How fast are we moving through space?

Ethan Siegel
Starts With A Bang!
7 min readAug 26, 2015

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According to relativity, there’s no universal frame of reference. But the Big Bang gave us one anyway.

“The slow philosophy is not about doing everything in tortoise mode. It’s less about the speed and more about investing the right amount of time and attention in the problem so you solve it.” -Carl Honore

Most likely, as you’re reading this right now, you’re sitting down, perceiving yourself as stationary. Yet we know — at a cosmic level — we’re not so stationary after all. For one, the Earth rotates on its axis, hurtling us through space at nearly 1700 km/hr for someone on the equator.

That’s not really all that fast, if we switch to thinking about it in terms of kilometers per second instead. The Earth spinning on its axis gives us a speed of just 0.5 km/s, hardly a blip on our radar when you compare it to all our other motions.

The Earth, you see, much like all the planets in our Solar System, orbits the Sun at a much speedier clip. In order to keep us in our stable orbit where we are, we need to move at right around 30 km/s. The inner planets — Mercury and Venus — move faster, while the outer worlds like Mars (and beyond) move slower than this.

Image credit: NASA / JPL, retrieved fromhttp://www.dailymail.co.uk/sciencetech/article-2454094/Could-life-Earth-end-March-16-2880-Scientists-predict-giant-asteroid-collide-planet-38-000-miles-hour.html.

But even the Sun itself isn’t stationary. Our Milky Way galaxy is huge, massive, and most importantly, is in motion. All the stars, planets, gas clouds, dust grains, black holes, dark matter and more move around inside of it, contributing to and affected by its net gravity.

Image credit: J. Carpenter, M. Skrutskie, R. Hurt, 2MASS Project, NSF, NASA, of the actual Milky Way in infrared.

From our vantage point, some 25,000 light years from the galactic center, the Sun speeds around in an ellipse, making a complete revolution once every 220–250 million years or so. It’s estimated that our Sun’s speed is…

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Ethan Siegel
Starts With A Bang!

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.