叶军的原子钟一百五十亿年不差一秒，他拿下了被称为诺奖风向标的沃尔夫物理学奖

Your phone shows the time.

You probably think the time on your phone is never off by even a second.

So where does your phone's time come from?

Ultimately, it comes from a very special kind of clock, called an atomic clock.

Atomic clocks are extremely accurate — far more accurate than the clock in your home.

The clock in your home might be off by more than ten seconds a month.

But the atomic clock we're talking about today won't be off by a single second in fifteen billion years.

How long is fifteen billion years?

The universe we live in, from its beginning to now, is roughly that long.

The universe means all the stars in the sky, the sun, and our Earth — everything put together.

So if this clock had started running on the day the universe began, it would still be off by less than a second today.

The scientist who made this clock is called Jun Ye.

A scientist is someone who studies questions and looks for answers.

Jun Ye is from Shanghai; he was born there in 1967.

He studied physics at Shanghai Jiao Tong University.

物理 is physics — it studies how the world moves.

Later, Jun Ye went to America and finished his PhD in Colorado in 1997.

He still works in Colorado today, and has kept working on atomic clocks.

On October 1st, Jun Ye won a very big prize.

The prize is called the 沃尔夫奖 — in English, the Wolf Prize.

There are several Wolf Prizes; Jun Ye won the one for physics.

Many people call the Wolf Prize 'the stop before the Nobel Prize.'

诺贝尔奖 is the Nobel Prize — you've surely heard of it.

Why do they say that?

Look at these two numbers: so far, seventy-two people have won the Wolf Prize in physics.

Of those seventy-two, twenty-six later went on to win a Nobel Prize.

That's about one in every three.

This year's Nobel Prize in physics will be announced on October 6th.

Just five days later.

Jun Ye is the second Chinese person to win the Wolf Prize in physics.

The first was Chien-Shiung Wu, in 1978.

Chien-Shiung Wu was a woman scientist who also worked in America.

From 1978 to today, forty-eight years passed before there was a second.

So what's the use of such an accurate clock?

The first use is something you use every day.

The map on your phone relies on atomic clocks to know where you are.

If the clock is off by a tiny bit, your position on the map will be off by a long way.

The second use is even more interesting.

You may not know this, but whether time runs fast or slow depends on how high up you are.

Einstein said this more than a hundred years ago.

Up high, time runs a little faster; down low, time runs a little slower.

So when you're standing, time runs a tiny bit faster for your head than for your feet.

That tiny bit is so small that ordinary clocks can't detect it at all.

But in 2022, Jun Ye's atomic clock detected it.

The top and the bottom were only one millimeter apart.

One millimeter is about a tenth of the thickness of your phone — very, very short.

Just one millimeter apart, and Jun Ye's clock found that time ran a little faster at the top.

What Einstein said holds true even across a single millimeter.

A scientist born in Shanghai made a clock that won't be off by a second in fifteen billion years.

On October 6th, let's see whether the Nobel Prize goes to him too.

Think about it: if your head were a tiny bit older than your feet, would that feel strange to you?