Dear Ariadne

Thank you for answer.

Please pay attention that question is based on the relation between the increasing of mass is caused by the heating (considet to relation E=mc^2).

Best Regards

Hossein

if so why does a dead human body 'dead weight' feel heavier than if alive? 

perhaps our soul causes a reduction in the stress energy tensor?

False. The temperature doesn't represent motion of the object, but of the constituents of the heat bath, with which it is in thermal equilibrium-the object itself doesn't move as a consequence.  Furthermore, some care is required, because the energy scale defined by the temperature represents a specific reference frame. 

Dear Roger

There is a lot answer to your question in net. For example see:

http://www.drug3k.com/forum1/Other-Health/Why-does-a-human-body-weigh-more-dead-then-when-its-alive-18507.htm

https://in.answers.yahoo.com/question/index?qid=20091122221507AAzSuLI

But I think there's another reason.

Man is dead, but his body tissues are alive and are being fed and Decomposition. His skin breathes oxygen more than when alive. Compare the mass of heat (m=E/c^2) with mass of oxygen.

Correct. When you put energy into a system, the mass of the system increases, if we define the mass of the system as the ration between momentum and center of mass speed when center of mass is moving slowly. This has not been seen experimentally, though, since the mass changes are minuscule.

On the other hand, this has only to do with the definition of mass for composite objects. It has nothing to do with photons. By the way, the statement that photons are massless is a bit misleading. Mass in this context is defined as rest mass. But photons cannot be at rest, so do not have a rest mass. On the other hand, a set of photons in a cavity *will* contribute to the mass, as stated by Charles. But it is not a good idea to try and ``add'' the photons' masses to the cavity's: it is simpler to think in terms of the rest mass of a composite body not being equal to the sum of the masses of its constituents. 

On a related theme, it has been shown experimentally that iron nuclei emit gamma rays with a lower frequency when the iron is hot, because of time dilation due to the irregular thermal motion. The shift is small, but measurable and qualitatively in agreement with the theory.

Dear Leyvraz

"...since the mass changes are minuscule." I agree with you about the small system, but the Sun loses around 4,200,000,000 kilograms every second!

So, independent of wave-particle duality, energy has mass.

Also, heat, temperature and the motion of molecules are all related.

So, seems energy is same as matter with high speed. In the other word, energy moves with speed of light c, and matter moves with speed of v

Dear Charles

You are right, but a part of it in the form of electromagnetic energy.

If you heat up a materially object it encrased it's mass. But we cannot measur such infinitesimal differences.

If you give energy to a photon it will get a higher frequency according to E=h*ν.

Dear Hans

Thank you for mention, I agree that is not measureable. But its scientific concept is very important. In my view it leads us to trying find the mechanism of system's heat.

https://www.researchgate.net/publication/279531060_Graviton_physical_time_and_thermodynamics?ev=prf_pub

Article Graviton: physical time and thermodynamics

For Newton, the force of gravity was merely a function of masses and the distance between them. Maxwell unified electric and magnetic fields into a symmetric coherent set of equations known as Maxwell's equations. For Einstein, gravity was caused by a deformation of space-time continuum. On this basis, he developed a highly complex algebra that merely describes it geometrically. Nowadays the majority of studies explain only the effects of gravity and not its nature. The unification of gravity with electricity has been a challenge for many great physicists of the last century.

Force and Energy are convertible. Also according to Relativity, mass and energy are equivalent. So, Force, Energy and Mass are three manifests of a unified entity. And it leads us to change our perception about force, energy and mass.

Unified Force, Energy and Mass

https://www.researchgate.net/publication/280626794_Unified_Force_Energy_and_Mass?ev=prf_pub

By using the unified force, energy and mass all laws and principles of physics can be concluded, including:

The Momentum Conservation law

The Conservation of Angular Momentum

The Law of Conservation of Charge

Conservation of mass-energy

Newton's laws

principle of constancy of speed of light

Relativistic mass

New definition of singularity

Physical nature of fields

Structure of sub atomic particle

https://www.researchgate.net/publication/280491440_Reconsidering_relativistic_Newton%27s_second_law_and_its_results?ev=prf_pub

Article Unified Force, Energy and Mass

Article Reconsidering relativistic Newton's second law and its results

True. It may be due to the thermal expansion of molecules at higher temperatures.

Dear Santosh

You are right. The argument "the same object weigh more when it is hot than when it is cold." is true regarless of its size (affectetd of heat).

What is the mysteries of mass?

