Earth Is Hurtling Towards Something Strange

In the 1970s, astronomers studying the leftover light from the birth of the universe, known as the Cosmic Microwave Background, discovered something remarkable: our galaxy, the Milky Way, and everything in it, including you, is hurtling through the universe at an astonishing 390 meters per second. Since you started reading this, you have physically traveled more than 11,000 miles.

Accurately measuring the speed of our galaxy for the first time was a significant achievement, but it was also a bit unsettling because nobody really knew exactly why the Milky Way was moving so quickly. A significant portion of our velocity could be explained by the expansion of the universe, described by the Hubble flow, and some of the rest was accounted for by gravitational interactions between the Milky Way and our nearest galactic neighbors, like Andromeda. However, something was still missing. We appeared to be moving at a speed and in a direction that we couldn't quite explain. It was almost as though our entire galaxy was being dragged off course by some vast, distant object.

It wasn't just the Milky Way that was being pulled towards this mysterious, unseen object; it was everything. Every single galaxy in our corner of the universe, around 100,000 of them in a region spanning more than 500 million light-years, is being inexorably drawn towards the same unknown force. Astronomers decided to call this object the "Great Attractor."

The challenge was determining what the Great Attractor could possibly be. The only force capable of nudging entire galaxies off course over hundreds of millions of light-years is gravity, created by mass. The more massive an object, the stronger the gravitational force it exerts. To attract 100,000 galaxies over such distances, the Great Attractor had to be unimaginably colossal.

Astronomers first tried to study the Great Attractor using telescopes, but they quickly realized that wouldn't work. The Milky Way's spiral structure, with its 100 billion stars concentrated along a plane 1,000 light-years thick, obscures our view of the deep space beyond it. This obscured section of the night sky is known as the "Zone of Avoidance," and the Great Attractor lies right in the middle of it.

For several decades, the Great Attractor's true nature remained a mystery. We could only study it indirectly by measuring its gravitational impact on the surrounding galaxies. This allowed us to determine its approximate location, between 150 and 250 million light-years away in the direction of the Norma constellation, and estimate its mass, equivalent to 10 quadrillion suns.

For a long time, nothing in the universe seemed to match the mass required to explain the gravitational effect of the Great Attractor. However, advancements in radio and infrared telescopes allowed us to peer through the Zone of Avoidance and catch glimpses of the sky containing the Great Attractor. What we found were more galaxies, loads of them.

This discovery helped us understand the true nature of the Great Attractor. The universe has a large-scale structure known as the "cosmic web." Stars form galaxies, galaxies form galaxy groups and clusters, and these groups and clusters form superclusters. Our local group of galaxies is part of the Virgo Supercluster, which is just one branch of a much larger structure called the Laniakea Supercluster, spanning about 520 million light-years and home to around 100,000 galaxies. The Great Attractor is the gravitational center of this supercluster.

As for what will happen when we reach the Great Attractor, the accelerating expansion of the universe means we will never get there. The distance between us and the Great Attractor will continue to grow, even as our speed towards it increases. This expansion will eventually cut us off from most of the universe, leaving us gravitationally bound to our local group of galaxies while the rest fade away into the dark reaches of space.