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Astrobiology Adventures: Exploring Life Beyond Earth | Space Nuts: Astronomy Insights & Cosmic... · Space News Today

• 0:00
  Hi there. Thanks for joining us again.
• 0:01
  This is Space Nuts, where we talk
• 0:04
  astronomy and space science. And my name
• 0:07
  is Andrew Dunley, your host. Great to
• 0:09
  have your company. Now, normally I'd be
• 0:11
  joined by Professor Fred Watson, but he
• 0:13
  is away visiting family at the moment.
• 0:16
  And because he was going to be away and
• 0:18
  then I'm going to be away and we tried
• 0:20
  to cram episodes in and uh we just we
• 0:22
  couldn't do enough in the amount of time
• 0:24
  we had, uh we invited Professor Jotty
• 0:27
  Horner to join us and uh we're going to
• 0:29
  do some specials. You might have heard
• 0:30
  the last one, uh which was very engaging
• 0:33
  and interesting and fascinating and
• 0:35
  long. Uh this time we we're going down a
• 0:39
  different road. We're going to focus the
• 0:40
  whole program on astro biology. Strap
• 0:44
  in. We'll do that right now.
• 0:46
  >> 15 seconds. Guidance is internal. 10 9
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  Ignition sequence start.
• 0:53
  >> Space nuts.
• 0:54
  >> 5 4 3 2
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  >> 1 2 3 4 5 5 4 3 2 1
• 0:59
  >> Space nuts.
• 1:00
  >> Astronauts report. It feels good.
• 1:02
  >> And here he is again. Professor of
• 1:04
  astrophysics at the University of
• 1:05
  Southern Queensland, Johnny her. Good
• 1:08
  day, Johnny.
• 1:08
  >> Good day. How are you going?
• 1:10
  >> I'm well. Good to see you again. And uh
• 1:13
  we've got a lot to talk about. So I
• 1:14
  think we're going to just dive on in.
• 1:16
  Now in preparation for this astrobiology
• 1:19
  chat, you sent me a paper that you wrote
• 1:22
  uh and published on the archive website.
• 1:25
  Uh it's um
• 1:27
  >> ancient.
• 1:28
  >> Yeah, it it's it's coming up on 16 years
• 1:31
  since you wrote that. But one of the
• 1:33
  interesting parts was uh look, it's been
• 1:36
  a couple of decades now that we've been
• 1:38
  finding exoplanets. And as technology
• 1:40
  improves, it's only a matter of time
• 1:42
  before we start finding Earthlike
• 1:44
  planets. And that's really going to make
• 1:47
  the search for life beyond our solar
• 1:49
  system really really interesting. So
• 1:53
  those 16 years have passed. Have we got
• 1:54
  the Have we got the equipment yet? I
• 1:57
  suspect we have. It depends where you're
• 1:59
  looking, I think. I mean, in terms of
• 2:01
  looking at the planets around other
• 2:03
  stars, we can now learn a lot more about
• 2:05
  them than we could 16 years ago when I
• 2:07
  wrote the paper. that particular paper,
• 2:10
  but we're still not there yet. And it's
• 2:12
  a perpetual thing. No matter how hard
• 2:15
  you work, there's always more to do. The
• 2:17
  other thing that goes along with it,
• 2:18
  which I think is worth saying right up
• 2:20
  at the very start, is that searching for
• 2:22
  life elsewhere is going to be one of the
• 2:24
  hardest things we've ever done. And
• 2:27
  absence of evidence is not necessarily
• 2:29
  evidence of absence. What I mean by that
• 2:33
  is we could in a remarkable turn of
• 2:35
  events in the next few months find life
• 2:37
  elsewhere. you know, that's kind of the
• 2:39
  ultimate extreme soonest possible. Um,
• 2:42
  very unlikely to happen. Alternatively,
• 2:44
  we might still be looking in a century.
• 2:47
  If we're still looking in a century,
• 2:49
  that doesn't mean that there isn't any
• 2:50
  life out there. But what it will suggest
• 2:54
  to us is that life is relatively scarce.
• 2:56
  So, to me, the sooner we find life
• 2:59
  elsewhere, that a it will be awesome
• 3:01
  because, hey, look, we found life
• 3:02
  elsewhere and we've answered the
• 3:03
  ultimate question. Are we alone?
• 3:06
  But the sooner we find life elsewhere,
• 3:07
  the other thing it's telling us is that
• 3:08
  life must be fairly common in the
• 3:10
  universe. The scarcer life is, the
• 3:13
  harder it will be to find and therefore
• 3:14
  the longer it will take us to find. And
• 3:17
  now the ultimate extreme of that is that
• 3:19
  this is the only place that there is
• 3:20
  life. And it'll be very hard to conclude
• 3:24
  that even if we were talking through a
• 3:26
  time warp in 10,000 years when humanity
• 3:29
  is taking its fledgling steps into the
• 3:31
  galaxy or whatever, if we haven't found
• 3:34
  life by then, we'll be confident that
• 3:35
  life is very rare and very precious.
• 3:38
  >> That doesn't mean that there is not life
• 3:40
  somewhere else in the universe. And it's
• 3:42
  what are the challenges with this? I I
• 3:43
  would like to think that we'll find the
• 3:44
  answer to that question in our lifetime.
• 3:47
  But the only way we'll get an answer to
• 3:48
  the question, are we alone within our
• 3:50
  lifetime is if that answer is no. If
• 3:52
  that answer is that there is life
• 3:54
  elsewhere. And this is one of the big
• 3:57
  really really big open questions for
• 3:59
  humanity, open questions for science.
• 4:01
  You know, when I was a kid, when you
• 4:02
  were a kid, one of the big questions was
• 4:04
  is the solar system unique or are there
• 4:07
  planets around other stars? And we'll
• 4:08
  talk about that more in the next
• 4:10
  episode. But there is nobody under the
• 4:13
  age of 30 31 alive on this planet that
• 4:16
  grew up in that shared universe with you
• 4:17
  and I. So that fundamental question got
• 4:19
  answered and answered in abundance and
• 4:22
  answering that question is the first
• 4:23
  real step to say is there life elsewhere
• 4:26
  beyond the solar system
• 4:28
  >> because in order to find life beyond the
• 4:31
  solar system we first need to know that
• 4:32
  there's somewhere that life could exist.
• 4:35
  The question of life in the solar system
• 4:36
  is a different one and that's all part
• 4:38
  of astrobiology. So if you bundle all of
• 4:40
  this together, that question of are we
• 4:42
  alone? Is there life elsewhere? Which
• 4:44
  brings with it questions like what is
• 4:46
  the origin of life? Why are we here? How
• 4:48
  did life begin? How did it get
• 4:50
  established? What are the processes
• 4:51
  needed? Everything like that.
• 4:53
  >> Yeah.
• 4:53
  >> Is what gets bundled in in astrobiology.
• 4:55
  And astrobiology is a very very weird
• 4:58
  science. I know certainly early in my
• 5:00
  career a lot of older scientists viewed
• 5:02
  astrobiology in a similar way to the way
• 5:05
  a lot of astronomers view astrology
• 5:07
  almost. you know, they viewed it as
• 5:08
  being speculation, fiction, and hook,
• 5:10
  you know, total bogus, waste of time
• 5:13
  stuff,
• 5:14
  >> but it really isn't.
• 5:16
  >> Yeah. But one of the real challenges is
• 5:18
  uh it's not a question that one single
• 5:20
  discipline on its own can answer, right?
• 5:22
  It's not like in astronomy, you you're
• 5:24
  studying how stars form, so you talk to
• 5:26
  astronomers. In astrobiology, if we're
• 5:28
  looking at everything to do with life,
• 5:32
  astronomers like myself can't do it on
• 5:34
  their own. Biologists can't do it on
• 5:36
  their own. You need geoysicists, you
• 5:38
  need chemists, you need every area of
• 5:41
  human scientific endeavor to come
• 5:43
  together because as scientists, our
• 5:45
  knowledge is somewhat siloed. I think
• 5:47
  I've said in previous episodes, the
• 5:48
  further you go away from what your
• 5:50
  specialtity is, the more out of date and
• 5:52
  the more superficial your knowledge is.
• 5:53
  So I always view my knowledge as being
• 5:55
  almost like a Christmas tree shape. I've
• 5:57
  got a lot of knowledge about a very
• 5:58
  narrow area at the top and the further
• 6:00
  you go from that area, the less
• 6:02
  knowledge I have, but the broader my
• 6:04
  knowledge base gets. And I think every
• 6:05
  human's like that. And you can almost
• 6:08
  imagine that if you're trying to answer
• 6:10
  the question of what you need for life,
• 6:11
  where we should look, which what we'll
• 6:13
  talk about a lot today, you need a level
• 6:15
  that's above a certain point on that
• 6:17
  Christmas tree of knowledge to be able
• 6:18
  to contribute to that from a scientific
• 6:20
  advancement point of view. And the area
• 6:23
  that you can cover yourself is generally
• 6:25
  fairly small. There's a lot of knowledge
• 6:26
  that is needed that is outside your
• 6:28
  silo. And so that's where the
• 6:30
  interdicciplinary nature comes in. No
• 6:33
  one discipline can answer it their own.
• 6:35
  And that means astrobiology conferences
• 6:37
  tend to be mind-bogglingly bonkers and
• 6:40
  you get people from very different
• 6:42
  disciplines along. And you learn a lot
• 6:45
  that updates your knowledge from when
• 6:47
  you went to high school. You also learn
• 6:48
  a lot that isn't about the science but
• 6:51
  is about the scientists. And it's really
• 6:54
  interesting because we all think we're
• 6:55
  individuals. It's like that Montipython
• 6:56
  thing, isn't it? We're all individuals
• 6:57
  and there's a voice at the back that
• 6:59
  goes, "I'm not.
• 6:59
  >> I'm not."
• 7:00
  >> Yeah. It's a bit like that. We're we all
• 7:02
  think we're all individuals and we're
• 7:04
  very unique in the way we think and the
• 7:05
  way we present. But when you go to one
• 7:07
  of these conferences that's so
• 7:08
  multiddisciplinary,
• 7:10
  the different disciplines present in
• 7:12
  different ways to one another. But
• 7:13
  within the discipline, there are
• 7:14
  similarities, you know. So if you see
• 7:16
  the talks I give, I have beautiful
• 7:18
  pictures and bright text, white or
• 7:20
  yellow on them, limited text, usually a
• 7:22
  dark background. And that's really
• 7:24
  common for astronomers. You go to a talk
• 7:26
  by a kind of plate tectonics person and
• 7:30
  suddenly you've got this mish mash of
• 7:31
  colors on a totally different background
• 7:34
  where there's a bit more text but the
• 7:36
  color schemes are a bit to me kind of
• 7:38
  psychedelic and like something you'd see
• 7:39
  out of a 1970s cartoon you know
• 7:42
  >> because they're used to working with
• 7:43
  these geological maps that um have a
• 7:46
  very different color palette and
• 7:47
  sensibility I think. And then you get
• 7:49
  talks from the biologists where they've
• 7:50
  got the name of one bacterium and it
• 7:53
  fills half of the page because it's such
• 7:54
  a lengthy scientific name and they've
• 7:56
  got loads of text.
