What happens if an unstoppable force meets an immovable object?

This paradox is a popular one that seems to have no resolution since the existence of one seems to deny the possibility of the other. After all, if you have an unstoppable force that must mean that there can be no such thing as immovable object and vice versa.

But while one can dismiss the paradox on those grounds, it is interesting to look more closely at it to try and get a better understanding of what we mean when we say ‘unstoppable’ and ‘immovable’ and try to give operational, as opposed to intuitive, meanings to those words. In doing so, we usually arrive at a deeper understanding of the paradox and of relevant physics principles.

Via Maggie Koerth-Baker I came across this interesting video that does just that.


  1. Alverant says

    I’ve watched his channel for some time now. It stopped be “minute” a long time ago in favor of longer videos (but they’re good videos so who cares). This was a thought provoking video because it means that the unstoppable force and immovable object were THE SAME THING.

    On a side note I also subscribed (past tense) to a channel called “Imagining the 10th dimension” which was cool for a while then got real metaphysical crossing over into quasi-religious at which point I stopped watching. Well since then commenters on minute physics have been going after him to the point where he put this “I’m being persecuted by minute physics” video up. I didn’t want to get involved so I unsubscribed to 10th D. But I’m still curious as to what happened.

    I suggest the following channels: numberphile, scishow, vsauce, and QualiaSoup.

  2. k_machine says

    To me, this whole “paradox” is one of those things that you can name and define but it doesn’t really make sense. I can write the term “sentient elbow”, and I can imagine a sentient elbow, but that doesn’t mean that such a thing exists or is even possible. Sort like the idea of the omnipotent god etc.

  3. Didaktylos says

    What happens when the unstoppable force meets the immovable object? The encounter will never be resolved, as occurred in legend when the inescapable hound was set in pursuit of the uncatchable hare.

  4. sailor1031 says

    It’s obviously a koan. And as we see from this video we have to eschew differentiation to understand it. Not this, not that!

  5. Johnny Vector says

    That was awesome. Now I want to start making stop-motion videos. As the guys on South Park once said, “How hard can it be?”

  6. Mano Singham says

    Thanks for the recommendations. I have come across some of them from time to time but should check them more regularly.

  7. MNb says

    MS, do you have telepathic skills or something? After my “complaint” you “punish” me by reminding me of a mistake I made some 35 years ago at my first test of physics ever. The question was about Newton’s Third Law and though I understood it I thought durin the test that I had found a counterexample in a feather blown by the wind against a huge building – un immovable object, so to say.
    Great video. Keep this stuff coming!

  8. says

    I don’t understand why they attempted a sciencey answer to that old chestnut. The better answer is to explain why it’s not “not even wrong” as a question because for either horn of the dilemma to be an actual possibility then the other is impossible. Thus there can be neither immovable objects or irrestable forces.

  9. Mano Singham says

    Newton’s third law is one of the trickiest. It sounds so simple and is so easy to state but it is actually quite subtle. When I teach physics, I have a lot of fun with creating scenarios where students find that it is not as simply to apply as they thought.

  10. Jared A says

    I recall that young adult author Diana Wynne Jones answered this question in the first page of Archer’s Goon.

    To paraphrase: The result of an unstoppable force meeting an immovable object is a family quarrel.

  11. Alejondro Maestas says

    Well this is what I got trying to put a answer to this question. First lets pretend that there is a unstoppable for and a unmovable object. Now with that out of the way let me put a example down. Lets pretend a meteor half the size of the sun is the unstoppable force and a planet, the earth is a unmovable object. The meteor (unstoppable force) has been going on for eons it has been ripping hole through planets and nothing ever stopped it. And now look at the planet (Unmovable object) which tons of other meteors and other planet ran into but still never moved. They both meet hence the question. The meteor (Unstoppable force) impacts the planet (unmovable object) with full speed and strength. OK, now according to me and my friends the unmovable object finally moved because it was just to strong but vice versa the unstoppable object finally is stopped. Because it took it all its strength. There’s the answer me and my friends got. I hope it helped.

  12. Willie says

    Physics 101: Throw a marble (unstoppable force) against a wall (immovable object). What happens? The marble changes direction. The paradox has nothing to do with physics per-se…… It’s more the impact that certain events will have in a person’s life…….. Psychology 101………

  13. Mano Singham says

    The marble is not an unstoppable force and the wall is not an immovable object.

Leave a Reply

Your email address will not be published. Required fields are marked *