Where is Earth located in the Milky Way?

Earth is located in a spiral arm in the Milky Way galaxy, but it's only relatively recently that this has become a widely-accepted fact.

Long ago, people thought that the Earth was at the centre of the Universe.

This ‘geocentric’ view was challenged as early as the 3^rd Century by those who argued Earth and the other planets actually orbited the Sun.

But the ‘heliocentric’ model of the Solar System didn’t really catch on until the 17^th Century, after Copernicus published the first mathematical model of a heliocentric model (in 1514) and Galileo then expanded on his ideas.

Later, astronomers would come to realise first that the Sun was merely one star in the Milky Way galaxy.

Then came the discovery by Edwin Hubble that the Milky Way itself was just one galaxy out of millions.

This make Earth and its inhabitants even less important in the grand scheme of things.

Where is Earth in the Milky Way?

The bad news for geocentrists is that our Solar System doesn’t even lie at the heart of the Milky Way.

In fact, Earth can be found on one of the Milky Way galaxy’s outlying spiral arms – the Orion-Cygnus arm, to be precise.

And Earth is sitting at a point roughly halfway from the galactic centre to its outer rim. To reach either, you’d have to travel about 25,000 lightyears.

How do we know where Earth lies in the Milky Way?

It’s hard to say much about the Milky Way’s structure with any certainty because we’re a part of it.

Unlike other galaxies that we can see through telescopes, we can’t look at the Milky Way face-on.

Its shape must be determined by extrapolating from other observed phenomena, so our current picture may not be entirely accurate.

But 'about halfway out, on the Orion-Cygnus' arm gives you a rough idea of where we’re at.

To make matters worse, the Milky Way isn’t a particularly large galaxy: its nearest neighbour, the Andromeda Galaxy, is roughly twice the size.

On the plus side, the two galaxies put together (plus some smaller neighbours) make up the Local Group of galaxies, which is part of the Virgo Supercluster, which in turn is part of the Laniakea supercluster, which is part of the Pisces-Cetus Supercluster Complex, which is one of the largest structures in the observable Universe.

In other words, far from being the centre of the Universe, Earth is actually a small, insignificant planet in a small, insignificant galaxy.

But it’s also part of something that’s absolutely mind-blowingly enormous.