If energy can’t be created or destroyed, what happens to heat when it eventually cools down?

Question

Energy cannot be created or destroyed, then where does it go when cooling or heating over time?

In: Physics

Answer 1

It dissipates. It just kind flows out into the space around it, one way or another. Like if you have a cup of hot coffee, it cools down, right? But the way that it cools down involves convection (transfer of heat to air currents), conduction (the mug warms up and then warms up the desk it’s sitting on) and a tiny bit of radiation (infrared waves moving out of the mug). All of these result in other things in the room warming up, except they’re a lot bigger and spread out so we don’t notice.