What Will Humanity Do If We Ever Discover Aliens?

[“There are around 1022 stars in the universe, and  life came into existence here once and only once.”  Upon reflection, this statement seems a little  unlikely. It’s no wonder then that through the   ages, humanity has wondered at the idea of  alien life beyond planet Earth. Do aliens   exist? Where are they? Are they like us? Would  we be able to find any common ground with them,   or would they be completely alien to us? What if I could tell you that I knew the answer?  Before you ask; no, I’ve not been read in into any  covert men-in-black government programs that have   been hiding the truth from the general population.  But neither are we simply reliant on our   imaginations when it comes to alien life. There is  much that science can tell us, through discoveries   and deductive reasoning, even though I assume  most of us have never met an alien in the flesh.  So, are we alone in the  universe? It’s time to find out.  I’m Alex McColgan, and you’re watching  Astrum. And in today’s supercut, I’m   going to share with you everything I know about  alien life… Everything. Men-in-black be damned.  When it comes to searching for alien life  out there, it pays to start with a very   relevant question.] What do we mean by life? Life on planet Earth comes in many shapes and   sizes. From the tallest trees to the smallest  microbes, from spindly insects to birds or fish   or humans, our planet is teeming with life.  We generally understand what we mean when   we say “a living thing”. We might define  it by it moving around, or by it growing.  Generally speaking, scientists define life as any  system that is capable of eating, metabolising,   excreting, breathing, moving, growing, reproducing  and responding to external stimuli. Essentially,   they are aware of their surroundings in  some way, they seek resources, they take   those resources into themselves, and use them  to grow or create more of themselves. And then   they get rid of any waste that’s left over. Ew. Some forms of life are much more active than   others, but even things like plants can  move to face the Sun, open their buds,   or spread out their roots over time. So, we  look at these things and consider them living.  Even on Earth, though, there are some systems like  viruses that push the boundary of what it means   to be a living thing. Viruses are so simple, that  they lack the ability to reproduce by themselves,   or to metabolise. Instead, they get cells  they infect to do that work for them. Are   viruses alive? They certainly have proved  devastating to other populations of living   things, and we can definitely think of  them that way. But it’s a debate that   still rages on in the scientific community. So, although there are certain qualities that   are fairly universal for living things here  on earth, we must be careful about how we go   about defining life. For instance, most living  things on Earth make use of water to function.   It carries important nutrients around our  bodies, and is so vital for all life on   Earth that we consider the absence of water to  be a serious red flag if another planet doesn’t   have it. But if an alien was somehow able  to exist by pumping liquid methane through   its body instead of water, would that stop  it from being a living thing? Probably not.  So, let’s keep an open mind, but roughly  let’s define life as those things that   seek out resources, grow and reproduce. [Still, although it’s good to keep our starting   definition general (just in case), we can actually  predict with some certainty what we expect to see   when it comes to alien life. Scientists and  science fiction writers throughout the ages   may have imagined all manner of living things;  from little grey men, to sentient rock monsters,   and even aliens made out of pure energy. All  of these are possible – even that last one,   which may sound speculative, but renowned  Astrophysicist] Neil deGrasse Tyson [did   say] he wasn’t opposed to the idea. (clip). [But not all of these are equally likely.   How do we know? It’s all thanks to one  simple principle: Form follows Function.]  As you look down at your own body, even if  you do not know what all of it does, you are   an incredible example of optimisation. You likely  have two hands complete with fingers and opposable   thumbs, ideal for grasping tools and performing  fiddly, delicate operations. You have a digestive   system that is capable of taking in matter,  extracting nutrients, and using them to build up   or repair yourself. You have legs for locomotion.  A brain for thinking. A heart that will on average   pump 2.5 billion times across your lifetime  without breaking. All of these parts of your   body perform specific functions, that have been  honed over millennia to be really good at what   they do (even if you don’t feel it sometimes). You are an example of form following function.   Thanks to natural selection and random mutation,  nature is really good at figuring out what works.  When Charles Darwin was voyaging through the  Galapagos Islands, he noticed that different   finches had different shaped beaks. After  observing them for a time, Darwin noticed that   the finches with larger, more heavy-set beaks ate  different types of food than finches with smaller,   daintier beaks. In fact, a large beak was ideally  suited to breaking open tough seeds or nuts,   while the smaller beaks were more suited to  getting in nooks and crannies for grabbing   insects. This observation was the basis  for his well-known theory of evolution.  In this theory, thanks to genetic variation and  competition, nature is constantly trying out new   things to see what works. And there are certain  things that give you an edge. For instance, thanks   to all the light that was bouncing around  from our Sun, organisms that evolved to   take advantage of this by developing sight had a  big advantage over organisms that did not. They   could find food better, or avoid predators,  or generally navigate their environment.  So useful is sight, that nature did not just  come up with it once. We believe the eye evolved   independently about 40 times over the course  of life on Earth. 40 different species that   previously could not see evolved eyes. This is called convergent evolution,   and eyes are not the only example of it  happening. Bats are not related to birds,   and yet both developed wings to fly. And speaking  of bats, both bats and dolphins independently   evolved echolocation, to help them see in  environments where light was not so plentiful.   Photosynthesis has arisen dozens of times. Koalas  have almost identical fingerprints to humans.  This happens because there are some selective  pressures that are simply universal. Everything   that lives needs to gain nutrients, grow,  and reproduce, and as a result, like a plant   bending its roots around rocks to find softer  soil, nature is good at figuring out the best   way of getting what it needs. Because of the  prevalence of light, eyes are just a good idea.  And when something works, nature  sometimes comes up with it more than once.  This means that on planets that are similar  to our own, it’s entirely possible that   evolution would end up going a similar way. Although hypothetical aliens on other planets   might not look exactly like us, they might look  surprisingly similar. I always thought that it   looked silly that so many aliens in sci-fi films  were humanoid, but perhaps this is more than just   a way of easing pressure on the film’s costume  department. Convergent evolution says this might   actually happen. If it worked with us, maybe  it just works generally. Any alien that made it   to the stars would need to have the ability to  work tools. So, fingers, or something similar,   would be a likely addition to an alien race. Large  heads filled with complex brains for analysis and   problem-solving would also be a benefit. The  human brain is the most complex of any animal’s   on earth, with 86 billion neurons. It’s not  so unreasonable that aliens would be the same.  Thanks to our brains, it became less important  to keep ourselves warm with fur as we could   craft clothes for ourselves, so aliens may not be  hairy or thick skinned if they are intelligent.  Of course, this kind of logic might not  carry all the way, because life might not   arise on a planet that’s exactly the same  as ours. If there are different selective   pressures, different adaptations might occur. For instance, on a planet with low gravity, plants   and animals would be able to grow to be much  taller than on Earth. There would be less energy   cost to lifting nutrients up through their bodies,  or pumping blood around (if aliens used those   kinds of systems). While conversely, on a planet  with very high gravity, you’d likely see stockier,   shorter, heavier-built aliens. Their bones would  need to be denser to support themselves in heavier   gravity. Or possibly they would be aquatic,  as gravity is less of a problem in water.  On a planet that is further out from its  star than ours, there would be less light,   so an alien’s eyes might be bigger. Or maybe  aliens on such planets would rely on things   like echolocation to see what is around  them. On planets with elliptical orbits,   seasonal temperatures would vary much more wildly.  Perhaps on such planets you’d see an increase   in the ability to hibernate, or even come back  from near death, such as tardigrades and their   incredible ability to return to animation after  being in the harshest of environments like the   depths of space. Temperature can also affect size,  such as in the depths of our oceans there occurs   deep-sea gigantism, as large bodies can more  efficiently be kept warm, while in deserts small   animals have a larger mass-to-surface-area ratio,  allowing them to disperse heat more effectively.  On a planet with fewer magnetic fields, more  bombarded by cosmic radiation, perhaps life would   have shorter life-spans, in much the same way as  around the heavily irradiated Chernobyl nuclear   power-plant, dogs and other short-lived organisms  thrive, while longer-living humans suffer.  In each case, form follows function. Life will  adapt to suit the conditions it finds itself in.  Extremophiles are life forms that are able  to live in very hostile environments. There   are lots of different kinds of extremophiles  that are well-adapted to different kinds of   extreme conditions like very high or very low  temperatures, pressures, dryness, radiation,   salinity, acidity, and heavy metals, or any  combination of those extreme conditions.  These organisms span the globe, inhabiting the  harshest parts of our world. From sulfuric hot   springs in Japan, to the Atacama desert in  Chile, to sewage treatment plants in Germany,   and even a hypersaline deep lake in Antarctica . What makes extremophiles so interesting is their   unique biology. As you can imagine, living  in such extreme conditions kind of forces   you to get creative. Extremophiles'  biochemistry and physiology are often   modified in very clever ways to help them  adapt to their harsh environments. And this   makes them an astrobiological goldmine. You see, many extremophile habitats on   Earth are surprisingly similar to the  conditions on other planetary bodies.   These regions on Earth are called analogues,  and they can teach us a lot about where we   might find life beyond our home planet. For example, the Atacama desert in South   America is a very arid environment, with  high salinity, high UV radiation levels,   and oxidizing soil, just like Mars. In fact, we've  been studying it as an analogue to Mars for years.   Life has been found across the Atacama desert,  but its presence is highly patchy. In a way,   this is good news. It helps scientists  identify the exact factors that cause   life to appear where it does, and therefore where  we might have the best chance to find it on Mars. Certain species of our haloarchaea are also  being studied as exciting astrobiological   models. Specifically, Halobacterium NRC-1 and  Halobacterium lacusprofundi. They are both   extremophiles that thrive in high salinity,  and are great candidates for understanding   potential life on icy, salty moons like Europa. [Through the study of extremophiles, we learn what   is plausible for life out in the wider universe.  