The video explores the parallels between modern astronomy and early mapmaking, with astronomers acting as contemporary mapmakers, seeking to chart the unknown territories of exoplanets. The primary motivation driving this endeavor is the fundamental question of whether humanity is alone in the universe, a quest that could span centuries or even millennia. The video compares this process to historic milestones in astronomy, such as Galileo's astronomical advancements, underlining the continuity and longevity required in the field to answer such profound questions.

In detailing the search for planets and the possibility of extraterrestrial life, the video discusses significant milestones and the challenges involved in these pursuits. It addresses the claims of Earth-like planets and life on planets like Gliese 581G, and the subsequent debunking of these claims. Additionally, it touches on the limitations of proving a negative hypothesis regarding the existence of life on Mars, while exploring concepts such as the Fermi Paradox and alternatives to conventional civilization models on other planets.

Main takeaways from the video:

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Key Vocabularies and Common Phrases:

1. exoplanets [ˈeksəʊˌplænɪts] - (noun) - Planets that orbit a star outside the solar system. - Synonyms: (alien planets, external planets, extrasolar planets)

We are looking out and trying to draw not the continents, but the maps of the exoplanets that our distant descendants might one day visit.

2. cosmology [kɒzˈmɒlədʒi] - (noun) - The science of the origin and development of the universe. - Synonyms: (universe science, astrophysics, big bang theory)

...and couldn't have imagined how astronomy and the discovery of exoplanets and cosmology would be born from his creation of the telescope.

3. anomalous [əˈnɒm.ə.ləs] - (adjective) - Deviating from what is standard, normal, or expected. - Synonyms: (abnormal, irregular, atypical)

There is a natural temptation to look at anything that seems anomalous, that seems a little bit different, and immediately reach for aliens.

4. confounding [kənˈfaʊndɪŋ] - (adjective) - Causing confusion by not conforming to a pattern. - Synonyms: (confusing, puzzling, bewildering)

...and all of the different confounding factors that might trick us, and trying to find those unique combinations that we really trust as being the smoking gun that this has to be life.

5. abiogenesis [ˌeɪ.baɪ.oʊˈdʒɛn.ɪ.sɪs] - (noun) - The original evolution of life or living organisms from inorganic substances. - Synonyms: (spontaneous generation, origin of life, life evolution)

Maybe the nascent conditions for the birth pangs of life to begin with, the abiogenesis event, the spark of life which created all life on the Earth, maybe that requires very special and subtle temperature range that cannot be violated.

6. extremophiles [ɪkˈstriː.mə.faɪlz] - (noun) - Microorganisms that live in extreme environments such as high temperature or acidic conditions. - Synonyms: (tough microorganisms, hardy bacteria, extreme condition organisms)

There's some thermophiles that can range from north -25 degrees Celsius and then you have other extremophiles which can live at 125 degrees Celsius.

7. photolysis [fʌˈtɒl.ə.sɪs] - (noun) - The decomposition or separation of molecules by the action of light. - Synonyms: (light breakdown, photo-degradation, light-induced separation)

One possible way this could happen is through a process called photolysis.

8. biosignature [ˈbaɪ.oʊˌsɪɡ.nə.tʃər] - (noun) - Indicators that provide scientific evidence of life, past or present. - Synonyms: (biological markers, life indicators, vital signs)

One is with a so called biosignature that is a signature of biochemistry essentially on another planet.

9. technosignature [ˈtek.noʊˌsɪɡ.nə.tʃər] - (noun) - A signature that provides scientific evidence of past or present technology indicative of a civilization. - Synonyms: (technology markers, civilization indicators, tech footprints)

And a second is a technosignature, the signature of technology.

10. cohabiting [kəʊˈhæb.ɪ.tɪŋ] - (verb) - Living together in the same place as a tenant or inhabitant. - Synonyms: (living together, residing together, sharing a habitat)

We don't see a civilization cohabiting the Earth with us.

How close are we to finding alien life? - David Kipping

For me, I think what we're doing right now is a bit like being the map makers. If you go back 400, 500 years, we really didn't know what the shape of the globe was or where the continents were. And people were voyaging out into the unknown and drawing the first maps of what might be out there. And I think a lot of what we're doing right now is kind of similar. As astronomers, we are mapmakers, essentially. We are looking out and trying to draw not the continents, but the maps of the exoplanets that our distant descendants might one day visit and perhaps even build colonies on.

