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  • We're all familiar with gravity as "the reason objects fall", but there's much, much more

  • to gravity than that.

  • Gravity is a long range attractive force between all objects with mass:

  • it's what keeps us from falling off the earth, it's what keeps the earth in orbit around

  • the sun, and it's what caused the sun itself to form four and a half billion years ago!

  • It's amazing to think that every massive object attracts every other in the universe

  • that means that your dog, the earth, and a black hole in the Andromeda galaxy 2.5

  • million light years away are all gravitationally attracted to you,

  • and you to them.

  • In the 17th century, Isaac Newton discovered that the strength of the gravitational force

  • decreases by the square of the distance between two objectsso if you're twice as far

  • away, gravity is only one fourth as strong! He also discovered that the strength of gravity

  • is proportional to the mass of the objects in question: the more massive an object, the

  • stronger the gravitational force. That's why we can all feel the Earth pulling on us, but

  • don't really notice the pull of the moonit's smaller, and farther away! (the moon's gravity

  • is strong enough to cause the tides, though!)

  • And when I said earlier that gravity is an attraction between objects with mass, I lied.

  • I meant objects with Energy. Because in addition to massive objects, gravity also attracts

  • light and other massless (but energetic) particles, so that a photon of light can be bent slightly

  • passing the sun, or trapped completely by a black hole.

  • Now do you understand the Gravity of the situation?

We're all familiar with gravity as "the reason objects fall", but there's much, much more


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B1 中級

ミニッツ物理学重力とは何か? (Minute Physics: What is Gravity?)

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    Why Why に公開 2021 年 01 月 14 日