h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

> "What happens when an irresistible force meets an immovable object? Goofy, yes, but it gives some people insomnia. The general consensus is that the question is meaningless, because the force and the object in question are impossible."

Well, technically it is impossible to have *both* an irresisitable force *and* an immovable object. You can have one, or the other, or neither, but not both. This is philosophy, remember - practicalities don't matter!

Bah humbug. I say they're both impossible. Physically impossible for certain, and maybe logically impossible (according to any recognizable set of definitions). Feel free to prove me wrong....

...but I know what you're saying. I guess I could ask to change that sentence, but I won't bother unless something more significant comes up.

Well, I dunno. I could conceive of an unanswerable exam question, and a student so intelligent it could answer any exam question, but not both simultaneously.

However, you're entitled to your opinion - which is just as unfounded as my own...

fair enough...



I wrote that post first thing in the morning, anyway.

*shuffles off stage-right, pauses, thinks, re-enters*



*Any* exam question? How about: "Write an exam question too difficult for you to answer". Either that question or its answer is too difficult for that student. Thence, God as student, etc.

Clever!

Yep - that's a pretty good proof that you can't have a student who can answer any question - though I still reckon you can have an unanswerable exam question...

I guess the appropriate question to ask is whether "irresistible force" and "immovable object" are each contradictions in terms on their own. I mean the question is already ill-posed just by including both in the same universe, but whether a universe could contain either is a different question.

Hmmm... maybe F=ma means that all forces are irresistible, because any non-zero force acting on any mass no matter how great will produce non-zero accelleration... and the idea of an immovable object is just silly because it assumes some kind of absolute frame of reference.

In some kind of simplified universe with objects all fixed in absolute position and no motion, then I guess all objects are immovable and the idea of a force, irresisitble or otherwise, is absurd. But that universe is boring.

Sortof related idea I was talking about to someone: What is the hardest possible puzzle? One possible idea is that the hardest possible puzzle is to answer the question 'What is the hardest possible puzzle?', because in order to find out which is the hardest puzzle you have answer all other possible puzzles, in order to find out how hard they are to answer. But if the above argument is right, then we've just gone and found the hardest possible puzzle, and it wasn't as hard as, say, proving Fermat's last theorem. Maybe the hardest possible puzzle is then really to answer the question, 'What is the second hardest puzzle?' (or should that be third hardest?) I think we finished up agreeing that there was no such thing as the hardest possible puzzle because you could make any puzzle harder by requiring that you do it standing on your head (for example).

The hardest possible puzzle must be "solve all puzzles", because any particular puzzle must be at least as easy as solving all of them...

How about 'solve all puzzles, then get a partial lobotomy and solve them all again'?

It would be hard to say that a Irresistable force or an Imovable object can exist AS SUCH. Because as soon as you say 'this obect is imovable' it automaticly states that there is nothing in the universe able to move it. And if nothing in the universe can move it, then you are limiting an infinite universe. And how can you put limits on infinity?
This question can, however, be posed differently. For example: one man must always and forever live in a certain doughnut shop, and always and forever buy chocolate doughnuts, no matter haw much he wants to go home or buy a jelly-filled. The shop its self can never ever produce, or have with in it's walls a chocolate doughnut. Hmm... Not the best example, but maybe you see what I mean? It's the mental version. It would be a sort of permanat stand still, the irrestable force of the man's will and the imovable object of the doughnut shop's. I suppose If it were possible for the physical irrestistable force and imovable object to exist, they would also be at a permanate stand still. Ahhh! I need to take a shower.

The immovable object may be the universe just before the big bang.
Maybe the irresistible force is then the trigger for the big bang.

Good theory. What do you all think? Tea and crumpets any one?

the immovable object deflects the irresistible force so it can keep going just in a different direction. The Irresistible Force remains just as Irresistible and the unmovable object remains just as immovable.

In what direction does it deflect it?

For reasons of symmetry, the only direction that can be chosen is that it deflects it straight back. If that isn't resisting it, I dunno what is.

Well if the force was irresistable, in order to deflect something it must be resisted , correct? The whole deflection thing doesn't work.

There's not necessarily a paradox here.

Assume that both an immovable object and an irresistible force are possible and one is hurtling towards the other. the question states irresistible FORCE not irresistible solid. A force (such as magnetism) would be able to pass through an immovable solid. No problem.

Or what if your irresistible force is a neutrino? They pass through virtually anything.

The irresistible thing would pass through the gaps between the matter of the immovable thing.

Simple.

"You can have one, or the other, or neither, but not both."

By elemenatry physice, F=ma where F=force, m=mass, a=acceleration.

An irresistable force must have the value of infinity, meaning that either m or a must also have the value infinity.

By relativity, as a approahces the speed of light, m approaches infinity, thus if a is infinite, so is m.

Hence for both cases, we have an infinite mass.

Infinite mass always ceases to exist.

Therefore, as soon as you get an infinite force or infinite mass, but will immediately cease to exist and thus they cannot collide.

>By relativity, as a approahces the speed of light,
what is meant is not true. A can be as big as it want's. Relativity only puts limits on speed(that it can not be bigger than that of light)and doesn't change the mass it only speed it up. Speed however is a different matter...

>, m approaches >infinity, thus if a is infinite, so is m.
depending on who you ask not true either. m always stays the same. Only to someone in a different frame of reference does m seem to increase as the speed of light is aproached.

And I think the whole logic is flawed in that it is not (very) possible to use old mechanics (f = m*a)in relativistic mechanics.
Also in relativistic mechanics there is no such thing as unmovable since there is no fixed frame of reference. If something is not moving in one frame of reference then it is to someone who is moving compared to that frame of reference (the only exception is light which moves for everyone with the same speed(confusing but true))

Then again there is always quantum mechanics in which almost anything is possible(not to sure on the immovable irresistable part though)
Anyway...
Rod

The only answers I can think of would be:

-The forces moves through the object.
-The object is destroyed.

And I'm not completely sure about either...

The irresistable force meeting the immovable object does appear to define an inconceivable event. However, such an event could be compared, due to its hypothetical nature, to any number of metaphorical events, or even the sum total of the events of all reality.

However, the immovable object is not necessarily impenetrable, nor is it incorruptable. Likewise, it is possible that the irresistable force is intangible.

As far as metaphorical solutions go, I would assign the title of "immovable object" to the individual observer, and the title "irresistable force" to the external environment.

Since you can never be moved from the space that you occupy, and you cannot resist the stimuli presented, the seemingly inconceivable event becomes, as life, merely indefinable. Indefinable in its entirety, at least, as the purpose of the universe appears to be to conceive of all the infinite ways such an event could manifest itself.