What is heat?
(a) A state of an atom
(b) A state of a collection of atoms that we call a body

If we choose (b) as the answer - to me it seems to be the right answer - then can a body have a cold state that is similar to the hot state in intensity and in the behavior of the individual atoms, except that it is represents an opposite state (say, like the positive and negative charges)?

I am not sure where you are going with this it actually makes more sense under you definition you prefered with Bill S that there is only potential and kinetic energy.

Under that setup its reasonably simple heat is the amount of kinetic energy of atoms.

Kinetic energy of atoms is the internal energy of the body, and so the potential energy as far the body is considered. So it is a potential state of the body, not the atom.

If the internal energy changes into the speed of the body, the body will get cooled. If the internal energy thus becomes very low and the speed very high, compared to the initial state, then the body should again be in a potential state, this time a cold state; that is what I propose.

Again you are playing with words .... show me cold energy and where I can derived it from.

See we don't use cold energy to take stuff to near absolute zero we use real energy and set up processes to take heat away it's not like a hot and cold tap on your bathroom we don't have a magic cold energy we can turn on we use hot water and a heat exchange process to cool thing down.

You see, it is just a proposal. Suppose a mass of atoms possesses a certain amount of energy. Let the speed- internal energy ratio of it be an ideal one that there is no energy transfer between speed and internal energy. Then it will move at a uniform speed; its density and temperature will remain constant. What I propose is that the mass would be at absolute zero if the temperature is to remain constant. If its internal energy increases at the expense of speed, then it would be in a hot state, and if its speed increases at the expense of its internal energy, then it will be in a cold state. Then Its temperature will be below absolute zero.

A very hot mass like sun is light and releases radiations. By symmetry, a very cold mass will be dense and will absorb all radiations falling on it. Naturally, black holes may be cold masses.

Usually the easiest way to do these sorts of worlds is as a computer simulation, Do you have any programming experience?

Nasa for example as Ringworld as there example of weird physics world (http://settlement.arc.nasa.gov/teacher/materials/ringworld/ringworld.html)

I have one thats even weirder I have a flat universe spinning via a centre of mass so the universe has centripedal force throughtout ... very funny effects.

No, I have no programming experience; all I have is mental simulation, and one can always go wrong. Any way, I have it all from the beginning to the end - starting from the fundamental particle of matter and ending in an Ensemble containing billions of universes. So I call it my 'theory of everything'. And, I just take it seriously.

Flat universe, just for fun or a serious work?

Was an initial thought I had when we got figures in that the universe appeared to be essentially flat.

I wondered if it could not be like a very large super galaxy essentially a flat disc spinning about a centre of mass of the universe.

The centrifugal force being the force that is hurling the galaxies away in all directions.

The problem is all galaxies should be following arc tragectories away and they aren't. It also leads to some well interesting problems and especially near the centre of rotation.

Now days its just a failed theory fun.

Here is my model: a universe oscillating between hot and cold states. The universe is spherical. As an entity it neither spins nor moves. The energy is possessed by the individual members, the galaxy-clusters; the energy remains divided as internal energy and speed. The transfer of internal energy to speed moves the clusters outwards, and the universe expands. When speed reaches the limit, the expansion ends and the speed starts changing into internal energy, causing contraction. This process continues, and the universe remains pulsating. When the internal energies are high, the masses are hot; some are very hot, and are stars. When the speeds are high, the masses are cold (having temperatures below 0K); some are very cold that they are black holes.

So what, how or who determines the limit?

The natural energy of any cluster is mc^2/2 ( that is my proposal).That is, any galaxy cluster is to move at the speed 'c', if the whole of its energy remains with it as speed. However, part of the energy is internal energy. When the speed- internal energy ratio is normal, the average temperature of the cluster will be zero. Any change in that ratio creates potential states which oppose the change - an increase in speed creates cold state and an increase in internal energy creates a hot state. Because of that, the speeds and internal energies have limits, and the system oscillates between two states - a super-cold state, when the the speeds are the maximum and the super-hot state, when the internal energies are the maximum.

Thats the bit I am still confused at aren't the two end states both stable points ... so when one reached an end point why would it start to go back the other way. I can't see such a system osscilatting ... or am I missing something?

Heat is a state of energy. Don't think too much. E= mc^2 is a theory that I not agree so much. If you add a Lorentz factor inside, you will get something that ridiculous enough(when you travel at speed of light, the energy is complex infinity). So please don't imagine all energy is measured in that. Some yes and some no.

Orac, you didn't miss anything. All the particles are obeying the conservation energy law. None of the particles want to be in a high kinetic energy state. If you didn't heat it, the particle will tell itself, " I am out of energy to stay in this state." And it will cool down itself. Just stick to the particle physics theories.

What system is that? You mean the Higgs Mechanism which oscillates between two state when you are having a spontaneous symmetry breaking.

This is a mental problem not a real one ... he is making a theoretical world with laws.

Here is NASA version of a weird world
(http://settlement.arc.nasa.gov/teacher/materials/ringworld/ringworld.html)

They are thought problems to think about why the universe is like it is.

No. I am visualizing a spherical universe containing a finite amount of matter and a finite amount of energy. It is a system of galaxy-clusters. When their internal energies change into their speeds, these move outwards causing an expansion, and when the speeds change into their internal energies these move inwards, causing contraction. What I propose is that the speed- internal energy ratio should be normal. However, the change towards the normal takes it to the other extreme and so the system remains pulsating.

You can consider heat and cold as potential states. As the universe expands, cold energy builds up, and ultimately this prevents further expansion. Being a potential state, the universe cannot remain in that state. So it starts contracting so as to return to the normal state, that is, the state when the temperature is 0K. However, the speed of contraction reaches the maximum by the time temperature reaches 0K, and so the process of contraction continues until the heat energy that builds up in it prevents further contraction.