
  Speaker 1: planet that might have life on this galaxy, it would
• 31:03
  Speaker 1: take you trillions of years. Yeah, exactly. It would take
• 31:05
  Speaker 1: you much longer than the age of the galaxy. So
• 31:08
  Speaker 1: even if you started when the galaxy was born, you
• 31:10
  Speaker 1: were like the first intelligent race in the galaxy, and
• 31:12
  Speaker 1: you started exploring in ten billion years, you wouldn't have
• 31:15
  Speaker 1: visited a significant fraction in the galaxy, you know, So
• 31:18
  Speaker 1: it could certainly be what that What that means is
• 31:21
  Speaker 1: it could be that there is an alien Picard out
• 31:23
  Speaker 1: there studiously visiting every solar system in the galaxy. Well,
• 31:27
  Speaker 1: Patrick Stewart isn't is an alien also, but let's not
• 31:29
  Speaker 1: get into that. He also seems to be about a
• 31:32
  Speaker 1: trillion years old. But he looks great. I want to
• 31:36
  Speaker 1: be that sexy when I'm tread. But you know, so
• 31:39
  Speaker 1: that means there could be an alien ship out there
• 31:41
  Speaker 1: exploring the galaxy, and it's reasonable that hasn't visited the
• 31:44
  Speaker 1: Earth yet. All right, that's interesting. But then you can
• 31:47
  Speaker 1: start to play the numbers game. You could say, well,
• 31:49
  Speaker 1: what if there are a thousand ships, what if there
• 31:51
  Speaker 1: are million ships? What if there are billion aliens out there? Right?
• 31:56
  Speaker 1: And you can do these calculations for for lots of
• 31:58
  Speaker 1: different ships. I see not that an alien would make
• 32:02
  Speaker 1: a billion ships, but let's say that each of the
• 32:05
  Speaker 1: billions of alien races out there made one ship to explore.
• 32:09
  Speaker 1: Surely one of them would have hit us by now
• 32:12
  Speaker 1: or found us. Yeah, exactly. So if there I did
• 32:14
  Speaker 1: the numbers, and if you have a billion exploring alien ships,
• 32:19
  Speaker 1: you know then it tis takes it takes about a
• 32:21
  Speaker 1: thousand years to explore the whole galaxy, right, yeah, because
• 32:26
  Speaker 1: you know there's lots of ships, and so what does
• 32:28
  Speaker 1: that tell you, Well, we've been around for a thousand years.
• 32:31
  Speaker 1: If aliens had come and made themselves known in the
• 32:33
  Speaker 1: last thousand years, we would certainly be aware of that
• 32:36
  Speaker 1: um And so what that tells you is there are
• 32:38
  Speaker 1: not a billion alien exploring ships. And again, you know,
• 32:42
  Speaker 1: these are aliens that are interested in visiting us and
• 32:45
  Speaker 1: would make themselves known when they arrive right. Put aside
• 32:47
  Speaker 1: the question of how they visited in the government is
• 32:50
  Speaker 1: covering it up, etcetera, etcetera. But what if they came
• 32:52
  Speaker 1: while we weren't ready? You know, like what if they
• 32:55
  Speaker 1: came knocked on the door we weren't ready or maybe
• 32:57
  Speaker 1: even existing because humans have only been around for like,
• 33:00
  Speaker 1: you know, a couple of ten tens of thousands of years. Right, Yeah,
• 33:03
  Speaker 1: that's a great question. That time to mension is a
• 33:05
  Speaker 1: great one. But here's the thing is that a billion
• 33:08
  Speaker 1: ships can explore the galaxy every thousand years. And so
• 33:12
  Speaker 1: if you're out there looking for aliens, you might like
• 33:15
  Speaker 1: check on a planet and look back right and say like, okay, well,
• 33:18
  Speaker 1: you know, I got this one billion of the galaxy
• 33:21
  Speaker 1: to sort of patrol. I'm gonna come back every thousand
• 33:23
  Speaker 1: years and say, you know, are there aliens yet? I mean,
• 33:27
  Speaker 1: are there is there intelligence yet? And so every thousand years,
• 33:30
  Speaker 1: a billion ships can visit every planet in the galaxy.
