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  • Do you think there is life beyond the earth?

  • >> Yes, I do.

  • >> Why is that?

  • >> Scientifically been proven?

  • >> Are we alone?

  • Or is there life elsewhere in the universe?

  • This is a question humans have wondered about for millennia and one that people still have

  • pretty strong opinions about even though there isn't definitive evidence to answer the

  • question one way or the other.

  • >> Do you think that aliens have ever come to earth?

  • >> People say that there is like... there has been aliens and they implant...

  • I forget what it is called, but they have like made these fields and they have like

  • produced something on earth.

  • >> I think Area 51 could be possible and could be real.

  • >> You know how there is area 51 and all that kind of stuff.

  • I reckon they have got technology that they won't bring it out yet, you know.

  • >> Do you think it is technology that came from aliens?

  • >> Well, possibly.

  • They could have.

  • They could be sharing information and gaining technology from aliens.

  • >> On YouTube there seems to be some pretty good evidence about it, but I don't know.

  • >> You have seen some videos of aliens.

  • >> Yeah.

  • >> That looked convincing.

  • >> Kind of, yeah.

  • >> So {?} apparently were beings that came down from heaven according to the old Sumerian

  • texts.

  • >> The oil paintings and stuff and Sumeria.

  • >> I think people believe that aliens have visited us just because they are not aware

  • of how vast the universe really is.

  • I mean, what is an exoplanet?

  • How far is a light year?

  • These are the things you need to understand if you are to judge the probability that alien

  • life could come and visit us.

  • What is a galaxy?

  • >> Specifically I wouldn't know.

  • >> Is a galaxy something totally different, like another universe maybe?

  • >> A galaxy is a sun and a moon, isn't it?>>

  • So a galaxy is bigger than that.

  • >> Galaxies, hundreds of stars, blah, blah, blah.

  • >> In fact, hundreds of billions of stars.

  • >> Billions of stars.

  • >> Yeah, hundreds of billions.

  • >> Yeah, yeah.

  • >> What is a galaxy?

  • It is a collection of stars and gas that are held together in a gravitationally bound system.

  • Every point of light that you see here is a star.

  • When we say 200 billion stars, it is probably at least 200 billion stars.

  • The galaxy is 100,000 light years across.

  • So, you know, it is just... the distances are unimaginable.

  • One light year, don't forget, is 10 trillion kilometers.

  • >> What is a light year?

  • You are an engineer.

  • >> A light year is a thousand years, isn't it?>>

  • A light year is a thousand years?

  • >> Isn't it?

  • >> Oh, about 150 million years...

  • >> Would be a light year.

  • >> Would be a light year.

  • That is what I believe it would be.

  • >> It is a distance.

  • >> Is it a distance?

  • A light year?

  • >> Have you heard the term exoplanet?

  • >> No.

  • >> No.

  • Never.

  • >> Exoplanet.

  • No.

  • >> Like a planet that we are not aware?

  • >> Well, exo should be... could be short for something.

  • >> Extraterrestrial planet or extraterrestrial life, maybe.

  • >> Something outside our planet.

  • >> So an exoplanet is simply a planet that orbits a star other than the sun.

  • Exo just means external, outside, so outside our solar system.

  • So it is just a planet.

  • You know, you can...

  • >> How many have you found?>>

  • Me personally?

  • I have found six.

  • But overall we now know of over 800 planets that have been confirmed and another probably

  • 2000 planets that are waiting for information, but are pretty strong candidates.

  • So we don't see the planet directly, we see its impact on the start that it orbits.

  • We do it from the ground with a angle Australian telescope and we look for the wobble of the

  • star as the planet orbits it.

  • The planet goes around and the start moves backwards and forwards.

  • So if you can imagine seeing that from sort of along the line of sight a little bit more,

  • say like in this cartoon here, then you would see the star moving towards you and moving

  • away from you.

  • And so what we see here is the light from the star becoming ever so slightly bluer as

  • it moves towards us and ever so slightly redder as it moves away.

  • The big problem is that the main kind of planet you end up finding with this wobble technique,

  • because it is really reliant on the mass of the planet, basically like Jupiter, Saturn

  • and then we have started to get down to Neptune and Uranus.

  • >> To find smaller planets NASA launched Kepler, a one meter telescope with a 95 megapixel

  • camera.

  • Its mission is to observe 130,000 stars in our galaxy and look for dips in brightness

  • caused by planets passing in front of them.

  • >> So Kepler-62 is a solar system with five planets and the planets are very similar in

  • size to the terrestrial planets, the rocky planets in our own solar system.

  • They have a star in the middle and then you have three inner planets.

  • There is a green band which is this habitable zone, the goldilocks zone where you can expect

  • liquid water to exist on the surface of the planet.

  • And, in fact, there are two planets inside the habitable zone around Kepler-62.

  • If you are going to start looking for life around nearby stars, this is probably the

  • best one to start with.

  • >> Is there life beyond the earth?>>

  • Well we don't know for sure.

  • We can't say yes definitely.

  • But the probability is very high.

  • There are at least 200 billion stars in our galaxy.

  • We now know that on average there is at least one planet per star in our galaxy alone and

  • there are another 100 plus billion galaxies in the universe.

  • We also now know, thanks to the Kepler spacecraft, that at least one in six of those is earth

  • sized.

  • And so that is 33 billion potential earth sized planets.

  • Not all of them are going to be able to have life.

  • But the probability is getting pretty high already at this stage.

  • >> So there is no definitive evidence that alien life exists, but the sheer size of the

  • numbers suggest that they must be out there somewhere.

  • But with the vast distances across the universe, chances are it is going to be a long time

  • before we know for certain that we are not alone.

  • This video was created as part of a collaboration addressing 10 unanswered science questions.

  • So subscribe to Veritasium and then check out the other nine questions by clicking the

  • link.

  • >> Ok.

  • >> Is there more than one galaxy out there?

  • >> Yeah, probably.

  • >> How many would you say?

  • >> Oh, I couldn't tell you.

  • There is probably more than on my 10 fingers, I guess.

  • >> It is more than 100 billion.

  • >> A hundred billion?

  • Probably.

  • >> It is crazy.

  • >> Yeah.

Do you think there is life beyond the earth?

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外星人存在嗎? (Do Aliens Exist?)

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    林宜悉 發佈於 2021 年 01 月 14 日
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