• 7:57
  >> And so you learn a lot about how what
• 8:00
  you study at university and what
• 8:02
  discipline you go into trains you to
• 8:05
  think and trains you to problem solve
• 8:08
  because it trains you in a lot of
• 8:10
  different ways. essentially programs
• 8:11
  people and you know I find that side of
• 8:13
  things really fascinating because it's a
• 8:15
  good way to learn to improve your
• 8:17
  communication skills and you also pick
• 8:18
  up all this abundance of wow I never
• 8:22
  knew that you know and that's what we
• 8:24
  need if we are to answer questions like
• 8:26
  how did life begin where did life come
• 8:28
  from are we alone
• 8:30
  >> yeah and that's really an interesting
• 8:32
  question because uh it could be life not
• 8:35
  as we know it like we you know we're
• 8:38
  assuming carbon based life forms but
• 8:40
  there could be life forms that have been
• 8:42
  created out of a completely different
• 8:43
  soup mix. Uh two things I want to get
• 8:46
  out of the way quickly. The Drake
• 8:48
  equation which uh was created to try and
• 8:51
  assess how much intelligent life that
• 8:54
  was able to communicate existed in the
• 8:56
  universe and the answer is still one.
• 8:58
  And the Fermy paradox which says you
• 9:01
  know um that statistically there's a
• 9:04
  high probability of extraterrestrial
• 9:06
  life. So where is everybody? And that's
• 9:10
  what astrobiology is really, isn't it?
• 9:12
  Where is everybody? And and will they be
• 9:15
  people or will they be microbes? And I
• 9:19
  suppose my first question to you is uh
• 9:21
  you're talking about finding life
• 9:23
  outside the solar system. Aren't we
• 9:25
  likely to find it first within the solar
• 9:28
  system?
• 9:29
  >> So that's a really good question. I was
• 9:31
  going to talk about that a bit as well
• 9:32
  because I think there are two different
• 9:35
  places in a broad sense we're looking
• 9:37
  for life elsewhere. One is
• 9:39
  in the outer solar system or on Mars,
• 9:41
  you know, in our solar system on one of
• 9:43
  the planets or on the icy objects and
• 9:45
  the other is beyond the solar system.
• 9:48
  >> And those two things have very different
• 9:51
  characteristics.
• 9:53
  What I mean by that is that objects that
• 9:56
  are in our solar system are in our
• 9:57
  backyard. They're the only things in
• 9:59
  astronomy that we can get up close and
• 10:01
  personal with. So in the solar system,
• 10:03
  the search life elsewhere is being
• 10:06
  driven by robotic exploration in the
• 10:09
  main. Yes, there's a little bit of
• 10:11
  observation from Earth. We saw that with
• 10:13
  the phosphine story on Venus that I
• 10:15
  ranted about a little bit last week. Um
• 10:18
  and the wonderful caution shown by
• 10:19
  scientists that was not necessarily
• 10:21
  reflected in the coverage. Um but a lot
• 10:23
  of the search in the solar system is
• 10:27
  robotic in nature. We send spacecraft to
• 10:29
  places to study them up close and
• 10:31
  personal and we can't do that around
• 10:33
  other stars. Around other stars, it's
• 10:35
  very much a remote sensing type deal. So
• 10:37
  there are different ways of doing it.
• 10:38
  Now I think there is a realistic chance
• 10:41
  we'll find life elsewhere in the solar
• 10:43
  system. There's a lot of good reasons
• 10:45
  for that. Now, before I dive into that a
• 10:47
  little bit, I'll just take a step back
• 10:49
  and come back to that point you made
• 10:50
  about life like us and carbon based life
• 10:52
  versus other things because it's really
• 10:54
  important to make explicit what is
• 10:56
  normally an implicit bias when
• 10:59
  scientists are talking about
• 11:00
  astrobiology.
• 11:01
  Um, it's really made clear when you
• 11:03
  think about NASA and efforts on the moon
• 11:06
  where they have on on Mars, sorry, where
• 11:08
  they have aggressively said the strategy
• 11:09
  to look for life is to follow the water.
• 11:12
  M
• 11:13
  >> what they're doing there is making an
• 11:16
  implicit assumption that is an
• 11:18
  assumption that is not always written
• 11:19
  out and is clear but is at the back of
• 11:21
  it that life that we look for will be
• 11:24
  life like us and I mean life like earth
• 11:26
  life now we can imagine you see it on
• 11:29
  science fiction all the time you know
• 11:31
  life that is very other it might be
• 11:32
  molten metal monsters on a magma planet
• 11:34
  or it might be an intelligent hydrogen
• 11:36
  cloud that nevertheless wants to flirt
• 11:38
  with Captain Kirk it's very different
• 11:41
  kinds of life. But fundamentally, we
• 11:43
  only know of one type of life that does
• 11:46
  exist and that's life like earth life.
• 11:49
  And so when we look for life elsewhere,
• 11:52
  at least in what is the early stages
• 11:55
  still, it is really important to look
• 11:57
  for something that we know can exist and
• 11:59
  does exist rather than looking for
• 12:01
  things that we could speculate might
• 12:03
  exist. If you've got to focus your
• 12:05
  efforts with limited resources, it makes
• 12:08
  sense to follow the kind of welltrodden
• 12:10
  footsteps of what we know about life on
• 12:12
  Earth. And from an astronomer's point of
• 12:14
  view, life on Earth needs three things.
• 12:16
  You know, it needs liquid water, it
• 12:18
  needs a source of energy and a source of
• 12:20
  nutrients. And quite often those two are
• 12:22
  the same thing, but not always. And
• 12:24
  wherever we find those things on Earth,
• 12:26
  we find life in abundance. And once life
• 12:28
  gets there, it's really hard to get rid
• 12:29
  of. You know, anybody who's had ants
• 12:31
  getting into their kitchen or the mice
• 12:33
  plague that we talked about last week
• 12:35
  knows just how life once it gets
• 12:38
  established keeps going. And so it makes
• 12:41
  sense. And a lot of what I'll talk about
• 12:43
  for all the rest of the episode is kind
• 12:45
  of based on this assumption that we're
• 12:47
  looking at at least initially for life
• 12:50
  like us that has the same needs as us
• 12:52
  where the us is the broad the entire
• 12:54
  panel play of life on Earth rather than
• 12:56
  us as in me and the having this chat
• 12:58
  back and forward. What that leads to
• 13:01
  though is a lot of studies that have
• 13:03
  been done for the solar system are very
• 13:04
  waterdriven. And if you go back decades,
• 13:07
  you could go back to the late 1800s when
• 13:10
  people were obsessed with this idea that
• 13:11
  there was an advanced technological
• 13:13
  civilization on Mars that was running
• 13:15
  out of time because the planet was
• 13:17
  desolate and barren. And this was all
• 13:19
  motivated by the observations of the
• 13:21
  canali, the channels on Mars that don't
• 13:24
  exist, which were mistransated as
• 13:26
  canals. And canals on Earth are a very
• 13:28
  clear sign of human activity.
• 13:30
  >> Yeah. People at that time were so
• 13:32
  certain that we'd already found life
• 13:34
  that when there was a prize awarded um a
• 13:37
  prize laid out sorry and announced I
• 13:39
  think it was like in 1899 or something
• 13:41
  for the search for life for the first
• 13:43
  person to discover life elsewhere to
• 13:45
  find evidence of life elsewhere. That
• 13:47
  prize explicitly excluded Mars because
• 13:50
  it was felt that life on Mars was so
• 13:51
  well established that that was a
• 13:53
  no-brainer. You know, it was such a
• 13:55
  thing in popular culture that when the
• 13:56
  War of the Worlds broadcast happened in
• 13:58
  the 1930s, people thought it was live
• 14:00
  news coverage and panicked.
• 14:02
  >> Yes. You know,
• 14:02
  >> the night that panicked America.
• 14:05
  >> Yeah. And there's this whole heritage of
• 14:08
  our expectation of life being common and
• 14:11
  it being life like us requiring water.
• 14:14
  When we went to Mars, like in the 1960s
• 14:16
  with spacecraft, Mars was shown to be
• 14:19
  the desolate arid world we knew today.
• 14:21
  That put to an end the thoughts of an
• 14:23
  advanced civilization there. And from
• 14:25
  that time onwards there was a period
• 14:27
  where arguments in astrobiology fell
• 14:29
  very much out of favor, out of fashion.
• 14:31
  And it was kind of viewed much more
• 14:32
  likely that life was almost unique. We
• 14:34
  were alone. There was no way you could
• 14:36
  look. And there's this argument that I
• 14:38
  often hear as that water is scarce in
• 14:41
  the universe. And that makes my head
• 14:44
  hurt. I think this is one of those big
• 14:45
  myths that is a myth of miscommunication
• 14:49
  or a myth of
• 14:51
  language being a personal thing. What I
• 14:55
  mean by that is and I I'm always try to
• 14:57
  be very aware of this when I'm as a
• 14:59
  communicator that words have different
• 15:02
  meanings to different people. And so the
• 15:05
  same word that I say you'll hear and it
• 15:08
  doesn't always mean the same thing to
• 15:09
  you or me. One of one of the best
• 15:10
  examples of this is when you get people
• 15:13
  who are trying to argue against an area
• 15:16
  of science, maybe vaccines, maybe
• 15:17
  climate change, maybe something less
• 15:19
  controversial. You'll often hear people
• 15:21
  say that, well, climate change is just a
• 15:23
  theory, or vaccines are just a theory,
• 15:25
  or the Big Bang is just a theory. And to
• 15:27
  a lot of people, a theory just means a
• 15:31
  loose idea. A lot of people will say,
• 15:34
  "Why isn't your car starting this
• 15:36
  morning?" Well, I've got a theory. To a
• 15:38
  scientist, a theory is a very different
• 15:40
  beast and it's tied to the ability to
• 15:42
  make testable predictions and repeated
• 15:45
  testing. There's a lot of philosophy of
• 15:47
  science. I did a philosophy of physics
• 15:50
  course at university when I was 18 and I
• 15:51
  wish I'd done it when I was at the end
• 15:52
  of my degree, not the start cuz I'd have
• 15:54
  got a lot more out of it. But there are
• 15:56
  people who have aggressively studied the
• 15:58
  philosophy of the scientific method. And
• 16:01
  even that philosophy varies a little bit
• 16:03
  discipline to discipline. A lot of other
• 16:05
  disciplines that are the experimental
• 16:06
  ones are are very much more hypothesis
• 16:08
  driven than astronomy where we say I'm
• 16:11
  interested in what this is. Let's have a
• 16:12
  look. There's not really a hypothesis. I
• 16:14
  just want to look at it and find out. At
• 16:15
  least that's how I work. But you also
• 16:18
  have this thing where at least from my
• 16:20
  philosophy, you can never prove a
• 16:22
  theory, but you can disprove a theory.
• 16:24
  What I mean by that is if you test a
• 16:26
  theory a million times and each time
• 16:29
  it's backed it up, you haven't proven
• 16:31
  that theory. You've just shown that
• 16:32
  theory is a very good approximation to
• 16:34
  what's actually happening. So take the
• 16:36
  example of me flipping a coin. I can
• 16:38
  have a theory that says coins will
• 16:40
  always land heads or tails. Test that a
• 16:43
  million times and odds are a million
• 16:44
  times you'll land heads or tails. But
• 16:46
  you've not proven that theory. You've
• 16:48
  just said it's a very close
• 16:49
  approximation to the truth. You could
• 16:51
  toss them 10 million times and one time
• 16:52
  your coin lands on its edge and
• 16:54
  balances.
• 16:54
  >> Yeah.
