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TEDYouth 2013

Henry Lin: What we can learn from galaxies far, far away

Filmed:

In a fun, exciting talk, teenager Henry Lin looks at something unexpected in the sky: distant galaxy clusters. By studying the properties of the universe's largest pieces, says the Intel Science Fair award winner, we can learn quite a lot about scientific mysteries in our own world and galaxy.

- Student scientist
At 17, Henry Lin won an Intel Foundation Young Scientist Award for his mathematical models of distant galaxy clusters. Full bio

Here are some images of clusters of galaxies.
00:12
They're exactly what they sound like.
00:16
They are these huge collections of galaxies,
00:18
bound together by their mutual gravity.
00:20
So most of the points that you see on the screen
00:22
are not individual stars,
00:25
but collections of stars, or galaxies.
00:28
Now, by showing you some of these images,
00:30
I hope that you will quickly see that
00:33
galaxy clusters are these beautiful objects,
00:35
but more than that,
00:37
I think galaxy clusters are mysterious,
00:39
they are surprising,
00:41
and they're useful.
00:43
Useful as the universe's most massive laboratories.
00:44
And as laboratories, to describe galaxy clusters
00:48
is to describe the experiments
00:51
that you can do with them.
00:53
And I think there are four major types,
00:55
and the first type that I want to describe
00:57
is probing the very big.
01:00
So, how big?
01:02
Well, here is an image of a particular galaxy cluster.
01:04
It is so massive that the light passing through it
01:08
is being bent, it's being distorted
01:11
by the extreme gravity of this cluster.
01:14
And, in fact, if you look very carefully
01:16
you'll be able to see rings around this cluster.
01:18
Now, to give you a number,
01:21
this particular galaxy cluster
01:22
has a mass of over one million billion suns.
01:24
It's just mind-boggling how
massive these systems can get.
01:28
But more than their mass,
01:31
they have this additional feature.
01:33
They are essentially isolated systems,
01:35
so if we like, we can think of them
01:37
as a scaled-down version of the entire universe.
01:39
And many of the questions that we might have
01:43
about the universe at large scales,
01:45
such as, how does gravity work?
01:47
might be answered by studying these systems.
01:49
So that was very big.
01:52
The second things is very hot.
01:53
Okay, if I take an image of a galaxy cluster,
01:55
and I subtract away all of the starlight,
01:58
what I'm left with is this big, blue blob.
02:01
This is in false color.
02:03
It's actually X-ray light that we're seeing.
02:05
And the question is, if it's not galaxies,
02:07
what is emitting this light?
02:10
The answer is hot gas,
02:12
million-degree gas --
02:14
in fact, it's plasma.
02:16
And the reason why it's so hot
02:17
goes back to the previous slide.
02:19
The extreme gravity of these systems
02:21
is accelerating particles of gas to great speeds,
02:24
and great speeds means great temperatures.
02:27
So this is the main idea,
02:29
but science is a rough draft.
02:31
There are many basic properties about this plasma
02:33
that still confuse us,
02:36
still puzzle us,
02:38
and still push our understanding
02:39
of the physics of the very hot.
02:41
Third thing: probing the very small.
02:43
Now, to explain this, I need to tell you
02:47
a very disturbing fact.
02:49
Most of the universe's matter
02:51
is not made up of atoms.
02:54
You were lied to.
02:56
Most of it is made up of something
very, very mysterious,
02:58
which we call dark matter.
03:01
Dark matter is something that
doesn't like to interact very much,
03:03
except through gravity,
03:07
and of course we would like to learn more about it.
03:09
If you're a particle physicist,
03:10
you want to know what happens
when we smash things together.
03:12
And dark matter is no exception.
03:14
Well, how do we do this?
03:16
To answer that question,
03:18
I'm going to have to ask another one,
03:19
which is, what happens when galaxy clusters collide?
03:21
Here is an image.
03:24
Since galaxy clusters are representative
03:26
slices of the universe, scaled-down versions.
