ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: This giant laser can simulate a planet’s core

This building contains a truly gigantic laser.

The National Ignition Facility...

is about a hundred feet tall...

as big as three football fields...

And packed to the brim with tubes and wires that look the bowels of a spaceship.

It makes sense that one of the Star Trek movies shot a few scenes there.

"Do you know what this is?!" "It’s a warp core." Actually, it’s NIF’s “target chamber”.

The laser beam starts over here in this room as a tiny pulse of light about as weak as a regular laser pointer.

But then it bounces around the building getting amplified over and over until it’s a quadrillion times stronger.

And then, it’s focused onto a single point.

So... what do you do with a laser this big?

Well, right now, scientists are using it to study the secret inner lives of planets.

It started in second grade, when I was younger my teacher showed me pictures of Jupiter.

I remember in class vividly that she said that no one knows what's on the inside of the planet.

I was like oh well, maybe I could be the one that figures that out!

Now, Tanja Kovecivic is a planetary scientist at UC Berkeley and she and her colleagues are asking broader questions.

Why are we here?

How did our solar system form?

How planets form, how the moon formed and especially now with the search for exoplanets...

How do we find a habitable planet?

What does that look like?

How did earth or anything else go from a molten ball to something that we can all now survive on.

The features that define Earth: its rich atmosphere...

its vast oceans...

its magnetic field...

its solid but shifting crust...

these features that fostered life as we know it they were shaped by unseen processes hidden deep within the globe.

If we want to understand the engines that sculpted Earth, or Jupiter or the thousands of recently discovered worlds we need to look under the hood.

But that’s not easy.

On the surface of the Earth, we exist under very unique conditions.

We’re here, in this tiny range of relatively low temperatures and low pressures.

But if we drill deeper.

Most of the matter, even within Earth, exists under extreme temperatures and pressures.

A trip into Jupiter is even more intense.

At these depths, the laws of physics predict that familiar substances will start to act...

pretty weird.

When you're subjecting matter to intense pressure, you're squishing it right?

So you're actually causing the atoms to re-orient themselves.

When you heat it up, you're also causing vibration.

You're just kind of irritating this thing into being a whole new material sometimes.

For a long time, physicists have theorized that deep within a planet iron can flow like water.

And those swirling currents generate Earth’s magnetic field.

Also in theory, sodium can turn completely transparent.

Water can form a hot black ice that conducts electricity.

And hydrogen condenses into a metallic liquid.

To understand the strange chemistry and geology and physics happening inside planets we have to study substances we’d never encounter on the surface.

And it’s not like we can just go down there in an elevator.

The closest humans have gotten to the Earth’s core is the Kola Superdeep Borehole in Northwest Russia: 7.6 miles straight down.

But that’s less than 0.2% of the way to the center of the Earth.

A probe we shot into Jupiter, stopped transmitting when it was just 0.1% of the way to that planet’s core.

Our instruments can’t survive in the very temperatures and pressures we want to study.

But scientists have come up with a few different ways to get around this problem.

The first is to create detailed computer models.

So we have oxygen or little white hydrogens.

All the little brown ones are going to magnesium.

You can look at it in 3D.

Oh it rotates!

Yeah. Tanja programmed this collection of 300 some atoms.

It’s a tiny microcosm of a barrier between rock and ice inside a planet.

Her model simulates how each atom and every last one of its electrons will act and interact.

It’s a simulation of just a few billionths of a second.

But it takes one of the most powerful supercomputers in the world a bit longer than that to complete.

138 hours. OK gotcha.

Little by little, painstaking simulations like these are starting to paint a picture of what’s happening inside planets.

And they’re helping guide experiments in the real world.

We don't have that much time and facilities that we can sort of go out and sample all kinds of worlds material that all the conditions.

And so they say hey, maybe you should look in this direction.

There could be something interesting there.

So we have all these questions.

We have all these theories.

But we want to confirm that with “real world experiments”.

Yeah. What does that look like?

That looks like a few different things: the first one of those would be a diamond anvil cell.

You take very high purity diamonds.

You think of the diamond in the diamond wedding band.

You basically compress a sample within just the between the two.

This setup can create some of the temperatures and pressures seen inside earth.

And if you want to go further, you can use...

The gas gun method.

With a gas gun you're launching basically a plate of metal into the sample that you care about.

Temperature and pressure spike on impact.

That’s pretty good.

But sometimes, you want to peer even deeper into a giant planet.

The third, and kind of most extreme of those would be laser compression.

And for that, you need a truly gigantic laser.

NIF wasn’t built to explore other worlds — not at all - it was built to save our own.

In the 1970s, scientists were trying to harness nuclear fusion: the reaction that powers our sun.

It would be cheap, it would be clean, it would be...

the ultimate energy.

The dream was (and still is) to hit a tiny fuel pellet with powerful lasers and create a miniature star here on earth "We need to build a laser 1000 times more powerful than any laser presently available." Scientists have spent decades designing and building larger and larger lasers.

Lawrence Livermore National Laboratory built NIF.

And the University of Rochester built their giant OMEGA laser system.

These facilities are still plugging away at understanding nuclear fusion but they've also become important tools for astrophysicists and material scientists.

Researchers at the Center for Matters at Atomic Pressures use OMEGA and NIF to recreate the interiors of planets and stars and create revolutionary states of matter.

Instead of loading up a target chamber with pellets of fusion fuel they put in a sample, like a tiny speck of iron.

We have to place it inside of this little apparatus which you can actually hold in the palm of your hand.

It looks like this.

And it happens to be the same semicircular shape as UC Berkeley’s Greek Theater.

Which is where I interviewed Mercedes.

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So if we imagine that we're standing inside of the apparatus we could imagine this would be the sample not much thicker than a hair.

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—Teeny-tiny. —Yeah.

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So our sample is mounted right on the front of that little hole in the center there.

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Which, in the Greek Theater, would be at the doors at the back of the stage.

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Then we would actually have another layer of material right behind it.

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We call that layer the ablator.

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Our laser is going to come in from this direction...

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they're going to hit the back surface of this ablator.

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That's going to cause a kind of a mini localized explosion...

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Which drives the compression waves towards our sample.

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The temperature and pressure within the sample skyrockets.

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You'd have to have a comet colliding at 20-30,000 miles an hour to start reaching the conditions that NIF can do on a daily basis.

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The experiment only lasts about 30 billionths of a second but that’s long enough to take an X-ray snapshot.

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The x-rays bounce off the sample...

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and leave patterns on the walls of the device that scientists can later decode.

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The x-rays are telling us what's going on inside the sample, you know, is it melting?

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Does it stay solid?

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Is it changing the arrangement of the atoms itself?

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Using NIF, Rick saw that iron will be a liquid under pressures found in giant rocky planets much bigger than Earth – and so planets like that could also have magnetic fields.

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Other high pressure experiments have shown that sodium does become clear.

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And water can form hot, black ice.

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And hydrogen does turn metallic.

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Scientists think there’s an immense ocean of this form of hydrogen beneath Jupiter’s clouds and its currents generate Jupiter’s magnetic field.

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All these phases of matter that we had predicted, potentially existed now we're able to theoretically prove through models and through experimentation that they do exist.

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By peering at a handful of atoms a little crumb of matter - for just a tiny fraction of a second scientists are unraveling the billion year histories of massive planets millions of miles away.

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ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: This giant laser can simulate a planet’s core

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