• 16:55
  >> That one observation. And so as long as
• 16:56
  it's well documented and is repeatable
• 16:58
  is enough to kill that theory and then
• 17:00
  you need to develop something more
• 17:01
  complex. You know
• 17:03
  >> that's where it goes from. Now that's a
• 17:05
  very roundabout way of coming back at
• 17:07
  this water being scarce myth. I think
• 17:11
  where that comes from is when you talk
• 17:13
  to me about water I am just thinking
• 17:17
  about the molecule. I'm not thinking
• 17:19
  about the physical state. So to me water
• 17:22
  can be water ice. It can be liquid
• 17:24
  water. It can be water vapor. But to
• 17:26
  most people, if you say water, they
• 17:28
  visualize liquid water. Yeah.
• 17:30
  >> Right. If if I say, "Would you like some
• 17:31
  water?" You're not expecting me to
• 17:33
  immediately start steing your face.
• 17:35
  You're expecting a glass of water.
• 17:36
  Right?
• 17:38
  What that means is that when people look
• 17:40
  out at the solar system and look
• 17:41
  everywhere else, we see this thing that
• 17:43
  Earth is the only place where we have
• 17:45
  abundant liquid water all the time on
• 17:47
  the surface. And so people have this
• 17:50
  idea that water is scarce where what
• 17:51
  they're really thinking is liquid water
• 17:54
  on the surface of an object is scarce.
• 17:58
  >> But that drove a lot of this idea that
• 18:00
  life will be scarce because life needs
• 18:02
  liquid water on Earth. The Earth's the
• 18:04
  only place with liquid water. Ergo life
• 18:06
  will be scarce. That's moved on though
• 18:09
  in about the last three or four decades.
• 18:10
  partially with the exploration of Mars
• 18:12
  where we're getting an overwhelmingly
• 18:15
  greater amount of evidence that Mars in
• 18:17
  the past was warm and wet, that it had
• 18:19
  oceans and lakes. They may have been
• 18:20
  slushy or they may have been properly
• 18:22
  liquid, but it had oceans and lakes for
• 18:24
  a long time of liquid water. And we've
• 18:26
  even got evidence that there is
• 18:27
  permanent liquid water on Mars as we're
• 18:29
  talking now in the form of liquid water
• 18:30
  in the Martian polar ice caps and you
• 18:33
  get temporal liquid water running on the
• 18:34
  surface. The other thing we found in the
• 18:36
  solar system is liquid water in
• 18:39
  astonishing abundance in the outer solar
• 18:41
  system protected by shells of ice on the
• 18:44
  icy satellites of the giant planets on
• 18:47
  the dwarf planet Pluto or inside the
• 18:48
  dwarf planet Pluto probably in the
• 18:50
  larger edge kipeld objects transepun
• 18:53
  objects maybe in other places as well
• 18:56
  even in places as small as Enceladus so
• 18:58
  there's been this revolution from the
• 19:01
  point of view of the solar system
• 19:02
  through my lifetime that actually liquid
• 19:04
  water isn't scarce.
• 19:06
  >> Coupled to the fact that the earth is
• 19:08
  actually remarkably dry as a planet that
• 19:10
  suddenly opened up people's perspectives
• 19:12
  again that the solar system is a good
• 19:13
  place to look for life and that's
• 19:15
  driving a lot of exploration missions
• 19:17
  all the Mars exploration past and future
• 19:20
  focused around that idea. the fact that
• 19:22
  we've got two missions going to the
• 19:23
  Jovian ICE satellites at the minute
• 19:25
  juice um the Jupyter moons explorer and
• 19:27
  the Europa Clipper which are to
• 19:29
  characterize those moons better to
• 19:31
  prepare for potential future landings in
• 19:33
  the 2040s or 50s to get through the ice
• 19:35
  and look at what's underneath. We've got
• 19:37
  the Dragonfly mission going out to
• 19:39
  Titan, launching in a couple of years
• 19:41
  time, probably next year. Hoping to get
• 19:43
  there 2034 that will land on the only
• 19:46
  other place that has liquid on its
• 19:47
  surface exposed to the atmosphere in the
• 19:50
  solar system and that's Titan with lakes
• 19:51
  of liquid methane and ethane. The water
• 19:54
  there is harder than granite and makes
• 19:55
  up the mountains. But there's this huge
• 19:57
  effort to explore our solar system and
• 19:59
  actually go there and look, which we
• 20:01
  can't do when we're looking at planets
• 20:03
  around the stars. And by going there and
• 20:05
  looking if there is anything there past
• 20:08
  or present eventually we'll find it.
• 20:10
  >> Now that immediately then poses a really
• 20:13
  fascinating one. So if we find life on
• 20:14
  Mars or we find life on Europa
• 20:18
  if we can look at that life and figure
• 20:21
  out its heritage figure out its DNA and
• 20:24
  I'm not a biologist so I'll be a little
• 20:26
  woolly on that. It will be very quick
• 20:29
  and very apparent whether that life has
• 20:31
  a shared origin to life on earth or
• 20:32
  whether it has a separate origin to life
• 20:34
  on earth. Now the separate origin would
• 20:36
  mean that life got started
• 20:38
  simultaneously
• 20:40
  on two objects in the same planetary
• 20:42
  system in an icy backwater of a fairly
• 20:45
  unremarkable galaxy. If it got started
• 20:48
  two places side by side, surely that
• 20:49
  means life gets started more easily than
• 20:52
  we expect. Therefore, life should be
• 20:54
  common in the universe. That would be an
• 20:56
  obvious logical continuation. The other
• 20:59
  option is that we find life elsewhere in
• 21:00
  the solar system and it has a shared
• 21:02
  heritage life on Earth. What that means
• 21:04
  is that we analyze its makeup, we find
• 21:06
  that it has DNA like Earth DNA that has
• 21:09
  a shared universal common ancestor. And
• 21:11
  what that suggests is that once life
• 21:13
  gets started somewhere, it's
• 21:14
  transmissible. You know, you've got that
• 21:16
  old thing of don't go near Earth. It's
• 21:18
  got humans. They're contagious.
• 21:20
  This is the same kind of idea. If we
• 21:22
  find life on Mars and that life has a
• 21:24
  shared heritage with life on Earth, that
• 21:27
  validates strongly supports the idea of
• 21:29
  panspermia, which I've had a student
• 21:32
  just submit his PhD thesis studying. The
• 21:35
  idea that life can transfer between the
• 21:36
  planets. Now again, if life can transfer
• 21:39
  easily enough to be found in multiple
• 21:40
  locations in the solar system from a
• 21:42
  simple single origin and maybe even
• 21:45
  Earth wasn't that origin, you know,
• 21:46
  maybe we're Martians, maybe we're
• 21:48
  Venucians or Venerians. I think that
• 21:51
  Venerian used to be the adjective for
• 21:52
  Ven adjective the right word used to be
• 21:54
  the word for Venus in the way that
• 21:55
  Martian was for Mars but it was a bit
• 21:57
  too close to venerial um because
• 22:01
  >> so they changed it but anyway um but we
• 22:03
  could be venerial creatures um we don't
• 22:05
  know but what that suggests is that if
• 22:07
  life is transferred easily and
• 22:09
  effectively once it originates life
• 22:11
  could be common in the universe so to me
• 22:14
  finding life in the solar system would
• 22:15
  be awesome I think it's eminently
• 22:17
  feasible and either way it will shed new
• 22:20
  on the commonality of life beyond the
• 22:22
  solar system. We will be looking for
• 22:24
  life like us. It is possible to imagine
• 22:27
  life that is not like us that has
• 22:28
  different requirements but that will
• 22:29
  probably be a bit harder to find and we
• 22:32
  don't know what it would be. Whereas
• 22:35
  with life like us, we know things to
• 22:36
  look for. So that makes it a bit easier
• 22:38
  for us to look for life like us. It also
• 22:41
  makes it, I'd say, a little bit stronger
• 22:44
  as a case when you're asking for funding
• 22:46
  because you can say, well, we already
• 22:48
  know this kind of life can exist. So,
• 22:50
  we're going to look at a place where the
• 22:51
  conditions are similar to where we know
• 22:52
  it does exist and see if we find it
• 22:54
  there as well.
• 22:56
  >> Okay, let's take a short break. Uh, this
• 22:58
  is Space Nuts with Andrew Dunley and
• 23:01
  Professor Jonty Horner.
• 23:04
  Let's take a short break from the show
• 23:06
  to tell you about our sponsor, NordVPN.
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• 24:53
  >> I'm going to step off the mount.
• 24:57
  That's one small step for man,
• 25:02
  one leap for mankind.
• 25:05
  >> Space nuts.
• 25:07
  >> It's not Professor Fred Watson at the
• 25:09
  moment. He's away. We've got Professor
• 25:10
  Jonty Hoer and we're talking
• 25:12
  astrobiology in this uh little special
• 25:15
  edition. Um, one thing I heard in the
• 25:18
  news recently, I think Fred and I talked
• 25:20
  about it was uh, you know, we've been
• 25:21
  talking about water and if you want to
• 25:23
  find the people, find the water, that
• 25:25
  sort of thing. But there was one
• 25:27
  particular study that uh was recently
• 25:30
  released that says if you want to find
• 25:31
  the people, find the coal. What do you
• 25:34
  think of that theory?
• 25:35
  >> That's an interesting one. So that's the
• 25:37
  idea that if you want to find somebody
• 25:39
  to talk to,
• 25:40
  >> there needs to be something to fuel an
• 25:42
  industrial revolution. And again, this
• 25:44
  is
• 25:45
  >> I think science fiction sometimes does
• 25:46
  this really ask this really interesting
• 25:48
  questions of
• 25:50
  >> almost is the path that we have followed
• 25:54
  the one that everyone will follow? you
• 25:55
  know because there's so much to some
• 25:57
  degree randomness in the things that
• 25:59
  have driven our knowledge and our
• 26:02
  development of things you know um
• 26:04
  obviously a good example is a famous
• 26:06
  myth about penicellin that if um you
• 26:08
  leave your bread out and it goes moldy
• 26:10
  that makes your pus more effective um
• 26:13
  and that was an incredible scientific
• 26:15
  re revolution driven by that discovery
• 26:17
  there
• 26:19
  who's to say other civilizations would
• 26:21
  have the same discoveries in the same
• 26:22
  order now to advance. We have required
• 26:26
  advances in energy in order to allow us
• 26:29
  to better develop technology and develop
• 26:32
  the things that everything's made of.
• 26:34
  You know, if we didn't have anything
• 26:36
  that you could burn, it would be very
• 26:38
  very challenging to smelt metal. If you
• 26:40
  couldn't smelt metal, how do you build
• 26:42
  electronics?
• 26:43
  >> You are spot on. That's exactly what the
• 26:45
  article was all about. And uh the bottom
• 26:48
  line was uh that because of the timing
• 26:51
  required, it lessens the likelihood of
• 26:55
  us finding uh people like us. It reduces
• 26:59
  the odds.
• 27:00
  >> And this is where there's a difference
• 27:02
  between the search for extraterrestrial
• 27:04
  intelligence and the search for life. So
• 27:06
  the search for extraterrestrial
• 27:07
  intelligence is like a subset of the
• 27:09
  search for life. Search for life is a
• 27:12
  search for bacteria as much as it's the
• 27:14
  search for communicative aliens. And
• 27:17
  there's been a lot of stuff written and
• 27:19
  discussed about whether evolutionary
• 27:22
  quirks have benefited us by being here,
• 27:24
  you know, in terms of we're a social
• 27:26
  communal animal that shares resources
• 27:27
  and shares learning. There have been
• 27:30
  other ones like that from Aunt Collins.
