Name: 月の誕生 (Birth of the Moon)
Uploaded: 2021-01-14T04:58:44.000Z
Duration: 24 min 26 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：

上級受動態

The Earth, over its 4.5 billion year history, has been pummeled by asteroids.

Wrinkled and gouged by shifts in its crust.

Most traces of its distant past have long since been destroyed.

But there is a place where clues to the early history of our planet are still largely intact.

Scientists have been reconstructing its history by scouring its surface, mapping its mountains

and craters, and probing its interior regions.

What are they learning about our own planet's beginnings, by going back in time, to the

The space age made possible rockets with enough power to blast humans and their life support

More than three hundred manned space flights have shown that humans can live and explore

None of these missions have done more to shape our connection to the cosmos, and define who

were are, than the fabled flights of Apollo. But not for reasons you might think.

We sent astronauts to the moon as a symbol of confidence in the face of the great cold

war struggle. Many hoped that would lead to further journeys to Mars, and to an age of

Those goals proved too grand in the face of all the preoccupations, turbulence, and change

that would crash onto our own planetary shores.

Landing on the moon was a giant leap for mankind. But it's what the astronauts picked up from

the lunar surface that may turn out to be Apollo's greatest legacy.

When the astronauts of Apollo stepped out of their landing craft, they entered a world

draped in fine sticky dust, strewn with rocks, and pocked with craters.

They walked and rambled about, picking up rocks - 382 kilograms worth -- that they packed

Back in earth-bound labs, scientists went to work probing the rocks for clues to one

of the most vexing questions in all of science.

The answer promised to shed light on an even grander question. Where did Earth come from?

And how did it evolve into the planet we know today?

The apollo rocks have brought us closer to the answer, but basic mysteries still remain.

The moon orbits Earth at an average distance of 384,400 kilometers. It's relatively small,

with less than one percent the surface area, two percent the volume, and one percent the

With no atmosphere, temperatures range, in Celsius, from -233 degrees at night to 123

As the brightest object in the night sky, the moon has guided people for millennia...

by defining the rhythms of life and animating our myths.

The nature of the moon began to come into focus four centuries ago.

Galileo Galilei had heard of an instrument built by Dutch opticians capable of "seeing

Galileo, in many ways the first modern scientist, saw this new instrument as a tool to help

What was the nature of the heavens, and how did the world of men fit within it?

To some philosophers, the moon was a perfect, crystalline sphere of divine substance, free

Galileo, with his telescope, saw a more familiar reality.

He noted mountains and valleys on the moon, features like those of Earth.

Flash forward to the modern age of lunar studies. 1959 saw the first in a fleet of probes launched

by the Soviet Union and the United States to shoot closeup pictures, take readings,

We learned then just how different the moon is from Earth, with its cratered and dessicated

landscapes, and lack of a magnetic field. That intensified a debate about the moon's

The so-called fission theory, championed by George Howard Darwin, son of Charles Darwin,

held that the moon was once part of the Earth, cast off by the rapid spin of its young parent.

For proof, look no farther than the Pacific Ocean, a giant hole in the Earth's surface.

Then there's the capture theory, which holds that the moon was a wayward object that floated

through our solar system and was pulled into orbit by Earth's gravity.

A third idea came from the American astronomer Thomas Jefferson Jackson See, also known for

his attacks on Einstein's theories and for charges of plagerism that were leveled at

He suggested that the Moon formed near Earth and gradually fell under its gravitational

spell. In that case, the moon should be a mini-Earth, which we now know it's not.

The astronauts of Apollo lifted off on a series of missions to get a close up look at the

Because there's no atmosphere there, the astronauts entered landscapes that are nearly frozen

in time. They could scour the lunar surface for evidence of events going back almost to

Indeed, eons of impacts had opened up the Moon's interior, leaving a wealth of information

Scientists had already noticed that some large old craters were surrounded by concentric

rings. You can see one of the most pronounced examples in this image of the Mare Orientale,

captured recently by NASA's Lunar Reconnaissance Orbiter, or LRO. The colors show differences

The old view was that the impact had melted the rock below. A newer view held that the

impactor had actually splashed down on a molten surface.

That gave rise to the radical notion that, early in its history, the moon's surface was

When the astronauts arrived, they found relatively light rocks known as anorthosites. Their presence

suggested that heavier material had sunk toward the moon's interior, forcing lighter material

The rocks they brought back were found to be strikingly similar to those on Earth, in

part because they share forms of oxygen, called isotopes, that scientists regard as "blood

Then there was this. The moon appeared to be completely, utterly, dry, with no evidence

that water was ever present on its surface.

Not long after the last Apollo mission went into the history books, this initial evidence

coalesced into a radical new idea first presented in 1974 by the scientist and artist, William

His theory of the moon's formation is played out in this contemporary scenario.

Sharing an orbit with Earth was a Mars-sized body called Theia, named for a Titan in Greek

myth who gave birth to the moon goddess, Selene.

Its orbit became unstable and it headed in Earth's direction.

Theia hit at an oblique angle, causing the Earth to spin faster and debris from both

When the dust settled, the debris began to coalesced in Earth orbit, forming the Moon.