Irresistible force paradox

The Irresistible force paradox is a classic paradox formulated as follows:

What happens when an irresistible force meets an immovable object?

Common responses to this paradox resort to logic and semantics.

• Logic: if such a thing as an irresistible force exists, then no object is immovable, and vice versa. It is logically impossible to have these two entities (a force that cannot be resisted and an object that cannot be moved by any force) in the same universe.

• Semantics: if there is such a thing as an irresistible force, then the phrase immovable object is meaningless in that context, and vice versa, and the issue amounts to the same thing as, for example, asking for a triangle that has four sides.

This paradox is a form of the omnipotence paradox, but that paradox is most often discussed in the context of God's omnipotence (Can God create a stone so heavy it cannot be lifted, not even by God Himself?).

The paradox should be understood as an exercise in logic, not as the postulation of a possible reality. According to modern scientific understanding, there are not and indeed cannot be either irresistible forces or immovable objects. An immovable object would have to have infinite inertia and therefore infinite mass. Such an object would collapse under its own gravity and create a singularity. An irresistible force would imply an infinite energy, which by Albert Einstein's equation E = mc² is equivalent to an infinite mass. Because the force is of infinite energy, as it moves through space, it will be "converted into" or "create" matter of infinite mass spontaneously. The result is essentially another immovable object which collapses and creates a singularity. Ultimately, the paradox will lead to two singularities or black holes colliding and resulting into one singularity or black hole.

Note that, in the modern view, a cannonball which cannot be deflected and a wall which cannot be knocked down are both types of the same (impossible) object: an object with infinite inertia.

An example of this paradox in non-western thought can be found in the origin of the Chinese word for paradox (Chinese: 矛盾; pinyin: máodùn; lit. 'Spear-Shield'). This term originates from a story (see the Kanbun example) in the 3rd century BC philosophical book Han Feizi.. In the story, a man was trying to sell a spear and a shield. When asked how good his spear was, he said that his spear could pierce any shield. Then, when asked how good his shield was, he said that it could defend from all spear attacks. Then one person asked him what would happen if he were to take his spear to strike his shield; the seller could not answer. This led to the idiom of "zìxīang máodùn" (自相矛盾), or "self-contradictory".

The irresistible force paradox in popular culture

In sports, these terms are commonly used to describe a game when a high-powered offense meets an excellent defense.

The Johnny Mercer song Something's Gotta Give contains the lyric "when an irresistible force such as you/meets an old immovable object like me"

In a Knight Rider episode (Trust doesn't Rust), the paradox is wrongly attributed to Zeno of Elea and its meaning is intentionally distorted.

This paradox was popularized by pro wrestling play-by-play announcer Gorilla Monsoon in the 1980s with reference to World Wrestling Federation nemeses Hulk Hogan (the irresistible force) and André the Giant (the immovable object).

A variant of the paradox appears in the novel Walking on Glass by Iain Banks, where the solution is: "the immovable object moves; the unstoppable object stops."

Another answer is given in a Mensa puzzle book by Victor Serebriakoff (the former chairman of Mensa): by allowing the two to come together, a realistic answer that matches the semantics of the question is "an inconceivable event".

In World of Warcraft, when a player gets exalted reputation with the Alterac Valley battleground, among the rewards are The Unstoppable Force (a two-handed mace) and The Immovable Object (a shield). While they are specifically made for player versus player combat, they have no special properties contradicting each other, so the paradox itself is not addressed in-game. (As an additional joke, a common, low-quality mace exists that is called "The Stoppable Force".)

In the World of Warcraft Trading Card Game, the aforementioned pieces of equipment (The Unstoppable Force and The Immovable Object) are portrayed as cards, both sporting powers that destroy both The Unstoppable Force and The Immovable Object. The flavor text of The Immovable Object is "What happens when..." and the flavor text of The Unstoppable Force is "Oh. So that's what happens."

Jarvis Cocker references the paradox (in a sexually suggestive way) in the Pulp song "Seductive Barry" (on the album This Is Hardcore), concluding that "when the immovable (or unmovable) object meets the unstoppable force, there's nothing you can do about it." Many lyrics websites misquote him as saying "unbelievable object".

In the comic All Star Superman, Lois is threatened with death by the Ultra-Sphinx. To save her, Superman must answer the Ultra-Sphinx's question correctly: "What happens when the unstoppable force meets the immovable object?" He thinks for a moment, and then "correctly" answers: "They surrender".

The tagline of the 1988 movie Bulletproof is "An unstoppable force is about to meet an unmovable object!"

In the movie Imagine Me & You, the question is asked by the young girl called H. Heck doesn't have an answer, but Luce gives the logic response, as seen above.

In Marvel Comics's X-men title, the Juggernaut (comics) is the irresistible force to the Blob's immovable object. An alternate version involves the Hulk as the immovable object; however, it has been established that the Hulk is the stronger of the two, because while Juggernaut's limits are physical, the Hulk's are limited only by his emotion, and there is no limit to the mind.

In Phoenix Wright: Ace Attorney, the former King of Prosecutors award was a halberd and a shield, based off an old Chinese tale of a man who presented the king with a halberd that could slice through any shield, and a shield that could block any attack. The king noted the contradiction, which became a symbol for the Prosecutor's Office. This story might be based off of the derivation of the Kanji of contradict. 矛盾 is the Kanji for contradict. The first symbol, 矛, is the Kanji for some sort of Pole weapon (spear, halberd, or pike), and the second symbol, 盾, is the Kanji for shield.

In Madden 05, one of John madden's quotes is "That's kind of like when an unstoppable force meets an immovabe object... well the unstoppable force won that one.'

In the book Bent Perceptions, one of the captions is "What happens when an irresistable force meets an immovable object? An inconceivable disturbance." paired with a picture of farmland as if seen from a helicopter, and one of the fields peeling upward like tape off an object.

In the book Horus Rising, based on Warhammer 40000's Horus heresy, it is stated that "The Imperial Fists were an immovable object to the Luna Wolves' unstoppable force." Because, whereas the Luna Wolves could storm a fortress like no other, the Imperial Fists could hold it.

In The Elder Scrolls game series, there were an order of philosopher-mages named the Psijics that took their name from the concept of PSJJJJ - another name for the Irresistible force paradox.

In English Football during the late 1990's, Sky Sports football commentator, Martin Tyler often referred to Arsenal and Manchester United as the Immovable Object and the Irresistible Force respectively. For Example, after the FA Cup Semi-Final replay in 1999, he said "Arsenal are the immovable object but the irresistible force is still with Manchester United."