• 27:31
  And I'm listening to a very chill and
• 27:34
  very silly um lit RPG. I think would be
• 27:38
  the description of the genre book called
• 27:39
  series of books called Chrysis at the
• 27:41
  minute where a young boy who dies for
• 27:44
  reasons is reincarnated in the b body of
• 27:47
  an ant. And it's a book about him as an
• 27:50
  ant and his life in the colony and stuff
• 27:52
  and it's bonkers but um you've got an
• 27:55
  advanced social species there and he
• 27:57
  finds ways without too many spoilers of
• 27:59
  giving them intelligence and what
• 28:00
  happens afterwards.
• 28:01
  >> There's a few species in the history of
• 28:03
  earth that have that kind of communal
• 28:05
  sharing of information thing. we're the
• 28:07
  only ones that have achieved what we've
• 28:09
  achieved. Some arguments are that's down
• 28:11
  to the development of language and our
• 28:13
  ability to produce complex language and
• 28:16
  also the opposable thumb being quite
• 28:17
  important. So there's a lot of stuff
• 28:20
  that there are many steps between the
• 28:22
  development of life and the development
• 28:24
  of intelligence and the development of
• 28:26
  intelligence itself doesn't necessarily
• 28:28
  mean the development of technological
• 28:30
  intelligence. You know, a lot of
• 28:31
  discussions about all the things octopi
• 28:33
  or octopods or octopidles octopi could
• 28:36
  achieve if they lived for more than 3
• 28:38
  years and if they were a social animal.
• 28:41
  They've got incredible brains. We're
• 28:42
  learning more and more about some of the
• 28:44
  brain power that birds exhibit.
• 28:47
  But none of them have become
• 28:48
  technological intelligences. And the
• 28:50
  search for extraterrestrial intelligence
• 28:52
  is very much centered around a
• 28:55
  technology that allows civilizations to
• 28:58
  communicate with one another. that
• 29:00
  therefore is based on many prerequisites
• 29:02
  that lead to the development of the
• 29:03
  ability to broadcast your existence to
• 29:05
  the cosmos. The coal thing's
• 29:07
  interesting. I mean, I'm not
• 29:09
  sufficiently archaeologically minded to
• 29:13
  be able to say with certainty that
• 29:16
  without coal, we wouldn't have got here.
• 29:18
  And the reason that I express caution on
• 29:19
  that coal and oil is that we have things
• 29:22
  that people burn for energy that are not
• 29:24
  coal and oil. M
• 29:26
  >> and I think a lot of the smelting that
• 29:28
  was done, and I may be wrong on this
• 29:29
  because I'm not an archaeologist. I just
• 29:30
  pick bits up when my partner's watching
• 29:32
  time team and things like that. She
• 29:34
  loves her archaeology, so I get a little
• 29:36
  bit of that as a very thin veneer. But I
• 29:38
  think a lot of the times when people
• 29:39
  smelted metals, talking about bronze and
• 29:41
  iron, they used wood or they use
• 29:44
  charcoal, which is a byproduct of
• 29:45
  burning wood.
• 29:46
  >> Yeah.
• 29:47
  So maybe it would be more challenging
• 29:50
  without the easy available energy of
• 29:53
  fossil fuels, without the easy available
• 29:55
  energy of coal, oil, gas. But it might
• 29:58
  be that that wouldn't be an
• 29:59
  insurmountable hurdle, but it would
• 30:00
  result in a different path being
• 30:01
  followed. You know, what would we get in
• 30:04
  terms of seam power if we were using
• 30:06
  wood and if we were using charcoal
• 30:08
  rather than other things? Would it lead
• 30:11
  to an earlier adoption of renewable
• 30:13
  energy in the form of wind power which
• 30:15
  was actually being used for hundreds of
• 30:17
  years? You go back to Europe and you see
• 30:18
  the windmills people use
• 30:20
  >> and watermills people's use.
• 30:22
  >> So I I don't know whether
• 30:26
  and this is a problem with all of
• 30:28
  astrobiology and it's a problem with a
• 30:30
  lot of the stuff that I'll talk about
• 30:31
  later about what makes a planet more
• 30:33
  suitable or less suitable. People have
• 30:35
  this tendency to find something that is
• 30:37
  unusual about us and there's a lot
• 30:40
  that's unusual about us. I mean there's
• 30:41
  a lot that's unusual about me and I hold
• 30:42
  my hand up about that. But they find
• 30:45
  things that are unusual
• 30:47
  and they say we are as far as we know
• 30:49
  unique in the cosmos. We are a
• 30:50
  technologically advanced civilization
• 30:52
  able to have this discussion.
• 30:54
  There has to be a reason that we're
• 30:56
  here. Everything that is unusual quite
• 30:59
  often gets held up as could this be the
• 31:01
  switch? If you didn't have this, we
• 31:04
  would not be here. And I tend to view
• 31:06
  them not as an on-off switch, but as a
• 31:08
  slider. They're like, and again, a
• 31:10
  gaming analogy would be varying the
• 31:12
  difficulty on your game. Some games,
• 31:14
  it's very kind of onoff, hard mode, easy
• 31:16
  mode. Others, particularly some of the
• 31:18
  role playing type games people play,
• 31:20
  have sliders for everything. And so, you
• 31:22
  can change things to the nth degree to
• 31:26
  tweak the challenge level. And I think
• 31:28
  all of these things like the existence
• 31:30
  of coal that get proposed as being a
• 31:34
  boundary, as being something that would
• 31:36
  be a block if you didn't have it, are
• 31:38
  actually probably more like one of those
• 31:39
  sliders. They're things that can
• 31:40
  facilitate,
• 31:42
  but it's really interesting to discuss
• 31:44
  them because we don't know how big a
• 31:46
  filter they are. We don't know how big a
• 31:48
  hurdle they are without digging into it
• 31:50
  more. And the more we can suggest these
• 31:51
  things, the more we can narrow them
• 31:53
  down. Ultimately, the only way we can
• 31:55
  finally test them is when we get a
• 31:57
  response to us, when we find
• 31:59
  technologically advanced life and then
• 32:02
  we learn about their heritage. What path
• 32:04
  did they follow? Did they invent fire
• 32:07
  before the wheel? Did they invent modern
• 32:10
  medicine before fire? And I've seen
• 32:14
  there's a fabulous famous old thread, I
• 32:17
  don't know, it wasn't from Reddit, it
• 32:18
  predates Reddit, but from one of the old
• 32:20
  messaging boards that talks about humans
• 32:24
  as the horror movie monsters of the
• 32:27
  universe. Because we always in science
• 32:29
  fiction, all the monsters we face, all
• 32:31
  the aliens we face are usually more
• 32:33
  something than us. And we overcome
• 32:35
  incredible odds to beat them. But this
• 32:37
  is taking the other perspective of
• 32:38
  another species kind of looking at us
• 32:40
  and going, "Those humans are
• 32:41
  terrifying." And it's listing all the
• 32:42
  ways we are. You know, we're an
• 32:44
  exhaustion hunter. We didn't beat things
• 32:46
  by speed or anything. We'd follow them
• 32:48
  until they died of exhaustion because we
• 32:51
  can go longer than they can. We're un
• 32:54
  they were saying, you know, it's the
• 32:55
  only intelligent technological species
• 32:57
  that invented amputation before
• 32:58
  painkillers.
• 33:00
  >> You know, we've got things like this
• 33:02
  that are very bizarre about us. So that
• 33:04
  takes this perspective I've got of these
• 33:07
  things are a hurdle and you develop
• 33:09
  things you know that things are not
• 33:11
  onoff switch but they're more of a
• 33:12
  slider and the idea of will things
• 33:16
  naturally be developed in the same order
• 33:18
  and turns it around and said what would
• 33:19
  another species think looking at us and
• 33:22
  I always find that really good fun and
• 33:24
  it's effectively leads to the thing that
• 33:25
  humans are space and we're this terri
• 33:28
  terrifying weird little species and
• 33:31
  maybe that's what it'll turn out to
• 33:33
  Well, it yeah, look, I don't uh I don't
• 33:36
  dispute that because look how we treat
• 33:39
  each other or have treated each other um
• 33:42
  since civilization began. Basically, uh
• 33:45
  I I don't think you could add up how
• 33:47
  many wars we've fought against each
• 33:48
  other.
• 33:50
  I I don't think that would stop if we
• 33:53
  found another intelligent life form. I
• 33:55
  don't think we'd go in saying, "Hi, hey,
• 33:57
  we're really nice." I I got a feeling
• 33:59
  we'd, you know, it'd be a bit
• 34:01
  adversarial.
• 34:03
  >> It It's a really It is a really
• 34:05
  interesting one. It's one of the things
• 34:06
  that people factor into a lot of the
• 34:08
  discussions about the the rights and
• 34:11
  wrongs of active SETI. So active SETI is
• 34:14
  sending out a message saying, "Hi, we're
• 34:16
  here. Please talk to us." Whereas
• 34:18
  passive SETI is listening for people
• 34:19
  saying, "Please turn neighbors off.
• 34:21
  We're sick of seeing it." You know,
• 34:22
  they're effectively the two ways you can
• 34:23
  do SETI. There are a lot of people in
• 34:27
  the past that have argued that active
• 34:28
  set is a bad idea because it will
• 34:30
  attract the wrong kind of attention.
• 34:31
  >> Well, Steven Hawking certainly thought
• 34:33
  that.
• 34:34
  >> Um, and throwing no shade, I think the
• 34:37
  great Mark Camode, who's a film reviewer
• 34:38
  in the UK, um, often says, you know,
• 34:41
  other opinions are available. They're
• 34:43
  wrong, but they are available. I mean,
• 34:45
  this, I think, is a case of that. I
• 34:47
  think if any for me, and I will admit
• 34:49
  I'm an optimist. I'm also not exactly
• 34:51
  the world's most aggressive person, but
• 34:54
  for me, if you have survived as a
• 34:55
  species for long enough to be a thriving
• 34:58
  civilization to the point of wanting to
• 35:00
  communicate to the upsc upstarts that
• 35:02
  are broadcasting, you know, Big Brother
• 35:04
  and all the rest of it to the universe,
• 35:06
  that suggests that to some degree you've
• 35:08
  overcome your martiality. Um because I
• 35:10
  think for us to survive to the point
• 35:13
  where we're moving out into the stars
• 35:15
  will require us not to first wipe
• 35:17
  ourselves out. And the more advanced you
• 35:19
  get, the more you disperse probably,
• 35:22
  fingers crossed, hopefully, the less
• 35:24
  likely that becomes. Now, we look at the
• 35:26
  world around us today, and without
• 35:27
  digging into politics, there's always
• 35:29
  something nasty going on. There's
• 35:30
  >> many, many tragedies that are both
• 35:32
  frontline in the news and forgotten by
• 35:34
  the news. But I saw a great article few
• 35:38
  years ago that was arguing that you know
• 35:40
  when was the worst time to ever live and
• 35:42
  saying that actually despite the fact
• 35:44
  that all this war all this aggression
• 35:46
  all this violence is so front and center
• 35:48
  this is actually the safest era to live
• 35:50
  in that humanity's ever experienced the
• 35:53
  number of people dying before their time
• 35:55
  dying before they reach scessians is
• 35:58
  lower per thousand people up 100
• 36:00
  thousand people than ever before you
• 36:02
  have a much lower chance as an average
• 36:04
  person of ever fighting in a war have
• 36:06
  ever been murdered or assaulted.
