Is This Why We Haven’t Found Alien Civilizations? | STELLAR

Is This Why We Haven’t Found Alien Civilizations? | STELLAR

Thank you to Draper and its Hack The Moon
initiative for supporting PBS Digital Studios. People have always dreamed of ways to be closer
to the stars. That’s what brought us here to Mauna Kea
in Hawaii. From this spot, we can stand nearer to the
sky, and see farther and clearer than almost anywhere else on Earth to wonder what and perhaps even who is out there. On Earth and in space, advanced telescopes
have stared for weeks even months into patches of sky and they’ve seen that other stars are surrounded
by planets of their own. At least a planet for every star. But what sort of planets are they? Astronomers have learned that our galaxy is
home to many kinds of planet/sun systems: from hot Jupiters to warm Neptunes, even super-Earths
of lava and diamond. These planets have expanded our view of where
life may be possible. But what drives astronomers to study them is to
find an answer that ultimate question: Is life abundant or are we unique? We’re standing in front of two of the most
sensitive, precise, and advanced ground telescopes ever constructed – the Keck Observatory. These instruments, and others that are being
designed, will allow scientists, for the first time, to characterize these far-off exoplanets,
to paint a detailed picture of their sizes, their orbits, even the chemicals in their
atmospheres, to understand where and how life might exist. Combined with knowledge from biology, physics,
and chemistry, we’re learning a great deal about how life and planets coevolve. We call it the science of astrobiology. Decades before we discovered the first
exoplanet, one scientist asked what we’d need to know in order to know whether another intelligent, technological civilization is, or was, or might one day be out there. That scientist was a young radio astronomer
named Frank Drake. He gave us a way to estimate the number of technological civilizations that are out there. N* tells us how often stars are born. It’s now known around one star per year born in the Milky Way, so we put a “1” there. f sub p is the fraction of stars with planets, which we now believe is 1, or at least 1 planet
for every star. Solar systems are the rule, not the exception. n sub p is the estimate of how many planets
orbit their stars at distances that allow for liquid water. We think is many as 1 in 5 planets sit in
these so-called “habitable zones”, or a value for n sub p of 0.2. In all, there may be as many as 40 billion
Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarfs in
the Milky Way. Now so far, our discoveries have filled nearly
half of the equation and expanded what is possible, but the Drake Equation is still incomplete. We don’t yet know how many host life (f
sub L) if any of that life is intelligent (f sub i) if it’s built a civilization
(f sub c), or how long that civilization might last so that we might find it. When astronomers are searching for maybe that
ultimate question of is life abundant or is it unique, what sorts of actual experiments
are they doing here to try and get at that question? Well the first thing you have to do is to
find the planets, right? And so that’s one of the things that Keck does
wonderfully well and many other telescope facilities, is we find them, either by transiting
when the planet goes in front of its star and dips the light down a bit, or through
the radial velocity method. Or through direct imaging with Keck adaptive
optics. So you’ve gotta find the planets, that’s
step one. Step two is are the planets at a distance
from their host star where water could be liquid on the surface? And then you want to know something about
the atmosphere of that planet. And that’s when things get really, really
hard. Because to be able to measure the atmosphere
of that planet you either have to have an extremely precise measurement of the star
before and during these eclipses, or you have to be able to measure the light that’s bouncing
off of that planet, and measure the chemistry in its atmosphere. And both of those things require extremely
precise instrumentation, very, very large telescopes, and just sheer force of will to
keep in the game. This telescope is amazing. Each of its 36 hexagonal mirror segments is
polished so smooth, if they were the size of the Earth, their largest imperfections
would only be three feet high. And twice every second, these segment’s
