Why do we watch the sky?
I like watching the sky.
You may like watching the sky or not, but why does humanity watch the skies?
It has been since a very long time ago that humanity started observing the sky,
and we still watch the skies now, and will watch the skies in the future.
Why do we watch the sky?
It makes one's neck hurt, have you ever stared above you for an hour?
Probably not,
if you have,
you will have gained an understanding to why neck discs occur.
So, humanity has been watching the skies since its birth.
Why?
This is a photograph of the magnificent night sky.
Does it have a purpose other than that of being pretty?
When we take tests, we make these little star marks
when we encounter something we don't know.
Why?
Why a star?
I tried to find the reason in these television drama series.
The one on the right is Queen Seondeok,
and the one on the left is The Moon That Embraced The Sun.
A common plot element in the two shows was this:
an eclipse.
Imagine that you're a commoner in the United Shilla Dynasty.
Suddenly, the sky darkens and after a bit,
it is dark around you.
Even more amazingly, sunlight is restored after a bit.
Observing this phenomenon without prior knowledge of its mechanism,
it scary would it be?
Think about it,
it becoming suddenly dark in a place without electric lights of any sorts.
You would shiver in such a situation.
So, our ancestor thought of the sky like this:
something unknown,
but something to be feared.
And something to be curious about.
Today, we know what the sky is,
but to the people of the past,
the sky was a domain of the Gods.
This is the reason why they worked to observe the stars in the first place,
because knowing the sky was knowing the Gods.
The person on the right is Plato
and the one of the left is Aristotle.
He is pointing at the sky and saying that the sky holds the ultimate truth.
Well, then how did they observe the sky?
With their eyes,
of course.
Likewise, our ancestors invested much effort
in attempting to glean the intentions of the Gods.
If you have a ten-thousand won bill,
please take it out.
Since you're mostly students,
most of you probably don't have any.
This is a honcheonui.
It was made as a tool to observe stars.
If the Gods is the one who created the world,
then the King is his son.
His duty is to glean the will of the gods and
pass it on to the people on matters such as agriculture.
Now, that was honcheon-ui,
but look at these little dots on the backside.
This is the Ch'on-Sang-Yul-Cha-Bun-Ya-Ji-Do.
It is the first star chart made in the Joseon dynasty, and it is rather well-made.
The milky way and the constellations are shown, and they are both ways
they used to express the sky in forms they could understand.
However, in my opinion,
the best sky had to offer were the wandering stars.
What does 'wander' mean?
It is your present state, students.
Lost.
A wandering star,
a planet.
Knowing how the planets move was the zenith of ancient astronomy.
The first person to know how the planets move was Ptolemy.
Ptolemy correctly predicted the movement of stellar objects,
including students and in the ancient world,
that was equal to understand the will of the gods.
Ptolemy said this:
the world is circular in its nature,
but the movement of that circle is quite complex.
Ptolemy's version of the gods' intentions massively
influenced Christianity and medieval worldview
by providing a background to the New Testaments.
This lasts for 1,500 years until a single man rebels against Ptolemy's worldview.
He devised a different system while observing the sky, as the ancients did.
He didn't like the original system devised by Ptolemy
because he felt that it was far too complicated for his taste.
So he started to observe the sky.
He thought surely God would have created simpler world.
So he attempted to come up with a simpler model using telescopes.
But he was thwarted when he was subjected to religious trials.
His thoughts, however, were vindicated by Kepler and Newton.
Newton was the one who proved that Ptolemy, the Bible,
and what the people before him had thought was wrong.
Personally, I think that he was one of the best scientists in the history of humankind, untouchable.
In Principia Mathematica,
he claimed that the laws of nature was one and the same in the heavens and on Earth.
That meant we could finally see the sky not as a domain of gods
but something that can be explained from Earth,
and science is closer to us now than ever.
I ask all of you now.
"Why do you watch the sky?"
Think about it.
"Why do we watch the skies?"
Because we're frustrated?
I watch the sky when frustrated, too.
I see interesting things.
We can relieve some of our frustrations with watching the sky,
and for some people, observing the sky is simple a way to relieve stress.
But there are people who watch the skies for more serious reasons.
Like this.
Now, what did I say the reason we watch the sky was?
To observe the will of the gods.
But even Newton could not say anything about this subject:
why the universe started,
why we are here,
and how the universe will change in the future.
The answer to this question began to emerge from the sky.
This is recent research data that earned its authors a Nobel Prize,
and it's very interesting.
The universe started with an explosion of sorts, called the Big Bang.
Usually, the shock waves from explosions get slower as they progress, right?
But observing the sky, humanity learned
that the expansion of the universe was accelerating.
An amazing fact.
Why is it accelerating?
We don't really know.
To know, we must continue observing space.
That's the scientific reason for observing the sky.
If this doesn't really impress you, there are other reasons.
This is something that recenetly happened in Russia.
This is a meteor strike;
we can see a very bright object falling from the sky.
It's leaving a trail, right?
It leaves something other than trails.
After the meteor fell, this happened.
This is footage from a nearby city.
A man and a woman are chatting amiably.
What happens to the man?
He fell due to the shockwave from the meteor strike.
If you're not impressed by this, then see this:
a steel door blown apart by the shockwave.
This incident hurt a lot of people.
What astronomers say is that these sort of incidents occur more often than you'd expect.
In the past, we didn't know about these incidents
because we didn't know they were meteor strikes.
This is the aftermath of a 1908 meteor strike in the Tunguska region in Russia,
caused by a meteorite only thirty-one meters in diameter.
It fell every tree in the twenty-four kilometer radius,
and melted down all the silverware.
It had twice the power of the bomb that fell in Hiroshima.
The fact is that the number of extremely dangerous asteroids is extremely large
and that they are a constant threat to us.
We have been made aware of this problem in the 21th century.
Why?
Because these things seem to be happening more and more often.
The ones marked in red are the ones that are a potential threat,
and we have started the exploration of these asteroids.
This probably delivers to you the reason we are observing the sky.
Perhaps it will be even more evident in the future, when you are adults.
The person on the right is James Cameron, the director famous for Titanic.
The one on the right is the former Google Vice President Larry Page,
the other Microsoft's Charles Simmons.
They created a company called Planetary Resources in 2012.
These people dream of a world like this.
These people's ideas are that although there are hazardous objects in outer space,
there are others that contain valuable mineral resources.
So these people have founded Planetary Resources and is trying to do business.
Personally, I'm not sure whether that's viable now,
but in 20, 30 years, space mining will certainly be a reality.
Another reason to observe space.
So, to relieve stress,
to satisfy our curiosity,
to find dangerous asteroids,
and to find resources.
Whatever the reason,
astronomy is a very meaningful activity.
It has already made us more bountiful
throughout the technology gained from space exploration.
Past and future, it will be a world of wonder.
Aristotle pointed to the ground,
and Plato pointed to the sky.
This is the world we will live in the future.
Thank you.
-TEDxYouth@YCHS-