• 33:34
  Speaker 1: You're saying that maybe they could have come a thousands
• 33:37
  Speaker 1: or tens of thousands of years ago, but then said,
• 33:40
  Speaker 1: you know, their trash is not quite ripe yet, Let's
• 33:44
  Speaker 1: come back when they're totally abusing their environment, throwing out
• 33:49
  Speaker 1: prime trash. Yeah, exactly, and the time tomension has a
• 33:52
  Speaker 1: lot of complications. You know, did they come when we
• 33:55
  Speaker 1: couldn't recognize them? Are they about to come? This sort
• 33:57
  Speaker 1: of stuff. But a billion ships have come, you know,
• 34:00
  Speaker 1: every thousand years or so, and then you can crank
• 34:03
  Speaker 1: the numbers down and say, okay, well there's definitely not
• 34:05
  Speaker 1: a billion ships, because then we'd be visited every thousand
• 34:07
  Speaker 1: years and we certainly would have noticed that. You know,
• 34:10
  Speaker 1: but if there were a million ships. But if there
• 34:12
  Speaker 1: were a million ships exploring the galaxy, and so I
• 34:15
  Speaker 1: have the numbers here, that would take you know, about
• 34:18
  Speaker 1: a million years. So a million ships will take about
• 34:21
  Speaker 1: a million years to explore the whole galaxy. And so
• 34:24
  Speaker 1: then you can wonder, like, well, if aliens came here
• 34:26
  Speaker 1: a million years ago, would they have stuck around where
• 34:29
  Speaker 1: they have like left us a note saying, hey, when
• 34:33
  Speaker 1: you get it together and figure out technology, here's how
• 34:36
  Speaker 1: to contact us, or here's what to do or something.
• 34:39
  Speaker 1: Or maybe they just figure oh, we'll come back in
• 34:40
  Speaker 1: another million and see what's going on. Or maybe they
• 34:43
  Speaker 1: did stick around and they are on that's right, we
• 34:48
  Speaker 1: are the aliens and so this gets harder. But you
• 34:51
  Speaker 1: can also do the same trick where you invert it.
• 34:54
  Speaker 1: You can say, well, look, i'm pretty sure there are
• 34:56
  Speaker 1: not a billion alien ships exploring the galaxy. Right. We
• 35:01
  Speaker 1: can't really say there aren't a million, though, Right There
• 35:03
  Speaker 1: could be a million alien ships exploring the galaxy and
• 35:07
  Speaker 1: they would only get to Earth every million years or so.
• 35:10
  Speaker 1: And so it certainly could be that there are million
• 35:12
  Speaker 1: aliens out there exploring the galaxy looking for us, but
• 35:16
  Speaker 1: they came by a million years ago we weren't ready, right,
• 35:18
  Speaker 1: And again you're assuming that you're ruling out a class
• 35:22
  Speaker 1: of anies that would be interested in us or making
• 35:25
  Speaker 1: themselves known, right, Like what if they're just looking for
• 35:29
  Speaker 1: you know, raccoon gold poop and they don't see it
• 35:32
  Speaker 1: here until they keep going. Yeah, exactly, ruling out aliens
• 35:35
  Speaker 1: that that don't make themselves known or stay hidden or
• 35:38
  Speaker 1: just come by and steal the you know, heavy metals
• 35:41
  Speaker 1: they're particularly interested in and move on. Okay, all right,
• 35:45
  Speaker 1: So that that helps narrow it down a little bit, Yeah, exactly,
• 35:48
  Speaker 1: that helps narrow down. It's like exploring the kind of
• 35:51
  Speaker 1: ways they could see us, and does physics limit us?
• 35:54
  Speaker 1: And it turns out that you know, physics doesn't really
• 35:56
  Speaker 1: limit us because while the galaxy is large, there is
• 36:00
  Speaker 1: there's been a lot of time to do this exploration.
• 36:02
  Speaker 1: So if you have enough ships, you certainly can visit
• 36:06
  Speaker 1: every solar system in the galaxy and not a significant
• 36:09
  Speaker 1: fraction of the age of the galaxy, which is billions
• 36:11
  Speaker 1: of years. Well, there is a way you were telling
• 36:14
  Speaker 1: me that shoots that number up super high and makes
• 36:17
  Speaker 1: it super likely that we would have been contacted by
• 36:20
  Speaker 1: aliens um, which is a pretty interesting idea. And then
• 36:23
  Speaker 1: we can get into have they been here at all?
• 36:26
  Speaker 1: But first let's take another quick break. Okay, so I
• 36:41
  Speaker 1: think we can sort of rule out that there are
• 36:43
  Speaker 1: billions of aliens out there that have heard is and
• 36:46
  Speaker 1: one of visitors or that even are out there exploring
• 36:49
  Speaker 1: and want to say hi to us. UM. Just from
• 36:53
  Speaker 1: the fact that we haven't been contacted by them, sort
• 36:57
  Speaker 1: of rules out that there are a whole lot of
• 36:59
  Speaker 1: them out there ready to do that. But you're saying,
• 37:01
  Speaker 1: there's another way that we could explore or they could
• 37:03
  Speaker 1: explore the galaxy that we should have seen by Now,
• 37:06
  Speaker 1: that's right, and the idea is you want a lot
• 37:08
  Speaker 1: of ships because you there are a lot of stars
• 37:12
  Speaker 1: and it's sort of awkward to build all those ships.
