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??