Name: 美國宇航局的量子傳感器正在使用原子來測量地球的重力，下面是如何測量的。 (NASA’s Quantum Sensor Is Using Atoms To Measure Earth’s Gravity, Here’s How)
Uploaded: 2021-01-14T09:58:43.000Z
Duration: 3 min 37 s
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You know what’s really keeping me down?

Scientists noticed this too, and since 2000 have used satellites to map the Earth’s

Now they’ve developed a new instrument that uses quantum phenomena to deliver the most

You may be wondering what point there is to mapping the Earth’s gravity.

If you’ve taken high school physics you probably learned that Earth’s gravity pulls

things toward its center at a rate of 9.8 m/s2.

It turns out that while that’s a good enough approximation for the kinds of math problems

you’ll tackle in high school, it’s not entirely accurate.

The Earth’s gravitational pull isn’t uniform, it varies from one place to another, and it

What might cause the Earth’s gravity to change?

Well, gravity is directly related to mass, and the more massive an object is, the more

And what has a lot of mass that covers most of the Earth and can shift around?

There are other things that can contribute to a change in Earth’s gravity, but the

shifting mass of water is the biggest factor.

If a glacier melts or water gets trapped underground, its mass will be redistributed.

So measuring the minute changes in the gravitational field is a way to track what Earth’s water

is doing, and how the water cycle is being affected by climate change.

Previous NASA missions like GRACE and its successor GRACE-Follow On used twin satellites

The principle was one satellite would follow the other, and as they passed through fluctuations

in the gravitational field, they would get closer or farther apart.

Measuring the change in distance would tell scientists how the gravity over that part

But since the goal is always more accuracy and precision, NASA teamed up with the company

AOSense, Inc. to try an entirely different approach.

The new prototype sensor uses about 100 million cesium atoms sealed in a vacuum near absolute zero.

This keeps the atoms insulated from outside factors that may affect the measurements.

The only force pulling on these atoms is gravity.

Thanks to the bizarre nature of quantum physics, these atoms are coaxed into behaving like

Lasers can split and send these waves down different paths, and as they travel they interact

Finally the waves meet up again, and when they do, they form an interference pattern

where some sections of the waves have a higher amplitude while others have a lower amplitude.

By studying this interference pattern, the instrument can determine how gravity affected

While past atom-based instruments needed components the size of a room, the new sensor is small

That doesn’t mean it’s sacrificing sensitivity; during testing, the device reported different

gravitational measurements after the scientists came back from their lunch break... because

it was detecting the added mass from the food in their stomachs.

And once it’s up in space, the sensor will map the Earth’s gravity 10 times more precisely

than GRACE-Follow On, at four times the spatial resolution.

An instrument like this could have uses beyond Earth one day, like measuring the interiors

It could also be tuned to detect gravitational waves in new frequency ranges that we haven’t

Whatever it ends up being used for, the new instrument is an ingenious application of

scientific principles to solve a problem and a testament to just how clever scientists

Gravity mapping satellites can also help us probe the Earth's secrets, like what’s happening

If you liked this video, let us know down in the comments, and make sure to subscribe

Thanks for watching and I’ll see you next time.