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  • You're spinning and I'm spinning and the Earth is spinning and the sun is spinning and the

  • solar system and the WHOLE DAMN GALAXY. BUT WHY!

  • You might remember from our "How Fast Is the Universe Moving" video that you're moving

  • really fast right now. For example, the Earth is rotating around it's axis at 1,040 miles

  • per hour (465 m/s). Planets rotate. That's what they do, right? But then science comes

  • along and asks WHYYYand once you start thinking about it, it's staggering.

  • To figure it out, we have to go back to the beginning. Four and a half billion years ago,

  • our solar system began to form from clouds of helium and hydrogen -- kind of like a nebula.

  • As the gas was moved and undulated through the universe, some of it was denser and some

  • thinner. Something, perhaps a nearby supernova, caused the gases to begin to coalesce, and

  • as the gravity of these particles increased, they fell toward each other -- and began to

  • spin.

  • Funnily enough, every time this happens, the spin rotates the same direction, counter-clockwise.

  • There's no UP in space, of course, but if you think about the angular moment of the

  • spin as a FORWARD direction, then most things, Earth, Mars, the Sunthey all rotate counterclockwise.

  • Because they're all conserving their angular momentum. As the gases continued to gravitate

  • toward each other, constantly moving, they formed a tossed pizza dough shape. A ball

  • in the middle, slowly expanding outward into a disc. This is the shape we see most often

  • in the universe, because of the laws of physics.

  • As interstellar clouds rotate and collapse onto themselves they fragment, according to

  • Scientific American, and then those smaller parts collapse again, and again. And over

  • the next few hundred million years, all that gas gathers and fuses into suns, planets,

  • asteroids and (eventually, after lots more time) you and me! All the while, the angular

  • momentum of the original cloud it maintained; that original gaseous angular momentum set

  • the stage for all the rotation to follow -- inertia keeps it going. Yes, it IS slowing over time.

  • A day in 100 years will be 2 milliseconds longer, but ultimately we'll all keep spinning

  • unless something big smacks into us.

  • Strangely, Venus rotates clockwise, and we're not sure why. Either the axis of the planet

  • was flipped upside down at some point, or it slowed rotating counterclockwise, stopped

  • and began to rotate the opposite -- possibly due to its dense atmosphere and closeness

  • to the sun. It's not the only weirdo; Uranus was knocked on it's side, her rotation is

  • ALL screwed up.

  • Even on a macro level, everything is spinning. But galaxies, relative to Earth, spin both

  • clockwise and counterclockwise. Though spiral galaxies DO tend to spin with their arms trailing

  • behind them, but even that isn't a hard rule. In 2002, the Hubble spotted galaxy NGC 4622

  • whose arms LEAD her rotation, but they believe it's because it interacted with another galaxy.

  • Sounds hot.

  • In the end, everything in the universe is spinning. Energy must be preserved over time;

  • so when a figure skater spins with his arms in, he'll spin faster, but with his arms out

  • he'll move slower. That's simple physics, but it operates on a galactic level too!

  • Does a science question have your head spinning??

You're spinning and I'm spinning and the Earth is spinning and the sun is spinning and the


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B2 中高級

宇宙中的萬物為什麼會旋轉? (Why Does Everything In The Universe Spin?)

  • 63 13
    Cheng-Hong Liu 發佈於 2021 年 01 月 14 日