Now the question is, why do we have this urge? I think, deep down, the natural endpoint of this whole goal of looking for planets is to answer the question, are we alone? The fact that space is simply so large means this is a challenge that humanity undertakes over not just centuries, but maybe millennia into the future. In the similar way that Galileo 400 years ago was first starting astronomy and couldn't have imagined how astronomy and the discovery of exoplanets and cosmology would be born from his creation of the telescope.

We have a long journey ahead of us in astronomy, too, to answering this question about life in the universe. But it is the great question and a question which I think many of our future descendants will be inspired to continue studying. My name is David Kipping. I'm a professor of astronomy at Columbia University and director of the Cool Worlds Lab.

There's a long history of people claiming planets which look Earth like Earth 2.0 Earth Twins. I think a famous example was Gliese 581G. That got a lot of people very excited. But of course, within I think, two or three weeks, another independent team showed that this planet was not real. And so we've already had several claims of not only Earth like planets, but even life. There's been claims of life on Venus. There's been claims of life on interstellar asteroids, and of course, there's many UFOs that we often hear about. And so there is a sense of exhaustion at this point. I think a lot of people probably naively assume that we have a whole bunch of Earth twins at this point. And that's really not the case.

One of the hardest scientific aspects of this is that you can't prove a negative. So I can never prove to you that Mars does not have life on it. I can look at the surface and claim, on the surface I am 99% sure there are no microbes. But then you could also say, well, what about underneath the surface? Have you checked there? What about underneath that rock over there or behind that canyon or behind that hill? And so I can never totally prove, totally prove even on the nearest planet to us, Mars, that it does not have life on it.

So there is a natural temptation to look at anything that seems anomalous, that seems a little bit different, and immediately reach for aliens. And when we're looking for aliens, of course, the question is the Fermi paradox. Then Rico Fermi asked this question, look, if there's so many good arguments as to why life should be out there, how come we don't see any evidence for them?

And Hart's fact a named after Michael Hart, points out that there are no aliens on Earth right now. We don't see a civilization cohabiting the Earth with us. We haven't been totally colonized by an alien civilization. It appears to be a very lonely planet with just one civilization, which is us living on it right now. Now, what I like about facte is it's kind of indisputable. It's one of the hardest points we can really say in astronomy.

I can't claim that a distant exoplanet doesn't have an extraterrestrial civilization on it, but I can be much more assured about the fact that we are not currently cohabiting Earth with another alien civilization. For it turns out that even traveling the galaxy at sort of Voyager 1, Voyager 2 type speeds, the speeds of our current spacecraft, it should have been eminently possible to have colonized the entire galaxy many times over during its 13 billion year history.

And even that claim, as weak as that might seem, does put some interesting limits upon the behavior of other civilizations. It means really that a galactic civilization does not exist, that there is no instances of a marauding berserker type civilization that just decided to gobble up every exoplanet, every real estate it could find, and turn it into another colony for itself. Because if that had happened, the whole Milky Way would have been colonized by now and we wouldn't be here.

That is probably one of the strongest data points I think we have. One of the primary tools that astronomers use to think about the abundance of life in the universe is the famous Drake equation, first written down by Frank Drake. It is essentially the number of stars in the galaxy multiplied by a long list of possible factors such as how often do you have planets? How often are those planets Earth like, how often does life begin on those planets? And so on and so on.

Now when we look at this it's like a narrowing filter. And you can imagine with the rare Earth hypothesis by Ward and Brownlee adding on extra terms such as having how often does the planet have a large moon, how often does it have the same mass as the Earth, how often does it have the same land mass fraction the Earth has, or the same ocean salinity or chemistry etc, etc, and you can imagine adding on hundreds, even thousands of extra parameters onto the Drake equation which get ever ever narrower.

And of course if you multiply a very large number of fractions together, you'll eventually get zero. Now on each one of those criteria you can make a good case as to why life on Earth indeed requires those conditions. However, we really don't know whether life elsewhere does or does not require the same conditions that we enjoy here on the Earth. So for example there's some thermophiles that can range from north -25 degrees Celsius and then you have other extremophiles which can live at 125 degrees Celsius.

But the fact that extremophiles today can survive in such an extreme range of temperatures doesn't mean that life could begin under such an extreme range of temperatures. Maybe the nascent conditions for the birth pangs of life to begin with, the abiogenesis event, the spark of life which created all life on the Earth, maybe that requires very special and subtle temperature range that cannot be violated. These are questions, we just don't know.

