If we consider thermodynamics and its law that heat travels from hot to cold, I was curious as to how or what occurs when sunlight is travelling to Earth. The gap between the Sun and the Earth is effectively a vacuum and also the low pressure at high altitudes mean that it is very cold, surely the heat should be dispersed by then and not reach sea level.

I would like to know how we still manage to feel the heat.

Thank you

I've been told that temperature can be explained by how fast molecules are moving around, the higher the temperature the faster they move and the more kinetic energy they have.  This is however confusing as different molecules will move around at different paces and will exist as different states at the same temperature i.e. at room temperature oxygen will be a gas whereas molecules in a chair will be solid.

 Therefore how do you define temperature?

If one drops a frozen turkey from a table, it hits the floor. If one instead drops it from space, it burns up in the atmosphere. Thus, there should be one altitude in between from which you can drop it for it to be done when it comes down.

I realize that it's probably going to go black on the outside and still stay frozen on the inside. How can you deal with this? I will accept leaving it for some time after the fall to allow the heat to distribute properly, I will also accept some or a lot of the outside to burn up if the centre is cooked, burned turkey can be removed but I've heard bad things about uncooked bird.

How does this change with the stuffing? Will it help a lot to thaw it?

Earth, for instance - does it emit more energy than it receives from solar wind?

I found this article today and there is a statement that planets are generally giving away more than they get, in energy terms. I'm not sure if it's meant to be read in general context though.

So... do we calculate the thermodynamic properties of the planets in that manner? Are there 'hot' and 'cold' planets? Is this property significantly related to star proximity and is there a general trend?*

*I suspect the answer of the last question is - 'yes, they all get colder, due to enthropy'. But still, what do you think?

I have a small computer datacenter that consumes about 25kw. Airconditioning cools it to about 25C.

When renewing the airconditioning, I suggested replacing it with air heat pumps for 'green' cooling, so the heat could be used to heat water for radiator space eating or hot water heating. I was hit by a barrage of reasons why this wouldn't work, although my calculations suggest it would. However, I can't find any suppliers for this, which suggests I am wrong.

Would it work, and if not, why not?

Jenny Phillips, Warwick England

Human beings have identified four fundamental forces of nature (the strong nuclear force, the weak nuclear force, the electromagnetic force, and gravity), and it appears that these four fundamental forces enable us to account for everything we observe in the universe (including all matter – i.e. all particles and subatomic particles are understood to be stable manifestations of these four fundamental forces). It appears that all other forces observed in nature can be derived from these four fundamental forces.

If it is correct that Energy is defined not by what it is but by what it can do, then is it correct to assume that energy must be some measure of the fundamental forces of nature acting upon one another?

The fact that mass (such as matter) can be converted into energy (such as in a nuclear explosion) in accordance with Einstein’s equation suggests that everything we observe in the universe is simply the various stable manifestations of the four fundamental forces acting upon one another. If this is correct, then what is a force, exactly (i.e. what is a force, not what does it do)?

According to the second law of thermodynamics, the energy of a closed system always tends towards equilibrium (because an equilibrium state has a higher probability than any other) and the overall entropy always increases. Can energy (all forms including heat, potential energy, kinetic energy, chemical energy etc.) be explained and defined by the fundamental forces of nature tending towards equilibrium?

Imagine you heated a room to more than the temperature of a fire and then lit a fire in that room, would the fire heat up the room further or cool it down? I thought of this question when i noticed that you blow on hot food to cool it, and blowing on ice cream melts it.