We have so many negative models around that it is hard to think accurately sometimes. What I mean by negative forces, is explanations that propose a mysterious force, which can’t be measured, pushing, or more often pulling things around.
Case 1: Hot Air
Some people claim that ‘hot air rises’.
It’s as if the hot air has a little motor in it, or perhaps a battery that enables it to propel itself upwards. I doubt that.
A more useful model, for the real world, is that cold air, being more compressed, hence heavier, falls to the ground. We see this when we open a freezer and see the heavy cold air tumble out.
Now when that heavy, cold, compressed air pushes downward, due to gravity, it squeezes the lighter less compressed hot air out of it’s way, thus giving the illusion that hot air rises, when in fact, the cold air, as a side effect of its falling, due to gravity, pushes the hot air upward.
Try it yourself.