Translator: tom carter
Reviewer: Bedirhan Cinar The universe contains about 100 billion galaxies. Each of those galaxies contains about 100 billion stars. Many of those stars have planets orbiting them. So how do we look for life in all that immensity? It’s like searching for a needle in trillions of haystacks. We might want to focus our search on planets that we know can support life as we know it — what we call habitable worlds. What do such planets look like? To answer that question, we don’t look out there. Instead, we look at ourselves. At Earth. Because this is the one planet in the universe that we know for certain is habitable. When we look at Earth from space, we see a blue, watery world. It’s no coincidence that three quarters of the surface is covered by oceans. Because of its unique chemical and physical properties, water is absolutely essential for all life as we know it. And so we get especially excited about other worlds on which water is abundant. Fortunately, water is very common in the universe. But life needs water in the form of liquid, not ice, and not vapor, and that’s a little bit less common. For a planet to have liquid water at its surface, three things are important. First, the planet needs to be large enough that the force of gravity keeps the water molecules from flying off into space. For example, Mars is smaller than Earth, and so has less gravity, and that’s one important reason that Mars has a very thin atmosphere, and no oceans at its surface. Second, the planet needs to have an atmosphere. Why? Because without an atmosphere, the planet is in a vacuum, and liquid water isn’t stable in a vacuum. For example, our moon has no atmosphere, and so if you spill some water on the moon, it will either boil away as vapor, or freeze solid to make ice. Without the pressure of an atmosphere, liquid water can’t survive. Third, the planet needs to be at the right distance from its star. Too close, and the surface temperature will exceed the boiling point of water, and oceans will turn to vapor. Too far, and the surface temperature will fall below the freezing point of water, causing the oceans to turn to ice. Fire or ice. For life as we know it, neither will suffice. You can imagine that the perfect zone where water stays liquid looks kind of like a belt around a star. We call that belt the habitable zone. So when we search for habitable worlds, we definitely want to look for planets in the habitable zones around their stars. Those regions are the best bets to find planets like Earth. But while habitable zones are a pretty good place to begin the search for planets with life, there are a couple of complications. First, a planet isn’t necessarily habitable just because it’s in the habitable zone. Consider the planet Venus in our solar system. If you were an alien astronomer, you’d think Venus is a pretty good bet for life. It’s the right size, it has an atmosphere, and it’s in the habitable zone of our sun. An alien astronomer might see it as Earth’s twin. But Venus is not habitable, at least not at its surface. Not by life as we know it. It’s too hot. That’s because Venus’ atmosphere is full of carbon dioxide, an important greenhouse gas. In fact, its atmosphere is almost entirely carbon dioxide, and is almost 100 times thicker than our own. As a result, the temperature on Venus is hot enough to melt lead, and the planet is dry as a bone. So finding planets of the right size and distance from their stars is only a beginning. We also want to know about the makeup of their atmospheres. The second complication emerges when we look a little more deeply at planet Earth. In the last 30 years, we’ve discovered microbes living in all sorts of extreme environments. We find them in fissures of rock miles beneath our feet, in boiling waters of the ocean floor, in acidic waters of thermal springs, and in cloud droplets miles above our heads. These so-called extremophiles aren’t rare. Some scientists estimate that the mass of microbes living deep underground equals the mass of all the life at Earth’s surface. These subterranean microbes don’t need oceans or sunshine. These discoveries suggest that Earth-like planets may be only the tip of the astrobiological iceberg. It’s possible that life might persist in aquifers beneath the surface of Mars. Microbes may thrive on Jupiter’s moon Europa, where liquid water ocean probably lies beneath the icy crust. Another ocean beneath the surface of Saturn’s moon Enceladus is the source of geysers erupting into space. Could these geysers be raining microbes? Could we fly through them to find out? And what about life as we don’t know it, using a liquid other than water? Maybe we are the crazy creatures living in an unusual and extreme environment. Maybe the real habitable zone is so large that there are billions of needles in those trillions of haystacks. Maybe in the big scheme of things, Earth is only one of many different kinds of habitable worlds. The only way to find out is to go out and explore.

