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

Do you have a clock at home?

You look at the clock, and you know what time it is.

Is your clock any good?

Lots of clocks are off by more than ten seconds a month.

A second is very, very short.

A minute has sixty seconds.

What does it mean to be off by one second?

It's eight o'clock, but your clock says: eight o'clock and one second.

Your clock is off by one second.

Today, let's talk about a very, very good clock.

This clock won't be off by even one second in fifteen billion years.

How long is fifteen billion years?

Look: a hundred years is already long.

Fifteen billion years is much, much, much longer than a hundred years.

Who made this clock?

The man who made this clock is called Jun Ye.

Jun Ye is Chinese; he's from Shanghai.

Jun Ye was born in Shanghai in 1967.

Shanghai is in China, and it's very, very big.

Jun Ye studied at a university in Shanghai.

Then he went to America.

Now he works in America, and his job is making clocks.

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

What is a prize?

You do your work very well, and lots of people say: you're amazing, this is yours.

That thing is called a prize.

Jun Ye's prize is called the 沃尔夫奖.

沃尔夫奖 is the Wolf Prize.

There are several Wolf Prizes; Jun Ye's is the one for physics.

物理 is physics.

There's another prize that lots of people know, called the 诺贝尔奖.

诺贝尔奖 is the Nobel Prize.

What's the connection between the Wolf Prize and the Nobel Prize?

Listen: up to today, seventy-two people have won the Wolf Prize in physics.

Of those seventy-two people, twenty-six later won a Nobel Prize too.

So lots of people say: if you've won the Wolf Prize, you might win the Nobel too.

Who will win this year's Nobel Prize?

On October 6th, we'll find out.

How many Chinese people won the Wolf Prize before Jun Ye?

The first was in 1978.

That person was called Chien-Shiung Wu.

Chien-Shiung Wu was a woman professor; she was Chinese too, and also worked in America.

Forty-eight years later, Jun Ye is the second.

Why is Jun Ye's clock so good?

It's so good that it can see something very, very tiny.

You're standing here.

Your head is up top, and your feet are down below.

Did you know?

Time doesn't run at the same speed for your head and your feet.

Up top, your head is a tiny bit faster.

Down below, your feet are a tiny bit slower.

This tiny bit is far too small; your clock can't see it.

But Jun Ye's clock can.

Two clocks, one higher and one lower, with only a tiny difference in height.

Jun Ye's clock says: the higher clock is a tiny bit faster.

Your head is a tiny bit faster than your feet.

Interesting, isn't it?

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

The man who made it is Jun Ye from Shanghai.

On October 6th, let's see whether he wins the Nobel Prize too.

Think about it: how many seconds is the clock in your home off by each month?