# Is a hot object heavier than the cold one?

Tom S 09/13/2018.

No, hot air balloons float better than cold air balloons, so they weigh less (lighter than air), as one example.

goring 09/12/2018.

In the same gravity field two one kilogram mass weighs the Same.

However if one mass is injected by massive radiation it will contain more mass than the cold one.

That means as the temperature of an atom increases, its mass will also increase accordingly.

Atoms are in a continuous mass change; the stability of an atom vacillates between the points of equilibrium.

A cold potato will always weight less than a hot potato.

oldprof 09/11/2018.

That's the claim. Why? Because the higher energy content adds just a smidgen of rest mass to the object. And therefore the pull of gravity is acting on a slightly heavier mass giving that object more weight than its cold version would have.

Jim Moor 09/10/2018.

SAME

Here's why, look at your question: "Is a hot object heavier..."

"Heavy" is defined as "force"

Force = mass * acceleration

That's it

neb 09/10/2018.

Yes, but by an almost infinitesimal amount. Mass/energy is more complicated in general relativity involving not just energy density, but momentum density, pressure, and stress. If you have two identical objects, the hotter one will have more energy, therefore more gravity. Note that you should think in terms of energy rather than mass since they really aren’t the same thing. They have an equivalence, but mass does not increase, energy does.

sojsail 09/10/2018.

If we suspect that energy HAS mass, should we expect that the mass would increase if we give it more gravitational potential energy?

I can't see it, but ... there are many accepted Physics theories that I can't see.

Vaman 09/10/2018.

Yes. It should. Mass is proportional to the energy. Energy of a mass m = mc²+ n kT

n is the number of particles, k is the oltzmann constant and T is the temperature. According to this mass increases with energy. This is also seen in the relativity also.There the kinetic energy plays role of kT.

Anonymous 09/10/2018.

Yes, adding heat to an object will double it weight per degree.

Where does this stupid **** come from.

flyingtiggeruk 09/09/2018.

Its density may reduce marginally if it expands, but the mass will be the same.

Kevin7 09/12/2018.

If there is a weight difference such a difference would only clearly detectable to current human technology on a very big object like a star. or a quasar .Albert Einstein did say Energy is mass,so i understand your logic

Doc Awesome 09/12/2018.

By weight, not generally. Yet, because most heated objects expand by volume, its overall mass may to some degree, be changed. There are cases where charged particles can be absorbed by objects and those ions may transfer their unstable charge to object open to gaining electrons and increase its atomic weight. Further, bombarding elemental lead with energetic protons in a collider can cause some of them to fuse into the atomic lead nuclei and transform them into gold atoms. Those are heavier atoms, thus a slightly heavier material is created from the process along with a lot of relative heat.

Smelting processes also infuse iron molecules with carbon and other elements to create alloys. Since the alloys are compound materials, they are heavier (slightly) than the iron in pure state would be.

Andrew Smith 09/10/2018.

This is a very interesting question. We are not able to measure it with enough precision.

But one argument is that energy HAS mass. A different one is that mass is CONVERTED to energy.

If the first was correct then the mass should increase by the mass of the energy.

If the second, current, view is correct then the mass should not be altered at all ie the energy has no mass itself.

If we were able to measure the mass with sufficient precision it would support one or other of these views but must contradict the other one of them.

I would love to be able to do the experiment and get an answer now instead of building ever more physics on an untestable foundation.

Julien 09/09/2018.

Please be more specific. You mean the same object in both cases but put at different temperatures?

Then the object is marginally heavier when it's hot, something like deltaM = N*kB*deltaT/c^2, but I can't think of any "real-life" or industrial situation in which it would be non-negligible.