There are a number of ways of answering this, but I like Asimov's answer best: Asimov says that in a universe that allows an immovable object which will not move under the action of any force howsoever great, then by definition, no force can be invincible. Similarly, in a universe that allows an invincible, unstoppable force, that can move any object, then by definition, it cannot contain an immovable object. Thus a universe containing both an invincible unstoppable force and an invincible immovable object is a contradiction in terms and cannot exist.

Negating the impracticality of the answer, the unstoppable force would be unimpeded and the immovable object would be simultaneously unmoved.

The force would reverse it's direction without changing it's magnitude and the immovable object remains as it is. Thom64:Okay, I'll compare it with a light ray. When a light ray is incident on a perfectly reflecting surface, it reflects itself without changing it's magnitude(of velocity). It may not be a force, but it is a good example that there are some things in this universe that can change their direction without changing their magnitude. And because it's an unstoppable force, it changes it's direction without getting stopped(i.e., without changing it's magnitude.). And also a force may not have momentum, but it surely has direction.

It's impossible for these objects to exist together. The concept of such objects can exist as a thought experiment only. Think about it: If something is unstoppable, by definition it will keep moving no matter what it strikes. The unstoppable object would MOVE an immovable (unmoveable) object that it struck. That's not possible, because the immovable object could not have been called "immovable" if the unstoppable object was able to move it. Likewise... If something is immovable, by definition it will not move no matter what strikes it. So if the immovable object was hit by the unstoppable object, the unstoppable object would be stopped, and you couldn't really call it an unstoppable object. Do you have a headache now?

In the only scenario I can quickly imagine that would allow this condition, the unstopable object would pass through the un-moveable object leaving the first unstopped and the second unmoved.

They would both innihilate each other. I have noticed several contradictions in other answers and I believe this is the only answer that settles both parts of the 'unstoppable force colliding with an immovable object?' scenario. When an object is annihilated, it ceases to exist and is converted into energy, like when anti matter particles meet matter particles. So the unstoppable force is not stopped and the immovable object is not moved, both are converted into energy. Apologies for any miz spelt words, I dont have a spell chekker!

The world and everything on it would die. Example, the asteriod (unstopable force) hit the earth (immovable object) billions of years ago. when this occured everything that inhabited the earth died except for tiny micro organisms. so if this happens again, my friend, we would be toast as well as everything else in this world. :-)

You get a Mexican stand off of cosmic proportions!

They combine to create Chuck Norris

If the immovable object would be a black hole it wouldn't matter how much force moved in its direction. The black hole would absorb any amount of force.

Nuclear implosion.

I think that I need to take a physics class.

You have a modern day relationship.

you quickly realize you've been playing too much world of warcraft.

One hell of an explosion, I would imagine

it causes catstrophies of mighty porportions.The world would be blown to bits.

Explosion.

Somebody winds up with a headache from head butting.

Here's my theory just for a fun example: (For this question to work by the way, we have to assume that both are indestructible.) For the unstoppable object to be unstoppable, it would have to be moving so fast that it would cause a space time distortion rendering it's molecular structure so small that it passes through the immovable object (between it's molecules) without leaving a hole. =0) Have fun!

One of three things follows: 1. The force wasn't really unstoppable 2. The object was not immovable 3. The universe ends because it has an unresolvable contradiction.

diarreah

they both get distroyed

it breaks apart and goes off to the sides.

A "force" of any kind, unstoppable or not, need not be an object; it just needs to be a force. Debatably, the expansion of the universe might qualify as an unstoppable force. If we take "immovable" literally, then an immovable object would have to be unaffected by the expansion of the universe. Perhaps it would also not vibrate at the subatomic level, since that is also movement of sorts. I don't know whether a massless particle such as a neutrino counts as an "object" or not. But could the inertia of some type of massless particle be considered an unstoppable force? When a particle passes through a solid object (happens all the time), is it fair to say that one "collides with" the other? I don't think so. When a neutrino passes through a rock, the neutrino will not be stopped by the rock, and the rock will not be moved by the neutrino. Relative to one another, one is unstoppable, and the other is unmovable. But can we say that the two really collided? Intuition tells me that an immovable object and an unstoppable force cannot be governed by the laws of the same universe. I don't think that the problem is that an object can't be immovable or that a force can't be unstoppable. I think the problem is that they can't collide because they can't both be governed by the same physical laws.

Firstly you can't have a 'force' colliding with something. A force is a way of describing the way an object behaves towards others things. If the said scenario did occur with an object that had unstoppable force this would be infinite force. Since F = ma then the object would either have infinite mass or be accelerating at an infinite rate. Both are impossible because there isn't an infinite amount of mass in the universe and if it accelerating at an infinite rate then its velocity would change in 0 time which would be impossible. IF we did somehow get this unstoppable object then the collision would have infinite energy. Which is a little silly. Long answer short. We would all die along with the rest of the universe.

