I give up :(

@WilliamJohn Yes, that's correct.

@JohnRennie Thanks John now I can continue my study :)

:-)

@JohnRennie sir can you come to my room

@JohnRennie Hi !

@KavinIshwaran Hi :-)

Are you free ?

Yes

In general relativity, gravity comes from whole of the mass of the body right ?

The curvature is related to an object called the stress-energy tensor.

In most cases this is basically the same as the mass of the body.

then why gravity decreases while we go approach center of an object

while we approach the center, the curvature is increased right ?

If we go into classical mechanics

in the Newton's law of gravitation

I answered exactly this question a while back :-)

I will have a look into it now !

You'll probably find the maths a bit too complicated but you can ignore the details.

The point is that the curvature depends on how the mass is distributed, not just on the total mass.

density ?

The density as a function of position.

@JohnRennie So it depends on the density at that particular spacetime ?

Density is a function of position isn't it. If you model the Earth by a ball of constant density then ρ(r) is constant for r < R and zero for r > R, where R is the radius of the Earth.

ohh

@JohnRennie sounds complicated.....

Well general relativity is complicated :-)

Is there a way to explain it with classical mechanics

@JohnRennie yes :)

@KavinIshwaran Yes, have you heard of Newton's shell theorem?

yes

So you know that inside a uniform spherical shell the gravity is zero. Yes?

yes

Suppose you are inside the Earth at a distance r from the centre, then we can divide the Earth into two parts. The part of the Earth farther from the centre than you forms a shell with internal radius r and external radius R. Because this is a shell the gravity inside it is zero, so the end result is that you do not feel any gravity from the part of the Earth outsde you.

OK so far?

yes

So the only gravity you feel is from the part of the Earth inside you, and this part is a ball of radius r. Yes?

so the gravitational influence I experience is of the mass that is between me and the centre, which is less than the whole of the mass of earth. so the a decreases ? yes ?(if I got it right)

Yes :-)

We can write down the equation for the gravity if you want ...

nice

@JohnRennie sure

Suppose the mass of the whole Earth is M. Then the mass of the part of the Earth inside a radius r is m = M r³/R³

This should be obvious because mass scales as volume, which scales as r³, but we can go through it in detail if you want.

@JohnRennie assuming uniform density ?

Yes, assuming uniform density.

@JohnRennie yes

And the gravitational acceleration is a = Gm/r²

Substituting for m we get a = GM r/R³

And that's the gravitational acceleration at a distance r from the centre of the Earth.

Got it !

:-)

thank you for some clarification sir :-)

Tornado by battery cells

You first use spoon to stir it then dip battery cells there.