If life can exist in certain environmental   analogues here on Earth, those same sorts of  environments plausibly contain life elsewhere.  We also learn what’s less plausible. Life  here on Earth is diverse, and has adapted   to all sorts of niches, but there are some places  even it cannot go. Bacteria such as Methanopyrus   kandleri – one of our hardiest extremophiles –  can survive at temperatures of 122°C. But putting   one into thousands-of-degrees lava would quickly  annihilate it, as the bonds that hold its chemical   structures together would be torn apart by the  excessive energy. While tardigrades can survive   the freezing cold of space, they’re not exactly  mobile there. They dry out and cease all activity,   and only revive when brought back into  more suitable, energy-rich environments.  So, if not all environments are equally likely  to foster life, what sorts of conditions are   the most likely for enabling a fledgling alien  race to begin and thrive? And what conditions   might put an end to an alien evolutionary  tree before it even had a chance to start?]  When choosing [a nursery world for alien life],  just like with buying a house, it’s a good idea   to start by establishing your non-negotiables.  Some of this is fairly simple to consider:   for instance, temperature. You want a nice,  temperate climate, somewhere that’s not too warm,   and not too hot. Given that temperature  drops the further you are from the Sun,   every planetary system has a sweet spot where  the temperature of a planet is likely “just   right” – not too hot, and not too cold – similar  to Goldilocks and her bowls of stolen porridge.   As a rough rule of thumb if a planet is at the  right distance from a star, it may well have a   suitable temperature for [aliens] to set up shop. Of course, this is in no way a guarantee. After   all, Venus - a planet residing in this zone -  in theory should be perfect, but its choking   atmosphere makes it the hottest planet in our  solar system in spite of its relative distance   from the Sun compared with Mercury. So it's  clear atmosphere also plays a part in all this.  [Essential for life on Earth, and likely useful  for aliens too, is the presence of water on your   prospective planet. Water comes with some  surprisingly handy chemical properties.   It’s a solvent, allowing a wide array of molecules  to dissolve inside it and then be transported   around an organism’s body. It’s important for  key chemical reactions. While it’s conceivably   possible that alien organisms have learned to make  do with a less optimal liquid to form the basis   of their own lifeblood, so important is water to  life on Earth that we don’t have a single example   of an organism that’s learned to make do without  it. Remember, not all living things need oxygen,   or sunlight, or particular kinds of food -  but everything needs water. And in all of   evolutionary history when organisms adapted  themselves into every niche imaginable,   not a single one figured out how to do without  it. Water could well be a non-negotiable.]  However, sometimes a non-negotiable is simply the  neighbours that live close by. So, let’s consider   [another] major reason why [many of] the galaxy’s  exoplanets fall short – their neighbouring stars.  Our own star is known as a G-type yellow dwarf, a  relatively fast-burning, short-lived sort of star,   at least compared to some of the other options  out there. Stars like our Sun tend to live for   10 billion years before their cores collapse and  they transform into a red giant. It is stable,   and that stability has been useful for the  life that eventually flourished here. However,   yellow dwarfs are far from common in the Milky Way  – they represent only 10% of the total stars. Far   more common in occurrence are the longer-lived  red dwarfs, which make up 75% of the stars in   our galaxy, and can live for around 14 trillion  years, longer than our universe has existed.   And unfortunately for the planets orbiting  them, red dwarfs come with numerous drawbacks.  For starters, red dwarfs have a much closer  goldilocks zone compared to their yellow cousins.   They burn less brightly – with luminosities  between 10% and a measly 0.0125% that of   our Sun’s – so unless [aliens] live on a world  shrouded in perpetual night (which sounds cold   and depressing to me, and will make [getting  energy from sunlight] a bit of a challenge),   [an alien world would probably need] to be  a lot nearer to its red dwarf to compensate.  This wouldn’t be in and of itself a  problem, if it weren’t for the second   characteristic of red dwarfs that make them  very unpleasant neighbours – their instability.  Our Sun is the main source of our space weather.  It shoots out a frequent stream of solar winds,   flares, and coronal mass ejections. However,  this doesn’t compare to the amount of space   weather created by red dwarfs. Flares from red  dwarfs can be 100 to 1000 times more powerful   than those emitted by our Sun. The frequent bursts  of plasma and radiation coming from red dwarfs are   powerful and dangerous enough to strip away the  atmosphere, and even boil liquid water on planets   in the habitable zone. And given how much closer  planets are to their star in a red dwarf system,   the odds of life getting enough time to arise  before being hit with a life-sanitising dose   of x-rays is pretty slim. If you want  to live on a planet around a red dwarf,   you’ll likely need some serious sun-cream. This rules out many exoplanets, such as   astronomer favourite Kepler 186 f, which  some scientists hoped might be habitable.  But even during periods between harsh  solar weather events, there’s another   problem with planets around red dwarfs  – their tendency to be tidally locked.  Being tidally locked means that the same side of  the planet always faces the star as it orbits.   There is no rotation between day and night –  one side of the planet is in perpetual heat,   and the other side is in permanent shadow.  Due to gravitational constraints, planets   near their sun have a tendency towards being  tidally locked – just take a look at Mercury,   with its days that last 176 Earth-days,  or 2 Mercurian years. This lack of   rotation could render most of the planet  uninhabitable – you’d either face scorching,   desert-creating heat on the day side,  or freezing ice on the night side.  Even if [aliens] tried to live in the narrow  band of twilight that would ring a tidally locked   planet, liquid water might prove difficult  to find. Any moisture in the air that found   its way to the night side of the planet would  get locked there, solidified as ice. Overall,   the planet would be very dry; and even in  the twilight zone, there would be no rain.  [But the real clincher is] the low power  of a magnetic field that would likely be   found on a tidally locked planet. The dynamo  effect that powers the magnetic field on Earth   is thought to be influenced by the Coriolis  effect – the rotation of the Earth imparting   momentum to rising and falling liquid metal in  its core. Without this rotation, such a magnetic   field would be inevitably weaker, [once again  subjecting you to that lethal space radiation.  So, we can conclude that if alien life  exists, it probably is going to come into   being around stars much like our own due  to their stability and brightness. It’ll   be on a world that’s not too hot or too cold,  probably has some liquid water, and likely is   surrounded by a protective magnetic field to  shield that life from deadly space radiation.  We don’t have to look out across the  stars to try to find such an environment,   but can actually begin our search for  alien life much closer to home; here,   in our own solar system. It may seem a little  obvious, but life has birthed here once already.  Could it have done so again? Well, not everywhere here is   hospitable.] Mercury does not tick many boxes  in regards to what would be needed for life   to form. It has a very tenuous atmosphere, and  is far too close to the Sun. This combination   means that temperatures on the day side rise to  over 400c, and the night side can drop as low as   minus 170c. It has been discovered that Mercury  was geologically active in the past, but the last   eruption was thought to be one billion years ago.  Many extinction events would have happened during   Mercury’s history that would most likely have  prevented life from getting anywhere. There   is water ice to be found in the permanently dark  craters around the planet’s poles, but we theorise   that only liquid water can support life. Mercury  seems to be a dead, inactive and sterile planet.  The next place to visit is Venus. Venus does have  a rather substantial atmosphere, but the problem   is that it still isn’t quite far enough away  from the Sun to be in the “goldilocks zone”,   [although it’s kind of right on the border of it].  On Venus’ surface, it is even hotter than Mercury,   well over 400c all over the planet. This is  due to the greenhouse gasses in the atmosphere,   carbon dioxide making up 96% of it. This  heat means that water could not stay in   liquid form on the surface. There is a slight  possibility, however, that there could be some   form of microorganisms high in the clouds of  Venus that would use UV light from the Sun as   an energy source. The temperature and pressure  high in the atmosphere is much more hospitable   than on the surface, so this possibility exists. [Indeed, scientists have even detected phosphine   in Venus’ atmosphere. Phosphine is a gas that’s  only produced on Earth by microorganisms in a   very low-oxygen environment. Either there’s  an unknown process on Venus that’s doing a   similar thing, or it’s an indicator that similar  microorganisms could be found there. Intriguing!  [We’re skipping Earth, for obvious reasons.  Yes, life is here, but let’s for now not get   into the debate about whether any of it is alien…  although perhaps we’ll return to that idea later.]  Moving on, one of the best bets in the solar  system is Mars. It is situated nicely in the   goldilocks zone, and has an atmosphere. The big  problem with Mars though is its lack of a magnetic   field. The magnetic field on Earth prevents  the solar wind from the Sun stripping away the   particles in the upper atmosphere. Because  Mars doesn’t have this, its atmosphere has   been stripped of all but the heaviest molecules,  [meaning it now consists] of 96% carbon dioxide.   At one point in its history it did have surface  water, as can be evidenced by dried up rivers   and lake beds. However, today that water has gone  and if there was any life on the surface, this has   most likely gone too. Scientists have been keen  to find evidence in rocks with the Viking missions   and looking for methane in the atmosphere with the  rovers currently on the planet, but they have so   far found only traces of evidence. But NASA are  not deterred, finding solid evidence of life on   Mars is now one of their primary objectives, so  they clearly think there is still a good chance   of finding something. There are a few tell-tale  signs that life could have existed or still does   on Mars. There are possible bio signatures like  methane in the atmosphere, often the by-product   of life. Scientists can’t quite agree on where  the quantity of methane gas comes from, and   life is a definite possibility. We also have 34  meteorites which originated from Mars. These are   highly valuable as they are the only samples from  Mars that we possess. A few of these meteorites   even contain what looks to be fossilised bacteria,  although they are much smaller formations than any   terrestrial bacteria on Earth. This is not  conclusive evidence however, as even these   formations can be explained by natural processes. At this point in time, there are a couple of   possible places to find life on Mars. One would  be about 10 meters under the surface. Water can   be in liquid form this far down, and any life  would be much more protected from cosmic and UV   radiation. Another theory is that microorganisms  could exist under the polar ice caps. Potential   evidence of this could be the darkening of these  spider patterns next to geysers on the poles. The   darkening could be these microorganisms, as they  photosynthesize the Sun's UV light from under the   surface. With all the attention Mars is getting  from the global scientific community, I would   guess we will know conclusively whether or not  there is life on Mars within the next 30 years.  