position are adjusted by an accuracy of 4 nanometers or 1/25,000th of a human hair. The next phase of exoplanet exploration
will be the search for biosignatures, these are telltale chemical signs like oxygen or methane in those
far-away atmospheres. These will be detectable from future space
telescopes and giant ground-based observatories planned on Earth. Then comes the big question: How many of them actually show hints of life
in their atmosphere? And are we being fooled? Just because you see ozone and methane and
carbon dioxide and water vapor in the atmosphere, is that a slam dunk for life? Not necessarily. We want to be able to do that, and then we
want to get at the essence of your question which is, if we look at a hundred planets,
and they’re all in the habitable zone, and we see nothing, then that’s told you something
statistically. If you look at a hundred planets, and fifty
of them or sixty of them have something, that tells you something really amazing about the
universe. So we need to have the power and the precision
to go after as many planets as possible, but at the same time just by exploring Earth,
we’re finding out that life is thriving in places where we thought impossible. So when you combine those two things and when
you think about solar systems which are radically unlike ours, the mind really starts to stretch
out and think that life could really be abundant out there in the universe and we should stop
being so Earth-centric sometimes when we think about that. But if the cosmos is so vast, and full of
so many places where life and intelligence may arise, then where are they? Perhaps there’s some “Great Filter” which prevents
other life-bearing planets from reaching our level of civilization. Maybe the appearance of even simple life on
habitable worlds is so unlikely that biology itself is the Great Filter. Or while life is common, maybe the emergence
of even simple intelligence is rare. But there is another option: maybe the Great
Filter lies in technological civilizations themselves. In the millennia since human civilization
started, our most important discovery is the one that’s enabled us to burn 100 million
years of stored energy to power our technological growth: fossil fuels. As a rule, it takes energy to build and grow
a technological civilization and harnessing massive amounts of energy has some impact
on a civilization’s environment. Over there is the place where we measure the
planet’s atmospheric carbon dioxide concentration. It’s just crossed 415 parts per million
for the first time since humans came into existence. Now as evidenced by the measurements taken
there, human activities are changing our planet’s climate, and those changes may have dire consequences for us. We’re not the first life form to change
the climate on the Earth. Billions of years ago, ancient microbes breathed
the first oxygen into the atmosphere, making possible life as we know it today. But the result of that shift was the death
of massive amounts of Earth’s early life, to whom oxygen was poisonous. It’s an environmental shift that completely
changed the course of how life unfolded on this planet. Are we now about to shift the course of life
on Earth again? Is self-destruction in the process of harnessing
energy an inherent risk in the development of all civilizations, human or alien? Whether or not we are ever able to find another
technological civilization might depend on the question of if civilizations can harness
energy without destroying their own future. So, as we build ourselves up to be closer
to the stars, we should at least ask: will the same be true of us? Whether there’s life outside of our solar
system is one of the biggest questions we’ve ever asked, but so is whether there’s life
in the solar system. Check it out the next episode with Dianna from
Physics Girl. Thanks you to Draper and its Hack the Moon initiative
for supporting PBS Digital Studios. You know the story of the astronauts who landed on the moon. Now you can log on to to discover the story of the male and female engineers who guided them there and back safely. Hack the Moon chronicles the engineers and technologies behind the Apollo missions. Brought to you by Draper the site is full of images and videos and stories about the people who hacked the moon. PBS is bringing you the Universe with the
Summer of Space, which includes six incredible, new science and history shows airing on PBS and streaming
on and the PBS video app. Watch it all on

