# It's me again about mass

#### Merkur

Hallo everybody!

Now I’ve got another problem:

Is „mass“ really absolute or does it depend on the gravity?

(Here, I really think of „mass“, not of „weight“)

Thank you!

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#### chroot

Staff Emeritus
Gold Member
The word "mass" refers essentially to the proportionality constant between applied force and experienced acceleration:

F = m a

Weight is force -- the force pulling you to the earth right now, for example. On the Moon, a body with a mass of 1 kg will not weight 9.8 newtons like it does on Earth -- it will weigh less. However, if you apply the same force to the 1 kg mass on both the Earth and the Moon, the mass will accelerate the same way in both places.

- Warren

#### turin

Homework Helper
From what I understand of GR, mass is more massive in a stronger gravitational field, because the field equation has a sort of positive feedback. In other words, a mass in a g-field has an energy because it is in the g-field. This energy contributes to the amount of gravitation, which is directly related to the mass.

#### benzun_1999

i feel.................

before i begin, this is my own idea not any sort of a theory. i feel mass is something that exist when there is a charge. Look at an atom it has charge(inside it) and it has mass. but now look at light, it has no charge and it has no mass. So i feel that mass is something caused by charge in space time.

I might be wrong, if i am please correct me.

-Benzun
All For God.

#### Merkur

Originally posted by chroot
The word "mass" refers essentially to the proportionality constant between applied force and experienced acceleration:

F = m a

Weight is force -- the force pulling you to the earth right now, for example. On the Moon, a body with a mass of 1 kg will not weight 9.8 newtons like it does on Earth -- it will weigh less. However, if you apply the same force to the 1 kg mass on both the Earth and the Moon, the mass will accelerate the same way in both places.

- Warren

But I do know the difference between mass and weight ...

But does the relativity theory cause any mutation of mass, too (when anything passes anything with a particular speed)?

Mille grazie!

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