100 thoughts on “A needle in countless haystacks: Finding habitable worlds – Ariel Anbar”

  1. …What. Uh. Let's see if i can explain this to your….simpler mind. O said the first goverment to invest more money in science then in war will be taken over, because if they can't protect themself, them are basically just free land for whichever goverment get's there first. for each comment you made here is my responce 1) i did, you didn't 2) so..did…i..? 3) 'warmongering'? is that even a term?? also, yes, i am and idiot who watches teded, because, y'know, that makes sence 4) yes it does, t

  2. the only reason wars are insanly common is because everyone has an army so they are smart enough to not start a war. 5) that is debatable, but either way, its a defensive offence, and an offensive defence, no army is purley offence or defence 6) yeah, they do, congradulations of pointnig out the one goverment that disproves my argument, while ignoring the dozens of others 7) again, i didn't really argue against that…so….yeah?

  3. 10 years ago I wanted to live in a mansion. Today I want to live in a solar Earth Home with grass growing on the roof and Nikola Teslas free energy.

    You Too?

  4. The relative sizes of Earth and Mars depicted at 1:30 is way off. The diameter of Mars is more than half that of Earth, not the 1/8th or 1/10th shown.

  5. They have maybe found an earth-like planet 'only' 42 light years away!

    space.com/18393-alien-planet-super-earth-habitable-hd-40307g.html

  6. This exactly what I am thinking. The quote of Picard in First Contact must be our goal. To live for better ourselves and humanity. (still 400 more years to go, though. Too bad I'll be dead by then)

  7. As if the 6-day-timeframe was the only unbelievable thing in the christian creation-myth….
    "it's always been that way" is a better explanation, than the religious ones….
    ๐Ÿ˜‰

  8. I recommend you to read on "basic income guarantee".
    A very nice concept that is based on the state providing all basic needs for every citizen, transforming the need to work for your own survival to the ability to work for the change you want to see in the world.

    Switzerland is planing on introducing it in the next years. We can only hope that they prove it can work, so the doubt in the other countries can make room for a better, fairer system of economy.

  9. Heres the thing, god is a theory and because we dont know it becomes something called faith. But the habitable zone of a planet is not a theory, its fact. Im sorry but u really are quite stupid.

  10. That would never work. Civilizations have tried it before, but they went into chaos and were nearly wiped out because of it. The reason is that people aren't perfect. Some people are greedy, selfish, lazy, shy, etc. Some are even mentally disabled, which can also conflict with this. The reason economy works is because it makes people have to work for what they want. If you can find a way around every possible situation, it would not only be revolutionary, but would change the world forever.

  11. Woah, Mars isn't THAT much smaller. They should say that it's less massive. It doesn't have a dense iron core like earth to give it the mass it needs despite it's actual size.

  12. We're a greedy bunch of mammals. I don't think it's a good idea to take away money at a time when only a select few of the educated (in a massive global population) can recognize the importance of working together on a massive scale for the betterment of the world and us. Perhaps there will be a time in the future, but not now, not today.

    It sounds like a lovely idea, though I expect impractical once put into effect.

  13. Hi there, I'm glad to have a discussion! Discussions = informed, balanced understandings!

    I'd suggest that there is a major difference between a population of 300 or so (referencing your example, from Wiki) and a population of 7 billion. I suppose I should rephrase my statement. To quote Men in Black,

    "A person is smart. People are dumb, panicky dangerous animals…"

    I look forward to your response! ๐Ÿ™‚

  14. Even if we could travel the speed of light, we still couldn't travel any further than our own Solar System. We could travel to the closest of all solar systems, which is 4.2 light years away, but that will take 4.2 years to travel there with light speed travel. The closest star that actually has a planet at all, is 10.5 LY away. Basically, young scientists would have to travel to that planet in 10.5 years, stay for maybe just a year, and return back in 10.5 years. Round trip is 22 years. Isadnow

  15. that didnt make sense. 1st of all, everyone wants freedom (i dont know about equality). so if some one is "rebelling" against the government then i m sure that something is going wrong. coz no one wants to start a war and fight a war where their life depends on it

  16. Mars diameter is about half of Earth's, which makes its volume much much smaller than Earth's (volume is three dimensional, diameter is two dimensional, and the volume would be about 12.5% of Earth's if it was exactly half diameter). Yes, it is sensibly smaller anyway you look at it.