The first planet after Mars is Jupiter.  Jupiter itself is not at all hospitable to   life [as] we know it. It barely has any form  of water, it doesn’t have a solid surface,   and the winds and convection forces on the  planet would drag down any microorganisms that   tried to form in the tops of the cloud layer. The  deeper you go into Jupiter, the more the pressure   and heat increases. The chances are very slim  that life could exist here in these extremes.  However, Jupiter has some moons  where the conditions are much better.  The biggest of Jupiter’s moons, called  the Galilean moons, are big enough to   have differentiated interiors. Smaller moons and  asteroids tend to just be the same throughout,   like a rock. However bigger moons will often have  layers and cores. The second of Jupiter’s Galilean   moons, Europa, is actually one of the most likely  places to find life in the whole solar system,   but not on its surface. The crust of Europa looks  extremely unusual with these fault lines running   all over. The crust is actually made of water  ice, and beneath this ice sheet is believed   to be a liquid water ocean that spans the entire  moon. Evidence of this is can be seen through the   rotation of the crust, which is thought to have  moved by up to 80°, very unlikely to have happened   if the crust and core were solidly attached.  Another piece of evidence is something that   has only just been confirmed in the old Galileo  spacecraft data. Galileo actually detected water   plumes or geysers shooting water far into space  when it passed by the moon very closely. In 2016,   the Hubble team suspected they might have  imaged water plumes shooting 200km into space,   and this rediscovered Galileo data has confirmed  it. NASA considers the prospect of life here so   intriguing that there will be a dedicated “Europa  Clipper” mission due to be launched in [October   2024]. The Europa Clipper will orbit Europa,  passing through the water plumes, sampling the   water that is ejected. We are not expecting to  find fish blasted into space by these geysers,   but the water samples will tell us what the  conditions are like under the crust, and if there   really is a possibility of life down there. Future  robotic missions that aim to reach and traverse   this ocean are still in the planning stages. Interestingly, while Europa is the most likely   place to habour life around Jupiter; it is not  the only moon that probably has an underground   liquid ocean layer. Three out of the four biggest  moons of Jupiter, Europa, Callisto and Ganymede   all could have life under their surfaces. Callisto  may have a water or ice layer up to 300km thick.   Ganymede has at least one water ocean layer,  but could also have several, all separated by   sheets of ice. Ganymede is probably the  second most promising moon of Jupiter,   as the bottom most water layer could be touching  rock. Water/rock contact could be an important   factor for life to exist as the rock provides  minerals [– just consider the deep-sea ecosystems   that have formed around oceanic hydrothermal  vents, right here on Earth]. Ganymede is already   the biggest moon in the solar system, but data  also suggests that its underground ocean could   also be the largest. There is a European Space  Agency mission underway to Ganymede right now,   known as JUICE, or the Jupiter Icy Moons Explorer,  which will be arriving at Jupiter in July 2031. Beyond Jupiter, there are three more planets  and their moons. Like Jupiter, the planets   are very unlikely to contain life. However, some  of their moons also share the same characteristics   with the moons of Jupiter. Particular moons of  note are Rhea, the second largest moon of Saturn,   Titania, the largest moon of Uranus, Oberon, the  second largest moon of Uranus, and Triton, the   largest moon of Neptune. The most exciting moon  with these characteristics though is Enceladus,   a moon of Saturn. It has extremely active  geysers which spew 250kg of minerals and   water into space per second at over 2,000kph. It  ejects so much material that it has formed a ring   around Saturn called the E ring. Cassini,  a spacecraft that used to orbit Saturn,   was able to pass through these water plumes, and  detected carbon, hydrogen, nitrogen and oxygen,   all key components of life. There is definitely  heat being generated under the ice crust, as can   be seen in this heat map. These are the tiger’s  stripes of Enceladus. The evidence of hydrothermal   activity, water, and essential chemicals mean  that this tiny moon could be the most likely   place in the whole solar system to find life. Sadly, we are far from proving any of this. [While   there are some plans to return to Enceladus, these  are a long way from launch,] and [the orbiters   set to explore Jupiter’s Icy Moons from above have  not yet arrived]. Actually exploring the oceans is   still a [very] long way off. I can understand the  problem though of getting a robot that deep into a   moon, but it’s a little disheartening to think we  [don’t even have a timeline for such a mission].  Beyond the planets and their moons, we have  dwarf planets like Pluto, Eris and Sedna. If   they follow the patterns we see in the larger  moons, they too could have liquid water oceans   under their surface. But we are very far  away from being able to prove that too.  There are just two more curious places to look for  life in the solar system. The first is Titan, the   largest moon of Saturn. It is extremely cold, and  so is dismissed by some as uninhabitable. However,   it is unusual from any other moon in the solar  system in that is has a thick atmosphere with   methane in it. In fact, the temperature is just  right that liquid methane can form on the surface.   The moon actually has a methane cycle similar to  Earth’s water cycle. There is evidence of seas,   lakes, and rivers of methane and ethane on the  surface of Titan. Other factors essential to   life also exist there, including chemicals and  minerals on the surface, plus the moon orbits   mostly within Saturn’s magnetic field, which means  it is protected from solar and cosmic radiation.   Theoretically, lifeforms could exist that replace  water with liquid hydrocarbons. Such hypothetical   creatures would take in H2 in place of O2, react  it with acetylene instead of glucose, and produce   methane instead of carbon dioxide. Titan has been  compared to primordial Earth. [Excitingly, NASA is   launching a robotic rotorcraft to Titan, set to  blast off in 2028. If it flies above the methane   lakes and spots something splashing around there,  perhaps we’ll have a definitive answer to the   question of alien life sooner than we thought.] The last place to look in the solar system for   life is on comets. A long standing  theory is that life has propagated   through the galaxy on the backs of comets,  although it is quite an outside possibility.  Numerous missions have been conducted [to comets],  which have studied [them] closely. Some of these   missions, like ESA’s Rosetta mission, rather  surprisingly found complex organic compounds   on the comets surface. Compounds like nucleic and  amino acids, which are the building blocks of DNA   and life. However, none of these missions  had dedicated instruments which were able   to detect life, meaning we still don’t know  definitively if there are alien microbes to be   found on comets. I should note though, that while  complex organic compounds are a fascinating find,   there is still a massive gulf between organic  compounds and even the simplest of life forms.   Scientists just don’t think that a comet or  asteroid can provide the environment needed   for life as we know it to develop, for instance,  no atmosphere, no liquid water, no protection from   the Sun. [Perhaps comets could be the universe’s  taxi service for alien life, but it seems   unlikely that they’re a place life could start. Inhospitable locations aside, there are places   in the Solar System where life could have formed  beyond Earth. But at this stage, we have no proof   that life did form in any of them. Does beyond the Solar System   give us any more room to hope? To answer that, it’s time we talked about Kepler.]  You may have heard many news stories about  all the thousands of exoplanets that have   been discovered using the Kepler  telescope. [As of June 2023] Kepler   has confirmed the existence of 2778 planets. Now, we have not been able to actually image   exoplanets in any kind of detail. In fact, this is  the clearest real image we have of an exoplanet,   taken by ESO’s very large telescope. Which may  make you question: if this is the best image of an   exoplanet we have, how can we discover exoplanets,  and how do we know life could be on one?  To answer the first question, we have to have  a look at how Kepler worked. Kepler [was] a   space probe which constantly monitored about  150,000 stars in a fixed field of view using   its camera. The field of view [focused] on a  patch of sky near the constellation Cygnus.   This is what Kepler [could] see. The data it  [collected was] sent to Earth and analysed to   see if any stars [dimmed] periodically. You  see, the concept is that if a star’s planet   [passed] in front of Kepler’s view, the star  [would] dim. If it [dimmed], for instance,   once every 100 days, we [could] confirm that it  [was] a planet and it takes 100 days to orbit.  Kepler [was] really good at finding exoplanets.  Before Kepler came into operation, these were   the exoplanets we knew about. As you can  see, most of them are many times the size   of Jupiter. Since Kepler came into operation,  we have discovered and confirmed the existence   of thousands of exoplanets, with thousands more  still unconfirmed. Remember, these are planets   which have been discovered in only this patch  of sky. There is still a lot more out there.  Kepler’s [mission ended in October 2018]. However  the good news is that there is a new exoplanet   finding spacecraft called TESS which [came into  operation a few months earlier] which [covers] an   area in the sky 400 times larger than the Kepler  mission. It is expected that during its mission it   will be able to find more than 20,000 exoplanets! [In fact, based on what we’ve seen, scientists   can hypothesise there are more than 100  billion exoplanets in the Milky way.]  Using other telescopes, like Hubble, [ESO’s  telescopes, the Webb and the Nancy Grace Roman   Space telescopes], these exoplanets can  be studied to find out their composition,   particularly of their atmospheres. The way that is  done is again from the spectra of the exoplanet’s   light. To give you an example of how this is done,  imagine white light shooting through a prism,   producing what is actually a blend of colours  spanning from violet to red. Light from a star   shooting through an atmosphere produces a similar  effect, except certain bands of light are not   present. This indicates there is a certain  gas in the atmosphere that is absorbing the   light in that wavelength, not allowing it to pass  through. The dips in this image shows what Earth’s   spectrum looks like as sunlight passes through the  atmosphere. The dips show that oxygen is present,   as well as water vapour, carbon dioxide and  methane. These gases all absorb the Sun’s light   at these wavelengths. Looking at a section of  wavelengths and comparing them with other planets   in the solar system, sulphur compounds can clearly  be seen on Venus, and methane on Neptune is   apparent. This means that as we study exoplanets  in detail, and determine their spectra, we can   search for atmospheres that resemble our own. If  it does, then the chances are that it could be   a habitable world and also that it may already  harbour life. Inhabited planets, [particularly   those home to intelligent life] could have  tell-tale signs of life like smog and pollution   which would be seen in a planets spectrum. So have any exoplanets like these been found?   