What were the initial conditions on the Earth that led to the emergence of life? And if you just go another step further, even defining life is an incredibly difficult task. And there is definitely no consensus about how to cause such a thing. Maybe it's actually better to call it more like porn, like you will know it when you see it, rather than having a strict textbook definition of it. NASA have certainly tried to have a definition for a long time.

We had a definition from NASA that said it is a self replicating chemical system capable of Darwinian evolution. And that's pretty good. But maybe chemistry isn't actually necessary. Maybe you could have an AI system or self replicating technology that would still resemble life in many ways, but wouldn't actually involve the kind of chemical systems that, that we're familiar with.

And I think this is one of my big problems with the rare Earth hypothesis is that it's a very narrow view of how life began and how life must survive on other planets. All of these factors have to be true. It is a singular path and that is a path which has indeed led to success. But perhaps there are different paths parallel to us, which are completely different, yet also lead to life. And so the Drake equation simply multiplies fractions by, by each other.

But perhaps truly what is missing is an additive sign. There is a second path below it, a different way of getting to intelligent civilization, and a different way after that, and a different way after that. And it is that addition that we just really can't do without a lot of creativity and discovery, because right now we only have this sole example to look at.

So there are two basic strategies which we might attempt to search for life in the universe. One is with a so called biosignature that is a signature of biochemistry essentially on another planet. And a second is a technosignature, the signature of technology. Now technology obviously requires that not only do you have life, that an advanced civilization also developed on those planets. And so that naturally seems like a smaller piece of the pie to look at.

However, those technosignatures could be very, very loud, heard from millions of light years away, potentially, and could also perhaps be very persistent. We can imagine a civilization maybe building a beacon or something that could last for billions of years to perpetuate its knowledge into the cosmos. So a simple balance is not so easy in weighing which of these options would be most fruitful.

The biosignature case certainly has had, I'd say, greater attention from entities like NASA and government funding agencies, because after all, you don't require all this evolutionary complexity. You can just have simple life and potentially still be able to see them. The way biosignatures work is to look for gases that are emitted into the atmosphere, which are uniquely produced by life. At least that's the theory.

The problem is it's very difficult to find gases which are indeed uniquely produced by life, like lots of gases can produce through geological processes as a side product. And so that can become a false positive to our search efforts. A classic example of this is oxygen. Of course, plant based life manufactures oxygen on the earth through the process of photosynthesis. And so it would seem like oxygen would be a good thing to look for.

But we could imagine different types of planets where oxygen is being manufactured without the need for life at all. One possible way this could happen is through a process called photolysis. So ultraviolet radiation from the sun strikes the upper atmosphere. And if there is water in the atmosphere, that water will be split into hydrogen and oxygen, generating a significant amount of oxygen in a planet without any life involved.

And so that signature would be a false positive for Us, if we're not careful, we would interpret that to be life, whereas in fact it is not. And so astronomers, chemists, biologists, we're involved in this game now of trying to imagine all of the different signatures that life could produce and all of the different confounding factors that might trick us, and trying to find those unique combinations that we really trust as being the smoking gun that this has to be life.

And once you have two starts to life in the solar system, that would essentially establish that life really would be everywhere in the universe. Foreign SETI S E T I is the Search for Extraterrestrial Intelligence. It is essentially an effort to try to detect the radio signals, or possibly even more broad than that, laser signals, whatever signals you might want to look for from another civilization out there in the galaxy. Now, there is a strange aspect of seti.

We have this kind of paradox that we are listening for radio signals from beyond, from these other planets, but we don't really transmit much. In fact, when the field first began, it was actually called ceti, and that C stood for communication. Very quickly they changed their minds and realized that the idea of a two way communication was maybe a bit ambitious. And it might be better just to focus on circumstances searching for the signal, rather than truly trying to have a dialogue in the remote contingency that there are interstellar space faring societies, we thought we would put a message on it to indicate a little bit of where we are, when we are and who we are. So on the other side, we have the idea of METI messaging Extraterrestrial Intelligence, also called active seti. So this is where we actually send out a message, hoping to get a reply at some point in the distant future.

Of course, that could be hundreds or even thousands of years, given the vast expanse of space beyond us. Now, METI is a little bit controversial. Stephen Hawking had the concern that, you know, maybe we should be very careful about communicating to the civilizations, because whenever you've had a more advanced civilization engaged with a less advanced civilization on the Earth, that has usually ended very badly for the less advanced one. And so if you extend this out to the galaxy, maybe we should be careful about sending out our presence into deep space. And certainly this is a trope that has been played with in science fiction as well.