• 36:08
  >> So, we're already moving that way if it
• 36:10
  doesn't feel like it. And so, to me,
• 36:12
  with that optimistic viewpoint, I would
• 36:15
  like to think that there is no reason
• 36:17
  for conflict and no reason for friction.
• 36:19
  And I think a lot of the arguments that
• 36:22
  humanity's future encounters with aliens
• 36:25
  must by necessity be violent is telling
• 36:28
  you more about people than it's telling
• 36:29
  you about aliens because it's saying
• 36:31
  when we look in the mirror, we see the
• 36:32
  angry snarling tribalist. rather than
• 36:35
  the rational modern human that is a
• 36:38
  veneer on top. We're still a tribal
• 36:40
  species. We're still the product of our
• 36:43
  evolution. And society is a veneer that
• 36:45
  we put on top of that as we learn to be
• 36:48
  better, to be the kind of thinking
• 36:50
  social ape, I guess. And the evidence is
• 36:54
  that over time we're getting better at
• 36:55
  that. Even though we're now more capable
• 36:57
  of killing each other than we ever were
• 36:59
  before.
• 37:00
  >> Yeah.
• 37:00
  >> We're doing it less often.
• 37:01
  >> Yes, we are. All right. All right, we'll
• 37:03
  take a quick breather because I want to
• 37:05
  get into the um the area of u finding
• 37:10
  this life beyond our solar system. How
• 37:12
  how are we going to do it, where we're
• 37:14
  going to look, and what we've got to
• 37:15
  look for. That's all coming up on this
• 37:17
  edition of Space Nuts.
• 37:21
  >> Roger. Also,
• 37:23
  >> Space Nuts.
• 37:24
  >> So, Jotty, look, lead the way. Where do
• 37:26
  you want to go from here? We got to uh
• 37:28
  this is our final segment. So, um I
• 37:31
  suppose if you're going to try and find
• 37:33
  life beyond our solar system, uh you got
• 37:36
  to find the right environment, um you
• 37:39
  know, rocky planet, habitable zone
• 37:41
  perhaps, um
• 37:44
  >> and and there's a lot more to it than
• 37:45
  that. It's not just a planet with
• 37:48
  perhaps liquid water on its surface.
• 37:51
  There's you got to have, I suppose, the
• 37:53
  right kind of star. You don't want a red
• 37:55
  dwarf because you probably just, you
• 37:57
  know, get really bad sunburn. Uh there's
• 38:00
  a lot to take into account.
• 38:02
  >> There's a huge amount of depth to it.
• 38:03
  And I think as we saw with the previous
• 38:05
  episode, we could have talked another
• 38:07
  hour and we could have talked another
• 38:09
  week. To be honest, when we're talking
• 38:10
  about this stuff, one of the things I
• 38:12
  most adore about science is the infinite
• 38:15
  complexity. So you ask a question when
• 38:17
  you get an answer. That isn't it. But
• 38:18
  you get another 10 questions. And the
• 38:21
  more you know about a subject, the more
• 38:22
  complexity there is. To me, that's just
• 38:24
  a wonder. And that's fascinating. And
• 38:26
  this is a really good example of that.
• 38:28
  Now, one of my strongest arguments
• 38:32
  through my career has been that we can't
• 38:36
  just when we're trying to think about
• 38:37
  where we're going to search for life
• 38:39
  beyond the solar system, use a habitable
• 38:41
  zone and that's it. You know, it seems
• 38:43
  like a lot of coverage and a lot of
• 38:46
  papers just go earthlike planet found in
• 38:48
  the habitable zone. Wee and and that's
• 38:50
  about it. Now, the habitable zone has
• 38:53
  become a really effective communication
• 38:55
  tool in much the same way the Drake
• 38:56
  equation has. The Drake equation is this
• 38:59
  fabulous tool with all the sliders where
• 39:00
  you can make your own inhabited universe
• 39:03
  with lots of few aliens by varying the
• 39:05
  variables. The habitable zone has become
• 39:08
  another of these catch all kind of
• 39:10
  visualizations and it's born of the idea
• 39:12
  that life needs liquid water
• 39:14
  >> with the implicit extension of that that
• 39:17
  life needs liquid water on a planet's
• 39:19
  surface. Now that's initially motivated
• 39:22
  by the fact that the earth is the only
• 39:23
  place with life and back when this was
• 39:26
  being discussed the only place with
• 39:27
  liquid water that we knew. So therefore
• 39:29
  it was natural to say you need surface
• 39:31
  liquid water. As we discussed earlier
• 39:33
  there are plenty of places in the solar
• 39:34
  system that do not have liquid water on
• 39:36
  the surface but do have it underneath.
• 39:38
  They've got soft centers. But the
• 39:40
  habitable zone says you need liquid
• 39:43
  water on the surface of a planet for
• 39:46
  that planet to be considered suitable
• 39:47
  for life to be habitable.
• 39:49
  Now, that isn't entirely true, but for
• 39:52
  the purposes of this, it's still useful
• 39:54
  because life buried beneath ice is so
• 39:57
  hard to find that we can't find it in
• 39:59
  our own solar system because the ice is
• 40:00
  in the way. We wouldn't have a chance to
• 40:02
  run planets around other stars. So, even
• 40:04
  though I think the habitable zone is a
• 40:06
  big oversimplification, I see merit to
• 40:08
  it because life on a planet's surface
• 40:10
  with only atmosphere above is much more
• 40:13
  likely to be detectable than life burden
• 40:15
  the interior. So, fair enough, we'll go
• 40:16
  with it. The idea of the habitable zone
• 40:19
  though is that the closer you are to a
• 40:21
  star, the hotter you are. The further
• 40:22
  away you are, the cooler you are. And
• 40:24
  just like Goldilocks and the three
• 40:26
  bears, which why it's often called the
• 40:27
  Goldilock zone, there's a place where
• 40:28
  it's just right. It's not too hot, not
• 40:30
  too cold,
• 40:31
  >> and therefore there could be liquid
• 40:32
  water on the surface of the planet. Now,
• 40:35
  a lot of the time when people say a
• 40:36
  planet is in the habitable zone,
• 40:39
  that's often taken as meaning that
• 40:42
  planet could and potentially will have
• 40:44
  liquid water on the surface. But
• 40:46
  actually what it's saying is if you took
• 40:48
  the Earth as the Earth is today and put
• 40:51
  it in that system, would it still look
• 40:53
  like the Earth? Would it have liquid
• 40:54
  water on its surface? Now we've extended
• 40:58
  a bit beyond that. There are a couple of
• 41:00
  fabulous papers bit more than a decade
• 41:01
  old now that set what are our very
• 41:04
  contemporary scientific mathematical
• 41:05
  definitions of the habitable zone that
• 41:08
  people use for their papers. And they
• 41:10
  take the flux from the star, take into
• 41:12
  account the different colors of the
• 41:13
  stars. And there are two versions.
• 41:16
  There's the optimistic and conservative
• 41:18
  versions where the optimistic version is
• 41:20
  a wider set of distances and the
• 41:22
  conservative version is a smaller set of
• 41:24
  distances. But it effectively uses Venus
• 41:27
  and Mars as a roughing edge in our solar
• 41:29
  system and then scales that window up
• 41:31
  and down depending on the kind of star
• 41:32
  you're around.
• 41:34
  >> But that illustrates immediately
• 41:37
  that this is an oversimplification
• 41:39
  because you can do a thought experiment.
• 41:40
  Let's take our solar system. Venus is
• 41:42
  way too hot. Mars is way too cold and
• 41:45
  the Earth is just right. All well and
• 41:46
  good. Swap the Earth. Sorry, swap Mars
• 41:49
  and Venus around. If you put Venus where
• 41:51
  Mars is, Venus's thick atmosphere and
• 41:53
  greenhouse effect wouldn't mean it would
• 41:54
  be warm enough liquid water on the
• 41:56
  surface. It wouldn't have cooled as much
• 41:57
  as Mars. So Venus would be habitable on
• 42:01
  the surface outside the habitable zone.
• 42:04
  If you put Mars where Venus is, with its
• 42:06
  very thin and tenuous atmosphere, it
• 42:07
  doesn't have much greenhouse effect at
• 42:10
  all. Mars would potentially still be
• 42:12
  habitable where Venus is when Venus
• 42:15
  isn't. And so that's immediately
• 42:17
  pointing that this story is actually
• 42:19
  significantly more complex.
• 42:21
  >> Yeah.
• 42:21
  >> That you can't just say, let's calculate
• 42:25
  the habitable zone. Let's calculate the
• 42:26
  equilibrium temperature on a planet,
• 42:29
  which is a temperature it would have if
• 42:31
  it didn't have a greenhouse effect that
• 42:33
  it was a certain reflectivity and it was
• 42:35
  in equilibrium with the light coming in
• 42:37
  and the light going out. And if that
• 42:39
  temperature is from about minus20
• 42:40
  upwards, it's probably warm enough for
• 42:42
  water because, well, you'll have a bit
• 42:43
  of an atmosphere. To me, that's never
• 42:46
  been enough. Now, the reason it's really
• 42:48
  important, at least from my perspective,
• 42:50
  is that finding planets is hard. We'll
• 42:53
  talk about that in another episode, but
• 42:55
  once you find the first of something,
• 42:58
  astronomy, history, and probably every
• 43:00
  other form of scientific endeavor,
• 43:01
  history tells us, finding the first of
• 43:02
  something is hard. But once you've got
• 43:04
  one, you quickly find more and more as
• 43:06
  your technology gets better. Finding
• 43:08
  evidence of life on a planet that is
• 43:10
  similar to the Earth is fundamentally at
• 43:13
  least an order of magnitude if not more
• 43:15
  harder than finding that planet was. So
• 43:18
  it'll take time for our technology to
• 43:20
  get good enough to search comfortably
• 43:22
  for life elsewhere. So initially that
• 43:24
  search is going to be very restricted
• 43:26
  because we've got limited resources. So
• 43:28
  you're only going to be able to look at
• 43:30
  a few planets aggressively at first to
• 43:32
  try and tease out any indication of
• 43:34
  life. But you're going to have loads to
• 43:37
  choose from. How should you choose?
• 43:38
  Well, to me, it can't just be the
• 43:40
  habitable zone.
• 43:44
  >> Yeah, that's a valid point. Um, and and
• 43:47
  we've reached a point where we've found
• 43:50
  thousands upon thousands of exoplanets
• 43:52
  and counting. Like, we haven't stopped.
• 43:54
  We're finding them more and more and
• 43:56
  more often of all different shapes of
• 43:58
  sides sizes. Um,
• 44:02
  some rocky planets, they've been harder
• 44:04
  to find cuz they're they're usually much
• 44:06
  smaller and and don't sort of indicate
• 44:09
  themselves like a gas giant does. But
• 44:12
  we're getting better at finding uh rocky
• 44:15
  planets. Um,
• 44:17
  I suppose the big question is given how
• 44:20
  much we are finding, how do you identify
• 44:23
  prime targets for life?
