Unstoppable object vs. Unmoveable object

[El Elvis Rojo]

Okay, it's a stupid question from back in high school, but noone ever had enough intelligence to give it a good answer, so I come to you guys.

What would happen if an unstoppable object were to collide with an unmoveable object?

[pravnik]

It can't happen. It's a logical impossibility. The existence of an immovable object precludes the existence of an irresistable force, and vice-versa, by definition. You can't have a universe with both.

[CalMeacham]

There's an interesting example of this in mythology. I'm not sure of the character's names, but there was a dog -- Laelaps, I think -- who was said to be capable of running down any prey. And there was some sort of beast -- a deer or something -- that was supposed to be able to evade any predator. One day Laelaps went off after the beast. And.......




















....Well, Zeus changed them both into stone, so as to avoid any sort of resolution or logical conundrums.




I suspect the story evolved to explain a pair of natural stone formations that looked kinda like a dog and deer/rabbit/whatever. The final fillip of the reason for their being turned into stone was, I bet, a really late addition to the spiel the locals gave. But it was too good not to write down.

[mbh]

According to my high school physics teacher, there are two possibilities:

#1 An infinite amount of heat would be generated.

OR

#2 They would get married.

[pravnik]

I hope he/she was joking about the heat one.

[KneadToKnow]

Originally posted by pravnik
The existence of an immovable object precludes the existence of an irresistable force, and vice-versa, by definition. You can't have a universe with both.

While your conclusion based on your analysis of the more traditional wording of the paradox may have merit, El Elvis Rojo didn't ask about an irresistable force. He asked what would happen if an "unstoppable object" (emphasis mine) collided with an "unmoveable object."

The answer, it seems to me, is that the "unstoppable object" would interact with the "unmoveable object" in such a way as to allow it to continue on its way. This could be as simple as rebounding off it like a billiard ball, oozing around it and then continuing in a straight line the way honey might if while drizzling it over your pancakes you stuck your finger into the stream, or simply parting and passing around it in the more traditional style of a river passing around an island. None of these interactions interfere in any way with the given definitions of "unstoppable" and "unmoveable."

[Trigonal Planar]

Your example of it bouncing back would not work, as motion does come to a stop at the moment the direction changes.

[stypticus]

Not if it bounces at an angle.

[KneadToKnow]

Perhaps I should have said "deflecting off it" instead of "rebounding off it."

[gazpacho]

This is one of the many cases where Newtonian mechanics break down and you must resort to quantum mechanics. In these situations the unstoppable object would quantum tunnel through the immovable one.

[pravnik]

Originally posted by KneadToKnow
While your conclusion based on your analysis of the more traditional wording of the paradox may have merit, El Elvis Rojo didn't ask about an irresistable force. He asked what would happen if an "unstoppable object" (emphasis mine) collided with an "unmoveable object."

The answer, it seems to me, is that the "unstoppable object" would interact with the "unmoveable object" in such a way as to allow it to continue on its way. This could be as simple as rebounding off it like a billiard ball, oozing around it and then continuing in a straight line the way honey might if while drizzling it over your pancakes you stuck your finger into the stream, or simply parting and passing around it in the more traditional style of a river passing around an island. None of these interactions interfere in any way with the given definitions of "unstoppable" and "unmoveable."

Interesting, but I'm 99% certain that's not what he meant. If "unstoppable" means only "able to bounce off of or flow around, but never stopping", there's no paradox, only a question that can be answered without much difficulty. If the object that is able to bounce off of or flow around any object without ever stopping meets an immovable object, it's obvious what happens; it bounces of off or flows around it without stopping. I think what he meant to describe was the classic "irresistable force v. immovable object" paradox, and that "unstoppable" was intended as continuing forever in a straight line and moving any object in its path.

[KneadToKnow]

Originally posted by pravnik
Interesting, but I'm 99% certain that's not what he meant. If "unstoppable" means only "able to bounce off of or flow around, but never stopping", there's no paradox, only a question that can be answered without much difficulty.

Then we are in agreement. I was not trying to assess what he meant, but what he asked.

[pravnik]

Originally posted by KneadToKnow
Then we are in agreement. I was not trying to assess what he meant, but what he asked.

I gotcha.

[shy guy]

I realze I'm not quoting Newton on the subject or anything, but in an old issue of Wizard (yes, the comics magazine) someone asked what would happen if the unstoppable Juggernaut ran into the immovable Blob. They're answer was that the Juggernaut just bounces off him - not stopped, just redirected.

I remember that off the top of my head, for some reason.

[moriah]

Three million quatloos on the irresistable force.

Five million quatloos on the immovable object.

Thirteen million qatloos on the new comers!

Peace.
----------------
"Norman... coordinate. <beeeeeep>"

[Shade]

Is it merely unstoppable or unslowdownable? If unstoppable maybe it'd approach the immovable object asymptotically, never stopping or changing course, but slowing down constantly so it never gets there.

[nitpick]relativists, think 'unmovable in a given reference frame[/nitpick]

[zev_steinhardt]

The Marvel Comics version of this question would be Juggernaut vs. The Blob. That's a fight I would have liked to have seen. Too bad they were both bad guys.

Zev Steinhardt

[Splanky]

The Unstoppable object would get infinitely slow and would never collide with the unmoveable object.

[Shade]

Rereading the OP they actually have to collide. Maybe the immovable object could be compressed though, as the unstoppable object slows down.

[sleestak]

I asked a friend, Luba, this question once. Luba has a PHD in physics and her specialty was impacts. (She worked on developing bunker buster warheads at one point)

Her response- infinite impact. Then again she could have been joking.

Slee

[scr4]

A photon is an example of an unstoppable object. When it interacts with nearly immovable objects, it gets deflected or destroyed. (Unstoppable does not necessarily mean indestructable.)

[shep proudfoot]

There is no such thing as an unstoppable force (outside of God) or an unmovable object. Thus the argument is rather silly.

[Mephisto]

Originally posted by zev_steinhardt
The Marvel Comics version of this question would be Juggernaut vs. The Blob. That's a fight I would have liked to have seen.

I know "me too" posts are frowned upon by many here, but in this case I really can't help it: me too!

[NotMrKnowItAll]

Would not the universe in it entirety be considered an immovable object. I can't image how one could even define movement of the universe as a whole...

A photon on the edge of the universe's expansion could be considered an unstoppable object as well...

[scr4]

Originally posted by NotMrKnowItAll
Would not the universe in it entirety be considered an immovable object. I can't image how one could even define movement of the universe as a whole...

If you can't define movement, how can you define it to be immovable?