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

The Solar System is the total of all our enormous cosmic motions, not a vortex. This is how we move about in space.

Planet Earth's travel through space is characterised by 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, not merely by our axial rotation or our motion around the Sun. Only by combining everything and comparing it to the Big Bang's residual light can we arrive at a meaningful conclusion. (Credit: Jim slater307/Wikimedia Commons; background: ESO/S. Brunier)

The Earth rotates on its axis, orbits the Sun, and travels through the Milky Way, which is in motion in relation to all other galaxies. We can calculate our cumulative cosmic speed by accurately measuring the objects around us and the light left behind from the Big Bang. Still, there's a sense of dread that we'll never be able to shake. This is why.

Planet Earth isn't stationary; it's always moving through space.

This image of the Earth was provided by NASA's MESSENGER spacecraft, which had to fly by Earth and Venus in order to lose enough energy to reach its final destination of Mercury. The round, rotating Earth and its properties are indisputable, as rotation explains why the Earth bulges in the middle, is compressed at the poles, and has differing equatorial and polar diameters. (Image courtesy of NASA/MESSENGER)

With each passing day, the Earth spins on its axis, spinning a full 360 degrees.

The Coriolis Force's impact on a rotating pendulum at 45 degrees north latitude. At this latitude, it takes two full rotations of the Earth for the pendulum to accomplish a single, complete rotation; the rotation angle, like the speed at the Earth's surface, is latitude-dependent. (Photo courtesy of Cleon Teunissen / http://cleonis.nl)

This correlates to an equatorial speed of 1700 km/hr, which decreases as latitude increases.

The Earth appears to move in a closed, unchanging elliptical orbit around the Sun while rotating on its axis. However, if we look closely enough, we can see that our planet is spiralling away from the Sun at a rate of around 1.5 cm per year, and that its orbit precesses on timeframes of tens of thousands of years. (Photo courtesy of Larry McNish/RASC Calgary)

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

Perihelion and the winter solstice coincided only 800 years ago. They are progressively migrating apart due to the precession of Earth's orbit, which completes a full cycle every 21,000 years. The Earth moves away from the Sun somewhat over time, the precession period lengthens, and the eccentricity changes. (Photo courtesy of Greg Benson via Wikimedia Commons)

The perihelion in early January causes the quickest motions, while the aphelion in July causes the slowest.

Even the most eccentric planets orbit the Sun in ellipses that are virtually circles, with only a few percent deviation among them. Any planet's rotational speed is insignificant in comparison to its orbital speed, but the orbital speeds of the planets are insignificant in comparison to the Solar System's velocity across space. This animation depicts our upcoming gravitational collision with asteroid 99942 Apophis in 2029. (Photo courtesy of the ESA/NEO Coordination Centre)

On top of that, the Milky Way is the centre of the Solar System.

The Sun, like all the stars in our galaxy, travels at hundreds of kilometres per second around the galactic centre. The speed of the Sun and other stars in our neighbourhood around the galactic centre has a 10% uncertainty, or 20 km/s, which is the highest source of uncertainty when it comes to estimating our cumulative motion. (Photo courtesy of NASA and Jon Lomberg)

Our heliocentric speed, which ranges from 200 to 220 km/s, is 60 degrees from the plane of the planets.

Despite the fact that the Sun circles within the Milky Way's plane at a distance of 25,000-27,000 light years, the orbital directions of the planets in our Solar System do not correspond with the galaxy at all. Planetary orbital planes, as far as we can determine, occur at random inside a stellar system, often aligned with the central star's rotational plane but randomly aligned with the Milky Way's plane. (Image courtesy of Science Minus Details)

Our motion, however, is not vortical, but rather a simple sum of these velocities.

An accurate representation of how planets orbit the Sun, which subsequently moves across the galaxy in a separate direction. The speeds of the planets around the Sun account for only a small portion of the Solar System's motion through the Milky Way galaxy, with Mercury's revolution around the Sun accounting for only 20% of our galaxy's overall velocity. (Photo courtesy of Rhys Taylor)

On a larger scale, the Milky Way and Andromeda are speeding toward each other at 109 kilometres per second.

A series of stills showing the Milky Way-Andromeda merger, and how the sky will appear different from Earth as it happens. When these two galaxies merge, their supermassive black holes are fully expected to merge together as well. At present, the Milky Way and Andromeda move towards one another at a relative speed of ~109 km/s. (Credit: NASA; Z. Levay and R. van der Marel, STScI; T. Hallas; A. Mellinger)

Our Local Group is torn between attractive clusters and unpleasant underdense zones.

This illustrated map of our local supercluster, the Virgo supercluster, spans more than 100 million light-years and contains our Local Group, which has the Milky Way, Andromeda, Triangulum, and about ~60 smaller galaxies. The overdense regions gravitationally attract us, while the regions of below-average density effectively repel us relative to the average cosmic attraction. (Credit: Andrew Z. Colvin/Wikimedia Commons)

In comparison to the cosmic average, we travel at a speed of 627 22 km/s.

Because matter is distributed roughly uniformly throughout the Universe, it isn’t just the overdense regions that gravitationally influence our motions, but the underdense regions as well. A feature known as the dipole repeller, illustrated here, was discovered only recently, and may explain our Local Group’s peculiar motion relative to the other objects in the Universe. (Credit: Y. Hoffman et al., Nature Astronomy, 2017)

The remaining photons from the Big Bang, on the other hand, provide a cosmically unique rest frame.

At any epoch in our cosmic history, any observer will experience a uniform “bath” of omnidirectional radiation that originated back at the Big Bang. Today, from our perspective, it’s just 2.725 K above absolute zero, and hence is observed as the cosmic microwave background, peaking in microwave frequencies. (Credit: Earth: NASA/BlueEarth; Milky Way: ESO/S. Brunier; CMB: NASA/WMAP)

In comparison to the Cosmic Microwave Background, the Sun moves at a total speed of 368 km/s (CMB).

Although the cosmic microwave background is the same rough temperature in all directions, there are 1-part-in-800 deviations in one particular direction: consistent with this being our motion through the Universe. At 1-part-in-800 the overall magnitude of the CMB’s amplitude itself, this corresponds to a motion of about 1-part-in-800 the speed of light, or ~368 km/s. (Credit: J. Delabrouille et al., A&A, 2013)

Because the amplitude of the intrinsic CMB dipole is unknown, there is a 2 km/s inherent uncertainty.

Although we can measure the temperature variations all across the sky, on all angular scales, we cannot disentangle whatever the intrinsic dipole in the cosmic microwave background is, as the dipole we observe, from our motion through the Universe, is more than a factor of ~100 larger than whatever the primordial value is. With only one location to measure the value of this parameter at, we cannot disentangle which part is due to our motion and which part is inherent; it would take tens of thousands of such measurements to reduce the uncertainties here below their current values. (Credit: NASA/ESA and the COBE, WMAP, and Planck teams; Planck Collaboration, A&A, 2020)

We can only dream of taking such observations because we are constrained to the Milky Way.

The initial fluctuations that were imprinted on our observable universe during inflation may only come into play at the ~0.003% level, but those tiny imperfections lead to the temperature and density fluctuations that appear in the cosmic microwave background and that seed the large-scale structure that exists today. Measuring the CMB at a variety of cosmic locations would be the only feasible way to disentangle the intrinsic dipole of the CMB from that induced by our motion through the Universe. (Credit: Chris Blake and Sam Moorfield)