• 44:25
  >> Yeah. And that is what the paper that I
• 44:28
  put together with Barry Jones back in
• 44:29
  2010 was all about. So Barry was a very
• 44:33
  dear friend of mine. He was my boss when
• 44:34
  I moved to the Open University from 2006
• 44:36
  to 2009. I think he knew Fred very well
• 44:38
  as well. So you can always mention to
• 44:40
  Fred that we talked about Barry. I
• 44:42
  started work at the Open University in
• 44:44
  2006 on the day Barry was forced to
• 44:46
  retire by the government because he'd
• 44:47
  hit 67. So he hired me and promptly
• 44:50
  retired but um he kept working anyway as
• 44:53
  ameritus professor. And Barry and I did
• 44:56
  a lot of work on this during my time
• 44:57
  there. Barry unfortunately passed away a
• 44:59
  little bit more than a decade ago. So
• 45:00
  he's fondly remembered. I organized a an
• 45:03
  award in the UK in his memory every
• 45:05
  couple of years. What we did in this
• 45:07
  2010 paper was to essentially have the
• 45:11
  thought process we just outlined. So,
• 45:13
  we're going to have a huge number of
• 45:16
  potential exo earths, planets that could
• 45:18
  potentially be Earthlike that could be
• 45:20
  places to look for life, but we're only
• 45:23
  going to be able to search a handful of
• 45:24
  them initially. So, what should we do to
• 45:27
  select the best target? Now, obviously,
• 45:29
  the closer the planet's hosts are is to
• 45:32
  the solar system, the easier the
• 45:33
  observations will be. That's just a
• 45:35
  fundamental thing of if you're twice as
• 45:37
  far away, we only receive a quarter as
• 45:39
  much light from you. But also, if you're
• 45:41
  twice as far away, the separation
• 45:42
  between the planet and the star on the
• 45:44
  sky will be half as much because the
• 45:47
  angle gets smaller the further away you
• 45:49
  go essentially. And we will want targets
• 45:51
  that are far enough from the star in the
• 45:52
  sky that with future missions like
• 45:54
  potentially the habitable world's
• 45:55
  observatory, we can separate the light
• 45:57
  from the planet from the light from the
• 45:58
  star. So, probably even more important
• 46:01
  than the habitable zone is this
• 46:03
  proximity thing. The planets in the main
• 46:06
  found by the Kepler space telescope
• 46:08
  won't be suitable for this search
• 46:10
  because they're mainly very far from the
• 46:12
  sun and so therefore they'll be very
• 46:14
  hard to study. We want to look locally.
• 46:16
  That's a given,
• 46:18
  but we want to look for places where
• 46:20
  there is the possibility of liquid water
• 46:22
  on the surface because that means that
• 46:24
  the life will be in contact with the
• 46:25
  atmosphere and that might generate a
• 46:27
  signature we can detect in the
• 46:28
  atmosphere.
• 46:29
  >> And that's where the habitable zone
• 46:30
  comes from. But there's actually much
• 46:33
  more to it than that I think. And I'm
• 46:35
  far from able to give an exhaustive list
• 46:36
  because I'm not an expert in all all
• 46:38
  areas of astronomy. But we decided to
• 46:41
  put together a review paper which about
• 46:44
  32 pages long, probably a little bit
• 46:46
  outdated now because science has moved
• 46:48
  forward, but was saying effectively you
• 46:51
  can't just use a habitable zone. We need
• 46:54
  to think about all of the different
• 46:56
  factors that can contribute to make a
• 46:58
  planet more or less suitable for life.
• 46:59
  Now, many of these have been in the past
• 47:02
  suggested as that onoff switch. And I do
• 47:04
  think that they're more sliders like the
• 47:06
  numbers in the Drake equation or sliders
• 47:07
  on a mixing desk. But there are a lot of
• 47:10
  different things that have been
• 47:11
  suggested. And as I dug into the paper,
• 47:13
  there were even more than I thought of.
• 47:14
  You can broadly break them down into
• 47:17
  four areas. The first is galactic
• 47:19
  influences. So the impact of the galaxy
• 47:22
  itself, where you are in the galaxy,
• 47:24
  stuff like that. You've then got stellar
• 47:26
  influences, so the role of the star.
• 47:28
  You've got the planetary system. And
• 47:30
  then you've got the planet itself. So th
• 47:31
  those the kind of four broad areas. The
• 47:34
  galactic influences one is probably the
• 47:37
  least useful and the least well
• 47:38
  constrained. But the idea of the
• 47:40
  galactic influence is tied a bit to a
• 47:42
  theory that's been put forward by a few
• 47:44
  people called the galactic habitable
• 47:45
  zone. It's an idea that ties back to the
• 47:50
  origin of stars and planets and also to
• 47:51
  the dangers that are experienced because
• 47:53
  of your environment. The idea that as
• 47:55
  time goes on, the universe is becoming
• 47:57
  more metalrich. And by that I mean
• 48:00
  enriched in everything other than
• 48:01
  hydrogen and helium because generations
• 48:03
  of stars run their furnaces and turn the
• 48:05
  light elements to the heavy ones and put
• 48:07
  them back into the cosmos. You need a
• 48:09
  certain amount of heavy elements to form
• 48:10
  planets like the Earth and to have the
• 48:12
  carbon, nitrogen, phosphorus for life.
• 48:15
  So as time goes on, the universe getting
• 48:17
  more enriched is a good thing. But
• 48:19
  there's also possibilities that too much
• 48:21
  enrichment will change the chemistry or
• 48:23
  it will make planet formation too easy.
• 48:25
  There's all sorts. So you might have a
• 48:27
  sweet spot from that side of things. Now
• 48:30
  in the middle of the galaxy, star
• 48:32
  formation occurs at a more rapid pace
• 48:34
  and stars live and die quicker. So you
• 48:36
  get faster change in the abundance of
• 48:40
  materials. So you can imagine we have
• 48:42
  this concept in astronomy called
• 48:43
  metallicity which is the amount it's
• 48:46
  usually measured in the amount of
• 48:47
  hydrogen compared to the amount of iron
• 48:49
  in a star and that gives you a number on
• 48:51
  a logarithmic scale and that is a an
• 48:54
  approximation to when the star formed
• 48:56
  and how enriched the world was at the
• 48:57
  time and as time goes on things get more
• 48:59
  and more metalrich within our galaxy
• 49:02
  you'd expect there to be a gradient in
• 49:03
  this. So the things near the middle will
• 49:04
  be much more enriched in heavy elements
• 49:06
  of things near the outer edge and
• 49:08
  there's probably sweet spot in the
• 49:10
  middle that moves outwards over time
• 49:12
  where conditions to form planets like
• 49:14
  the earth and planetary systems like the
• 49:15
  solar system are perfect. So that's part
• 49:18
  of the galactic habitable zone idea. The
• 49:20
  other idea is that if you're too close
• 49:22
  in and the stellar density is too high,
• 49:25
  eventually the stellar density gets so
• 49:26
  high that the likelihood of life being
• 49:28
  exterminated by nearby supernovi or
• 49:31
  planetary systems being stripped and
• 49:32
  disrupted becomes too high. So there's
• 49:34
  always been this idea that location
• 49:36
  within the galaxy is important. The
• 49:40
  challenge to that is twofold. Firstly,
• 49:42
  the proximity argument. We're going to
• 49:44
  have to look at stars that are very
• 49:45
  nearby which are all at the same
• 49:47
  distance from in the middle of the
• 49:48
  galaxy as we are. So where you are in
• 49:51
  the galaxy won't realistically impact
• 49:54
  this search because we're going to be
• 49:55
  looking locally. The other things though
• 49:57
  is that stars have a huge degree of
• 49:59
  mobility. There was a recent story
• 50:01
  talking about finding s solar twins,
• 50:03
  stars that have the same chemistry as
• 50:05
  the sun that may have formed with the
• 50:07
  sun and a suggestion that the sun and
• 50:10
  other stars may have formed as much as
• 50:11
  10,000 light years nearer the middle of
• 50:13
  the galaxy than we are now. Stars are
• 50:15
  getting scattered inwards and outwards.
• 50:17
  So seeing a star here now doesn't imply
• 50:19
  that it's always been here.
• 50:21
  >> Yeah.
• 50:21
  >> So the galactic influences I'm not going
• 50:24
  to go into really any more than that,
• 50:25
  but it's worth knowing that they're
• 50:27
  there. It's worth knowing that it's
• 50:28
  point of discussion and that there is
• 50:30
  good research going on about this. It's
• 50:32
  really interesting area, but it doesn't,
• 50:34
  I think, impact our initial search for
• 50:36
  life because we're going to be searching
• 50:39
  our local area. So, it's a bit like me
• 50:41
  saying I want to search for signs of
• 50:42
  life on Earth. It's a lot easier for me
• 50:44
  to search in King Soap where I live than
• 50:47
  to search in Mumbai or in London, places
• 50:50
  like this. You've got to look locally.
• 50:52
  Now, talking about that, you know, what
• 50:54
  would I expect to find?
• 50:55
  you know the people in King have not all
• 50:58
  but many of them have a similar
• 50:59
  background to me formed in similar ways
• 51:01
  with similar culture all the rest of it
• 51:03
  so this it's a not a great analogy I
• 51:06
  admit but we've got to look locally so
• 51:08
  the galactic influences stuff is
• 51:11
  interesting but I wouldn't say it is a
• 51:15
  big factor but it's worth noting I guess
• 51:18
  >> so that leads us on to um I don't know
• 51:22
  finding the right targets uh And and if
• 51:25
  we do find those targets,
• 51:28
  what what do we do then to look for
• 51:31
  potential life on those targets?
• 51:33
  >> Absolutely. And that's a very hard
• 51:34
  question. Now, in terms of finding the
• 51:36
  right targets, there's a lot that comes
• 51:38
  into it from the star itself. Now, stars
• 51:43
  live very long lives. First question
• 51:45
  then is how old is a star? Now, if we
• 51:47
  look at life on Earth, the oldest
• 51:49
  fossils on Earth that are widely
• 51:51
  accepted are about 3 and a half thousand
• 51:52
  million years old are in the Pilra,
• 51:54
  which is about a billion years after the
• 51:56
  Earth formed. There are some that are
• 51:58
  older that are still controversial,
• 52:00
  possibly as old as 4 billion years. But
• 52:01
  if we take the 3 1/2 billion years as a
• 52:04
  threshold and we do what we're doing
• 52:06
  with the liquid water thing and we say
• 52:07
  we expect life to follow a similar path
• 52:09
  to us, the fact that it took a billion
• 52:11
  years for life to get established enough
• 52:13
  to leave fossils we could find possibly
• 52:15
  means that it might have taken a similar
• 52:16
  length of time for that life to modify
• 52:18
  its environment enough to be detectable
• 52:20
  from elsewhere. So we can put an
• 52:21
  arbitrary kind of timer here saying that
• 52:24
  any planetary system younger than say a
• 52:26
  billion years may have planets that are
• 52:29
  suitable for life but that life might
• 52:30
  have not had enough time to get
• 52:32
  established yet. So that might
• 52:35
  immediately say that's not as good a
• 52:38
  place to look as a star that is more
• 52:39
  like the age of the sun where life's had
• 52:41
  four billion years to get going. Now
• 52:43
  tied to that is the fact that the lives
• 52:46
  of stars are very dependent on their
• 52:48
  mass. So the more massive a star is, the
• 52:50
  brighter it shines, but the shorter its
• 52:52
  life is. And at a very rough level, this
• 52:55
  number varies a little bit depending on
• 52:56
  the mass of the star. But typically the
• 52:58
  luminosity of a star is proportional to
• 53:00
  its mass to the power four. So if you've
• 53:03
  got a star that is 10 times the mass of
• 53:04
  the sun, it will be roughly 10,000 times
• 53:06
  brighter than the sun. But these stars
• 53:09
  are burning their own material. They're
• 53:10
  turning hydrogen to helium and they're
• 53:12
  made of hydrogen. So a star that is 10
• 53:14
  times the mass of the sun will only have
• 53:16
  10 times as much fuel as a sun. But it's
• 53:18
  burning that fuel 10,000 times quicker,
• 53:21
  which means it'll run out a lot quicker.
