How do planets and other celestial bodies stay in orbits? Shouldn't all the planets go towards the sun? How are we staying in orbits?

Answer 1

There are two answers to this question depending on whether you are asking based on classic physics or

post Einstein physics.

Classic physics states that you have two equal and opposite forces acting on the planet.

The momentum of the planet which cause it to move at a angle away from the sun and the force of gravity which causes the planet to move towards the sun. Since these two forces balance the planet achieves a stable

orbit around the sun.

Einstein changed the description of gravity from that of a force to a curvature of space time. So a object having a lot of mass such as the sun will create a dimple in the flat surface of space time. The heavier the object the more pronounced is the curvature. The planet follows a path similar to the marble in a roulette wheel.

Answer 2

You are right that all the planets are falling towards the sun.

But they also are traveling in a circle perpendicular to the sun at the same time. Because of this they travel perpendicular and fall a little bit at the same time. This is what makes the circular orbit that they are in. Moving straight in space and falling a little at the same time.

Here is a diagram:

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Being in orbit is falling constantly around a center point.

Think about shooting an arrow. If you pull the string a little the arrow will go a little ways. If you pull the string more the arrow will go farther. Imaging that you had a very good bow and were strong though that you could pull it back far enough to get the arrow to go 1/2 way around the world before it hit the ground. Now think about pulling it back a little more and the arrow will go all the way around the world. Now pull it back even more and when it gets back to you it will still not hit the ground and it will go around a second, a third, a forth time, ..., and more. You will have sent the arrow into orbit.

This is how a space ship is put in orbit. We get the space ship to go fast enough that it will never hit the ground.

It is the same with planets.

They are going so fast that they never fall far enough to hit the sun and stay in orbit.

An orbit is constantly falling around a center point.

Newton had a thought experiment about it.

To see diagrams that explain it better than I can with only words

go to: https://en.wikipedia.org/wiki/Newton%27s_cannonball

or: https://spaceplace.nasa.gov/how-orbits-work/en/

Answer 3

Grab something solid like a bucket. Tie a rope to the handle, then start spinning like a lunatic while you hold your arms out. Very shortly, you will have that bucket traveling horizontally as it circles around you. Does it fly inward toward you instead? Nope. Believe it or not, the mechanics of an orbit aren't that different. The gravity of the planets draws them toward the sun, sure, but unless they were already failing straight inward, they will fly off to one side, and get hurled around the other side of the sun, much like that unfortunate bucket you're abusing.

The speed of the fall can grow so strong that it actually hurls the planet out into space, creating what we call a "rogue planet". We also see lots of extrasolar planets slowly falling into their parent star, but that can take millions of years, even when the planet is suffocatingly close already. Another thing to remember is that while the sun is enormous, Earth averages about 93 million miles away from it, and we are considered an "inner planet"! The outer ones are huge (which boosts their gravitational attraction to the sun) but also so distant that they experience a lot of tugging from the other planets much more strongly than little ones do. That helps keeps them stable. Indeed, Jupiter is often called a "shepherd" because, given its size and convenient location as 5th planet out, it helps keep other planets in line and tends to keep the asteroid belt well-behaved.

So: why don't planets fall into a star? They do! Ours aren't at the moment because we have a tangled web of fields and velocities keeping them relatively stable.