Well, out of the thousands of exoplanets that have  been discovered, [59] of them are thought to be   rocky planets [that] sit in the “goldilocks” zone,  or the habitable zone of their respective stars. [Of course, this doesn’t mean that they’re  necessarily inhabited. We’d need a lot more   evidence to be able to confirm that an  alien organism actually lived on one   of these exoplanets for certain. But fascinatingly, there is some   evidence of that starting to come in. Let’s talk more about biosignatures:  Biosignatures are substances, signals or  patterns that could be a sign of biological   activity. This could be something  as obvious and direct as a fossil,   or something more subtle like the composition of  a planet's atmosphere. They are important because   they indicate not only the potential presence  of life, but also its level of sophistication. There's no official classification system  for biosignatures, but it's useful to think   about them falling into three categories -  gaseous, temporal, and surface signatures.  Gaseous biosignatures are direct or indirect  products of metabolic activity. The most common   manifestation of this is the composition of  the atmosphere. For example, the presence   of haze could be an indirect byproduct of a  methane-rich world. This could tell us that a   particular planet hosts microbial life similar to  what we had on Eearth over 2.5 billion years ago,   before the Great Oxidation Event. It's similar  to the example we explored earlier of how having   free oxygen in the atmosphere could be a  biosignature for photosynthesising life.  Temporal biosignatures are time-bound  changes that can correlate with biosphere   activity. For example, on Earth, the concentration  of carbon dioxide in the atmosphere rises and   falls with the seasons. Vegetation grows  in the spring, and decays in the autumn.   This oscillation is way stronger in the northern  hemisphere than the southern hemisphere because   it has more land mass. In theory, we can use this  kind of information to see where on an exoplanet   life is most likely to be. However, nothing  is so black and white. Temporal biosignatures   can be caused by abiotic factors, too. I personally find surface biosignatures the   most interesting. Basically, every planet reflects  some light from its star. Different materials on   the surface of the planet will reflect different  combinations of wavelengths of that light. This   results in a unique reflectance spectrum for  every material. Surface features like rocks,   snow, water and soil can all be deduced from  reflectance spectra. Life can also influence   the reflectance spectra of a planet. This  is an example of a surface biosignature.  [In September of 2023, just a few months  ago at time of recording this video, the   JWST provided a tantalising result – the  detection of a gaseous biosignature in an   exoplanet’s atmosphere. Dimethyl sulfide (DMS) is  a molecule that on Earth is only produced by life,   mostly by phytoplankton in marine environments.  It was discovered by the Webb in the atmosphere   of K2-18 b, an exoplanet with a hydrogen-rich  atmosphere that data suggests might be covered in   an ocean. K2-18b is 124 light years away from us. Scientists are not saying that this is alien life   for certain. It’s still possible that the DMS  was produced by some natural process we’re not   familiar with. But while that’s true, to  me this makes the whole subject a lot more   worth investigating. It’s one thing to say  “aliens probably exist out there somewhere.”   It’s another to say “aliens exist, and  it’s possible we might have seen them.”  Perhaps we should take a step back. One of the  objections I have heard to the idea of discovering   alien life is just how unlikely it sounds. Is  there any way of exploring how often scientists   expect alien life to have arisen in our galaxy? Yes. As it happens, there’s maths for that.   And although so far we’ve focused on just  the most basic level of life – microbes,   and simple organisms – some scientists have also  tried to tackle the next question after that:  How likely is it that we’ll  find life that is intelligent?]  Once an alien race has evolved to the  point where it has become intelligent,   unless it came into being through some  weird mechanism we don’t understand,   it probably did so through out-competing its  rivals and collecting resources for itself and   its offspring. Civilisations made up of such  creatures will most likely also have a hunger   for space and resources. Whether they gain these  things through clever diplomacy or aggression,   it is most likely that they will want them. [As  we mentioned earlier, form follows function, and   this applies to cultures and civilisations too]. This quest for expansion and seeking more and more   energy and resources led soviet astrophysicist  Nikolai Kardashev in 1964 to propose the Kardashev   scale for classifying the different kinds of  alien civilisations that might exist out there.   He grouped civilisations into three kinds. Type 1 civilisations can completely utilise   the energy available on their planet. We have  not quite reached this point as a species,   so we are roughly a 0.7 on Kardashev’s scale. Type 2 completely utilise the energy available   from their star, possibly by building a giant  mega-structure such as a Dyson sphere to   capture and utilise all of its energy output. Type 3 civilisations would be able to utilise   the entire energy output of its galaxy. We have  seen no evidence of an alien civilisation such   as this one, which is for the best, as  they would likely see us in the same way   we see bacteria – mildly interesting, but  otherwise completely beneath their notice.  Other scientists since Kardashev have proposed  further additions to this scale – type 4s that   use all the energy in the universe, type 5s  that use all the energy in multiple universes,   or even the enigmatic Type omega, capable of  utilising energy sources beyond even that,   perhaps existing outside of time entirely. Such  a civilisation would essentially be gods. We   would have no way of detecting them, because  nothing in this universe would exist except in   the way they wanted it to, and we would have  nothing to compare their existence against.  While this may seem like a bleak outlook for  humanity – if ever we come across another race,   under this theory we would almost certainly end  up competing for resources in one way or another,   or just getting steamrolled by a vastly higher  power – there actually are other possibilities   for alien development too. After all, not all  humans are interested in expanding ever outwards.   In fact, with the advent of the internet  and online cyberspace, more and more human   interaction is taking place in virtual spaces. Carl Sagan proposed a model that classifies alien   races based on how many unique pieces  of information they collectively know.   Although much harder for us to detect at a  distance, and admittedly hard to measure,   this way of gauging advancement does not require  an alien race to infinitely expand. An intelligent   race that started looking internally, or even one  that spent its entire conscious time in some kind   of cyberspace could still learn more and more  about itself and the universe as a whole, while   taking less and less space within that universe.  For the record, Carl Sagan’s scale is alphabetic,   where we were at about a type J civilisation, as  we apparently knew 1013 bits of unique information   in 1973. While I haven’t been able to find out  exactly how he worked out that figure (mention   in the comments if you know), we are probably  further along this scale now, 50 years on. But   as a comparison, a Z type civilisation would  need to know 1031 bits, more information than   exists in the whole universe, so it’s unlikely  that such a race exists, at least not yet.  While it’s true that we have not met an  alien civilisation, it is comforting to   know that it’s entirely plausible there would be  something about them that we could understand,   and even find relatable. Form follows function.  We as humans are the beings that think and gain   mastery of our world. Perhaps one day, if we meet  another race that does the same things we do,   rather than seeing something truly alien, it  perhaps will be like looking into a mirror.  I’ll leave it to you to decide whether  that is a comforting thought or not.  [But to get to that level of intelligence],  there are still a number of things that need to   go right. [And if we are to also discover them in  the night sky, the odds get even less favourable.]  To [recap, for them to even get started] they  would most likely need a star to orbit. As   near as we can tell, life cannot exist without  energy. They would need a planet that suited   them. They would [likely have competed]  with other organisms for limited resources,   thus encouraging them to adapt and progress. In  time, they would need to develop problem-solving   skills and intelligence as a way of gaining  those resources and out-competing their rivals.  Their civilisation would then have to survive  without accidentally becoming extinct due   to a freak meteor strike or earthquake or  global freezing. They would also have to not   destroy themselves. They would have to invest in  technology, and would have to develop a level of   technology that allowed them to reach out across  the universe. They’d also have to have a desire   to talk to any potential neighbours as opposed  to being intensely isolationist, and finally   would have to broadcast a signal out to us for  long enough that we would be able to spot them.   All of this is by no means certain. However, as  was pointed out by astronomer and astrophysicist   Frank Drake in the first SETI (Search for  Extraterrestrial Intelligence) meetings in 1961,   all of this could be used to calculate  the probability of us finding alien life.  He laid all this out in his famous Drake Equation: This may look a little complicated, but its based   on a very clever and logical idea. Using the  same logic that says you can figure out how   many students are in a school by calculating how  many students were inducted into the school at the   start of each year, and then multiplying that by  the number of years students studied for, Drake   reasoned that the way of calculating the number of  civilisations in our galaxy whose electromagnetic   emissions are detectable could be calculated,  provided you knew the rates at which all those   other steps happened. Let’s break it down. N is the number we’re looking for – how many alien   races are out there for us to see or hear. This  will give us an idea of the odds of finding them.  R* is the rate of formation of stars suitable for  the development of intelligent life, in number per   year. Not all stars are very suitable for life  to develop, as some are too cold, or too hot,   or generally too unstable. We need to know how  many are being born that could support life.  fp is the fraction of those stars with planets. ne is the number of those planets, per solar   system, with atmospheres and material compositions  suitable for life. If they’re covered with lava,   or are completely devoid of atmosphere  or water, it’s unlikely that life could   form there, based on our own planet’s example. fl is the fraction of how many of those planets   that could support life actually do support life. fi is the fraction of planets for which that   life becomes intelligent fc is the fraction of times   that life advances enough technologically to  start sending out signals of their existence.  