100 thoughts on “Is This Why We Haven’t Found Alien Civilizations? | STELLAR

  1. Note: Mauna Kea is sacred land in Hawaii. For more, see this story from PBS NewsHour:

  2. Why just look for planets that are simular to ours that our thought of life can only live on, maybe the real reason these scientists can't find other life is due to them keeping in their little life reasons box,
    Who's to say for a fact another alien life doesn't breath nitrogen or another gas or even need water.
    Aliens are reported to wear a special suit just like humans do when we go to space, why be ignorant and say they need what we need to live..

  3. Has it occurred to anyone that we here on earth may be the special case? The evidence of UFOs we are seeing in such increasing abundance may well represent the larger, true reality. We could be heading for a great awakening that may not be to our liking.

  4. Just watched. They are forgetting something. Havent they considered that when observing these planets they are actually looking at the earlier stage of these planets. They are so far away that before their image reach us had billions of years already passed by. 🤔

  5. What if another civilization just didnt have an abundance of energy lying around like we have (e.g., fossil fuels)?

    Say their planet never underwent as many mass extinctions as ours, thus never developed as rich a wealth of potential energy available as we did, making electronics an extremely difficult feat?

  6. Drakes Equasion is all fine and dandy, But it was after all, Pure Guess Work, And I’m afraid was miles and miles slightly Of a bit, because instead of hundreds of thousands of habitable planets their is only one and it’s called EARTH

  7. What an imagination no proofs just ifs and buts candies and nuts theory presented as fact then conclusion based on what-ifs PBS supports this make-believe science, ? Tax money well spent good job PBS, I Presume this make-believe is shown to grade school children as fact

  8. I think most likely the great filter was behind us. We know so little about how life forms after all. In the equation in the video, we filter out planets that don't have water. But perhaps we need to filter out the lack of many other conditions too. It sounds plausible that a complex mechanism like life might require much rarer and specific conditions than just the presence of liquid water. Sure, life is found in diverse conditions on earth, but that can be explained as the evolution of life after the first life forms started reproducing. The inception of life might still require very specific conditions.

    On the other hand, I find the climate change argument unlikely. Although climate change can be devastating and wipe out millions of human lives, it seems extremely unlikely it will make us go extinct. Life and humans are known for our ability to adapt after all. Even if the climate becomes very hostile in 100 years or so,

    I see no reason why we wouldn't work to overcome it and invent ways of terraforming our planet back. Especially with the strong incentive which we will have then.

  9. 1:05 'ultimate question'

    Me : oh that lollipop video u made

    Link – (if u didn't understand the joke)

  10. If our singular planet is any evidence for the formation and function of life in general, I'd say the great filter is intelligence. I bet the universe is teeming with microscopic, purely reactionary life. Maybe plants and basic animals have come into being elsewhere in the vastness.
    But of all the millions and billions of forms of life on this planet in its history, only the humanoids achieved intelligence, and only humans were able to adapt and survive utilizing that intelligence.

    The butterfly effect has monumental impact on the formation of life, I think. If those first humans didn't ever stand erect, then would any still have gone on to evolve into us?
    If humanoids didn't come into being on the plains of Africa, would they have ever come into being as we know it?
    If dinosaurs hadn't been wiped out, would mammals have survived at all?

    Our planet had millions and millions of years of unintelligent life before a SINGLE drop of intelligence shined through… what's to say that there aren't millions of planets out there with millions of forms of unintelligent life?
    Maybe we'll find something very closely related to dinosaurs. Maybe we'll just find algae on the surface of water.
    But I am willing to bet everything on Earth that it is not the only one with ANY life on it.

  11. I think we should focus more on not killing our planet rather than looking for new life across the infinite universe. Yes it’s important to study the universe but our planet should be more important

  12. Sir I have a doubt like the earth as 2 half like if one side as night and other side will be morning right sir the nearest people can travel between Knight and day in few hours right sir please clear my doubt

  13. I designed and printed a tee shirt that shows the Drake equation, and beneath it, the slogan: "What the L, Humanity?" It's one of my favourite shirts, as it gets people asking questions…

  14. This is a topic I find so interesting (which could explain my passion for sci-fi, especially involving aliens), but I'm no scientist, and I'm so glad to hear that guy saying not to be so earth-centric when we think about life somewhere else. I've always found it weird to hear scientists saying that life on said planet is impossible because the conditions are not good for earth-like life, but didn't life forms here adapt to their environnement? There could be other forms of life, maybe so different from what we know we might not be able to perceive it. I think it'd be better to say "life as we know it is not possible on this planet" rather than concluding life is impossible there.