• 53:23
  And what that means is that the more
• 53:24
  massive a star is, the longer, the
• 53:26
  shorter its life will be. And the less
• 53:28
  massive a star is, the longer its life
• 53:30
  will be. That means that beyond a
• 53:33
  certain stellar mass, the star will die
• 53:35
  before that billionyear cutoff. So we
• 53:38
  can probably rule out the most massive
• 53:39
  stars. They'll just live fast, die
• 53:41
  young, and it's unlikely that life will
• 53:43
  get well enough established. On the flip
• 53:45
  side, the dim little red dwarfs will
• 53:47
  just go forever. You know, Proxima
• 53:48
  Centtory will still be traveling along
• 53:50
  in a trillion years when we're a distant
• 53:52
  memory. So, they might be a good place
• 53:54
  to look. The challenge there though is
• 53:56
  that those stars are quite active quite
• 53:59
  often. And to be in the habitable zone
• 54:02
  around them, you've got to be very close
• 54:03
  in because they're called little embers.
• 54:04
  You've got to snuggle up to the fire. So
• 54:06
  there's a lot of discussion about the
• 54:07
  fact that M dwarf planets planets around
• 54:10
  these coolest smallest stars are
• 54:12
  probably not ideal places to look for
• 54:13
  knife initially. Few reasons. One is
• 54:16
  that activity and a lot of discussions
• 54:18
  that the activity of red dwarfs when
• 54:19
  they're young could scour a planet's
• 54:20
  atmosphere away and that seems to have
• 54:22
  possibly been backed up with a trappist
• 54:24
  one planets that all seem to be airless
• 54:26
  worlds. The other is that those planets,
• 54:30
  if they are close enough in to be warm
• 54:31
  enough for liquid water on the surface,
• 54:33
  would have to be tidily locked like the
• 54:35
  moon is to the earth, which means
• 54:37
  they'll keep one face permanently
• 54:38
  pointed towards the star and the other
• 54:39
  permanently away, which may make it
• 54:42
  harder to look for light on them. It
• 54:43
  might be the case that any life would be
• 54:45
  on the sunwood side, and that's kind of
• 54:47
  hard to observe because when that side
• 54:49
  is best presented to us, it's near the
• 54:51
  star. So, that's challenging. Another
• 54:54
  thing that factors into it ties into
• 54:56
  something called the faint early sun
• 54:57
  paradox on Earth. The
• 55:01
  lives of stars, they shine brightly.
• 55:03
  Their brightness is measured compared to
• 55:05
  their mass, but their brightness
• 55:06
  increases with time. Stars get more
• 55:09
  luminous as they age a little bit. And
• 55:10
  it's a slow process. But with the sun,
• 55:13
  we think the sun was 30% dimmer when it
• 55:16
  was born to how it is now. So that means
• 55:19
  the earth at the time got 30% less
• 55:21
  energy which would have put it with its
• 55:24
  current atmosphere
• 55:26
  too cold to support life. Um that was
• 55:29
  offset by the fact we had a very
• 55:30
  different atmosphere then and a
• 55:32
  significant
• 55:33
  greenhouse effect which was lessened due
• 55:35
  to the influence of life stripping out
• 55:38
  carbon dioxide particularly from the
• 55:40
  atmosphere and keeping us mostly there
• 55:41
  and thereabouts. But what that means is
• 55:44
  that if we find a planet now and that
• 55:47
  planet is near the outer edge of the
• 55:48
  habitable zone, everybody will go,
• 55:50
  "Well, it's in the habitable zone.
• 55:51
  That's great." Whereas my question would
• 55:53
  then be, "But how long has it been in
• 55:55
  the habitable zone?" Because when the
• 55:57
  star was younger, it was a little bit
• 55:59
  dimmer. The habitable zone would have
• 56:01
  been closer in, and that planet might
• 56:02
  well have been outside it. So, I don't
• 56:04
  necessarily think that that 1
• 56:05
  billionyear clock would start until the
• 56:08
  planet was in the habitable zone. So
• 56:09
  we'll probably then be able to rule some
• 56:11
  planets out on the basis of the fact
• 56:14
  that they could be in the habitable zone
• 56:17
  now, but they haven't been full long
• 56:18
  enough.
• 56:19
  >> Yeah.
• 56:19
  >> So the star has all these effects. Never
• 56:21
  mind the fact that astronomers often
• 56:23
  joke that three out of every two stars
• 56:25
  are in a multiple star system. um
• 56:28
  multiple stars are very very common and
• 56:30
  that adds a whole extra level of
• 56:32
  complexity both to the understanding of
• 56:35
  the lives of the planets in those stars
• 56:37
  but also in our ability to study them
• 56:39
  because you've got more than one stars
• 56:41
  like to factor in all close together.
• 56:43
  It's much nastier and much more
• 56:45
  complicated. So there's a lot of ways
• 56:47
  that the stars can factor in and I think
• 56:49
  that's only a very very broad brush
• 56:52
  strokes for view. But you can see how
• 56:54
  what I'm thinking is you can bring in
• 56:56
  all these different ideas and have them
• 56:59
  as a slider. This kind of star could
• 57:01
  have planets around it with life, but
• 57:02
  it's not as good a target as this one.
• 57:05
  Now, everybody could build their own
• 57:06
  algorithm out of this, but I'd like to
• 57:08
  think that when we're trying to pick the
• 57:09
  target, you take into account the star
• 57:12
  that it's going around, how active it
• 57:14
  is. Is it a single star? Is it old
• 57:16
  enough? All these kind of factors. And
• 57:19
  then you can start looking at the
• 57:21
  planetary system that it's in. And
• 57:23
  there's a lot to talk about there, I
• 57:24
  think.
• 57:25
  >> Yes, absolutely. Uh and in our next um
• 57:30
  uh special um between Q&A episodes, we
• 57:34
  will um look more into um the the planet
• 57:37
  side of things. I I guess just to
• 57:39
  conclude um I'll throw one at you. Um
• 57:43
  and and this answer is always different
• 57:45
  depending on who you ask, but uh what do
• 57:47
  you think the odds are that we will find
• 57:50
  some form of life?
• 57:53
  >> Um I I'm an optimist. I think the answer
• 57:56
  to it will be yes, we will find some
• 57:58
  sort of life. I think the harder
• 58:00
  question is when. Now, if we find life
• 58:04
  in a million years time when we're not
• 58:06
  even human anymore, but we've hung
• 58:07
  around, we've managed to survive. That's
• 58:09
  not very edifying for me and you cuz
• 58:10
  it's a long time to wait. But as I said
• 58:13
  earlier on, I don't think it's a
• 58:14
  question of if, it's a question of when.
• 58:16
  Because I find it vanishingly improbable
• 58:19
  for us to be the only system with life.
• 58:23
  >> And it's a numbers game for me. You
• 58:24
  know, we've got a galaxy with between
• 58:26
  200 and 400,000 million stars. There are
• 58:30
  more galaxies in the visible universe
• 58:33
  certainly than there are planets in our
• 58:35
  galaxy. probably more than there are
• 58:37
  grains of sand in our galaxy. All of
• 58:39
  them with hundreds of thousands of
• 58:41
  millions of stars.
• 58:43
  To say that out of if you run the
• 58:45
  numbers you get sectillions,
• 58:47
  septillions, even octillions
• 58:50
  bonkersly full-on numbers of planets out
• 58:54
  there that were the only place that got
• 58:56
  life. That tells you that life is
• 58:58
  effectively impossible and we're a
• 58:59
  fluke.
• 59:00
  >> Now, that could be the case. If that's
• 59:04
  the case, what we've got here on Earth
• 59:05
  becomes even more precious and there is
• 59:07
  an even greater incentive for us to keep
• 59:10
  an eye on what we're doing so that Earth
• 59:13
  is still capable of hosting life in the
• 59:14
  future. But I think in reality, life
• 59:17
  will actually be more common than that.
• 59:19
  And you don't need to be much more
• 59:20
  common than that for life to be abundant
• 59:22
  in the galaxy. Let's imagine that life
• 59:25
  is found on one planet in 1 billion.
• 59:29
  That's billion with a B. So one in a
• 59:31
  thousand million. Now, we're finding
• 59:33
  that on average all stars have planets,
• 59:35
  probably have a number of planets. So,
• 59:37
  if we say roughly there are 10 planets
• 59:39
  per star, there will be four trillion
• 59:41
  planets in our galaxy. If one in a
• 59:43
  billion had life on it, that would mean
• 59:46
  there were 4,000 inhabited planets in
• 59:49
  our galaxy.
• 59:50
  >> Not a big number. The nearest one would
• 59:52
  be so far away in that case, we wouldn't
• 59:54
  find life for a long time. But life
• 59:56
  could be common and we still wouldn't
• 59:58
  find it. The more you increase that
• 1:00:00
  likelihood of life, the nearer the
• 1:00:03
  nearest examples will be and the sooner
• 1:00:05
  we'll find it. And that's why I think
• 1:00:06
  proximity will tell us a lot about the
• 1:00:08
  probability of life in that if we find
• 1:00:12
  life, the next step is to figure out we
• 1:00:15
  are not alone. We know we're not alone.
• 1:00:17
  How common is life? Now the other thing
• 1:00:19
  I think factors into it I think is a
• 1:00:21
  lovely kind of sci-fi thing to discuss
• 1:00:23
  all the way through you mentioned early
• 1:00:24
  on carbon based life and technologically
• 1:00:27
  advanced life and we drifted away the
• 1:00:30
  one place where I think that life that
• 1:00:33
  is different to us is something we could
• 1:00:34
  possibly find is siliconbased life now
• 1:00:38
  the reason for that is not from the
• 1:00:41
  point of view of um silicon people who
• 1:00:45
  have evolved in the way we have done I'm
• 1:00:48
  thinking more kind of second generation
• 1:00:50
  life. Now, our exploration of the solar
• 1:00:52
  system is done by our robot envoys and
• 1:00:54
  we're sending them near enough to home
• 1:00:56
  that we can tell them what to do.
• 1:00:58
  >> But we are developing to certain
• 1:01:01
  controversy at the current time. We're
• 1:01:02
  developing a greater and greater ability
• 1:01:04
  to develop things that can make
• 1:01:06
  decisions for themselves without human
• 1:01:07
  input. Things like AI and other systems.
• 1:01:11
  And if we get to the point where we want
• 1:01:12
  to explore around other stars, we'll
• 1:01:16
  need to develop spacecraft that have
• 1:01:18
  enough autonomy to make their own
• 1:01:19
  decisions. You go back to the idea, and
• 1:01:22
  I don't know what's happened to it in
• 1:01:23
  recent years, but the idea of project
• 1:01:24
  star where they made a little
• 1:01:25
  spacecraft, shot them off with laser,
• 1:01:27
  then they got to Proxima Centuri in 25
• 1:01:29
  years traveling at a fifth of the speed
• 1:01:31
  of light. You do that, they get to
• 1:01:35
  Proxima Centuri. If they've got to ask
• 1:01:36
  us what to do, they send a signal to us.
• 1:01:38
  takes 4 and a bit years to get here.