And finally, L is the length of time  a civilisation exists, on average.  If you combine all of these elements,  you could accurately predict how many   alien civilisations we would be able  to see up in the night sky, right now.  Of course, you might have noticed a drawback  with this equation. Some of these numbers are   simply not known by us. But, where’s the fun  in not giving it a go anyway? By inputting   the numbers that scientists currently believe to  be most likely, and by making a few assumptions   of my own along the way, we will attempt  to solve the drake equation. If you think   that any of my numbers seem unreasonable,  let me know in the comments down below!  So, with that, let’s see how many  alien civilisations we might reasonably   expect to see out in the night sky. To begin with, we can input our values   with reasonable certainty. Scientists looking  at the Milky Way galaxy can accurately predict   how many stars form every year, as we have many  examples to draw from. Depending on who you ask,   the number ranges from between 3 and 7.  Let’s say 5, at a conservative estimate.  Fp is easy to solve too. Through recent  astronomical observations by the Kepler   space telescope, it’s become apparent that  planets are very common in the [galaxy],   with each star on average having one. So, let’s  set this number high as well – let’s say 90%.  However, the number that we currently predict  is at a suitable distance from their stars,   as well as having the ideal mix of elements that  would produce life similar to ours is much lower.   Of the 100 billion planets in the [Milky Way  Galaxy], perhaps as few as 300 million fit into   this category. Obviously, this does not account  for alien life that’s significantly different   from us, but let’s discount them for the moment  as then this would be even harder to predict.   This gives us a percentage chance of 0.3% - quite  a small chance that one of the planets in a solar   system is suitable for life. So, 0.003 for ne. So far, so substantiated by evidence. Here   is where things get a little tricky. For  the number of times that life has arisen,   we have only one example to draw on – life on  Earth. To date, we have not proved that life arose   on Mars or Ganymede, for all the conjecture on  that front. So, we can take this estimate one of   two ways. As near as we can tell from the fossil  record, as soon as the planet cooled down enough,   life came into being, which might indicate a high  value for fl. Perhaps as high as a certainty [1].   But on the other hand, from what we know,  all life originated from a common ancestor.   Which is to say, life formed on this planet from  non-biological matter exactly once, and has never   risen up again since. Scientists have looked for  evidence of bacteria that might have independently   come into being, but so far haven’t found any. This may be a coincidence. Perhaps life did arise   multiple times, but the life that arose first  was more advanced and so out-competed the newly   formed simple bacteria into extinction. Still, it  means that life is either incredibly certain, or a   million to one. Let’s go with the more pessimistic  number, and see where that takes us. fl = 0.0001%  We encounter the same problem for the arising  of intelligence. There are numerous examples of   animals displaying forms of intelligence. Octopi  can open jars and solve puzzles, and some birds   and apes can use tools or even use sign language.  Perhaps this proves that given enough time, life   always evolves into becoming more intelligent.  However, if we want to be strict about it,   we could also accurately say that of all the  millions of species that have existed on the   Earth, only 1 actually was intelligent enough  for our purposes. Us. Which makes the odds seem   very low for it happening. Let’s once again  input our one million to one value for fi,   again to just be pessimistic. [fi=0.0001%] In terms of how many become technologically   advanced enough to start communicating, I  think that this number is likely much higher.   Although we only have one species to compare  to again, it’s worth noting that humans are   unintentionally chatty with the universe, quite  by accident. Thanks to industry and transport,   we are altering the chemical composition of  our atmosphere, which is something an alien   race could detect, certain molecules in our  atmosphere are only there because they are   man-made. We also send signals out into space  thanks to our radio signals and satellites.   Sometimes we even send signals out into the stars  deliberately, such as the Arecibo message which   was broadcast from Earth in 1974, and contained  information about human civilisation and history,   expressly so any aliens that heard it could  learn about us. Although these signals would   not travel far on the grand cosmological  scale of things before becoming dispersed and   indistinguishable from background radiation,  we WOULD count as a communicating race. So,   I’m going to predict this number as high. Let’s  say 70% of intelligent races reach this level.  Finally, how long do civilisations survive?  For this number, we sadly do not even have   a single example. We will not know how long  our race will survive until we all die out,   by which point there will be no-one left to  write down the final figure. However, although   there are numerous dangers that could end us as a  species, ranging from meteor-strikes, nuclear war,   or even solar flares, the longer we are able  to survive, the more likely it is that we will   go on surviving. This is because once humanity  spreads out, we become more and more resilient   to a species-threatening catastrophe. If we are on  multiple planets, a comet hitting Earth would no   longer threaten the survival of our species. If  we are in multiple solar systems, a solar flare   would no longer be able to get all of us. Species  could in theory reach a sort of immortality level   in this way, lasting for potentially billions of  years as long as they could get out of the danger   range. Let’s be optimistic and use this figure.  What does that give us for the Drake Equation?  Based on these assumptions,  our answer is… 0 in our galaxy.  If civilisations lived for a trillion years (which  is longer than the universe has existed for),   we’d still be at 0 for these values. Given  these odds, our chances of ever hearing from   another civilisation is next to non-existent. But that’s just the thing with this kind of   estimate. If we instead assumed that life arising  was certain, and that intelligence arising was   certain too, our final answer for even a 1000  year civilisation would no longer be 0. Instead,   that comes to an answer of 9 in our galaxy. Nine  intelligent races, who might be up in the stars   right now trying to communicate with us. And  if races routinely do make it to functional   immortality to the point where their civilisations  last for a billion years, then we would see   as many as 9,450,000 in our galaxy. Or more! I know these are hypotheticals, but I find this   very interesting. Putting the numbers through the  equation make it a bit more tangible, a bit more   magical and exciting even. According to the Drake  equation, the sky could be completely silent,   or absolutely teeming with alien life. If it  is the former, then we should probably prepare   ourselves for a long, lonely existence. We  should learn to get along with each other,   because we are all the life we are ever going  to see. There will be no aliens stopping by   to say hello. [We also have an even greater  responsibility to preserve life here on Earth,   as there likely won’t be any more to replace it.] But if it’s the latter, [then space should be   filled to bursting with alien races, getting  discovered all the time. So…] Where are they all?  [This was the question first asked by  nobel-prize-winning physicist Enrico Fermi,   in his famous “Fermi Paradox”. But as I’m about to  show you, there are actually numerous answers to   this question ranging from the plausible, to the  fanciful, to the worrying, that all might account   for why we might not have discovered aliens yet.] Let’s start by addressing the elephant in the   room. Maybe there’s no-one to see. If it was true  that it’s quite difficult for life to arise from   non-living materials, or if it’s unlikely that  that life would go on to become intelligent as   we have done, then it’s entirely possible that  there would be no ships or signals in the sky,   simply because there are no aliens. We could  be the first ones to ever make it this far.   All other planets could be desolate and empty.  It would then be our opportunity to spread out   across the universe and discover all these empty  rocks, and the only life we’d ever encounter is   whatever we brought with us from Earth. While this is a perfectly reasonable   possibility – there is no conclusive evidence to  prove it wrong – this is not the only explanation   that exists for why the sky isn’t full of  signals. We should also be aware that we are   constrained by a surprising natural limitation. For us to discover or make contact with an alien   civilisation, one of two things needs to happen.  Either we need to send a message out to an alien   civilisation and then have them send a message  back to us, or the alien civilisation needs to   have made the first overture, messaging us  directly. There are different ways of doing   this – for instance, we might be sending  spaceships to each other, or we may be   using unmanned probes – but there are significant  issues with doing anything other than messages.  Sending a spaceship is a tricky business. At the  current speeds our spaceships are capable of,   it will take potentially millions  of years for an astronaut to reach   their destination. The Voyager 2 probe took  about 49 years to even leave our heliosphere.  The nearest star is 4 light years away.  In other words, it would take over 81,000   years to get even there, or about 2,700 human  generations. And that’s assuming that we have   aliens as our closest next-door neighbours. Even if we make allowances for technology to   improve, it takes colossal energy to accelerate  an object up to light speeds. Actually,   it would take more energy than exists in the  universe, for reasons we won’t go into here.   Mass just does not like to travel at those  speeds. So unless we or our alien friends are   able to come up with some kind of workaround, most  likely the easiest way to communicate with other   civilisations is to send them radio signals. In fairness, it’s not implausible that this   speed cap will one day be broken. Scientists have  hypothesised some [intriguing] things involving   moving the space around you in warp bubbles rather  than by moving yourself directly. The speed of   light limit only applies to movement within a  local area, so if it’s your local area that’s   moving, you’re fine. We have actual examples of  this in nature around black holes, which I explore   in one of my other videos [Black holes part 5]. But until that becomes a scientific reality, let’s   just go with the fact that it’s much easier to  call than to visit in person. It’s significantly   easier and cheaper to send light or radio waves  – as simple as turning on a sufficiently large   lightbulb. So let’s assume that this is how  our first contact with aliens will occur.  Even here, however, we hit a roadblock. Radio  signals and light are more than capable of   travelling at relativistic speeds – it’s  called the speed of light for a reason,   after all. However, that’s its limit – light  speed. 299 792 458 m / s. No signal can go   faster than that, and this in turn limits  how far we are able to see through space.  