Why does hot air balloon rotate with the earth? This might be a silly question but I have been wondering this for quite a while. 
When a hot air balloon is flying in the sky, the earth is rotating at the speed of 1000 mph. Why does it move along with the earth when it's not attached to the earth? It would be cool to watch the earth rotate hovering in the sky! 
My guess is that the force of gravity keeps it. If that's true, can you see the earth spin from the space?
 A: A hot air balloon floats immersed in the air, similar to the way a fish might float immersed in the ocean. The fish doesn't see the seafloor below it zoom off at 1000 miles per hour because it is inside the ocean which is rotating with the Earth. Similarly, a hot air balloon rests inside the atmosphere which is rotating with the Earth. The ocean and the atmosphere both rotate with the Earth for the same reason: friction with the solid Earth would prevent them both from moving (on average) across the surface.
A: The same reason you can jump up in a bus and not be slammed into the back of it.
The balloon already has the same velocity as the earths rotation. As does the air around it (ignoring air currents). 
Lets take the bus example again. If you are in a bus, and it goes 50km/h, everybody else in that bus wouldnt seem to be moving at all. Because the bus is the closed system and you observe it from within that system. If you jump, it looks like you only traveled vertically, because you would land at the same spot on that bus. Why? Because you tarvel just as fast as the bus does.
Now, imagine someone from outside observing this. To them, you would jump and move forward at the speed of 50km/h.
You can view the earth and its atmosphere as a closed system.
Lets say you observe that balloon on earth, which means your point of reference is a point within the system. You wouldnt be able to notice earth rotation, because you rotate with it. Same goes for the balloon.
Now, lets say someone from the sun would look at that balloon. What would they see? They would see the balloon turn around earth with the same speed that earth rotates. 
So you could say the balloon doesnt rotate with the earths surface, they just have the same velocity in the same direction, just like the air around the balloon.
EDIT:
To clarify, make no mistake. You do not rotate with the earth because you are attached to it. If that were the case, you would need to counter balance the 1000mph you mentioned evey second of your being. And I dont think thats humanly possible for even a moment. You just rotate with the earth seemlessly because you already have the same velocity.
A: The balloon is affected by the earth's rotation in relation to the atmosphere in a way, the coriolis force causes patterns in the movement of air in the atmosphere.
https://en.m.wikipedia.org/wiki/Coriolis_force
But if you start a hot air balloon from the ground, which is rotating with the earth, if you raise the balloon it will keep rotating with the earth unless something moves it otherwise (like wind). 
If you bring in a hot air balloon from space, it most likely will not be rotating with the earth to begin with, then you could see the rotation of the earth as you descend,  until the atmosphere starts to drag you along. 