03:29
They are mostly made up of dark matter,
03:33
and that's what you see in this bluish purple.
03:35
The red represents the hot gas,
03:37
and, of course, you can see many galaxies.
03:39
What's happened is a particle accelerator
03:41
at a huge, huge scale.
03:43
And this is very important,
03:45
because what it means is that very, very small
03:47
effects that might be difficult to detect in the lab,
03:49
might be compounded and compounded
03:52
into something that we could
possibly observe in nature.
03:54
So, it's very funny.
03:58
The reason why galaxy clusters
03:59
can teach us about dark matter,
04:01
the reason why galaxy clusters
04:03
can teach us about the physics of the very small,
04:05
is precisely because they are so very big.
04:07
Fourth thing: the physics of the very strange.
04:10
Certainly what I've said so far is crazy.
04:14
Okay, if there's anything stranger
04:17
I think it has to be dark energy.
04:20
If I throw a ball into the air,
04:22
I expect it to go up.
04:24
What I don't expect is that it go up
04:26
at an ever-increasing rate.
04:28
Similarly, cosmologists understand why
04:30
the universe is expanding.
04:33
They don't understand why it's expanding
04:34
at an ever-increasing rate.
04:36
They give the cause of this
04:38
accelerated expansion a name,
04:40
and they call it dark energy.
04:42
And, again, we want to learn more about it.
04:44
So, one particular question that we have is,
04:46
how does dark energy affect the universe
04:49
at the largest scales?
04:51
Depending on how strong it is,
04:53
maybe structure forms faster or slower.
04:54
Well, the problem with the large-scale structure
04:58
of the universe is that it's horribly complicated.
05:00
Here is a computer simulation.
05:03
And we need a way to simplify it.
05:05
Well, I like to think about this using an analogy.
05:07
If I want to understand the sinking of the Titanic,
05:11
the most important thing to do
05:13
is not to model the little positions
05:15
of every single little piece of the boat that broke off.
05:17
The most important thing to do is
05:20
to track the two biggest parts.
05:21
Similarly, I can learn a lot about the universe
05:23
at the largest scales
05:27
by tracking its biggest pieces
05:29
and those biggest pieces are clusters of galaxies.
05:30
So, as I come to a close,
05:34
you might feel slightly cheated.
05:37
I mean, I began by talking about
05:39
how galaxy clusters are useful,
05:42
and I've given some reasons,
05:44
but what is their use really?
05:45
Well, to answer this,
05:48
I want to give you a quote by Henry Ford
05:50
when he was asked about cars.
05:52
He had this to say:
05:54
"If I had asked people what they wanted,
05:55
they would have said faster horses."
05:58
Today, we as a society are faced
06:00
with many, many difficult problems.
06:03
And the solutions to these
problems are not obvious.
06:05
They are not faster horses.
06:09
They will require an enormous amount of
06:11
scientific ingenuity.
06:13
So, yes, we need to focus,
06:15
yes, we need to concentrate,
06:17
but we also need to remember that
06:18
innovation, ingenuity, inspiration --
06:20
these things come
06:23
when we broaden our field of vision
06:25
when we step back
06:26
when we zoom out.
06:28
And I can't think of a better way to do this than
06:29
by studying the universe around us. Thanks.
06:31
(Applause)
06:34

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About the speaker:

Henry Lin - Student scientist
At 17, Henry Lin won an Intel Foundation Young Scientist Award for his mathematical models of distant galaxy clusters.

Why you should listen

Henry Lin studies the very hot, very large and very strange -- that is, distant galaxy clusters. (Obviously.) Lin, who matriculated at Harvard University in the fall of 2013, thinks we can learn a lot about astrophysics by studying these giant celestial bodies. In early 2013 he won the Intel Foundation Young Scientist Award, the second-highest award at the Intel Science Fair, for his models of far-away galaxies. Lin is a graduate of Caddo Magnet High School in Shreveport, Louisiana.

More profile about the speaker
Henry Lin | Speaker | TED.com