Any signal from us would need to travel out  across space before reaching alien life,   and then even if they decided to respond  immediately, their response would need to travel   all the way back. If they decided to respond. Let’s imagine that happens, though. We only   invented the radio in the mid 1890s, so we have  not really been able to do this for very long.   As such, we would only be able to exchange  a message with aliens who lived at most 60   light years away from us – 60 years for a  signal sent out in 1900 to reach the alien   civilisation, and 60 years for it to come back. Our galaxy is roughly 100,000 light-years across,   so the 60 light-year bubble we could  have communicated with is truly tiny.  [So, another answer to Fermi is  that perhaps we’ve not existed   long enough for aliens to message us back.] In fairness, this limitation goes away if the   aliens contact us first. After all, we are now  receiving light in the James Webb telescope that   has been travelling for 13 billion years, from  nearly the beginning of the universe. If an alien   civilization came into being around 2 billion  years ago, and they’ve kept existing since then,   that means they now have a 2 billion light-year  bubble from which we could technically see them.   A 10 billion-year-old civilization now has a 10  billion light-year bubble. But if they were 10   billion light years away and only 9 billion years  old, they would be completely invisible to us.  [So, why haven’t we heard from these aliens  by now? Well, this line of thought may rest   on a faulty assumption – that there haven’t  been any signals coming in from the stars.  There have been signals. Although while  it’s a little speculative, perhaps we just   didn’t recognise them for what they were.] Obviously, when it comes to alien signals,   there is some ambiguity as to what exactly  we are looking for. Aliens are, after all,   alien. We are not quite sure what to expect  from them, as they will likely have evolved in   conditions different to our own, and may well have  cultural outlooks that make perfect sense to them   but are completely obscure to us. Their definition  of a good way to say hello to the universe might   be very different from ours. Researchers looking  into possible signals from other planets have   to remain very open-minded about what an  extra-terrestrial signal might look like.  But that means such signals can get confused with  signals from natural sources that we simply do not   understand yet. How can we tell the difference? Let’s explore this with a fascinating example. In   1961, in their pursuit of evidence  for the existence of alien life,   (which is worth noting because it opens  up the possibility of confirmation bias),   researchers at Ohio State University finished work  on a specialised telescope called Big Ear. It was   the size of three football pitches, and worked on  a similar basis to modern-day telescopes in that   it captured signals using its large “mirror”  on one end, and bounced them through smaller   “mirrors” on the other into two receivers in the  centre, where the results were then processed. You   may notice that these capture dishes are just  wireframes, though, not true mirrors. This is   because Big Ear was a radio telescope. It  wasn’t trying to see with visible light.  The way Big Ear worked meant that it was more  limited in its motions than a telescope that could   rotate in any direction. Big Ear could only tilt  its primary reflector up and down, which meant   that it was somewhat limited to only listening  to a point in a narrow strip of space at any   one time. This was cheaper and easier to design.  And the designers had an idea that would let them   get around Big Ear’s limitations – they built  Big Ear at just the right orientation so that   the rotation of the planet would be what turned it  left and right. With the Earth turning it one way,   and with its tiltable reflector adjusting it  along the other axis, you could point Big Ear   towards [almost] any point in the night sky if  you have enough patience. Quite a clever solution!  Big Ear’s direction of attention would sweep  around the night sky in large, circular arcs,   listening out to try to spot any unusual signals  that we did not have a natural explanation for.   And sure enough, in 1977, Big Ear found something. On the 15th of August, a 72-second-long pulse   of radio waves came in that were 30 times more  powerful than anything Big Ear had heard before   in the background chatter of the universe. It was  so out of the ordinary, that the researcher who   found it wrote “Wow!” on the computer printout  when they saw it, giving it the historical name   of the “Wow Signal”. It was incredibly uniform.  It rose in intensity, peaked, and then dropped   back down again in a smooth motion, instead of the  erratic fluctuations you might have expected from   cosmic radiation. This indicated that whatever  had made the sound was broadcasting consistently,   kind of like the beam of a lighthouse sweeping out  across the stars, with us turning to look at it,   and then turning away again. Except, it wasn’t consistent. Due   to Big Ear’s design, researchers had to wait  a few minutes before the second “ear” of Big   ear moved to look at that particular patch  of space the Wow signal had come from. And   when they got there, the signal had vanished. Ever since then, despite checking back in from   time to time, we have never heard another  Wow signal come from that region of space   to this day. So, what was it? A fault in the  machinery of Big Ear? A passing comet that   threw out a momentary burst of signals? Or  an alien civilisation trying to communicate?  [We currently don’t know.] Let’s take a look at another   candidate. The somewhat mouthier SHGb02+14a. When one of the first SETI experiments – project   Ozma – was started in 1960 by Frank Drake, it  began on the basis that if alien life were to   communicate with the rest of the universe, they  would do so at frequency 1420 MHz. The logic   behind this was that this was the frequency  emitted commonly by Hydrogen, one of the most   widespread elements in the universe. Aliens  looking to establish communication with other   civilisations might use such a frequency as a  sort of common ground – a wavelength that probably   holds a special significance to any race. This  might have been a leap of logic, but it certainly   made SHGb02+14a of interest later. Because this  signal – let’s call it SHG for the rest of this   video, for the lack of a punchier name – did  indeed broadcast at this exact wavelength.  SHG was spotted on three separate occasions  in 2003, using the Arecibo telescope and the   computational power of 5.2 million home computers  as part of the SETI@home initiative, a rather cool   program that sadly is no longer running. SHG had  no obvious explanation for its origins in nature,   and didn’t appear to be interference.  But it was also too weak to say for sure   whether it was clearly technological or not. On top of that, its location was peculiar.   It came from a spot devoid of stars up  to 1000 light years away from Earth.   And although it experienced drift, it did so  in a manner that made scientists suspicious.  If a signal originates from a planet, then  there are a few things we might reasonably   infer. A signal being broadcast from a planet  – either on the surface, or in orbit just   above it – would likely experience some doppler  shift as it alternated from moving away from us,   to coming towards us through the circular  path it was taking in space. There would also   be moments where it dropped out of view  entirely as it moved behind the planet.  While SHG did indeed experience fluctuation in  its signal frequency – ranging from 8 to 37 hertz   per second – this would only come from a planet  that was rotating 40 times faster than Earth,   which seemed high. It was also strange that  each time the signal was spotted again,   no matter where it had been when it had last  been sighted, it always began at 1420MHz. The   odds of you looking at an orbiting transmitter on  three separate occasions and each time spotting   it starting off at the exact same location is  incredibly slim, which is what you’d need for   this to make sense. [So, although this observation  pointed to it being more likely SHG was some kind   of glitch in the technology, examples like  this one do leave a little room for ambiguity.  For an example that might be aliens or might  just be a natural phenomenon, let’s look at]   fast radio bursts. If an alien civilisation were  ever to be detected, it might not be intentional   on their part. Powerful engines activating, or  beams firing, all might release bursts of energy   that give away a galactic civilisation. Which  makes Fast Radio Bursts (or FRB’s) interesting.  They are, just as the name suggests, very fast  bursts of radio waves. We have detected hundreds   of these strange, millisecond-long bursts across  the sky. Scientists theorise that there might   be thousands of them occurring every single day.  They have mostly been detected outside our galaxy,   but one was detected within the Milky Way in  2020, so they’re not completely foreign to us.   They seem to be coming from extremely powerful  magnetic fields. And as of yet, scientists have   no clear idea about what their origin might be.  There are plenty of theories – perhaps they are   emitted by neutron stars, or maybe black holes.  But there is no proof that puts any one theory   over another – including that of alien technology. [So, we might have already received alien signals,   and simply didn’t recognise them. There is of course a claim that takes   this idea even further. Some individuals have  claimed that aliens have not just sent us signals,   but have visited our planet directly, and  we still haven’t as a species recognised   it.] Here, sadly, the evidence starts to get  questionable. There have been so many hoaxes,   faked videos filmed on grainy, shaky cams, or  even genuine mistakes where natural phenomena   or satellites are taken for UFOs, that many  people are now a little wary of entertaining   such theories. There have even supposedly been  times when the US Government has deliberately,   subtly propagated UFO conspiracy stories to  draw attention away from their real top-secret   technological projects, like the stealth bomber.  All in all, ascribing extra-terrestrial origins   to these phenomena is often factually  incorrect, and poor science. Just because   we do not understand something does not mean we  should jump to the idea that it must be aliens…  [Still, it only has to be proven once for our  entire world-view to be forever shaken. I also   find it intriguing that so many governments  have started seriously exploring the topic   of UFO’s in the last few years. In just the last  year, countries like America, Japan, and Mexico   have held hearings on UAPs, or “Unidentified  Anomalous Phenomena”, with the intention of   not cynically swatting away the topic, or having a  good chuckle, but as a serious attempt to address   an issue congressmen are claiming to be a matter  of national security. Organisations like NASA are   being tasked with coming up with explanations  for UAPs, and are seeking to collect more data   on them. And so, if governments and scientists  are evaluating whether there’s actually some fire   behind all the smoke, let’s take a moment to do  the same. Could it be that at least some UFOs are   an alien civilisation’s efforts to visit us?] The first UFO sighting in modern times was by   an American businessman named Kenneth Arnold  in 1947. As he looked out across Mt. Rainer,   Arnold claims he saw nine crescent shaped silver  objects travelling at several thousand km per   hour through the air. He likened them to “saucers  skipping on water” in the way that they moved. He   initially thought they might be secret military  jets, but later he and other witnesses of these   crescent craft wondered if they might have been  extra-terrestrial in nature. The media picked up   his turn of phrase about the saucers, and the  idea of “flying saucers” entered the national   consciousness. Before long, other people  started reporting alleged UFO encounters.   