• 37:14
  Speaker 1: Like here on Earth, say, we wanted to do this
• 37:17
  Speaker 1: this exploration, We wanted to take this task on building
• 37:20
  Speaker 1: a billion ships from Earth. Sounds kind of hard, build
• 37:23
  Speaker 1: them one at a time. So there's a famous idea
• 37:27
  Speaker 1: by von Neumann. So Neuman probes and he said, well
• 37:30
  Speaker 1: what if we build a few ships and those ships
• 37:33
  Speaker 1: build more ships. So essentially you send out a ship
• 37:37
  Speaker 1: which then finds a planet, uses the raw materials on
• 37:40
  Speaker 1: that planet to assemble a ship building factory. Right, So
• 37:44
  Speaker 1: now one ship builds a factory that makes more ships. Right.
• 37:48
  Speaker 1: It's sort of the way like rats fill up a city.
• 37:51
  Speaker 1: You don't have one mama rat have a billion babies, right,
• 37:55
  Speaker 1: she has ten babies, and those ten babies have ten babies,
• 37:57
  Speaker 1: and those ten babies have ten babies, and pretty soon
• 37:59
  Speaker 1: you've got a billion rats, right kind of Or like viruses, right,
• 38:02
  Speaker 1: Like they invade a cell and they use the cell
• 38:05
  Speaker 1: to replicate exactly just like a virus. So we should
• 38:08
  Speaker 1: be the virus, rats and viruses. This is not not
• 38:12
  Speaker 1: favorable not favorable analogies here. Yeah, well, um and that's
• 38:18
  Speaker 1: the idea. And you know that might seem like, what
• 38:21
  Speaker 1: is that crazy? It's it's a little crazy, but it's
• 38:24
  Speaker 1: it's sort of weirdly not that far off technologically. I mean,
• 38:27
  Speaker 1: we have factories now that are mostly stocked with robots.
• 38:31
  Speaker 1: Robots can build cars, so can robots build themselves. I
• 38:34
  Speaker 1: don't think that's too far off. The tricky thing is,
• 38:37
  Speaker 1: you know, landing on a planet, finding those resources, mining them.
• 38:42
  Speaker 1: But you don't even need to land on planets like
• 38:44
  Speaker 1: asteroids we know are filled with valuable materials, iron and
• 38:48
  Speaker 1: all sorts of heavy metals that you might need to
• 38:51
  Speaker 1: build these things. So imagine that we can do that,
• 38:54
  Speaker 1: and you know, I would estimate where maybe a hundred
• 38:56
  Speaker 1: two hundred years away from being able to do that.
• 38:59
  Speaker 1: You launch just one of those things, it launches five more,
• 39:03
  Speaker 1: They launch five more very quickly. You get up to
• 39:06
  Speaker 1: millions and millions of ships exploring the galaxy. You do
• 39:10
  Speaker 1: the calculation, it doesn't take very long to explore the
• 39:13
  Speaker 1: entire galaxy. So so you have like a satellite orbiting
• 39:17
  Speaker 1: every single earth like planet in the entire galaxy within
• 39:20
  Speaker 1: tens of thousands of years. You can go viral. Yeah,
• 39:25
  Speaker 1: that's exactly we go viral. So that's fascinating, right. Um,
• 39:29
  Speaker 1: Now there's another question like, are these crude probes or uncrude?
• 39:33
  Speaker 1: I don't want to say man, because you know there
• 39:35
  Speaker 1: are men or women on them. You know, I don't
• 39:37
  Speaker 1: know that we want to send people on these things
• 39:39
  Speaker 1: and then have those people have kids and then put
• 39:41
  Speaker 1: those babies on the ships to explore. Just make more
• 39:45
  Speaker 1: ships and more people. Yeah, exactly, I don't know that
• 39:49
  Speaker 1: we want people to go viral. So imagine we're just
• 39:51
  Speaker 1: sending probes. Right, then those probes could send a message
• 39:54
  Speaker 1: back to Earth if they do find something. But again,
• 39:59
  Speaker 1: you can flip it around. You can say, well, shouldn't
• 40:01
  Speaker 1: aliens have thought of this idea? Um? Aliens? You know,
• 40:05
  Speaker 1: if we're pretty close technologically to being able to do this,
• 40:07
  Speaker 1: Aliens probably would be. Also, given the billions of years
• 40:10
  Speaker 1: that the galaxy has been around and yet no self
• 40:14
  Speaker 1: replicating probes have landed on Earth, and so that's kind
• 40:18
  Speaker 1: of disappointing. If you can have this viral exploration scenario,
• 40:23
  Speaker 1: then you might have even more than a million probes
• 40:26
  Speaker 1: out there. You could have billions of probes out there eventually. Yeah,
• 40:32
  Speaker 1: it grows pretty quickly. Yeah, you can go from millions
• 40:35
  Speaker 1: to billions pretty quickly. And so you would expect somebody
• 40:39
  Speaker 1: else to have this idea and frankly for the galaxy
• 40:42
  Speaker 1: to be filled with these things, and yet it's not.
