The Earth is round, everyone (ok, well, not everyone, but almost everyone) knows that. In day-to-day conversation, it is generally safe to say that the Earth is a sphere, but that is not entirely correct.

The Earth actually bulges a little bit in the middle near the equator, making it slightly oblong. Have you ever wondered why?

The short and simple answer is because of gravity.

The longer answer is…It’s complicated.

As an object is floating through space, it will eventually start to run into other objects. In some cases, the two will combine together to form a larger object.

Over time, some of these objects grow so large that their gravitational pull is able to draw in even more objects, adding to its mass, and therefore its gravitational pull.

In these cases, gravity will pull everything on the large object toward the center of its mass. Depending on what the object is made of, the shape will start to become more or less round.

If an object were made of a liquid, it would easily become almost perfectly spherical. Rocky objects, naturally, have more imperfections to them as it takes more gravity to move them toward the center.

In addition to just the gravity, however, these objects are also spinning in almost all cases, which means centrifugal force will come into play.

The faster the object spins, the more the material will be pushed outward at its equator. One dwarf planet known as Haumea spins so fast that rather than being a proper sphere, it is shaped much more like an egg.

So, Earth is mostly spherical with a bulge at the center because of the gravitational pull, the centrifugal force of it spin, and the overall makeup of the planet.

Sometimes it is just easier to accept that the Earth is round without trying to do all the calculations to explain exactly why.

If you are interested in learning more, however, take a few minutes to watch this informative video with Neil deGrasse Tyson:

Let’s just be glad that the Earth is as round as it is.

Thought that was fascinating? Here’s another story you might like: Why You’ll Never See A Great White Shark In An Aquarium