Name: 【TED】Natasha Hurley-Walker: How radio telescopes show us unseen galaxies (How radio telescopes show us unseen galaxies | Natasha Hurley-Walker)
Uploaded: 2017-10-11T22:11:18.000Z
Duration: 15 min 26 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...

I first heard these words when I was just six years old,

I wanted to see everything that the universe had to offer.

And those dreams, those words, they took me on a journey,

to do a PhD and finally to become a professional astronomer.

I wouldn't be piloting a starship anytime soon.

But I also learned that the universe is strange, wonderful and vast,

actually too vast to be explored by spaceship.

And so I turned my attention to astronomy, to using telescopes.

Now, I show you before you an image of the night sky.

And all of these stars are part of our local galaxy, the Milky Way.

Now, if you were to go to a darker part of the sky,

you might see the center of our Milky Way galaxy

spread out before you, hundreds of billions of stars.

And again, this is just a local corner of our universe.

You can see there's a sort of strange dark dust across it.

Just with our own eyes, we can explore our little corner of the universe.

You can use wonderful telescopes like the Hubble Space Telescope.

Now, astronomers have put together this image.

and they've spent hundreds of hours observing just a tiny patch of the sky

no larger than your thumbnail held at arm's length.

and we know that there must be hundreds of millions, billions of galaxies

some like our own and some very different.

So you think, OK, well, I can continue this journey.

This is easy. I can just use a very powerful telescope

It's actually really missing out if we just do that.

Now, that's because everything I've talked about so far

is just using the visible spectrum, just the thing that your eyes can see,

a tiny, tiny slice of what the universe has to offer us.

Now, there's also two very important problems with using visible light.

Not only are we missing out on all the other processes

Now, the first is that dust that I mentioned earlier.

The dust stops the visible light from getting to us.

So as we look deeper into the universe, we see less light.

But there's a really strange problem with using visible light

in order to try and explore the universe.

Say you're standing on a corner, a busy street corner.

The ambulance driver did not change the siren just to mess with you.

The sound waves, as the ambulance approached,

As the ambulance receded, the sound waves were stretched,

their light waves are compressed and they appear bluer.

their light waves are stretched, and they appear redder.

So we call these effects blueshift and redshift.

so everything is moving away from everything else,

and that means everything appears to be red.

And oddly enough, as you look more deeply into the universe,

more distant objects are moving away further and faster,

So if I come back to the Hubble Deep Field

and we were to continue to peer deeply into the universe

and that presents something of a problem.

Subtitles ListPlay Video

【TED】Natasha Hurley-Walker: How radio telescopes show us unseen galaxies (How radio telescopes show us unseen galaxies | Natasha Hurley-Walker)

entire

material

eventually

technique