• 40:45
  Speaker 1: And yet it's not, which means what we can put
• 40:48
  Speaker 1: a pretty hard limit. That means like, there are no
• 40:51
  Speaker 1: alien species in our galaxy that have had this idea
• 40:54
  Speaker 1: and done it, not even one. It would take only
• 40:56
  Speaker 1: one to fill the galaxy and completely explore it. Uh well,
• 41:01
  Speaker 1: it seems like a pretty crazy idea, isn't it. Why
• 41:04
  Speaker 1: would you even do that just just to reach out
• 41:06
  Speaker 1: out there into the universe, I guess yeah, because we
• 41:09
  Speaker 1: want to know, right, Like I want to know if
• 41:12
  Speaker 1: any earth like planet in the galaxy has life. So
• 41:15
  Speaker 1: I mean, if we have the technology to do this,
• 41:17
  Speaker 1: oh my god, I would send that pro about tomorrow.
• 41:19
  Speaker 1: Absolutely interesting, wouldn't you. Yeah? Well it would cost a
• 41:24
  Speaker 1: lot of money, wouldn't it. The R and D would
• 41:25
  Speaker 1: cost a lot, you know, to figure out how to
• 41:28
  Speaker 1: get a ship, to build a copy of itself, to
• 41:30
  Speaker 1: build a ship making factory. But once you send it
• 41:32
  Speaker 1: out then it doesn't use any more resources, right It
• 41:35
  Speaker 1: builds more of itself based on what it finds out there.
• 41:38
  Speaker 1: It's like viral marketing, right, It's pretty cheap to launch
• 41:41
  Speaker 1: and pretty effective, right right. So, but you're saying the
• 41:44
  Speaker 1: fact that we haven't seen these sort of rules out
• 41:48
  Speaker 1: that there are aliens who would have this idea and
• 41:52
  Speaker 1: the resources and the smarts. Yeah, exactly. The fact that
• 41:57
  Speaker 1: that we haven't seen them, that it has doesn't seem
• 41:59
  Speaker 1: to have happened, means that there's nobody else out there
• 42:03
  Speaker 1: who had this idea and did it right and and
• 42:05
  Speaker 1: would make themselves known. Maybe maybe they have come to
• 42:08
  Speaker 1: our solar system, but they just reported back and moved on. Perhaps,
• 42:12
  Speaker 1: But you know, if they came to our solar system
• 42:15
  Speaker 1: before they moved on, they would need to build more ships, right,
• 42:18
  Speaker 1: and so they'd have to like build a ship making
• 42:20
  Speaker 1: factory somewhere. And if if they landed on Earth and
• 42:23
  Speaker 1: mind the Earth to make a ship making factory, I
• 42:25
  Speaker 1: think we would see signs of that. Or I mean
• 42:28
  Speaker 1: it could be there out somewhere in the asteroid belt
• 42:30
  Speaker 1: and they like mind an asteroid and then left. But
• 42:34
  Speaker 1: you know, if the idea is you could leave a
• 42:36
  Speaker 1: probe in every solar system sort of sitting there orbiting
• 42:39
  Speaker 1: earthlike planets, waiting for intelligence to crop up, and so
• 42:43
  Speaker 1: it should still be here and we certainly would have
• 42:45
  Speaker 1: found it if there was a probe orbiting the Earth
• 42:47
  Speaker 1: from that was not terrestrial. Well, that's such an interesting exercise,
• 42:51
  Speaker 1: you know, to think about how it's possible to get
• 42:54
  Speaker 1: contacted by aliens and then flip it around and say, well,
• 42:56
  Speaker 1: if we have, that's the fact that we haven't been
• 42:58
  Speaker 1: contacted means that we can rule these possibilities. Yeah, And frankly,
• 43:02
  Speaker 1: that's the thing that dampens my enthusiasm the most. Like
• 43:04
  Speaker 1: I'm a big believer that there could be aliens out
• 43:07
  Speaker 1: there that are technological and worth talking to. But the
• 43:11
  Speaker 1: fact that none of them have sent have had this
• 43:13
  Speaker 1: idea and sent probes the physics Earth, that makes me doubt.
