kcdodd wrote:Define "somehow", then you can say QED. lol.
I can push on myself without moving, but I am not immovable.
Maybe if chrismb can clarify how such a thing would exist under his understanding.
Agreed.
chrismb wrote:
I beg to ask you to examine your own statement: If a force is applied to an object that alters its momentum, if it has not changed its displacement from the origin of that force (i.e. nothing has changed) then by what measure are you judging its momentum to have changed?
Well an impulse will change momentum without changing displacement. You judge the changed momentum by observations over an extended period of time after the change. Indeed without such a period energy (and hence in an isolated system momentum) cannot be measured. But introducing QM here is not needed. The point is that velocity (and hence momentum) is the first derivative of displacement.
chrismb wrote:
I take your point that if you can push yourself away from a thing that doesn't move then you've created momentum spontaneously, which is not possible. But that's not my point. What I'm saying is that if you find something 'stationary' then it is not so much that you can push yourself away from it, so to speak, but that you just can't find a way to apply a force at all! It won't have any 'handles' to push or pull on!
Words are poor tools to describe physics.. So forgive me if I am misunderstanding you. For better understanding, you need less ambiguous statements (not words!).
You are saying that acceleration is only possible for objects in a frame of reference other than that given by the universe COM. This is radical, since it breaks special relativity. It is also unclear how this works. Suppose your "immovable object" has a
small movement relative to COM frame. Does it behave normally, or with some increased inertia?
As kcdodd has pointed out, the existence of your "immovable object" creates grave problems. Difficult to see what mechanism would prevent lack of conservation of momentum.
Then you start talking about photons. This is less clear, and therefore less obviously inconsistent. But a transformation in which c -> 0 is pretty radical, worse than the > c <--> < c transformation (which is possible) because 0 is not, according to principle of relativity, well defined.
I have stayed clear of the above argument since it did not seem to be going anywhere. Now it IS going somewhere i am registering my disagreement with the destination!
Best wishes, Tom