  15. They are wise clever and way too advance than us. Humans have no idea at all about how advance these Alien civilizations are. They have no time for us. W Percival from New Zealand 🇳🇿 Gardenia Band 🌼

  16. This just made me sad because all I can picture is tons of planets with intelligent life killing their planets over and over again across thousands of solar systems before any real progress in space travel can happen. It seems so likely now that I watch this video that I am surprised I never considered it previously.

  17. Why, in these types of discussions, is it never considered that the amount of time for EM signals to reach us — never mind the light indicating planetary chemistry reaching telescopes — is ENORMOUS? A potential civilization's light cone probably hasn't reached us yet. The Milky Way is ~100,000 light-years across, think about that. Also, the generations of stars which spewed heavier elements aren't very old, so we have to allow for that.

  18. What makes people think that life MUST need water to live, or MUST need oxygen, for all we know, there might be organisms that are made of diamonds, living on gas giants.

  19. Have none of y'all seen the fighter jet UFO footage?

  20. Do not underestimate the power of airtight greenhouses. With them you could easily support a sizable population(at least several million) through an asteroid strike, a thermonuclear war, and a climate catastrophe. Remember, nuclear winter does not just blot out the sun but simply reduces available light.

  21. in my mind why should we look for what we think and believe are the characteristics of life cause that only applies to earth but what if (bare with me) other planets adapted to living and being alive in other ways breathing things other then oxygen living without water and using something else instead of emitting co2 they let out another chemical (idk i always thought like that lowkey tho pero like high key really hope we dont discover other life yet cause thats a lil spoopy)

  22. I put forth that there are multiple Great Filters. I bet it could be put into an equation, similar to Drakes'. EXAMPLE: I assume life similar to our own here on Earth. a. Star long term stability. b. Planet formation in the correct stable location. c. Chemical composition of the planet, such as carbon, iron, manganese, water, etc. d. Energy stability over a long term. e. Planet suitability for life over an unknown long time period. Unknown due to our sample of two, Earth and Venus. f. Luck? Planetary destruction events. g. Is Human Equivalent Intelligence with a machine civilization a given? The dinosaurs were around a very long time. Yet there is no evidence discovered indicating that they did. I point to the absence of any evidence on the Moon, not just here on Earth. h. Self Annihilation. Multiple ways and many of them could be simultaneous. Brief recap: Ozone destruction before recognizing the danger. Suffocation due to changing your atmosphere. Poisoning of your environment. Destruction of your root food sources that allow what you eat to grow. I didn't even have to mention Nuclear or Climate Change to get this far. I'm certain that their are other possibilities that I am forgetting or unaware of. I will stop here with the following one I worry about the most. i. Civilization Fossilization. I put forth China and Egypt and Japan and the Pre-Columbian societies. All of them achieved a high level of civilization and then froze. Froze until total destruction, forced change. I will give an example of this. Korea: First printing press and a very good and easy to learn writing system called Hangul. These technologies, which could have made Korea the first among east Eurasian societies, were suppressed by the elites. They feared a loss of control and a de-stabilization of their hierarchical structure. This is not uncommon. The Romans had all the pieces to begin a true industrial civilization that was not as based on slaves. Yet they never did. Just some observations and evaluations of mine own. Have a good day all.

  23. I think the Fermi's Paradox question is actually fairly straightforward. It comes down to three things. 1: Space, 2: Economics, and 3: Time. 1: Space is big. It seems there is no breaking the speed of light or even getting very close to it without consuming a massive amount of energy. 2: The economics of generating that much energy for most technologically advanced organisms would be obscenely high. Why spend money on a massive space program when you could make life better on your home planet for less. 3: While planet and star formation levels are quite high people forget that it wasn't until 3.5 billion years into Earth's history that simple life began. Life will end on this planet in less than 2 billion years due to increased solar activity as the Sun consumes more of its hydrogen fuel and begins to expand. The Earth will be consumed by the sun somewhere around its 13 billionth birthday. Life will have been on Earth only for 3 billion years of that time. Life on the planet is short. The cosmos (radiation, space, extra-planar bodies) destory life. Sooner or later time runs out for everyone and even whole planetary ecosystems.