If you look at Liu Shixin's three body problem, that's where we get the idea of the dark forest hypothesis, the idea that civilizations could be out there, dangerous marauding ones who want to take over and colonize your planet, and so it's much better to just be quiet, don't let anybody know that you're here. I do have a bit of an issue with this idea of resistance to METI and resistance to communication, and that's that we, humanity, are already engaged in the activity of trying to build telescopes and feature facilities that can detect life whether they want to be detected or not. So you don't have to send out a radio wave for me to be able to detect your civilization.

We could potentially detect their satellite systems, their starlinks. We could detect their solar, solar panels on their surface. We could detect their industrial space presence, even the chemical pollutants in their atmosphere from industrial processes.

There are so many ways that we could imagine being able to tell there was a planet that had an advanced civilization on it without the need for a radio message, that it's a little bit archaic to assume that that's the only way that a civilization would be able to know of another one's presence. I suspect if there is another advanced civilization out there in the galaxy, they already know that we are here. And so I think it would be difficult to argue that we should be very, very quiet, because otherwise they will never know we're here. I suspect they are well aware that this planet is inhabited with or without our radio signals.

Communicating over large distances, and really we mean extremely large distances when we're talking about the galaxy, requires a lot of energy. And so this is a real problem. If you want to communicate your presence across the entire galaxy, you're going to need a transmitter which is ultimately the size of a planet or even the size of a star. And it has to be turned on all the time. For as soon as you turn that signal off, of course, the light wave will stop. And so you're going to have a finite time in which you could be detected.

So an interesting question is how could we build a communication system that would be much more long lived? There's an interesting idea by Luke Arnold. He suggested that rather than trying to build a giant transmitter, be it radio or laser or whatever it is, instead you do something passive. And so his idea was to exploit the transit method of looking for exoplanets. We could build a giant structure in space of a very elaborate shape that that would transit in front of the star, maybe a giant triangle, for instance. And as this triangle transits in front of the star, it would create a very remarkable and alien looking transit signature, something which nature should never produce, that we would be able to tell from afar.

There must be a civilization who built that. And the beauty of this is that it requires no power system. The sun itself is powering that for billions of years. And it requires no mechanical parts, no maintenance. It's just going to sit there for billions of years saying, hey, there is somebody around this.

Another example is to leave something physical behind for them to find. And of course, this is an idea that was played with with the film 2001 A Space Odyssey, where there's these monoliths which are left within the solar system, especially beneath the lunar surface. I think that is a really terrific place to leave something. The moon has no active geology, it has no atmosphere, it has no weathering. Think about Neil Armstrong's footprints. They're going to be there for at least a million years.

So anything that you leave on the lunar surface is going to be preserved for a very, very long time, millions of years. We could potentially encode a message, maybe an LLM, an AI agent that can teach another civilization about who we were. And the extra benefit would be of course, to bury it maybe a meter beneath the surface, where you're now protected from micrometeorites as well.

I think to some people this idea can be a little bit depressing. We maybe have the idea that we want to actually meet them on the White House lawn, shake their hand like we see in sci fi films, and have a communication, a dialogue in real time. But if we're being more realistic about it, maybe that's just never going to happen. And if we concede that that might be an improbable circumstance, perhaps the next best thing we can hope for is to communicate not in a simultaneous sense, but through time.

We could leave something behind in the same way that our ancestors speak to us through the monuments they left. We too have an opportunity to build something on the moon. I would claim that could last for billions of years and be a record. And perhaps, perhaps the most likely advanced civilization that is going to discover that relic that we leave behind will be a future descendant of the Earth.

For the Earth has another billion years left to go in its evolutionary history. And think about all the advanced evolution that has occurred in just half a billion years. We've gone from single celled organisms to us. What's going to happen in another billion years?

We will probably disappear at some point. And I can imagine not just one, but perhaps multiple advanced civilizations re arising on this planet having their own space ages. And they will go to the moon, find this relic, and perhaps know something about who we were. To me, that is the most likely alien encounter we're going to have.

ASTRONOMY, EXOPLANETS, EXTRATERRESTRIAL LIFE, EDUCATION, SCIENCE, TECHNOLOGY, BIG THINK