Neutrinos have mass, but the Standard Model can't easily account for how they get those masses.

https://www.forbes.com/sites/chadorzel/2017/09/28/what-is-the-greatest-wrong-theory-in-physics/#6826c794d2eb

By proposing of the relativity and limit speed of light c, the Newton’s second law was corrected so that the limitation of speed must had applied. And relativistic Newton’s second law was propounded.

After 1906 Einstein have derived the second postulate of special relativity the constancy of the speed of light by assuming that the light quanta that he proposed in 1905 were massless particles.

It is just possible that we could allow m0=0 provided the particle always travels at the speed of light c. In this case above equations will not serve to define and so that for massless particle given by; E=Pc.

What does determine the momentum and energy of a massless particle? Not the mass (that is zero by assumption) not the speed (that is always c). Relativity offers no answer to this question, but curiously enough, quantum mechanics does, in the form of Plank's formula: E=mc^2. Only moving photon has mass as follows from the Einstein formula E=mc^2. Physicists have not stopped on assumption of massless. There are more attempts were made to clarify the photon massless in theoretical and experimental physics. There are good theoretical reasons to believe that the photon mass should be exactly zero, there is no experimental proof of this belief. These efforts show there is an upper bound on the photon mass, although the amount is very small, but not zero. The tight experimental upper bound of the photon mass restricts the kinematically allowed final states of photon decay to the lightest neutrino and/or particles beyond the Standard Model.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.021801

Theories and experiments have not limited to photons and graviton will also be included. For gravity, there have been vigorous debates about even the concept of graviton rest mass.

https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.82.939

Particles and NR-particles: There are two kinds of particles in physics:

1 - Some particles like the photon moves only with the speed of light, in all inertial reference frames. Let’s call these kinds of particles as Never at Rest condition particles (NR-particle).

2 - Other particles like the electron always move with the speed c in all inertial reference frames, they could be called particles.

According to the above definitions, photon and graviton are NR-particle, while electron and proton are particles.

This new approach helps us to review the relativistic Newton’s second law; See Section 5 of:

Beyond the Standard Model : Modern physics problems and solutions

https://www.amazon.com/gp/offer-listing/1939123623

Not true. Energy does not posses mass, nor does mass have energy, ther than the normal iternal energy and of course nuclear binding energy. If you could convert the heat in an object (which is just its internal (molecular or atomic motion like translation, vibrtion etc) and nuclear energy) into mass (given by Einstein's relation) it would cool and weigh more (for a completely isolated system). Similarly, mass converted into energy clearly weighs less, and of course is achieved through radioactive decay. The atomic bomb. Both fusion and fission realise this.

Dear William Gregory Jackson

Thank you for comment.

I suggest reading new research about energy and mysteries of physics.

Energy: theoretical and experimental incompatibility

https://www.researchgate.net/publication/326247617_Energy_theoretical_and_experimental_incompatibility

The Greatest Unsolved Mystery in Physics

https://www.researchgate.net/publication/330366766_The_Greatest_Unsolved_Mystery_in_Physics

The biggest open challenges of physics and solutions

https://www.researchgate.net/publication/340999864_The_biggest_open_challenges_of_physics_and_solutions

I talked to Dr C Y Lo, he has done the experiment - the opposite happens to what Einstein says; an object heated loses weight not gains. https://www.youtube.com/watch?v=oPw3xK-9tVQ

According to Dr Lo: Wheeler school of relativity has misunderstood relativity! And according to my researches: relativity must have been from Einstein's wife so Einstein misunderstood it: https://www.youtube.com/watch?v=2QrCJg23vAE

Dear Anderton

If hot iron loses weight, it is still because energy has mass.

Some warm atoms may ionize due to heat.

The problem is not Einstein, the problem is reality of science.

Another interesting aspect of the issue of relativistic atoms and ions. From the point of view of a motionless observer, due to the twin paradox, in a relativistic plasma (i.e., in a plasma hot enough for its particles to move with relativistic speeds) all reactions, and first of all nuclear ones (because of chemical reactions in such hot plasma can hardly speak) should slow down.

A nice thread (follow the comments) closely related to this. Answer for all these questions is a unified field theory, an ultimate explanation /model for everything, and nothing. Until that model emerges, all we can do is dwell in the metaphysical world.

https://www.quora.com/What-is-quantum-field-theory/answer/Barak-Shoshany

It is clear that the weight of a unit of MASS is always the same at a given point in space-time. As for the VOLUME unit, the original statement is erroneous. In fact, the mass of a unit volume of a material increases slightly on heating according to Einstein's formula, but at the same time decreases much faster due to thermal expansion.