Name: 宇宙はどれだけ寒いのか？ (How Cold is Space?)
Uploaded: 2021-01-14T07:49:10.000Z
Duration: 3 min 5 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：

I'm Fraser Cain, the publisher of Universe
Today

If you could travel from world to world, from
star to star, out into the gulfs of intergalactic

space, you'd move away from the warmth of
the stars into the vast and cold depths of

Better pack a sweater, it's going to get cold.

Unlike your house, car, or swimming pool,
the vacuum of space has no temperature.

It's only when you put a thing in space, like
a rock, or an astronaut, that you can measure

Remember there are three ways that heat can
transfer:

Heat up one side of a metal bar, and the other
side will get hot too; that's conduction.

Circulating air can transfer heat from one
side of the room to another; that's convection.

But out in the vacuum of space, the only way
heat can transfer is radiation.

Photons of energy get absorbed by an object,
warming it up.

At the same time, photons are radiating away.

If the object is absorbing more photons than
it emits, it heats up.

And if it emits more photons than it absorbs,
it cools down.

There is a theoretical point at which you
can't extract any more energy from an object,

this minimum possible temperature is absolute
zero.

As we'll see in a second, you can never get
there.

Let's look close to home, in orbit around
the planet, at the International Space Station.

A piece of bare metal in space, under constant
sunlight can get as hot as two-hundred-sixty

This is dangerous to astronauts who have to
work outside the station.

If they need to handle bare metal, they wrap
it in special coatings or blankets to protect

And yet, in the shade, an object will cool
down to below minus-one-hundred (-100) degrees

Astronauts can experience vast differences
in temperature between the side facing the

Their spacesuits compensate for this using
heaters and cooling systems.

As you travel away from the Sun, the temperature
of an object in space plummets.

The surface temperature of Pluto can get as
low as minus-two-hundred-forty (-240) Celsius,

just thirty-three (33) degrees above absolute
zero.

Clouds of gas and dust between the stars within
our galaxy are only ten (10) to twenty (20)

And if you travel out far away from everything
in the Universe, you can never get lower than

a minimum of just two-point-seven (2.7) Kelvin
or minus-two-hundred-sevety-point-four-five

This is the temperature of the cosmic microwave
background radiation, which permeates the

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宇宙はどれだけ寒いのか？ (How Cold is Space?)

entire

constant

vast

experience