How fast is Earth traveling through space? That depends.
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How fast are you, planet Earth, our solar system, and the galaxy moving right now? There's no one answer to that question because we're going in several directions and multiple speeds all at the same time. How is that possible?

Within the Milky Way galaxy, our solar system is orbiting around a massive black hole at the center of the galaxy at half a million miles an hour. Separately, the Milky Way galaxy is in the Virgo Supercluster, which is falling into the Great Attractor, a huge group of galaxies called the Laniakea Supercluster, at one and a half million miles an hour.

And all of that is superimposed on top of the natural expansion of the universe, which isn't really a speed, but is happening at 75 kilometers per second per megaparsec.
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MICHELLE THALLER

Dr. Michelle Thaller is an astronomer who studies binary stars and the life cycles of stars. She is Assistant Director of Science Communication at NASA. She went to college at Harvard University, completed a post-doctoral research fellowship at the California Institute of Technology (Caltech) in Pasadena, Calif. then started working for the Jet Propulsion Laboratory's (JPL) Spitzer Space Telescope. After a hugely successful mission, she moved on to NASA's Goddard Space Flight Center (GSFC), in the Washington D.C. area. In her off-hours often puts on about 30lbs of Elizabethan garb and performs intricate Renaissance dances. For more information, visit
NASA.
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TRANSCRIPT:

MICHELLE THALLER: Eugene, you've asked one of my favorite questions and a surprisingly deep one. The essence of it is: How fast are we really moving? We are a solar system; we are planets going around the Sun. But the Sun has its own motion around the galaxy, the Milky Way. And there are larger motions still because the Milky Way galaxy is also moving through space. So I'm going to try to break this down because there are a number of different ways to think about motion because when you get to these scales, one of the most important questions you have to ask is: Motion compared to what? And I'll explain that as I go along.

So one of the most easy to understand motions, but a kind of mind-blowing one is that the Sun is orbiting around the center of the Milky Way galaxy. Now, the Milky Way galaxy is a huge collection of about half a trillion stars, and it's about 100,000 light years across end-to-end. Now, we actually orbit around the center of the galaxy -- the center of the galaxy is about 30,000 light years away from us -- and we orbit around about once every 230 million years. OK, that sounds like a long time. So 230 million years to make one orbit around the galaxy. So how fast are we going? It turns out that the Sun, and us with it, it's going at about 560,000 miles an hour. That's over half a million miles an hour just around the center of our galaxy. So right now, you are moving at over half a million miles an hour around the center of the galaxy. And if you want to think about it in kind of a dramatic way, the center of the galaxy has a massive black hole at the middle, and it's about 4 million times the mass of the Sun. So right now, you are orbiting a massive black hole at half a million miles an hour. That's kind of fun.

But there are larger velocities as well. And here's where things start to get a little bit complicated because the universe is expanding. And what that really means is that space itself is expanding. It's not really correct to say the galaxies are flying through the universe with the expansion of the universe. That's actually not how it works at all. The galaxies in that sense are standing still, but the space in between them is getting bigger. It's a very strange thing to think about, but the expansion of the universe is not galaxies moving through empty space. And one of the reasons that this is important is because the farther away you look into space, the more expanding space you look through. And it's not that galaxies very far away are actually moving through space very, very fast, but they appear that way to us. There's something called the Hubble Constant, and what that means is how fast the universe is expanding for every amount of space that you look through. The Hubble constant right now is about 75 kilometers per second per megaparsec, and a megaparsec is about 3 million light years. So that means that every 3 million light years you go out, things are receding from yo...

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