[dipayankar]

Apart from Gravity is there any other force that is making the ball roll towards the center? What would happen if the same scenario was repeated in space. Would the ball roll towards the center?

Originally Posted by Profpat

I thought gravity wasn't a force but an effect. The old dimpled rubber sheet, where things tend to roll towards the impression.

[Farsight]

Originally Posted by Profpat

I thought gravity wasn't a force but an effect. The old dimpled rubber sheet, where things tend to roll towards the impression:

It is like that Pat, only a knot in a stretched rubber sheet is a better analogy. Gravity is a pseudoforce, when you're in free fall there is no force acting upon you. No force means no energy being added. So the kinetic energy of a falling body is coming out of the falling body itself. I describe how it works in my draft book, and nobody can point out where it's wrong, because it isn't. Here's an excerpt. PM me for a copy.

GRAVITY EXPLAINED

You probably think of gravity as “curved spacetime”. Surprisingly Einstein didn’t. The Foundation of General Relativity published in 1916 doesn’t use the phrase. So neither should you. To understand gravity you have to take the ontological view. You have to learn to see what it is, not what it does. You have to learn to see the cause, not the effect. And to do that, you have to put time to one side, because time isn’t the same kind of dimension as the dimensions of space. Because spacetime is space with motion through it. Yes, an object passing a planet traces a curved path, but you don’t stare up at a plane and decide it’s a silver streak in the sky. You take a mental snapshot, flash, a picture of it now, a timeless instant. It’s the same with gravity. Take the derivative of that curved spacetime. What you get is a gradient. And it’s a gradient in space, not curved spacetime.

But let’s tackle it an easier way, via an old favourite. Think about a cannonball sitting on a rubber sheet. The cannonball is heavy, and it makes a depression that will deflect a rolling marble, or even cause the marble to circle like an orbit. It’s a nice analogy, but it’s wrong. It’s wrong because it relies on gravity to pull the cannonball down in the first place. It’s circular. It uses gravity to give you a picture of gravity.

etc etc

[dipayankar]

So is the body losing energy when it is under free fall? What type of energy is it loosing to get converted into kinectic energy?

Originally Posted by Farsight

It is like that Pat, only a knot in a stretched rubber sheet is a better analogy. Gravity is a pseudoforce, when you're in free fall there is no force acting upon you. No force means no energy being added. So the kinetic energy of a falling body is coming out of the falling body itself. I describe how it works in my draft book, and nobody can point out where it's wrong, because it isn't. Here's an excerpt. PM me for a copy.

GRAVITY EXPLAINED

You probably think of gravity as “curved spacetime”. Surprisingly Einstein didn’t. The Foundation of General Relativity published in 1916 doesn’t use the phrase. So neither should you. To understand gravity you have to take the ontological view. You have to learn to see what it is, not what it does. You have to learn to see the cause, not the effect. And to do that, you have to put time to one side, because time isn’t the same kind of dimension as the dimensions of space. Because spacetime is space with motion through it. Yes, an object passing a planet traces a curved path, but you don’t stare up at a plane and decide it’s a silver streak in the sky. You take a mental snapshot, flash, a picture of it now, a timeless instant. It’s the same with gravity. Take the derivative of that curved spacetime. What you get is a gradient. And it’s a gradient in space, not curved spacetime.

But let’s tackle it an easier way, via an old favourite. Think about a cannonball sitting on a rubber sheet. The cannonball is heavy, and it makes a depression that will deflect a rolling marble, or even cause the marble to circle like an orbit. It’s a nice analogy, but it’s wrong. It’s wrong because it relies on gravity to pull the cannonball down in the first place. It’s circular. It uses gravity to give you a picture of gravity.

etc etc

[Farsight]

Originally Posted by dipayankar

So is the body losing energy when it is under free fall? What type of energy is it losing to get converted into kinetic energy?

No, it isn't losing any energy. Think of the free-falling body as a photon going round in a circle. That's basically what an electron is.

At the surface of the planet there's gravitational time dilation. That means the light there is going slower.

So once it's fallen down, our photon-going-round-in-a-circle is going round slower. The difference is the terminal velocity.

I explain it in the draft book. PM me for a copy.

[dipayankar]

Need one copy...

Originally Posted by Farsight

No, it isn't losing any energy. Think of the free-falling body as a photon going round in a circle. That's basically what an electron is.

At the surface of the planet there's gravitational time dilation. That means the light there is going slower.

So once it's fallen down, our photon-going-round-in-a-circle is going round slower. The difference is the terminal velocity.

I explain it in the draft book. PM me for a copy.