Name: 物理学を変えた小さな実験 (The Tiny Experiment That Transformed Physics)
Uploaded: 2021-01-14T10:38:29.000Z
Duration: 6 min
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：

In 1956, a team of scientists was working

on an experiment that, at first glance, seemed

They had lined up a bunch of cobalt atoms

and were patiently waiting to see which direction

this doesn't seem like that big of a deal.

of this tiny, quiet experiment were groundbreaking.

They challenged one of our fundamental beliefs

and ultimately opened the door to some of

Here's why this little experiment turned out

The reason these results threw physicists for a loop

that the laws of physics shouldn't differentiate

Because, really, those directions just depend on your perspective.

Normally, you might say gravity pulls things down. But of course, we only call it down

because that's where gravity is pulling things.

But if you change your perspective and stand on your head, that doesn't mean gravity

is going to start pulling everything “down” toward your feet and toward the sky.

It's going to keep pulling stuff toward the Earth, no matter what direction you say

And if that sounds obvious… well, yeah.

For decades, parity symmetry was this reasonable, inarguable thing, one that physicists had

used countless times to predict — correctly! — the results of experiments.

It felt like common sense, and was a major assumption we relied on when figuring out

But by the 1950s, some researchers had begun to realize that maybe we shouldn't always

two researchers pointed out that parity symmetry had been tested, but not in all circumstances.

Like, it had never been tested in certain particles decays.

So three teams of researchers decided to tackle this question — and one of them was responsible

This group was headed by a researcher named Chien-Shiung Wu, and they studied a type of

When the cobalt decayed, it spat out electrons. And if parity symmetry were true, those electrons

should have come out about equally in all directions.

It should have happened like this mainly because these atoms are basically sitting still, and

you can more or less ignore gravity when it comes to particle physics.

So it's not like there's some force on this cobalt that would cause it to decay in

Instead, if you did happen to see more electrons coming out a certain way, it would mean you

If, say, more electrons came out the tops of the cobalt atoms rather than the bottoms,

it would mean that electrons — for some reason — had an easier time moving up than

And according to parity symmetry, there shouldn't be any difference between those directions.

After all, what's up from one perspective is down from another.

To test if all of this were true, Wu's team used a magnetic field to line up all their

cobalt in the same way. Then, they set up equipment to figure out how many electrons

Instead of seeing the particles come out in random directions, they found that the electrons

tended to come flying out in the opposite direction of the atom's spin.

So if you swapped left and right in this experiment — in other words, if you gave the atoms

clockwise spin instead of counter-clockwise, you would get a different result: You would

see the electrons fly out in a different direction.

These results suggested that there is some kind of fundamental difference between left

and right. The universe somehow has a sense of direction.

So, yeah, something was very wrong with parity symmetry: It didn't exist!

Wu's team published their findings in January 1957, as did two other teams that had done

But just because we had made this discovery didn't mean we were out of the woods.

We might have figured one thing out, but a gigantic can of physics-worms had also been

For one thing, researchers had to grapple with the fact that directions might not be

as arbitrary as they once thought. Because apparently, there's an innate left and right

But they also had to figure out why this happened. What was so special about cobalt that made

Well, as research went on, it turned out that the cobalt wasn't necessarily the problem.

It was something called the weak nuclear force, which is the force that governs how atoms

the weak force tends to act differently than the other fundamental forces of physics.

And figuring out why is one of the most ambitious projects in the field right now.

Because the weak force doesn't just treat left and right differently. It also treats

matter differently than antimatter, which we believe shouldn't happen.

And it even treats time differently than all the other forces — which is exactly as bizarre

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物理学を変えた小さな実験 (The Tiny Experiment That Transformed Physics)

stuff

perspective

specific

apparently