for most of human history people used to think that our world is unique with the birth of philosophy and science we learned that Earth is among seven other planets that orbit our sun it took us quite a long while to realize other galaxies are out there and that the flickering lights in the sky are other Suns with whole worlds orbiting them which could possibly host alien life then we didn't know of any planets beyond our solar system because we haven't detected them so even if we thought well we can't be special we didn't know and
then in the early 1990s we started being able to detect planets and now we've detected well over three thousand we've got missions up there like the Kepler telescope that are just trying to detect planets so thousands of them so now this statement is that pretty much every star in the sky will have planets around it which is remarkable if you go out you know it's a clear night you go out and look at stars you can imagine that there will be solar systems around everyone so that allows us to start thinking how many potentially earth-like
planets might there be in the Milky Way galaxy and the answer is about 20 billion what you mean there is a rocky planet the right distance from its star possibly if everything's right to have liquid and water on the surface and so on in the nice distance from the Star perhaps one in ten Stars we talk about a thing called the habitable zone now in the solar system there are three planets in the habitable zone there's Venus Mars and Earth Venus is close to the Sun hours further away all of those planets though we think
had water on the surface so they all could have been habitable in that sense and still you know we're looking for Life on Mars to this day of course finding Life on Mars would be undoubtedly among the biggest discoveries in human history but if there is life on Mars most scientists think it's microbial life the more interesting kind of life we hope to discover that would change our worldview forever is multicellular life such as plants or animals luckily for us there is a place within our solar system that might host that kind of life enter
Jupiter's moon Europa NASA is preparing the Europa Clipper Mission which would launch in October 2024 and will arrive in 2030. the mission is currently planned to conduct four years of science observations at Europa this Moon shows strong evidence of an ocean of liquid water beneath its icy crust so it's a top candidate to explore and hopefully we will find evidence of alien life going beyond our solar system it's extremely difficult if not impossible with our current technology to send space probes and find evidence of alien life as the nearest star to our sun Proxima Centauri
is about 4.2 light years away so the best method is to stay put and listen for radio signals or direct our telescopes at the location of exoplanets and look out for Bio signatures obviously the most exciting type on the hierarchy of alien life is intelligence it is estimated that with our current pace of technological growth a civilization can colonize our whole galaxy within 10 million years and if that is the case where is everybody the flip side of this is there are loads of planets out there and there's been loads of time this has got
a name actually it's called the Fermi Paradox after someone called Enrico Fermi a great Italian physicist who asked this very simple question which is where are they because given the number of planets given the number of stars and given the amount of time in this galaxy the complex life to emerge it seems as if at least a few civilizations should have become a space-faring civilization so part of the evidence part of the Great conundrum here is that so on on the one side yes we've got the history of life on Earth which says that we
took a long time to emerge and so it looked quite like an unlikely process on the other side you've got all this real estate and you have this so if you think about where we could go what could we become as a civilization so already we are becoming a space-faring civilization now very quickly so give us a thousand years if we don't destroy ourselves or do anything stupid we're I'm sure we're going to be on Mars we're going to be on the moon we're going to be thinking perhaps taking our first steps out to the
Stars give us a million years 1 million from now if we survive we should become a space-faring civilization now one million years the galaxy has been around for the age of the universe 12 13 billion years so it only takes a few civilizations to have evolved a bit ahead of us a million years well they say a billion years a billion years is still nothing you get some civilizations that evolved a billion years before us why can't we see them so then people start saying well maybe there's a finite life that all civilizations have maybe
they destroy themselves maybe they don't become space-faring civilization one possible resolution of the Fermi Paradox is the great filter it presupposes that in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale there exists some particular barrier to development that makes detectable extraterrestrial life exceedingly rare this barrier to the evolution of intelligent life could be as a result of self-destruction meanwhile the evolution of telescopes that can detect techno signatures could provide insights into the great filter if planets with techno signatures are abundant then this
can increase confidence that the great filter is in the past on the other hand if finding that life is commonplace with techno signatures are absent then this would increase the likelihood that the great filter lies in the future there is another relatively recent and quite interesting hypothesis that attempts to resolve the Fermi paradox if an extraterrestrial species becomes Advanced enough to send signals we can pick up it will likely shed its traditional biological form and become a type of machine intelligence within this hypothesis it is speculated that a full digital civilization simply has no interest
in colonizing the Galaxy the other interesting solution to the Fermi problem which is popular among UFO fans is the so-called zoo hypothesis which entails we are being observed without our knowledge there is also the depressing solution to the Fermi Paradox which is that we're the first ones and will be extinct long before any other civilizations emerge in our galaxy what's interesting is when you talk to astronomers they say that we estimate that 20 billion potentially Earth-like planets out there in our galaxy surely there must be life all over the place right it's a guess because
we haven't found any anywhere but what we know from the history of life on Earth is that life began pretty much as soon as it could here on Earth so we have good evidence that life was around let's say 3.8 billion years ago so pretty much as soon as the Earth had formed and the oceans formed on the earth you see evidence of life so that might give you a sense that the origin of life on a planet might be a high probability right given the right conditions just because of what we see on Earth
but this is really important well when did complex life appear so not just single cell you know animals and plants and the evidence of complex multicellular things on earth goes back let's save 600 million years or so not much further than that so it's within the last billion so on Earth what happened was that there were single cells things doing interest in stuff photosynthesis and things but from for let's say three billion years from the origin of life nothing else not much going on slime the last billion half a billion ish right do you see
complex life so it took about well around a third of the age of the Universe on Earth to go from the origin of life to something that can think the star was stable and didn't run out of fuel and the orbit of the planet was stable it didn't get hit by too many asteroids so I think that if you start asking for stability art for billions of years if that's what it takes typically to go from the origin of life to something that can think then the very few places indeed there's a thing called the
eukaryotic cell right which is what we're made of and every complex living thing on the planet is made of every plant every blade of grass every insects it looks like those things evolved once on this planet what happened is one type of more primitive cell a bacteria in this case got inside another kind of cell called an archaea got inside and didn't die and somehow managed to multiply like that and it looks like that's the origin of all complex life on Earth so when you see things like that when you start seeing the things that
had to happen to make us you start to think that this place may be extremely special and you can make the argument and I do actually I think it's very important politically as well that this could be the only planet in our galaxy currently that has anything on it that can think if we are the only planet currently in the Milky Way where brains exist where conscious thought exists we are the only place where meaning exists in a galaxy the 400 billion stars imagine if we decide to press the button tomorrow nuclear war right we
press the button the person who does that my might wipe out meaning in a galaxy thanks for watching did you like this video then show your support by subscribing ringing the bell and enabling notifications to never miss videos like this [Music]
