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One of the grandest scientific tools ever made by mankind
is called an atom smasher.
And I mean literally grand.
The biggest one ever built,
the Large Hadron Collider, or LHC,
is a ring with a circumference of about 18 miles.
That's more than the entire length of Manhattan.
So what is an atom smasher?
It is a device that collides atomic nuclei together
at extremely high energy.
The most powerful one scientists have ever built
can heat matter to the hottest temperatures ever achieved,
temperatures last seen at a trillionth of second
after the universe began.
Our accelerators are full of engineering superlatives.
The beam-containing region of the LHC is a vacuum,
with lower pressure than what surrounds
the international space station,
and is 456 degrees Fahrenheit below zero,
colder than the temperature of deepest space.
A previous accelerator sitting in the LHC tunnel
holds the world record for velocity,
accelerating an electron to a speed so fast
that if it were to race a photon of light,
it would take about 14 minutes for the photon
to get a lead of about 10 feet.
If that doesn't impress you,
remember the photon is fastest thing in the universe,
it goes about 186,000 miles per second.
So how do these subatomic particle accelerators work?
Well, they use electric fields.
Electric fields make charged particles move in the same way
that gravity will pull a dropped baseball.
The force from the electric field
will pull a particle to make it move.
The speed will continue to increase
until the charged particle is moving incredibly fast.
A simple particle accelerator can be made
by hooking two parallel metal plates to a battery.
The charge from the battery moves
on to the two metal plates
and makes an electric field that pulls the particle along.
And that's it,
you got a particle accelerator.
The problem is that an accelerator built this way is very weak.
Building a modern accelerator like the LHC this way
would take over five trillion standard D-cell batteries.
So scientists use much stronger batteries
and put them one after another.
An earlier accelerator used this method
and was about a mile long
and was equivalent to 30 billion batteries.
However, to make an accelerator
that is equivalent to five trillion batteries
would require an accelerator 150 miles long.
Scientists needed another way.
While electric fields would make a particle go faster,
magnetic fields make them move in a circular path.
If you put an electric field along the circle,
you don't need to use miles of electric fields,
you can use a single electric field over and over again.
The beams go around the circle,
and each time they gain more energy.
So very high-energy accelerators consist of
a short region with accelerating electric fields,
combined with long series of magnets
that guide the particles in a circle.
The strength of the magnets
and the radius of the circular path
determines the maximum energy of the beam.
Once the beam is zooming along,
then the real fun begins,
the smashing.
The reason physicists want to get
those particles moving so fast
is so that they can slam them into one another.
These collisions can teach us
about the fundamental rules that govern matter,
but they'd be impossible without the feat of engineering
that is the particle accelerator.


【TED-Ed】How does an atom-smashing particle accelerator work? - Don Lincoln

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wikiHuang 2013 年 12 月 3 日 に公開
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