You mean like this.... http://www.youtube.com/watch?v=--_RGM4Abv8

You would get Superman silly! lol

BAM...! ;-)

I have just recently, as in like...10 minutes ago...came up with an answer that truly keeps the immovable object immovable, and the unstoppable force keeps moving. But first, I want to go over some answers I've come across to this question: One is their definition prevents them from existing in the same universe. An unstoppable force, by definition , means that it can move any object in the universe regardless of that objects size, mass, speed, or energy. Doesn't matter, the unstoppable force will meet those objects and will not be stopped. An immovable object, by definition, is an object in a universe that cannot be moved no matter what meets it, regardless of size, mass, speed, or energy. It can. Not. Move. So, by their definition alone, one universe cannot contain both objects, which negates the question. But, that contradicts the question a little bit, right? Another answer is that if the two meet, the universe would cease to exist. Lovely outlook. Another is that if the two meet, two identical universes would pop into existences, one with the unstoppable force, another with the immovable object to prevent the two from meeting. But how did the two get into the same universe in the first place, and it doesn't answer the question if they meet. Another answer I came across is you have an unstoppable with an infinite amount of energy meeting an immovable object that can absorb an infinite amount of energy. If the two meet, the two objects would appear to be at rest as the infinite energy is transferred. Well, now you have an unstoppable force stopped as it transfers energy. Another group of answers is that they simply cannot meet. That time would slow to a stop to prevent the two from meeting, which would stop the unstoppable force, or that space would expand to keep them from meeting, which fails to truly answer the question to what would happen if they actually met. So! I have finally figured out a solution. The problem seems to be is that everyone seems to be thinking immensely huge. But for this explanation, lets scale this WAAAAAAAAAAAAY down to a more Earthly level. Lets take something very simple...lets say a ball. For kicks and giggles, a baseball. Take this baseball and throw it. You have now created your unstoppable object at this scale. Don't think about gravity or anything, this is a simple experiment, and honestly, gravity wouldn't have a real effect on an unstoppable object. But, I'm getting side tracked. We have a thrown ball for our unstoppable force through kinetic energy. Now, we need an immovable object. For this scale, and this experiment, lets use a wall. Lets say a face of a wall. Now, the ball, our unstoppable force, meets the wall, the immovable object. Kinetic energy travels through the ball as the ball stops moving. The ball itself stops, but the force that the ball has, the kinetic energy, does not. It travels through the ball to the wall, bounces off, and carries the ball with in a different direction. On earth, the ball would bounce off and land on the ground, stopping and ending the experiment, but my point has been proven, that if an unstoppable force meets an immovable object, it would simply bounce off and carry on in a different direction. The unstoppable force continues moving, having not have been stopped, and the immovable object remains still and continues to be fat dumb and happy like fat kids eating chocolate cake. Ta-da!

You have a presidential debate.

Conservation of momentum, so the immovable object would start moving :P

I'd say that the irresistible force stops being irresistible and the immovable object is no longer immovable.

Seeing as how neither exist, nothing.

Both cannot exist in the same universe, by definitiion.

Neither thing exists, so... nothing?

The unmovable object would somehow remain solid but the unstoppable object would pass through it.

The only thing that i know about unstoppable forces and immmovable objects is that they go by the same name. Since i can't think so abstractly, i can only give these two "things" a name. That name is God. God is an unstoppable force. For example, look at all the things He gave us and continues to give us every day of our lives. When everyone else gets tired and needs to rest, God is still unstoppable. No amount of evil or lack of faith can deter Him. Same goes for being an immovable object. No matter how far we stray, God stays in the same place, waiting for us to go to Him. He is completely unmovable. He will NEVER leave us. So, if this is true, then if the two would ever meet it would be like God looking in a mirror and nothing at all would happen. Life would go on as we know it because there is NOTHING besides God that is unmoveable or unstoppable. Works for me!

Likely, they would annihilate one another.

I'm guessing it just bounces off in another direction.

Cruiser86 like your thinking, but there is a moment when the unstoppable force is stopped. when they ball travels towards the wall, then makes impact, the moment just before it heads in the direction away from the wall is one where the ball is topped in a directionless state

Cruiser86 like your thinking, but there is a moment when the unstoppable force is stopped. when they ball travels towards the wall, then makes impact, the moment just before it heads in the direction away from the wall is one where the ball is topped in a directionless state

Airbags deploy.