  17. In many ways, we're already there. Technologically. But our society is so dependent on capitalism that we simply can't have a system where some things are just "provided", even the things that are already post-scarcity. That is, things that can be infinitely duplicated in various ways. We have ways of providing all the books in the world to every single person living. Free knowledge for everyone. But nobody would make money on that, so we call it piracy instead and waste money fighting it.

  18. you never know we might pass the speed of light one day. yes modern physics says that is impossible but who's to know what will happen in the next few years there might be a day when a scientist discovers something that goes pass this speed something we can't see at the moment because we lack the technology. Leonardo Da Vinci believed we could make machines that could fly but this idea went against the laws of physics of his time and he was unable to come up with anything that worked.

  19. it took a few hundred years till 2 people who lived in a time that made many improvements to physics to figure out how to make a flying machine and since then these machines have been improving more and more. so today physics says it is impossible to go past the speed of light but in the future people will be looking at use in the same way we look at the people who said it was impossible to fly

  20. People ar etoo greedy and lazy for that. If the masses are provided with what they need without being forced to work for it, they will just gladly take it and live in luxury. That is the sad reality of humans and why Earth is not ready for Star Trek.

  21. Sadly its not the currency that needs to go its the way of thinking that needs to change. Stop focussing on greed and see that there are more important things to be achieved than personal wealth

  22. 1 million + 6 zero's = 1 trillion. i wouldnt suggest counting it out but i can imagine it. im sure youve listened to Lennon also (not his best work)

  23. Are you sure about that? Why do you think gas prices go up every few years? Because there is a limited amount of fossil fuels. Why do you think we use money at all? There is not enough resources to go around.

  24. Isn't it possible to have life that doesn't depend on water? so Venus might have liquid lead as its "water" instead

  25. Theres no life out there. There is nobody out there. THIS is the only habitable world. Doesnt mean we must stop doing research. Science is still awesome, without depending on hope for another life out there.

  26. "The only way to find out is to go out and explore."

    Yeah, but then you tell us we'll never travel faster than light, which means we'll never travel interstellar distancesย in anything remotely approaching aย practical timeframe.

  27. 1:30 That is NOT the size of Mars in comparison to Earth. I hope nobody got the wrong idea that Mars is that tiny. Mars is just over half the diameter of Earth.

  28. Yes. Maybe aliens like be transformers, eat steel and pee oil. Or maybe just like alien eat air and birth in something.

  29. wow one of the least accurate ted edโ€™s everโ€”donโ€™t automatically believe one source, this is a bunch of nonsense

  30. Theory: What if there was life on Veanus and then some microbe discovered how to use oxygen for breathing (like us) then it started multiplying and basically did what the microbe did.

  31. We can't find alien life because scientist thought the evolution theory is true.

  32. I like the art form of this video

    Can you do a video on Amnesia, Dimensia, Alzheimers, Cancer or HIV? I like medical science videos. Thanks.

  33. Different conditions could lead to evolution of different life forms… Earth had abundant water and oxygen so life used it.. Maybe in other planets, life would thrive in carbon dioxide..

  34. ๐ŸŒŽ๐ŸŒ๐ŸŒ๐ŸŒŽ๐ŸŒ๐ŸŒ๐ŸŒŽ๐ŸŒ๐ŸŒ๐ŸŒŽ๐ŸŒ๐ŸŒ๐ŸŒŽ๐ŸŒ๐ŸŒ๐ŸŒŽ๐ŸŒ๐ŸŒ

  35. There could have been microbial life on Venus several billion years ago when it likely had water oceans

  36. As the video suggests the middle most planet earth in the habitable zone harbours life.This might suggests that middle most planet in other habitable zones of other stars have possibility of sustaining life forms.

  37. we are never leaving this world. nothing wrong with trying & always dreaming. From the looks of it not a chance. @Mitch Kazaka

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