Why Are Most Planets Round and Not in Other Shapes?

 

Have you ever looked at the night sky and wondered: Why are all planets round? If yes then same pinch(lol). Why do planets end up smooth and spherical instead of cube-shaped or irregular?

To answer this, we have to travel back in time, to when planets were young.
I will be explaining in the form of questions and a bit of storytelling, do tell me if you find this bit more easy to understand.

A Young Planet Is Born

Imagine the early Solar System. It was not calm and quiet like today. It was a turbulent scene.

Dust swirled around a newly formed Sun. Rocks constantly collided. Gas clouds crashed into each other. Temperatures were extreme, hot enough to melt rock.

In this violent environment, tiny particles of dust began sticking together. Over time, these grew into larger clumps, often called planetesimals. At first, these young worlds were oddly shaped. They were uneven, jagged, and far from the smooth planets we see today.

So what changed?

Gravity The Shape Maker

The answer is gravity. yes yes yess yess gravity

Gravity acts as if it pulls from the center of an object. No matter where a rock is located on a forming planet, gravity pulls it inward. If this happens to a few rocks, nothing major changes. But when it happens to countless rocks, dust, molten metals, and debris over millions of years, the shape begins to change.

Gravity slowly erases sharp edges, high peaks, and deep dents. Over time, the object naturally smooths out into the most stable shape possible: a sphere.

A sphere is the shape where everything on the surface is as close as possible to the center. It requires the least energy for gravity to maintain. That is why planets gradually become round.

Why Small Objects Do Not Become Round

Not everything in space becomes spherical. Many small objects, such as asteroids and small moons, are oddly shaped. They may look like lumpy potatoes or irregular rocks flying through space.

Why do they not become round?

Because they are too small. Their gravity is weak, not strong enough to compress their structure into a sphere. Their rocks and materials stay firm enough to resist reshaping. Therefore

Large bodies become round.
Small bodies remain irregular.

As a forming planet grows larger, it eventually passes a point where gravity becomes powerful enough to shape the entire body.

Why Planets Are Not Perfectly Round

Even though planets look round from space, they are not perfect spheres. Most are slightly flattened at the poles and bulged at the equator. This happens because planets rotate.

When a planet spins, the rotation pushes outward at the equator, causing a small bulge. Earth has a minor one. Jupiter and Saturn rotate much faster, so their bulges are much more noticeable.

Scientists call this shape an oblate spheroid. It is still mostly spherical, just slightly stretched at the middle.

Stars Are Round Too

Planets are not the only round objects in the universe. Stars are shaped by gravity as well. Because stars are massive and their gravity is strong, they also form into nearly perfect spheres as they balance their internal forces.

A Simple Thought Experiment

Imagine a giant cube floating in space. What would happen to its pointed corners over millions of years if gravity were strong enough?

Gravity would pull each corner inward. Slowly, the cube would lose its sharp edges and become more and more rounded. Eventually, it would settle into a shape that is the easiest for gravity to maintain: a sphere.

Gravity always moves material toward balance.

Thats all from my side. If you are also an astrophile do tell me how much you liked this and I hope the next time you look at a planet or the Moon, you are seeing the result of millions of years of gravity quietly accumulating matter into the most natural shape in the universe.

I would like to also know how you got here, randomly or from my insta bio.
Lets see if I can be consistent in writing these things regularly.


By Gautam