# the problem of weight or weightless

#### sushi

##### Well-Known Member
the scientific definition of weight comes from the attraction between an object and the earth. Meaning the attraction between two objects cause gravity and fall , which cause weight effect.

An object alone cannot have weight, it can only have mass. But this definition is newton era and past.

Einstein redefine gravity as curvature of spacetime, rather just attraction between two objects.

this could imply that an simgle object could inherently have weight if it sits on space time. (maybe some field cause it) It does not take two objects and its attraction to create wieght.

To be completely weightless (absolute 0 weight) imply true nothingness, which is impossible.

is there any flaw on that kind of reasoning?

#### Cognisant

##### Prolific Member
Weight is mass under the effect of gravity.

If there's a ball in empty space you can't weigh it but you can accelerate it and the amount of energy it takes to accelerate an object to a certain velocity tells you its mass and if you know the mass you can calculate how much it will weigh in a gravity well.

What tickles my noodle is that if you have an electromagnet holding something off the ground where is that energy going? I mean the magnet is essentially doing work, some of the energy going into it is being lost as heat but it's not all being lost as heat, the object has stored kinetic energy but that stored energy isn't increasing, so where's all the energy from the current going through the electromagnet actually going?

#### Serac

##### A menacing post slithers
I have no expertise in physics, but I believe you would have to differentiate between relativistic mass and rest mass. Photons have zero rest mass, for example, yet they exist.

#### sushi

##### Well-Known Member
it seems absolute weightless and absolute masslessness for an object is impossible, because that would imply non existence. an object with 0 mass and 0 weight simply cannot exsit -

no matter how weightless in space an object seems its only relative.

anyone wants to point out flaws in my assumption?

#### Serac

##### A menacing post slithers
I think it's going to depend on definitions. Once again if you're talking about the "weight" of an object as the effect of gravitational fields on the object in stationary state, your conclusion is definitely wrong because e.g. light has zero rest mass but has energy (and thus relativistic mass) by means of momentum. If you're talking about "weight" as coming from relativistic mass, then if you assume that zero energy means non-existence, you are correct because relativistic mass produces a gravitational field. But whether zero energy means non-existence I think is a quantum-mechanics problem.