The Milky Way is on course to collide with the Andromeda galaxy in about 4 billion years

Andromeda, the nearest large galaxy to our own, is being drawn toward the Milky Way by gravity, and the two are predicted to meet in roughly four billion years. When astronomers say collision, though, they don’t mean stars smashing together.

The space between stars is so vast that almost none would actually strike one another; instead the two galaxies would sweep through each other, their gravity stretching and reshaping both into a single, larger galaxy over the following billions of years. Our Sun would likely be flung into a different part of the merged galaxy, but Earth itself would be in no danger from the encounter.

Newer measurements from the Hubble and Gaia missions have made the timing and even the certainty of the merger less clear-cut than once thought, with some studies giving it closer to even odds over the next ten billion years.

Either way, it is a reminder that galaxies are not fixed scenery — they move.