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C1 ScienceOct 15, 2026

How and why do we measure time? #atomicclocks #time #science #short #sciencefacts #trending

時間はどのように、そしてなぜ測定するのでしょうか？ #atomicclocks #time #science #short #sciencefacts #trending

The Royal Institution15 videos Open on YouTube

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Translation

Atomic clocks and atomic timekeeping is the basis of our global time scale as it stands now, and has been for many decades.
原子時計と原子による時刻保持は、現在の世界的な時間スケールの基礎であり、何十年にもわたってそうあり続けています。
And the reason we do we use atoms in the first place is that the Earth, which was used as the regulator for time and timekeeping for centuries, is not really a good regulator.
そもそも原子を使う理由は、何世紀にもわたって時や時刻保持の基準として使われてきた地球が、実はあまり良い基準ではないからです。
It is constantly slowing down and wobbling.
地球は常に減速し、ふらついているのです。
So essentially, we needed something that was better than that.
つまり本質的に、それよりも優れたものが必要だったのです。
And we have a we have an atom which has a nucleus, and you have electron shells around it.
そして原子があり、原子核があって、その周りに電子殻があります。
Now the electrons only jump from one level to the next if they get exactly the right amount of energy.
電子は、ちょうどぴったりのエネルギーを受け取ったときにだけ、ある準位から次の準位へ飛び移ります。
And we use this you could say property of the atom and this very very specific frequency that's needed to cause an electron to jump between one shell to the next.
そしてこの原子の性質とも言えるもの、電子をある殻から次の殻へ飛び移らせるのに必要なこの非常に非常に特定の周波数を利用します。
to make a clock, and the way we do that is we target or irradiate this atom or atoms with a frequency.
時計を作るために、その方法は、この原子または原子群に周波数を照射することです。
In the case of cesium, it's in the microwave, so in the gigahertz range, with approximately the right frequency to cause that jump.
セシウムの場合、それはマイクロ波、つまりギガヘルツ帯で、その飛び移りを起こすのにほぼ正しい周波数です。
And if we get that frequency just right, we see the jump, and the the atoms are excited.
そしてその周波数がちょうど合えば、飛び移りが見られ、原子は励起されます。
But if we don't, nothing happens.
しかし、そうでなければ、何も起こりません。
So when we get that right, we can then use the the signal that we put in as essentially the frequency of the clock and lock that using a closed loop control system to continuously get to that frequency.
ですから、それが正しく合ったとき、入力した信号を本質的に時計の周波数として利用し、閉ループ制御システムでロックして、その周波数に連続的に合わせ続けることができるのです。
Now that in itself is really a frequency standard.
それ自体は本当に周波数標準なのです。
So it's generating a frequency; it's not a clock.
つまり、周波数を生成しているのであって、時計ではないのです。
However, because we know that that nine point two gigacycles of That particular frequency defines what is the SI second.
しかし、その特定の周波数の92億サイクルがSI秒を定義すると分かっているからです。
So we start counting cycles, and when we get to 9.2 gigahertz cycles, we can say that's one second, and we can generate a pulse.
そこでサイクルを数え始め、92億サイクルに達したら、それが1秒だと言えて、パルスを生成できるのです。

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