    I am not suggesting that we shouldn't try to reach the stars or look for life. I am merely suggesting that the odds of us ever finding a technologically advanced civilization is remote.

  24. I don't even get why is this a question. How about the fact that the Universe is sooo big and finding life out there when we can't even make it to Mars is impossible? How about the fact that there are more galaxies that we can't ever observe in a lifetime therefore the odds of finding life are smaller than finding a ring you lost in the ocean. Earth is a very lucky planet and the fact that we exist is probably very rare in the universe but thinking we can find life with the technology we have is really crazy.

  25. Amazing Revelations and LIVE Initiation Happening Now!

    Missed the live? You can watch on YouTube:

    #Gravity #Levitation #nithyanandasanga

  26. What if the closest aliens in the galaxy are still microbes and just waiting for that mass extinction to kickstart life like us?

  27. If we ever came into contact with extra terrestrials we wouldn't be able to communicate with them. We can't even figure out what smart animals are saying to each other outside of very very basic reactions.

  28. Especially for astronomy videos, I wish they would put a note on all the artist renderings (like the exoplanet drawings). Not only for accuracy's sake, showing just how few astronomy targets we could directly image adds to the sense of awe.

  29. If you think climate change was at all able to kill humanity than you are so unbelievable stupid that you shouldn't be allowed to have a show on the internet. Maybe (I don't think so) climate change is able to cause major problems. It will of course never be able to erradicate mankind. D'oh!

  30. The answer to the fermi paradox lies in biological intelligence creating AI and AI shutting itself off for not seeing any meaning in existing.

  31. What if one possible Great Filter is based on whether or not a particular form of intelligent life evolved from a "high competition" environment? Perhaps there are planets where the sustaining resources are so abundant (and the life form so efficient), competition isn't necessary. Evolution would likely move far slower, but in terms of universal time, inconsequential. Intelligent life from "low competition" environments would, in this theory, have little need for the concepts of competition and greed. Perhaps THOSE are the forms of life that ultimately make it.

  32. Okay, so, I have to ask about this 'at least one planet per star' value in the drake formula. Ambient cosmic metalicity provides for a concentration average of four earth masses of terrestrial planetary bodies per stellar system. So, shouldn't that value in the drake equation be 4? When you consider that Earth is a high-mass outlier among the terrestrial planets in the solar system, shouldn't 4 be thought of as a minimum since other typical stars will likely have those metals formed into more than four planets?

  33. Or exoplanets are so far away that you see past images due too limit of speed of light, so you can't see anything because of that

  34. We know that universe is dividing into three zones, namely inner rim, middle rim and outer rim. Every celestial bodies within the middle rim have almost half of their energy in kinetic energy and another half in universal gravitational potential energy. Life forms tend to sprout and sustain within the entire middle rim due to its "moderated" energy level. On the other hand, kinetic energy is too high in inner rim but kinetic energy is too low in outer rim. Therefore inner rim and outer rim can't really sustain life forms. In order to sustain life forms, the need of a close star like the sun is a must. Of course, the exo-planet itself must also be alive where heat is dissipated from within its core. The fact that we know now that all dense and very dense radioisotopes will decay to form 30s lightest elements which are the crucial ingredients for the formation of life forms and their sustainability.If earth can give birth to all life forms including humankind, a almost similar conditions in other exo-planets would also able to replicate the same formation of life forms like the one on earth. Life forms are everywhere within the middle rim. The crucial questions are whether those aliens have already developed extreme advance technology that enable them to travel intergalactic or not that matter.  We now no  longer quest whether life forms or humankind too would exist on other exo-planets or not. Because we know life forms are everywhere and the existence of humankind is also rather common within the universe.  
    If you are interested in real discoveries, I would recommend you to read my book, The Unification Theory – Volume One and you will be amazed with lots of new, interesting discoveries. In God I trust.