The US became enraptured with the idea of UFOs. However, the US military did not take this idea   quite so seriously. While initially they were  understandably alarmed at the report of unknown   aircraft moving around in their airspace,  particularly coming right after World War II,   the programs they set up to investigate UFOs were  eventually shut down in 1969. Project Blue Book,   the last of these programs, collected 12,618 UFO  reports, but ultimately concluded that they were   almost all misidentifications of natural phenomena  or just man-made aircraft. With such a damning   report to go on, the US Government officially  pulled funding from the project, and investigation   into UFO sightings officially ceased. Partly as a result of project Blue Book’s   findings, a certain degree of stigma became  associated with seeing a UFO. Anyone who claimed   to have done so was often ridiculed or considered  crazy. It came down to a question of evidence.   If aliens were real, and were visiting our  planet, where was the proof of their existence?  Of course, to answer that, we need to define  what we consider to be reliable proof.  Let’s imagine that a person came up to you  and claimed that they’d seen a silver disk   shoot across the sky at a speed far faster  than any airplane was capable of. Would   you consider a single person’s account to be  proof that he’d seen an alien spacecraft? Well,   not necessarily. Human memory is unreliable. Even  if you trusted the character of the person in   question enough to believe that they weren’t lying  to you, they might be misremembering details,   or maybe had misjudged how fast the “spaceship”  they saw was going due to some optical phenomenon.  “Ah,” they cry, “but I recorded it on film!”  You look, but unfortunately, the video they   provide is grainy, and only gives you a blurry  glimpse of the spacecraft. Is that proof?  Again, you might well be sceptical. Even if this  video is not a deliberate hoax (and it’s so easy   to fake films these days), it could be a digital  artefact of some broken pixel in the camera. And   it still could just be some natural or man-made  phenomenon neither of you had seen before.  So, what would be a good proof of  alien spacecraft? Ideally, for me,   I would like evidence that was seen by multiple,  trustworthy people – the more, the merrier. It   would need to be recorded by multiple pieces of  hardware, to eliminate the risk of it just being   glitchy technology. And it would have to evidence  characteristics that completely ruled out it being   any man-made phenomenon or natural event. Best of  all, it would be repeatable. If it kept occurring,   it would provide more opportunities  for study, to rule out other causes.  Which brings us to the event that  started things all off again, in 2004,   and the USS Nimitz. The Navy aircraft carrier  was travelling through the ocean near Southern   California in November on a routine training  exercise. Another nearby vessel called the USS   Princeton had recently received upgrades to  its radar, and had started noticing strange   aircraft in the area. These crafts descended  from 80,000 feet to 20,000 in a blistering speed,   before vanishing out of sight entirely or later  shooting back up again. After a few days of this,   the Princeton called the Nimitz, asking them  to send someone to see what was going on.  Two F/A-18F Super Hornet jets were  scrambled. Each jet had a weapons camera,   but no weapons as this was only meant to be  a training exercise. Each jet had two pilots   on board. Upon arriving at the scene, all four  pilots quickly spotted what they were looking for.  A strange tic-tac shaped object was moving  weirdly, zipping back and forth above a frothy,   boiling patch of water in the sea below  them. It had no visible means of propulsion.   No wings. No rotors. It was about the  size of a jet, and a whitish colour.  The object suddenly stopped its zig-zag.  It had seen them. It whipped around,   and travelled up towards the jets, as if  it were intending to meet them in the air;   but then rapidly accelerated away, faster  than anything the pilots had ever seen before.  Baffled by what they’d witnessed,  the pilots returned to base,   only for the radio operator to inform them that  they’d begun tracking the craft again – except,   it was now over 60 km away. It had got there  in under a minute of leaving the pilot’s view.  [To be clear, we have no jet or technology  that is even remotely capable of mimicking   this. There is no natural phenomenon that we  know of that could do this. Whatever this was,   it did things human technology can’t do.] This was an object seen by 4 trained,   professional pilots on the clock [who have  publicly spoken on what they saw under oath],   aircraft cameras and modern, advanced ship-based  radar from one of the most technologically   advanced nations in the world. This ticks many of  the boxes for good, reliable sources of evidence.  This report was logged, and nothing else was  initially done with it. You might just point   to this being a strange story, if it wasn’t for  this authenticated footage that we have of it,   confirmed by the US government in  a Freedom of Information request.  [To me, that’s what makes this story compelling.  When a lone individual sees a light in the sky,   it’s easy to come up with any number  of explanations for what they saw,   including the fact that they might be lying. But  when a government unambiguously claims that the   event did indeed happen, and say they want to know  what it was, then the event probably did occur.]  But the strangest thing about  this was that it kept happening.   The phenomenon is currently repeating. Navy and air force pilots were spotting   strange objects in the sky so frequently,  some were claiming that it was almost a daily   occurrence. Many were embarrassed to mention  what they’d seen, fearing ridicule. That said,   it became so common that the Navy started handing  out cards to be kept in Navy pilot kneeboards in   their cockpits about what to do in the event  of such a sighting. Between 2004 and 2021,   144 reports came in from Navy personnel of seeing  unidentified objects in the sky, 80 of them being   observed by multiple sensors, 11 accounts of near  misses with jets, and only ever 1 being positively   identified. Between 2021 and 2022, sensing that  there might be something to all this after all,   the Navy began destigmatising reporting and  started actively encouraging its pilots to   record what they saw. 247 new reports came in,  and an additional 119 incidents were reported   to have happened in the past. Sure enough, that’s  1 almost every other day. In total, the number of   unidentified objects had risen to 510. So, what were these objects?  Their natures, and probably their origins, varied.  Some behaved like drones, with the Navy detecting   radio signals coming to and from them… only, they  stayed up in the air far longer than any drone   on the market was capable of doing. Some were  more like aircraft, travelling in formations,   exhibiting unheard of acceleration. Some could  both fly and submerge underwater, seemingly at   will. Some acted like balloons, albeit with  unknown means of remaining up in the air,   sometimes defying wind currents by remaining  completely motionless, or even moving against it.  No doubt, of those 510, some will simply be  glitches in technology. This strange triangle   in the sky is thought to not really be that shape.  Instead, the unique design of the night goggles   is thought to be distorting the light from this  apparent drone, in a similar effect to lens glare,   but uniquely tailored to this technology. However,  it’s still concerning that the Navy does not know   what these “drones” were doing circling a US Navy  vessel while it did training exercises at night.  The Navy started calling these objects  UAP’s, or Unidentified Aerial Phenomena,   in the hopes of removing negative connotations  associated with UFOs, and this has changed again   recently to Unidentified Anomalous Phenomena.  And while they do not want to assume that this   is alien in origin they’re also not ruling it out.  They reported their findings in a congressional   hearing on the 17th May 2021, and now are  regularly (and somewhat transparently) publishing   reports for the general public about the ongoing  investigation, provided it doesn’t give away too   much about classified sources or technologies they  are working on. Right now, they are attempting   to simply collect as much data as possible,  knowing that it will lead to better science.  And that right there is the biggest shift of  all. When you see the US government reaching   out to the wider community to ask “What are  these things we keep seeing?” it certainly   confirms that there is something to see. [Of course, as a reminder, although it   seems likely from our evaluations earlier that  alien life could well exist, we have no evidence   that it does, and no proof that it’s here. It does  raise perhaps the most important question, though;   a question that as we continue searching for  alien life out there, we really need to be asking.  What do we do if we find it? If alien life was ever proven to exist, and   could come here, what would we do? If it was far  away, it would be fascinating for humanity – an   answer to the question of whether we are alone.  But if alien life was found that was intelligent,   and indeed more advanced than us, and knew about  us and had the means to interact with us, what   then? Suddenly, this all becomes a bit more real. Suddenly, we need to answer another vitally   important question. What will  aliens do when they find us?  Let’s consider.] We are the only instance of  life arising in the universe that we know of.   The great human experiment of civilisation  has been going on for thousands of years,   and has produced many different types of society  – socialist, capitalist, hunter-gatherer, nomadic,   and theocratical, to name just a few. If we  want to understand the behaviour of alien   civilisations, we need to consider societies.  We thus have quite a few ideas to compare   when considering how aliens might behave. [As we’ve not seen them in spite of looking,   we know for a fact that either aliens do not  exist, or they are subtle about their existence.   If they exist in our galaxy, they’re not flashy.  Even if aliens are visiting Earth – which is a big   if – they are not making a big deal about it.  They are not building massive structures that   might tip us off as to their existence, and  they are not flying over our cities shooting   death beams or waving flags to say a friendly  hello. This allows us to conclude things.  Broadly speaking,] let’s examine two great  extremes, and see how they might influence   alien civilisation. These two extremes are  altruism, and aggression. Love and violence.  We’ll start with violence. While this may be a pessimistic starting point,   it is sadly one we must consider, because as  human civilisation has developed throughout eras,   different groups of humans have almost always  clashed violently. This ties into the evolutionary   idea that competition always occurs when there are  more organisms than there are resources. Humans   are organisms, and we need resources to live.  And so, all too often, war throughout the ages   has been fought over resources. Agricultural land.  People, and all the labour power and industry they   can produce. Oil. Gold. Even when a civilisation  develops space travel and reaches for the stars,   this issue will still likely exist. After  all, we are nearly at the stars ourselves,   and there certainly seems to be no shortage  of violent conflict amongst us today.  So, with a sample size of exactly 1, we  have to at least consider the possibility   that other alien races [if they exist]  are the same as us. Driven by a need for   resources to support an ever-growing population. Of course, when it comes to societies, there are   even more reasons why clashes might occur. For  instance, religious or ideological differences.   