It's possible this is already obvious in the math, but if so, I don't have the luxury of understanding equations on that kind of level.

 

So here goes.

 

I understand thermal energy always moves from a hotter source to a colder one. But logically, I would think it moves in both directions, but the hotter source moves faster and thus wins out.

 

The same logic I would think applies to similar events like diffusion. It's possible my thought experiment is correct but popularizations, and the way it's taught in earlier schooling, makes it less intuitive, as if some unknown force were biased towards heat and equilibrium.

 

Am I on track here?

Yes, I think you basically have the right idea. It is possible for a cold object to transfer energy to a hotter object or for a particle to move into a region of higher density on a molecular scale, but in macroscopic processes, the system will tend towards equilibrium.

That's thermodynamics.

If you want to, you can think of entropy as your "unknown force." Thermodynamical systems always like to maximize entropy (which is a macroscopic quantity).

You are completely correct.

Everything radiates heat. Colder objects just radiate less than hot objects.

 

With thermal radiation, you can calculate quite easily the difference.

 

When other forms of heat transport come into play (they always play a role, only not in a vacuum), our formulas are more and more based on empirical formulas so the two way transport is not described in the theories (the heat transfer is a function (among other things) of the difference between the cold and hot material.

This might be answered, but it raises a ton of possibilities. Maybe others already knew these, but for me it's a leap of insight.

 

Solids, liquids and gases are only distinguishable on the molecular scale by their behavior, which has a root cause identical to the mechanisms of diffusion and thermal equilibrium previously mentioned.

 

Amazingly, the sole reason for all of it is cause and effect, by the 4 known forces.