Name: TED-ED】重力波とは何か？- アンバー・L・スチューバー (【TED-Ed】What are gravitational waves? - Amber L. Stuver)
Uploaded: 2021-01-14T07:04:44.000Z
Duration: 5 min 25 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

At about six o'clock in the morning on September 14, 2015,

scientists witnessed something no human had ever seen:

Both about 30 times as massive as our Sun,

they had been orbiting each other for millions of years.

they circled each other faster and faster.

Finally, they collided and merged into a single, even bigger, black hole.

A fraction of a second before their crash,

they sent a vibration across the universe at the speed of light.

a detector called the Laser Interferometer Gravitational Wave Observatory,

The signal only lasted a fifth of a second

and was the detector's first observation of gravitational waves.

the force that pulls any  two objects together.

That's the case for everything In the observable universe.

You're pulling on the Earth, the Moon, the Sun, and every single star,

The more mass something has, the stronger its gravitational pull.

The farther away the object, the lower its pull.

If every mass has an effect on every other mass in the universe,

then changes in gravity can tell us about what those objects are doing.

Fluctuations in the gravity coming from the universe

Gravitational waves move out from  what caused them,

getting smaller as they travel farther from their center.

When Einstein devised  his Theory of Relativity,

he imagined gravity as a curve in a surface called space-time.

A mass in space creates a depression in space-time,

and a ball rolling across a depression will curve

like it's being attracted  to the other mass.

the deeper the depression and the stronger the gravity.

When the mass making the depression moves, that sends out ripples in space-time.

What would a gravitational wave feel like?

If our bodies were sensitive enough to detect them,

we'd feel like we were  being stretched sideways

stretched up and down  while being compressed horizontally,

This back and forth would happen over and over

as the gravitational wave passed right through you.

But this happens on such a minute scale that we can't feel any of it.

So we've built detectors  that can feel it for us.

There are gravitational wave detectors spread across the world.

These L-shaped instruments have long arms,

whose exact length  is measured with lasers.

If the length changes, it could be because gravitational waves are stretching

Once the detectors feel  a gravitational wave,

scientists can extract information about the wave's source.

In a way, detectors like LIGO are big gravitational wave radios.

Radio waves are traveling all around you, but you can't feel them

It takes the right kind of  detector to extract the music.

LIGO detects a gravitational wave signal,

which scientists then study for data about the object that generated it.

They can derive information,  like its mass and the shape of its orbit.

We can also hear gravitational waves by playing their signals through speakers,

just like the music a radio extracts from radio waves.

So those two black holes colliding sounds like this.

Scientists call this  slide whistle-like noise a chirp,

and it's the signature of any two objects orbiting into each other.

The black hole collision  was just one example

Other high-energy astronomical events will leave gravitational echoes, too.

The collapse of a star before it explodes in a supernova,

Every time we create a new tool to look at space,

something that might revolutionize our understanding of the universe.

like that black holes collide more often than we ever expected.

It's impossible to say,  but exciting to imagine,

what revelations may now be propagating across space

towards our tiny blue planet and its new way of perceiving the universe.

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TED-ED】重力波とは何か？- アンバー・L・スチューバー (【TED-Ed】What are gravitational waves? - Amber L. Stuver)

massive

depression

stretch

reveal