[Seany (OP)]

Hmm.. Einstein that lil cheater! LOL []

[JimBob]

My type of guy but not an example for his sons!

[Seany (OP)]

What does unstoppable and unmovable actually mean?

There can not be any absolute frame of reference where one thing is regarded as stopped, and another regarded as moving.  All motion is relative.  A thing is only stopped, or only moving, in relation to some particular observer.

To say something is unmovable is merely to say that the particular observer will be in a permanently fixed position with regard to that object - other observers might still see that object as moving.

I assume when you talking about an unstoppable object, you actually mean more than merely unstoppable, but an object which cannot alter its speed relative to you at all (e.g. it has some of the attributes of light travelling through a vacuum).  If all you mean by unstoppable is that it can never have zero velocity relative to you, but is quite capable of bouncing back the way it came, then that does not of itself in any way preclude the immovable object (although there would be other physical laws that would make the idea of an immovable object rather difficult).

I don't clearly understand.. From every perspective, surely a "stopped" object looks "stopped"?

There is a box. Two people are here. One is moving. The other is still. Both people can see the box. Both people think the box is still?

[Soul Surfer]

The question is not realistic and therefore not interesting a far more interesting result is what happens when two bodies of similar mass collide exactly in line with their centres and there is very little loss (like billiard balls)  Assume one is stationary and one is moving.  The one that is moving stops dead and the one that was stationary moves on at the same speed as the one that was moving.

[another_someone]

Stopped and moving with respect to what?

There is a box (no windows) that is sitting atop a moving train.  One person within the box is running towards the rear of the train at exactly the same speed as the train is moving forward (and so is stationary with regard to the ground beneath the train), while the other person sitting on a chair in the box (so is stationary with regard to the box, and the train; but is moving forward with regard to the ground).  So who is stationary and who is moving?

[Batroost]

So who is stationary and who is moving?

This is one of those questions again...

Surely the point is that it doesn't matter whose frame of reference you use provided it is 'inertial' i.e. not accelerating. All of the laws of motion will still be applied correctly whether you take the ground or the train as sytationary. However, you have to choose one to do any meaningful analysis at all.

[Monox D. I-Fly]

I read about it in TV Tropes once, and got this quote:

Used as a riddle in the far-future section in Ian Banks' "Walking on Glass". The actual answer is randomly tossed out in the other narrative. The unstoppable force stops, the immovable object moves.

[Colin2B]

I read about it in TV Tropes once, and got this quote:

Used as a riddle in the far-future section in Ian Banks' "Walking on Glass". The actual answer is randomly tossed out in the other narrative. The unstoppable force stops, the immovable object moves.

This isn’t an answer because the question is based on circular or conflicting statements eg “do not read this sentence”, “I always lie, so don’t believe what I say”.

[yor_on]

How about observer dependencies?

[Colin2B]

How about observer dependencies?

Valid point, the unstoppable object is already stopped for one observer and the unmoveable is moving.