Planet Earth’s motion through space isn’t just defined by our axial rotation or our motion around the Sun, but the Solar System’s motion through the galaxy, the Milky Way’s motion through the Local Group, and the Local Group’s motion through intergalactic space. Only with everything combined, and by comparing to the Big Bang’s leftover glow, can we arrive at a meaningful answer. (Credit: Jim slater307/Wikimedia Commons; background: ESO/S. Brunier)

How, exactly, does planet Earth move through the Universe?

The Solar System isn’t a vortex, but rather the sum of all our great cosmic motions. Here’s how we move through space.

Ethan Siegel
Starts With A Bang!
3 min readJan 17, 2022

Planet Earth isn’t at rest, but continuously moves through space.

This view of the Earth comes to us courtesy of NASA’s MESSENGER spacecraft, which had to perform flybys of Earth and Venus in order to lose enough energy to reach its ultimate destination: Mercury. The round, rotating Earth and its features are undeniable, as this rotation explains why Earth bulges at the center, is compressed at the poles, and has different equatorial and polar diameters. (Credit: NASA/MESSENGER)

The Earth rotates on its axis, spinning a full 360° with each passing day.

The effects of the Coriolis Force on a pendulum rotating at 45 degrees North latitude. Note that the pendulum takes two full rotations of Earth in order to make a single, complete rotation at this particular latitude; the rotation angle, just like the speed at Earth’s surface, is latitude-dependent.. (Credit: Cleon Teunissen /

That translates into an equatorial speed of ~1700 km/hr, dropping lower with increasing latitudes.

The Earth, moving in its orbit around the Sun and spinning on its axis, appears to make a closed, unchanging, elliptical orbit. If we look to a high-enough precision, however, we’ll find that our planet is actually spiraling away from the Sun by about 1.5 cm per year, and precesses in its orbit on timescales of tens of thousands of years. (Credit: Larry McNish/RASC Calgary)

Meanwhile, the Earth revolves around the Sun, with speeds ranging from 29.29 km/s to 30.29 km/s.

Just 800 years ago, perihelion and the winter solstice aligned. Due to the precession of Earth’s orbit, they are slowly drifting apart, completing a full cycle every 21,000 years. Over time, the Earth drifts slightly farther from the Sun, the precession period increases, and the eccentricity varies as well. (Credit: Greg Benson/Wikimedia Commons)

Early January’s perihelion causes the fastest motions, while July’s aphelion yields the slowest.

All of the major planets orbit the Sun in ellipses that are nearly circles, with only a few percent deviation among even the most eccentric planets. The rotational speed of any planet is tiny compared to its orbital speed, but the orbital speeds of the planets are small compared to the Solar System’s motion through the galaxy. This animation shows our future gravitational encounter with asteroid 99942 Apophis, scheduled for 2029. (Credit: ESA/NEO Coordination Centre)

Atop that, the entire Solar System travels around the Milky Way.

The Sun, like all the stars in our galaxy, orbits around the galactic center at speeds of hundreds of km/s. In our neighborhood, the speed of the Sun and the other stars around the galactic center have an uncertainty of around ~10%, or ~20 km/s, which is the largest factor of uncertainty when it comes to calculating our cumulative motion. (Credit: Jon Lomberg and NASA)

Our heliocentric speed of 200–220 km/s is inclined ~60° to the plane of the planets.

Although the Sun orbits within the plane of the Milky Way some 25,000–27,000 light years from the center, the orbital directions of the planets in our Solar System do not align with the galaxy at all. As far as we can tell, the orbital planes of the planets occur randomly within a stellar system, often aligned with the central star’s rotational plane but randomly aligned with the plane of the Milky Way. (Credit: Science Minus Details)

However, our motion isn’t vortical, but a simple sum of these velocities.



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.