Why Does Everything In The Universe Spin?


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 WHYYY… and 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 Sun… they 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??