  35. I think the biggest reason that we haven't found ET is that they are just too far away. It's 20,000 light years to the edge of the Milky Way. 50,000 light years to the nearest galaxy. That means a signal coming from the edge of the Milky Way would take 20,000 years to get hear. So the alien race may have gone extinct or evolved. If they did pick up a signal determined to be alien in origin, so what? We couldn't contact them or visit them or they us. I think looking for ET with a radio telescope might be a waste of time.

  36. I love the information but why do you have to speak like that? It's really annoying to listen to even tho I'm creaming for the information… speak like a normal human and it'll be alot more interesting and easy to follow, thanks x

  37. Wow! I took Astronomy 101 with John O’Meara at Saint Michaels College in my junior year! He is truly a fantastic professor, and this is coming from someone who has struggled greatly with the traditional American school system for my entire student career. I have to give him serious credit for jump-starting my now-huge interest in space and astronomy. Since taking his class, I’ve always been proud to tell anyone who will listen that one my professors works with the Keck telescopes! He presented probably the best lecture I’ve ever been to in my life on the last day of class about aliens and the Drake Equation. I remember the entire classroom standing up and applauding afterwards. Thank you for more than you know, professor O’Meara.

  38. I see myself as an atheist despite being raised as catholic. I sometimes wonder if science is some type of objective religion. Something that helps us keep moving forward and distracts from the fact that we are so alone in the galaxy.

  39. Certainly global warming and human CO2 release is a thing. But fifty some million years ago, the world was far warmer than even the direst predictions for the next century or two, and apparently lush, maybe even substantially moreso than now. Humans could very well kill themselves off, but the current anthropogenic warming is unlikely to in the next centuries. There will be consequences, but extinction is an overstatement. (It's even possible that renewables, storage technology and long distance low loss grids will drop in cost below the fossil fuel way of making and distributing electricity, ditto electric vehicles, and the problem will take care of itself. Or solutions will present over the next century. Concern, yes, but trendy over the top rhetoric undercuts otherwise sober science.)

  40. there is life everywhere. the universe is alive. we just don't yet understand life. or the many forms it can take. we don't even understand our own lives or the many forms we take or our connection to the universe and those realms many of us don't believe exist. if we ever began to see this we will live and do things much different than we do today. much of the stuff we make to do things is not needed to do those things. when we learn the truth of what we can do with only our thoughts and start to use that most of our technology with be worthless we do nothing with it but risk our destruction. and it only disconnects us from the universe and takes us farther away from our own inner powers.

  41. You chicken littles need to find another calamity myth to perpetuate. This global warming bill is getting old. Cow is a boon for plant growth and that produces more oxygen. R ed searches rdd at the University of Vancouver ffg found that the polar bear population has never been so high so they fired her. Libtards pushing communism.

  42. My personal opinion is that its the Energy Barrier..if it where not for the dinosaurs going extinct and leaving us "fossil Fuel" i think our civilisation might not be what it is today..The Energy requirements to build a civilisation like we have today is near to impossible without the Dinosaurs going extinct and leaving us the gift of fossil fuels..
    Think if all we had was the Coal and such to burn without Dinosaurs fossil fuel..our civilisation would not be the size it is and not even sure it would of survived wars and such…

  43. I read this somewhere and it says : Aliens might have Checked our review and it shows just one star.!…Not worthy at all for an alien dude.

  44. Just watch the Documentary "A funny thing happened on the way to the moon"……. You guys are Imposters and will be stopped soon enough.

  45. I've got a Garmin smartwatch that gives me my global position but do I really exist or am I just a Pawn in a chess game between Google/Microsoft/IBM etc:.

  46. Take a look around your own planet buddy!
    Who the hell do you think built all of the most ancient megalithic sites and ruins?

  47. Is there life in the universe?
    We have to take the age of the universe, the possible number of galaxies and the stars in them, each planet orbiting those stars, black holes, supernovae, asteroid impacts, germs, etc, the vastness between the stars and galaxies, and the difference in time from what we see when looking. Is there life in the universe? We don't know. But that's why scientists continue to search

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