What Happens When An Unstoppable Force Meets An Immovable Object?

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In short… nothing! An unstoppable force cannot be unstoppable in the same universe where an immovable object exists, as it would no longer be unstoppable.

Philosophy has been the premise of nearly every idea and approach of mathematicians and physicists throughout history, and will likely remain true, long into the future. Whenever you push your mind to ponder on the far side of reality, there is some conception of the darkness and emptiness within the universe.

chicken omlete meme

There are instances in life where you want to shut down your senses and dive deep to critically analyze a situation at hand; this might seem to be of less importance in other situations, yet this moment of mental juggling makes you feel Omniscient. Paradoxes might seem like vaguely inaccurate and apparently self-contradictory statements, but their underlying meaning is revealed only through careful scrutiny. The purpose of paradoxes is to arrest one’s attention and provoke fresh ideas through counter-intuitive thinking.

The following paradox is one of the most famous—and most frequently quoted!

What Is The Irresistible Force Paradox?

This paradox, greatly acclaimed as the unstoppable force paradox, is regarded as an “omnipotence paradox”. It dares to challenge the pre-eminent, namely, “What happens when an unstoppable force meets an immovable object?”

However, before you jump into brooding over this idea, bending your mind into all sorts of gymnastics, let’s take a look at a simpler form of this incongruity.


This paradox has its roots in a story from a philosophical book, Han Feizi, written in the 3rd century BC.

A man was trying to sell a shield and a spear. He claimed that his spear could pierce any shield and that his shield could defend against any spear and come out unscathed. One fine day, someone asked him that what would happen if he were to strike his all-piercing spear on his impenetrable shield. The seller was dumbfounded.

Another instance of this paradox is evident in an ancient example, the story of a Teumessian fox, who can never be caught, and a hound Laelaps, who never misses its quarry. Realizing this impossible contradiction, the Greek thunder god, Zeus, turned both creatures into static stars.

Also Read: What Is Zeno’s Dichotomy Paradox?

What Happens When An Unstoppable Force Meets An Immovable Object?

As this question engulfs your mind (if you’re truly ready to give this paradox some thought), you will come to a perplexing cessation. This paradox is truly larger than the universe, being consistent with the physical laws, yet not quite as creative. Without teasing you further with all sorts of philosophical re-definitions, let’s analyze the two entities at hand—the unstoppable force and an immovable object.

An unstoppable force seems like an imperious force, presumably more forceful than earthquakes and hurricanes (that alter the geology of our massive planet), regardless of the mass or size of the object that in its path. The energy of the force will not depreciate by any amount throughout the course of its transmission to other objects. Thus, an unstoppable force, in order to become unstoppable, needs to possess an infinite amount of energy.

On the contrary, an immovable object is the non-submissive entity of nature, which remains unfazed by force of any magnitude, whether that means being crushed under a falling asteroid or being sucked in a black hole. We can regard this as the perfect energy absorber and an ideal non-transmitting body.

The thought of both meeting each other is unsettling, to say the least. Who will win? Will nature choose sides? Which one would give in?

unstoppable force
A fictional example of the paradox: What if Thor’s hammer strikes against Captain America’s shield?

Also Read: Why Does Time Only Move In One Direction?

Irresistible Force Paradox Solution

Any force is unstoppable; it is the energy that the force carries that is merely transferred to the other object. Even if a force does not technically ‘move’ an object, it will surely raise its temperature. Although that is the physical reality, it is clearly not in the spirit of this question.

The question demands that you break your brain to overcome the paradox.

Consider an unstoppable force. In order for such a thing to exist, so that it can move absolutely anything, it requires an infinite amount of energy.

Now, consider an immovable object. The only property that can make it unmovable would be an infinite mass, in order for it to have infinite inertia (inertia is the resistance of a physical object with mass to any change in its velocity). It does not matter how much energy you apply; it would be impossible for you to overcome the inertia of infinite mass.

However, perhaps you suggest that our immovable object will collapse upon itself to form the greatest black hole ever. It won’t. To create a black hole, it would need to compress into a minuscule volume, which is contrary to the notion of being immovable. Instead, it will simply sit there.

Now, if you applied the two together, what would happen?

Absolutely nothing. As stated earlier, the only way for a force to be unstoppable would be for it to have infinite energy. Quite similarly, the only way for an object to be immovable would require an infinite amount of mass.

Taking a glimpse into the physical laws, you know that mass and energy are the same things in different forms. They are interchangeable. Think of mass as condensed energy. If there were an unstoppable force in existence, it would require every last bit of energy of this universe, including all the energy from the radiation, as well as the whole mass of the universe. This would leave nothing for you to assemble your immovable object.

Quite similarly, if you start with the immovable object, it would encompass all the mass of this universe, including all the energy from radiation, after it is converted to mass, leaving nothing to compose the unstoppable force. Hence, it’s evident that such an object and such a force cannot exist simultaneously. Obviously, we also wouldn’t be in the picture to propose this paradox in the first place.

Here’s a very good video explaining the paradox in more detail:

Also Read: Why Free-Falling Makes You Weightless, Even In The Presence Of Gravity?


This philosophical paradox is as old as humanity, yet philosophers still reflect on this imperial truth.

The question has been so masterfully oriented that both the unstoppable force and the immovable object are analogous to each other. In truth, the existence of one denies the existence of the other. An unstoppable force cannot be unstoppable in the same universe where an immovable object exists, as it would no longer be unstoppable.

The paradox encompasses the utility and substantial intellectuality of humanity, which we rarely pause to examine these days. It feels good to stretch the brain a bit, right?

How well do you understand the article above!

Can you answer a few questions based on the article you just read?

References (click to expand)
  1. Irresistible force paradox - ipfs.io
  2. What is inertia?. Northwestern University
  3. Infinite Mass-energy? | Physics Van | UIUC. The University of Illinois Urbana-Champaign
  4. Time travel is possible – but only if you have an object with .... Phys.org
  5. Does actual infinity exist in physics, particularly in quantum theory? | ResearchGate - www.researchgate.net
  6. Could Exotic Matter Provide an Infinite Source of Energy?. Phys.org
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About the Author

Dev is an undergraduate (Bachelor of Science) from St. Xavier’s College (India). He watches a lot of anime and documentaries on the universe and wildlife. He spends most of his time engaging in sports and exercise. He has represented his state at the National Volleyball tournament, in India. Along with that, he has a flair for sketching, photography and would be glad to take up gardening as a career.