What Happens When Air is Drained from a Hot Air Balloon with a Solid Shell?

[jbriggs444]

Yet another question:
If all matter is moving through space, is there such a thing as a truly stationary 'object', how would we know it was with nothing stationary to measure it against?

In other words - If an object in space is described as being in a complete state of rest, what is that relative to? Is there anything that is in a complete state of rest?

No. There is no such thing as a complete state of rest. The laws of physics do not allow for any experiment to detect a state of absolute rest. They can only detect a state of rest relative to something.

One way of stating this principle is that the laws of physics are "invariant" with respect to choice of rest frame. That is, you can pick any non-accelerated object that you like and consider it to be at rest. The frame of reference in which this object is at rest is as good as any other such frame. The laws of physics work identically in all of them.

 

[Zetan]

No. There is no such thing as a complete state of rest. The laws of physics do not allow for any experiment to detect a state of absolute rest. They can only detect a state of rest relative to something.

One way of stating this principle is that the laws of physics are "invariant" with respect to choice of rest frame. That is, you can pick any non-accelerated object that you like and consider it to be at rest. The frame of reference in which this object is at rest is as good as any other such frame. The laws of physics work identically in all of them.

Thank you, that's given me a nice clear picture.