• 1:01:40
  Takes five years to get back and by the
• 1:01:42
  time it reaches them, they're a light
• 1:01:43
  year beyond the system. It's that well
• 1:01:44
  too late. So, we have to give them a
• 1:01:46
  certain level of autonomy. And the more
• 1:01:48
  complex their mission is going to be,
• 1:01:49
  the more autonomous it have to be. Which
• 1:01:52
  leads to the very science fiction idea
• 1:01:54
  that when we move out beyond the solar
• 1:01:57
  system, if we move out beyond the solar
• 1:01:58
  system, we will be preceded by a wave of
• 1:02:02
  life that is not us. That is our life
• 1:02:06
  that has a creator. that creator is
• 1:02:08
  humanity that is silicant based life
• 1:02:10
  that we send out whether they're
• 1:02:12
  vonoyman machines whether they are
• 1:02:14
  incredibly advanced AI machines without
• 1:02:16
  the capacity to reproduce themselves we
• 1:02:19
  will send out artificially
• 1:02:22
  built silicon life forms and again
• 1:02:25
  there's a a lovely fairly low stakes
• 1:02:28
  sci-fi series called the Bobbyverse
• 1:02:31
  um which follows that kind of idea in
• 1:02:33
  terms of future earth well guy in the
• 1:02:36
  current day dies but has in invested in
• 1:02:38
  cryogenics and his head is frozen and he
• 1:02:41
  wakes up and he's essentially put into a
• 1:02:43
  van machine and shot out into the stars
• 1:02:46
  and that that's a really interesting one
• 1:02:48
  because it's silicon based life that is
• 1:02:49
  also human. I mean figure that one out
• 1:02:51
  but it's good fun
• 1:02:53
  >> following again that very dangerous
• 1:02:54
  assumption that other life would follow
• 1:02:57
  the same pathway we follow and it seems
• 1:02:58
  like we are going down this AI and
• 1:03:00
  increasing complexity and increasing
• 1:03:02
  autonomy route. You then argue that
• 1:03:05
  other species sending out craft into the
• 1:03:08
  galaxy would send out autonomous
• 1:03:11
  intelligent silicon machines before they
• 1:03:14
  send themselves out. And therefore, you
• 1:03:17
  know, I'd think we're more likely if
• 1:03:18
  we're ever to bump into aliens to run
• 1:03:20
  into one of these probes or one of these
• 1:03:22
  machines rather than the aliens
• 1:03:24
  themselves. So I think there is a very
• 1:03:25
  real chance that if we find intelligent
• 1:03:27
  advanced life it could be siliconbased
• 1:03:29
  rather than carbon based but it's
• 1:03:31
  siliconbased life that was created by
• 1:03:33
  carbon based life which I mean leads to
• 1:03:37
  really interesting questions about
• 1:03:38
  philosophy and religion and all those
• 1:03:40
  kind of things which are not my forte
• 1:03:42
  but you know it does ask in interesting
• 1:03:44
  questions about origin and creation when
• 1:03:46
  you think about it from the context of
• 1:03:47
  that which is one of the things that's
• 1:03:49
  driven like I say a lot of wonderful and
• 1:03:51
  wonderfully entertaining sci-fi over the
• 1:03:52
  years. Yeah. Yeah. Look, as you said
• 1:03:55
  earlier, we could we could talk about
• 1:03:57
  this for a week, but we can't. Um, but
• 1:04:01
  uh I do uh want to direct people to your
• 1:04:03
  paper if uh people are interested in
• 1:04:06
  reading your paper from 2010. Uh it's uh
• 1:04:10
  called determining habitability, which
• 1:04:12
  exo earths should we search for life?
• 1:04:16
  And you can find it on the archive
• 1:04:18
  website. Is that right, Johnny?
• 1:04:20
  >> Yeah. So that was published in the
• 1:04:21
  international journal of astrobiology in
• 1:04:23
  2010. So the ones who want the kind of
• 1:04:24
  scientific reference it's international
• 1:04:26
  journal of astrobiology volume 9 page
• 1:04:29
  273 onwards. But um if you find it on
• 1:04:32
  NASA ads it'll give you the archive link
• 1:04:34
  which is the preprint version which
• 1:04:37
  basically means it's in my formatting
• 1:04:39
  rather than journal formatting. And this
• 1:04:41
  is it's actually a handier aside that
• 1:04:44
  I'm sure has been mentioned before. The
• 1:04:47
  way that a lot of science works has led
• 1:04:51
  to the creation of the most profitable
• 1:04:53
  and um and problematic um companies in
• 1:04:57
  the world which are the publishing
• 1:04:58
  companies. And so the way a scientist
• 1:05:00
  works is we do all this work da da da da
• 1:05:02
  hooray hoay huray. We then write a paper
• 1:05:04
  to tell the world about it. We send that
• 1:05:06
  off to a journal who gets another
• 1:05:08
  scientist to volunteer their time unpaid
• 1:05:10
  for free to referee it.
• 1:05:12
  >> Y
• 1:05:13
  >> then they charge typically the scientist
• 1:05:15
  who's written that paper money to
• 1:05:16
  publish that paper for them and then
• 1:05:18
  charge everybody for the privilege of
• 1:05:20
  reading it. So if I want the journal if
• 1:05:22
  I want to read the journal versions of
• 1:05:24
  my papers fortunately universities have
• 1:05:26
  paid access to a lot of journals but I'm
• 1:05:28
  fundamentally paying to read my own work
• 1:05:31
  and this is not ideal. I think partly
• 1:05:35
  because as a scientist, you know, I'm
• 1:05:36
  paid by taxpayers money. People are
• 1:05:38
  paying me to do this work. To me, it is
• 1:05:41
  really important that they know what
• 1:05:42
  we're doing. They know what they're
• 1:05:44
  getting for their money. And part of
• 1:05:46
  that is be a science communicator. And I
• 1:05:47
  encourage any scientists or budding
• 1:05:49
  scientists, don't just focus on the
• 1:05:51
  science. Focus on communication as well.
• 1:05:52
  Because if you do science, but can't
• 1:05:53
  communicate it, no one will know what
• 1:05:55
  you've done. But to get around that,
• 1:05:58
  what we do in astronomy and what many
• 1:06:00
  disciplines do is that we put preprints
• 1:06:04
  up on a publicly accessible free place.
• 1:06:06
  And it's in astronomy, it's just
• 1:06:08
  accepted that with very rare exceptions,
• 1:06:10
  journals will let you do this. So when
• 1:06:12
  we get our paper and we've written it,
• 1:06:15
  some disciplines in astronomy will put
• 1:06:17
  the paper up on the archive when it's
• 1:06:18
  submitted. Some will wait until it's
• 1:06:21
  accepted by the journal, when it's
• 1:06:22
  refereed. I've always waited till
• 1:06:24
  acceptance, but occasionally if you've
• 1:06:25
  made a big discovery, you want to stop
• 1:06:27
  somebody scooping you. You put it up at
• 1:06:29
  submission. There's a growing effort by
• 1:06:31
  scientists to put it up at submission to
• 1:06:32
  actively solicit feedback from the
• 1:06:34
  community to improve the work, which is
• 1:06:35
  good. But those papers go up on archive,
• 1:06:38
  a rxiv.
• 1:06:40
  >> Yeah.
• 1:06:41
  >> Um, be very careful. There is another
• 1:06:44
  platform out there where the letters in
• 1:06:46
  archive are shifted around which is
• 1:06:48
  where a community of people who espouse
• 1:06:51
  ideas that are not scientifically
• 1:06:52
  verifiable will put their work and
• 1:06:55
  publish their own little papers. It's a
• 1:06:56
  different thing but archive is a
• 1:06:59
  repository of freeto view things. So if
• 1:07:01
  you are searching for papers NASA's ads
• 1:07:04
  system is wonderful. When you click on a
• 1:07:06
  given paper in there, most of them, but
• 1:07:09
  not all of them, will have a line that
• 1:07:10
  says journal version or ads version, but
• 1:07:12
  there'll also be a line that says
• 1:07:14
  preprint. And if you click on the
• 1:07:15
  pre-print links, it will take you to the
• 1:07:17
  archive and allow you to read the paper
• 1:07:19
  for free. Just to be aware that that is
• 1:07:21
  a version some of the time before
• 1:07:24
  refereeing, most of the time after
• 1:07:26
  refereeing, but before publishing and
• 1:07:27
  edits effectively. So, the link you've
• 1:07:30
  got to that is the pre-print version of
• 1:07:32
  that paper. The other caution I give to
• 1:07:34
  people is that it is 16 years old. So
• 1:07:36
  all of the areas I talk about in it have
• 1:07:38
  moved on. We've learned more. We can
• 1:07:41
  talk a bit more about it next time as
• 1:07:42
  well. But always when you read things be
• 1:07:44
  conscious of the fact that science is
• 1:07:47
  fluid. Science changes. Our knowledge
• 1:07:49
  changes. I see just in the news
• 1:07:50
  recently, Jayen Isaac Isacson, who's I
• 1:07:54
  think the head guy at NASA at the
• 1:07:56
  minute, who's a wealthy
• 1:07:57
  multi-billionaire type guy, um is
• 1:08:00
  arguing that the US is wanting to
• 1:08:01
  strongly build a scientific case why
• 1:08:03
  Pluto should be restored as a planet
• 1:08:05
  because fundamentally we discovered it
• 1:08:07
  so it should still be a planet and Clyde
• 1:08:09
  Tombbo would be turning in his grave.
• 1:08:12
  That is what it is. But it's um it is
• 1:08:16
  important to keep in mind that science
• 1:08:18
  is fluid. It moves. Whereas once
• 1:08:21
  something is published that's static.
• 1:08:23
  >> It's a window on our knowledge at a time
• 1:08:26
  rather than necessarily the modern
• 1:08:28
  version. If I were to rewrite that paper
• 1:08:30
  now there'd be advances.
• 1:08:33
  >> Of course. Absolutely. But um yes um I
• 1:08:36
  think we're trying to arrange to put the
• 1:08:38
  link on the show notes. I'll just have
• 1:08:39
  to remind Hugh about that. We might wrap
• 1:08:42
  it up there. Jonty. fascinating topic
• 1:08:44
  and uh it's one we get a heck of a lot
• 1:08:46
  of questions about. So, um yeah,
• 1:08:48
  hopefully there's a bit of information
• 1:08:50
  in there to uh keep people's minds
• 1:08:53
  worring. Johnny, thanks very much. We
• 1:08:56
  will uh see you again real soon. It's an
• 1:08:58
  absolute pleasure. Thank you for having
• 1:08:59
  me.
• 1:09:00
  >> Professor Johnny her, professor of
• 1:09:01
  astrophysics at the University of
• 1:09:03
  Southern Queensland, standing in for
• 1:09:05
  Fred Watson. And thanks to Hugh in the
• 1:09:07
  studio. Uh Hugh couldn't be with us
• 1:09:09
  today. Um he got a bit confused. We we
• 1:09:12
  know of one planet where there is life.
• 1:09:15
  Hugh thought we meant that he was the
• 1:09:17
  only life form on the planet, so he
• 1:09:19
  didn't see any need to turn up today.
• 1:09:21
  And from me, Andrew Dunley, thanks for
• 1:09:23
  your company. We'll see you on the next
• 1:09:25
  episode of Space Nuts. Bye-bye.
• 1:09:27
  >> Space Nuts.
• 1:09:28
  >> You've been listening to the Space Nuts
• 1:09:30
  podcast
• 1:09:32
  >> available at Apple Podcasts, Spotify,
• 1:09:35
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• 1:09:38
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• 1:09:40
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• 1:09:43
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