• 43:17
  Speaker 1: That makes me wonder, like maybe we are alone in
• 43:19
  Speaker 1: the galaxy, because surely somebody else would have had this idea.
• 43:23
  Speaker 1: That's not such a brilliant idea that only humans would
• 43:26
  Speaker 1: have come up with it. So frankly that that that
• 43:29
  Speaker 1: bums me out a little bit. You're saying you believe
• 43:31
  Speaker 1: physics more than you believe Joe rogan I believe the
• 43:35
  Speaker 1: physics more than I believe Bob Lazar, that's for sure.
• 43:39
  Speaker 1: All right. Well, I think that's sort of the conclusion
• 43:41
  Speaker 1: we set out to explore, is that basically, you're saying,
• 43:44
  Speaker 1: physics says that it is not impossible for us to
• 43:48
  Speaker 1: get contacted by other intelligent species, right, You're saying that
• 43:52
  Speaker 1: that's right, It's totally possible, and there are many ways
• 43:55
  Speaker 1: that they could do it. And there are many ways
• 43:57
  Speaker 1: they could have heard us and come visitors, or are
• 44:00
  Speaker 1: many ways that they could be out there exploring the star,
• 44:03
  Speaker 1: you know, checking out their bucket list and oh c
• 44:06
  Speaker 1: d um compulsions to to visit every star. And and
• 44:11
  Speaker 1: the fact that we haven't um maybe tells you a
• 44:14
  Speaker 1: little bit about how alone we are in the galaxy exactly.
• 44:18
  Speaker 1: And so I think buried in the in the physics message,
• 44:20
  Speaker 1: there is the reason for hope, right, it's possible to
• 44:23
  Speaker 1: go across the stars and define aliens. And then there's
• 44:26
  Speaker 1: also a reason for a disappointment. Um, physics isn't the
• 44:29
  Speaker 1: reason why we haven't been contacted, and so you have
• 44:33
  Speaker 1: to think about other reasons why maybe the aliens are
• 44:36
  Speaker 1: just so alien they heard our message. But didn't didn't
• 44:39
  Speaker 1: understand it, or maybe they came here and saw us
• 44:42
  Speaker 1: and weren't interested. You know. So there are lots of ways.
• 44:46
  Speaker 1: There are lots of ways this could happen. But blame
• 44:48
  Speaker 1: your breath. Don't blame physics. That's right. It's probably your fault.
• 44:55
  Speaker 1: It's not physics, it is you, that's right. That's right.
• 45:01
  Speaker 1: But this is a really fun kind of calculation. Think
• 45:03
  Speaker 1: about what's possible to do back of the envelope calculations.
• 45:06
  Speaker 1: None of the calculations we did here today are precise.
• 45:09
  Speaker 1: They're all approximate. They could be wrong by a factor
• 45:11
  Speaker 1: ten um. But you know, it gives us an idea.
• 45:14
  Speaker 1: And and that's the kind of thing that I that
• 45:15
  Speaker 1: I stay up late wondering about. When I'm camping and
• 45:17
  Speaker 1: I'm looking up in the stars and I'm wondering who
• 45:19
  Speaker 1: else is out there? Um, and my physics brain gets
• 45:22
  Speaker 1: engaged and tries to give me a reason for why
• 45:25
  Speaker 1: they haven't yet contacted us and made themselves know them. Well,
• 45:28
  Speaker 1: I stay up late wondering how do I stop these
• 45:30
  Speaker 1: recruits from going through my trash? And and why would you?
• 45:34
  Speaker 1: Because your trash is their chocolate? All right? Well, Hopefully
• 45:40
  Speaker 1: that gives you some solids that maybe we are alone
• 45:43
  Speaker 1: in the universe. But hey, Daniel, at least you still
• 45:45
  Speaker 1: have physics, that's right, and chocolate and gold pood possibly.
• 45:50
  Speaker 1: All right, Thanks for tuning in everyone, see you next time.
• 46:00
  Speaker 1: If you still have a question after listening to all
• 46:03
  Speaker 1: these explanations, please drop us a line. We'd love to
• 46:06
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• 46:08
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• 46:12
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• 46:16
  Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
• 46:19
  Speaker 1: the Universe is a production of I Heart Radio from
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