Why is everything in space always moving?

Nothing in our universe stands still: Earth orbits the sun, the sun circles the galaxy, and even galaxies are constantly on the move. So why is everything in space in motion?

It all comes down to how the universe and the objects within it were made, Edward Gomez, an astrophysicist and the education director at Las Cumbres Observatory, told Live Science. Scientists think the universe began with the Big Bang, a superfast expansion from an infinitely dense single point that eventually led to the formation of everything we see today.

"From the very beginning of the universe, it started expanding outwards because the force of the Big Bang caused everything to move apart," Gomez said.

"It's sort of the imprint of the beginning," said Carol Christian, an astrophysicist and outreach project scientist for the Hubble Space Telescope at the Space Telescope Science Institute in Baltimore. "The beginning was movement, and so movement has been built into the universe from the very beginning."

Related: Does the universe rotate?

So one reason everything in space is in motion is because the universe is expanding. But that expansion has effects only on very large scales. "We only see it really happening on things that are very far apart or far away, because it's not necessarily that these objects are moving through space," Gomez said. "It's that the space in between objects is getting bigger."

On smaller scales, though, rotation is the movement that rules objects in space. "This spinning thing is kind of endemic in the universe, too," Christian told Live Science. "There isn't anything that doesn't rotate."