Name: 【TED-Ed】The search for other Earth-like planets - Olivier Guyon
Uploaded: 2015-01-25T14:19:59.000Z
Duration: 6 min 21 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

when I look at the sky with other people,

Adverbs of frequency

"What is your favorite place in the universe?

This is a very special place, even for an astronomer.

but there's only one that we know of in the whole universe

there is an amazing number of things happening,

some of them, you are hearing about it today.

is this great adventure in astronomy that is happening

It's impossible to imagine the number of possibilities,

So that's what I'm going to tell you about.

The first thing we learn is that size matters.

We can't have a planet that's too small or too big.

If we look at a planet that is too small,

and it actually is mostly composed of gas,

Here I have a picture that was taken by a spacecraft

and the surface, although it's rocky and quite familiar to us

At the opposite end, if a planet is too far from the star,

that are at the right distance from their star

you know, you might think, "Oh, this is really hard

It only happened once in our solar system."

and here's a video that I took actually from Hawaii,

a dark place where you can see a lot of stars,

the first thing you notice is that there are a lot of stars.

That is a tiny fraction of the stars in our galaxy.

If you count all the stars in our galaxy,

and you also count at five stars per second,

it would take you also more than 1,000 years

to count all of the galaxies in the universe.

there's a lot of opportunities for exoplanets.

There has to be a large number of exoplanets

So let's imagine that maybe only 1 in 100 stars

If you could visit one of those planets per second,

to actually visit all of them in our galaxy alone.

That's, I think, one second is not enough to study them.