It never happens. If there's a thing that can't be stopped, it's not possible for there to be something else which can't be moved, and vice versa. They can't both exist. it's a trick question. And it is also referred to the Irresistible Force Paradox.

Read this. The grandfather paradox is a paradox of time travel, first described by the science fiction writer René Barjavel in his 1943 book Le Voyageur Imprudent (The Imprudent Traveller).<1> The paradox is this: suppose a man traveled back in time and killed his biological grandfather before the latter met the traveller's grandmother. As a result, one of the traveller's parents (and by extension, the traveller himself) would never have been conceived. This would imply that he could not have travelled back in time after all, which in turn implies the grandfather would still be alive, and the traveller would have been conceived, allowing him to travel back in time and kill his grandfather. Thus each possibility seems to imply its own negation, a type of logical paradox.

^^Yea I know that one. Our Math teacher told it to us when we were taking the lesson Logic. This can be also referred to as a Time Paradox. He gave us another example: Suppose that I'm using the internet to chat with people and I say that everyone who uses the internet is a lair; thus, if everyone using the internet is a lair then I'm a lair and then my statement will be false. But if my statement is false then everyone on the internet is actually telling the truth then I'm telling the truth and then this implies that everyone on the internet is a lair including me. hehe I got dizzy myself writing this :P I think that this is a Logical Paradox as well.

^^no actually that's logically wrong cos there can't be an irresistible force and immovable object at the same time. If a force can't be resisted then there can't be an object which it can't move, and vice versa. If there's an object which can't be moved then no force will be able to move it, that's why it's called a paradox. In addition, the existence of an immovable object and an irresistible force is impossible in physics see wikipedia on Irrisistible Force Paradox

Well, I guess you are right.

Suppose that we have a set of 5 horses. We wish to prove that they are all the same colour. Suppose that we had a proof that all sets of 4 horses were the same colour. If that were true, we could prove that all five horses are the same colour by dividing the horses into two overlapping groups of four horses each. By our supposed existing proof, since these are groups of 4, all horses in them must be the same colour. For example, the first, second, third and fourth horses constitute a group of four, and thus must all be the same colour; and the second, third, fourth and fifth horses also constitute a group of four and thus must also all be the same colour. For this to occur, all five horses in the group of 5 must be the same colour. But how are we to get a proof that all sets of 4 horses are the same colour? We apply the same logic again. By the same process, a group of 4 horses could be broken down into groups of 3, and then a group of 3 horses could be broken down into groups of 2, and so on. Eventually we will reach a group size of 1, and it is obvious that all horses in a group of 1 horse must be the same colour. By the same logic we can also increase the group size. A group of 6 horses can be broken down into groups of 5, and so on upwards, so that all finite sized groups of horses must be the same colour.

That needed a bit of thinking...

It's just hard.

I want to contribute to the worlds longest threat too!

World's longest threat? Aaaahhhhh......

:lol: He made a spelling mistake :P but it's a funny one... I have something going through my mind: Do you believe in love at first sight? <-- you probably have heard this a lot that it became a cliche and boring, but this question means more than it seems. By love at first sight I mean that would you look into someone's eyes and see their souls? i.e. could you know their inner characteristics and thoughts from their facial expressions? And you fall in love with that person you feel he is as soon as your eyes meet, and everything from then on proves that you have been right in that moment. Do you believe in this? If you don't, tell me why.

Actually I do. I met this girl once, and I was really in love with her. We came to know about each other from a friend, and then we met online on Orkut.

Aha that's really cool! Is your love mutual? and does she love you as much as you love her? and are you two still together?

I guess it was mutual. Nope, we aren't together any more. She moved away to the US, and found herself a new boyfriend.