Galaxies are moving away from Earth because the universe is expanding. This is not because galaxies are physically moving through space like cars on a highway, but rather because the space itself is stretching.

Here's a simple analogy: Imagine a loaf of raisin bread rising in the oven. As the bread expands, the raisins move farther apart from each other, even though they aren't moving on the bread's surface. Similarly, galaxies are embedded in the expanding fabric of space-time, and as space expands, the distance between galaxies increases.

This phenomenon was discovered by Edwin Hubble in the 1920s. He observed that the farther away a galaxy is from us, the faster it appears to be moving away. This relationship, known as Hubble's Law, is a cornerstone of modern cosmology.

Why is the universe expanding?

The exact cause of the universe's expansion is still a mystery, but the prevailing theory is that it's driven by a mysterious force called dark energy. This energy is thought to be evenly distributed throughout the universe and acts like a repulsive force, pushing galaxies apart.

Important Note: It's not accurate to say that galaxies are moving "away from Earth." The expansion is happening *everywhere* in the universe, so galaxies are moving away from *each other*. Earth just happens to be a fixed point in this expanding space.