The cold war was largely fought between countries  that espoused different political ideologies,   capitalism and communism, that threatened each  other. Alien civilisation might equally differ   from us ideologically (in fact, it would be  surprising if they didn’t), and so it’s possible   they might feel their ideology is threatened in  some way by ours. This could lead to conflict too.  This is not even to mention the fact that  some cultures idolise violence itself,   deeming themselves of worth only when they are  winning victories, such as Viking raiders or   Spartan hoplites. Others seek to build empires,  recognising that it’s much easier to take wealth   from others than it is to build it yourself.  All these reasons are perfectly plausible for   an intelligent race that has mastered its  planet, outcompeted other lifeforms there,   and likely feels good about doing so.  Survival feels good. We enjoy feeling strong.  But if this leads to conflict, what might an alien  conflict look like? Technology raises the stakes.  We currently lack the technology to move objects  to other solar systems. Given the vast distances   throughout space, unless we intend to just throw  insulting messages at each other through the void,   actual fighting cannot be achieved until we manage  to solve speed of light travel, and probably   something faster than that. But it is possible  that one day we might get around this problem.   And this instantly opens a dangerous possibility. It is theoretically impossible to move something   up to the speed of light, because of the  link between mass and energy. The more energy   something has, the more “mass” it has, because  the two are linked, and thus the more energy you   need to increase its speed further. This only  really is noticeable at relativistic speeds,   but it does mean that you’d theoretically need  infinite energy to move mass up to the speed of   light. But if you throw an asteroid-sized object  at a planet at near light speed, then all that   energy gets released in one go. This kind of  strike can easily wipe out all life on a planet,   and the people on it wouldn’t even see it coming. Any intelligent race would be very aware of the   impact potential of objects such as this. For us,  we only need to look at the dinosaurs. You don’t   need nukes, or soldiers on the ground, to fight an  alien war. Just rocks thrown really, really fast.  This opens up one possible answer to the Fermi  paradox. If alien civilisations exist, and any   of them proved to be willing to do this, maybe the  other aliens realised that it was simply safer not   to communicate. Letting another race know that  you are there would simply place a target on   your back. After all, if you could both do this,  and they wouldn’t see it coming, could they really   trust you not to strike first? They could see  us as a risk that they are not willing to take.  Known as the Dark Forest theory, this possible  answer to the Fermi paradox says that the only   aliens out there are silent simply because they  don’t wish to be on the possible receiving end of   these kinds of planet-buster weapons. Like hunters  travelling cautiously through a dark forest,   they are all either quiet, or dead. They  have been subject to this selective pressure.  However, this is not the only plausible model of  behaviour that might still prevent us from seeing   aliens. The second option is simply indifference: With billions of years of history at play,   it might not be the case that we are  on technological parity with all the   other forms of life that might be out there.  Alien life might simply be so far beyond us,   they regard us as dispassionately as we might an  ant. They might not be talking to us because we   have nothing interesting to say. Why do you not  try to talk to the insects in your garden? The   gap is too great. You understand what they want  perfectly, and they have no hope of understanding   you. Communication would be frankly, pointless. That said, life is [probably] rare in the   universe. If they desire resources, and are that  far beyond us, they probably don’t need to mine   our planet specifically. We may have value  as a curiosity, something to be left alone to   flourish simply because they have decided we have  some value as a specimen in some kind of grand,   cosmic zoo. And as any zookeeper will tell  you, the closer you can get an enclosure to   look like an animal’s natural habitat,  the happier that animal normally is.  While they may not care about us, perhaps they  do not wish to alarm us by stepping into our   natural habitat. In fairness, this is a valid  line of reasoning. Humanity would likely find   it very distressing to learn that we are  in fact not at the top of the food-chain,   and that our very existence depends on the mild  indifference of a vastly superior alien race.  Of course, if this was true, we would need to  be careful. In my home, I was perfectly willing   to live and let live when I found ants in my  garden, but when ants came into my kitchen,   I quickly got out the ant-killer. We  would do well not to provoke them.  Both of these ideas about alien behaviour are  bleak, so you’ll be glad to know there is one   alternative to hatred and indifference. And  in fact, it may prove to be the most realistic   for higher-levels of society. Cooperation. Cooperation exists within nature. Not all   life competes. Packs of wolves can cooperate to  achieve their goals, protecting those within the   group even as they attack those outside it. There  are giant super-colonies of ants that do this,   working together and spanning entire countries,  each hill all considering themselves as part   of the same colony. Aggressive to  those outside of it, but supportive   and even self-sacrificing towards those within. There are advantages to this, as we humans are   well aware. We would not have gotten anywhere  if we hadn’t learned how to work together.   Knowledge pooled allows the creation of all kinds  of technology. Ironically, no-one really knows how   to build a computer from scratch. But there are  some people who know how to build a motherboard,   other people who know how to build a screen,  and other people that know how to mine the   resources. And all these people know that the  other people exists, and so can work together.  Historically speaking, there is compelling  evidence that as time has gone on, we humans   have become better at this kind of cooperative  thinking too. It used to be that groups of humans   were localised into small tribes, fighting other  small tribes. However, that’s elevated to small   kingdoms, then big ones, then whole countries  and alliances spanning across national borders.   Following that to its natural conclusion, at some  point, a nation may exist that all humans in the   world feel a part of. A unified planet Earth. But why is this a more likely outcome than   violence? Simply put, technology forces it. Not  only do we remove barriers to communication the   more advanced our communication gets, but as  our ability to destroy ourselves increases,   there simply isn’t an alternative except  learning how to get along. Other than total   annihilation, of course, but that’s a pretty  unappealing alternative... one would hope.  And so, it’s possible that aliens  developed the same way. If they did, how   might they behave towards the universe at large? While they might still be aggressive to outsiders   initially, ultimately, they may have attempted  to take this to the next level, embracing new   alien races as brothers and sisters, part of a  great galactic whole. It’s just a continuation   of the trend. With potentially millions of years  of history drilling the dangers of violence into   them, they may actually abhor fighting, and there  may be millions of aliens of many different races,   all cooperating peacefully under one banner. Then, why don’t we see them?  Well, perhaps they prefer to let us learn our own  historical lessons about the value of cooperation   before speaking to us. An aggressive race would  not benefit the galactic community as a whole, so   until we learn to get along, advanced alien races  might not want to share with us their ideas and   technology. Particularly if such toys could then  be used by us as weapons. Perhaps they believe   that we will either figure out how to get along,  or else we’ll wipe ourselves out. Either way,   in the meantime it is better they stay hands-off. As any parent will tell you, sometimes telling   a child something is not enough for a  lesson to sink in. Sometimes experience   is the only effective teacher. There might be a galactic community   out there, just waiting to welcome us. [So, what is the point I’ve been trying to   make with all this? I hope that over the course of  this exploration of alien life you’ve seen that,   while we’ve not found aliens definitively,  there is a high chance that alien life is   out there somewhere. As such, as long as humans  continue to exist, it’s not just possible that   it’ll find us or we’ll find it; it’s almost  certain. It could have already happened. It   could happen tomorrow, or a million years from  now. But whenever it happens, we will be forced   to make a choice about how we wish to proceed. We hope that alien life will treat us well. We   hope that we can share knowledge and discoveries,  and will come to enter into an era of peace,   prosperity, and mutual respect and cooperation.  However, if this exploration on alien life has   taught me anything, it’s that much of the hunt  for alien life starts by taking a look in the   mirror. Aliens could be a lot like us. And the  day may one day come when we are the ones flying   our spacecraft down into the atmosphere of an  alien world, while indigenous life forms look up   at us in awe and fear. So, what will we do then? Perhaps we would do well to think carefully about   that interaction. Because if in that moment  we decide as humanity to exploit and control,   or even exterminate, then more alien eyes could  be watching from the stars and judging us for our   actions. They may one day be assessing us, whether  we are a species they feel they can work with.   And they could be much more powerful than us. I believe that we will find living alien life one   day. But if we hope for a good outcome after first  contact, perhaps we need to be the kind of aliens   we wish to meet. Rather than choosing violence and  war, perhaps we need to consider cooperation and   altruism, no matter how difficult it might be to  do, or how strange our neighbours might be to us.  After all, we hope that they will do the same.] Thanks for watching. Are you as convinced as me that alien life is out there? Or are you almost as  certain that it’s not? Let me know in the comments below. A big thanks to my members and patrons  who help make videos like these possible. If you want to support the future production of Astrum  videos, and have your name added to this list, find the links in the description.  A big thanks for making it this far,   this video has seen hundreds of hours of work put  in from my Astrum team, and we’re really proud   with what we made. If you did like it, please  consider giving it a like and a share, it will   help me know you want more videos like these going  forward. All the best, and see you next time.

Channel: Astrum

Views: 1,782,078

Keywords: astrum, astronomy, astrobiology, astrophysics, space, space science, aliens, alien life, searching for alien life, life on other planets, biosignature, alien contact, drake equation, wow signal, UFO, extremophiles, goldilocks theory, exoplanets, milky way, goldilocks zone, NASA, ESA, Europa, DNA, kepler, kepler telescope, solar system, TESS, hubble, JWST, Webb, intelligent life, habitable zone, SETI, Search for Extraterrestrial Intelligence, Fermi Paradox, blackholes

Id: u6a6MCeDfac

Length: 111min 35sec (6695 seconds)

Published: Wed Feb 21 2024