What makes the planets in our solar system round instead of another shape? How do they stay on their axis?

Question

Why aren't planets oblong, or square, rectangular, etc.?

Answer 1

In physics, a sphere occupy the smallest volume for the said mass. It is also the equilibrium state. This is where all the internal forces in the sphere are equalised.

Have you noticed? When you flick some water into the air, they form round water droplets? Why? This is because the forces inside a water droplet equalised and become round.

The same can be said of planets. During the early stage of the solar system, all the objects there are molten and very hot. Hence, by themselves, each of the molten objects will try to reach a state of equilibrium. Just like the water droplets, the objects started to become round. When cooled, they retained the roundness.

********************************************************************************************************************************************************
"However....how do the planets (and their moons) stay on an exact orbit? It is like they are "teathered" to the planet by a string so that it stays in the exact same orbit. Why don't they just float where the atmosphere (?) takes them?"

With regard to your question, a planet or moon stay in their orbit because of gravity. Gravity is similar to the string you mentioned.

If you tie an object to a string and swing the object in the air with your hand, the object swings around your hand and in a circular motion. It is technically speaking, orbiting your hand. It cannot go straight and fly off because the string holds it back. Neither can it stay still because you swing it and moving it. So the best path it takes is a circle around your hand.

The same can be said of a planet. If the planet is freely travelling in space, it can only go straight and in a constant speed.

However, if there is a large object nearby, the gravity of the large object will exert a pull to it, like a magnet. This will affect its path. If the planet is close enough to the object, eg the sun, the sun's gravity will capture it and lock the planet to it. As the planet was originally moving, the sun's gravity will change the path of the planet to make it go around the sun. The planet will now stay in an orbit around the sun.

It is here you must take note of the importance of speed. If the planet is moving at a speed that is too slow in space, the gravity of the sun will be so strong that the planet will FALL into the sun and CRASH.

If the planet is moving too quickly, the sun's gravity may be strong enough to hold the planet back, but it will make the planet orbit it in a BIG circle.

You must try to get the idea that the planet is always trying to pull away and fly off from the sun, but the sun is holding it back.

This situation is similar to our rockets. When the space shuttle is launched into space, the only way for it to get into space is speed. Flying at a tremendous speed, the speed it is in prevents the ship from falling back to earth. At a certain speed, the ship will reach orbit. This is what you call orbital speed or escape velocity. This is the speed where the earth's gravity can still pull on the ship, but not enough to pull it down to earth. So the ship orbits the earth.

********************************************************************************************************************************************************
And it will orbit the earth in a fixed path. This fixed path is the result of the original direction the ship is taking that is affected by gravity. Flying straight into space, the ship takes a straight path, but gravity pulls it back, like the string you mentioned. So the ship will be pulled back and orbit around the earth.

I hope by now you will notice the spaceship is travelling at a FIXED PATH which will NEVER CHANGE (unless something push it in another direction). This is path of Newton's law of motion. The same can be said of the planets which have always travel around the sun in fixed paths and fixed orbits. They will never change unless they are pushed away.

In interstellar space, all objects, from asteriods to planets to spaceships, travel in fixed paths that are usually straight unless affected by the gravity of a nearby object. It is not quite like what you see in the movies which show intergalactic spacecrafts that can zip zac across the galaxy.

*******************************************************************************************************************************************************

Answer 2

Eris, the largest dwarf planet known, was discovered in an ongoing survey at Palomar Observatory's Samuel Oschin telescope by astronomers Mike Brown (Caltech), Chad Trujillo (Gemini Observatory), and David Rabinowitz (Yale University). We officially suggested the name on 6 September 2006, and it was accepted and announced on 13 September 2006.

Answer 3

It is not because the planets were once liquid. The force of gravity is sufficient to pull all the material the planet is made of as close to the centre of Gravity as it can get.
In fact this is one definition of a planet.
Also all the planets are rotating and therefore they exhibit the property of a gyroscope.

Answer 4

Enursia which is like almost the oposite of gravity those to combined push nd pull the planets making them roll and they are stuck that way unless some how there is a large imbalance

Answer 5

Not what, but "Who"? That would be God's wise choice of design. As for their amazing axis, Well, He's also responsible for that 'tricky feat', too,also known as a miracle,

Answer 6

Surface tension.
They were liquid once.