this post was submitted on 02 May 2025
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xkcd

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Title text:

Unstoppable force-carrying particles can't interact with immovable matter by definition.

Transcript:

[An arrow pointing to the right and a trapezoid are labeled as 'Unstoppable Force' and 'Immovable Object' respectively.]
[The arrow is shown as entering the trapezoid from the left and the part of it in said trapezoid is coloured gray.]
[The arrow is shown as leaving the trapezoid to the right and is coloured black.]
[Caption below the panel:] I don't see why people find this scenario to be tricky.

Source: https://xkcd.com/3084/

explainxkcd for #3084

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[–] jsomae@lemmy.ml 0 points 5 days ago

Ugh. This is a good point. Force = energy, and even an immovable object can carry energy. I assume.

[–] AmidFuror@fedia.io 66 points 1 week ago (3 children)

The expression as I heard included "an irresistible force."

[–] SGG@lemmy.world 87 points 1 week ago (2 children)

That's on the nsfw version of xkcd

[–] Randelung@lemmy.world 7 points 1 week ago* (last edited 4 days ago)

xkcd after dark, or xkcdad. But not pronounced xkc-dad.

[–] sxan@midwest.social 5 points 1 week ago (3 children)

Yeah, irresistible force is the version I know. Now I'm wondering if there are even more versions. Are they regional deviations?

[–] wreckedcarzz@lemmy.world 26 points 1 week ago (1 children)

Well I'm from Utica and I've never heard the term "irresistible force"

[–] Tyoda@lemm.ee 17 points 1 week ago (1 children)

Not in Utica, no. It's an Albany expression.

Sure could go for some steamed hams right about now..

[–] Get_Off_My_WLAN@fedia.io 21 points 1 week ago

While not what you're asking for, but fun fact, in Asia, this sort of paradox is represented by the story of the all-piercing spear and the unpierceable shield in Chinese philosophy. So in Chinese and Japanese, the word for 'paradox' or 'contradiction' literally means 'spear-shield' (矛盾).

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[–] Goretantath@lemm.ee 64 points 1 week ago (5 children)

Facepalm Man i'm dumb, this is a great answer to that thought experiment.

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[–] ianhclark510@lemmy.blahaj.zone 27 points 1 week ago (1 children)

"What happens when an unstoppable force meets an immovable object?" that image doesn't show a force meeting an object

[–] BartyDeCanter@lemmy.sdf.org 132 points 1 week ago (3 children)

They met, they just didn’t interact. Kinda like me at a work party.

[–] Successful_Try543@feddit.org 7 points 1 week ago

There is no force without interaction, just linear momentum.

[–] wreckedcarzz@lemmy.world 3 points 1 week ago

"where's the food and booze?"

[–] InnerScientist@lemmy.world 2 points 1 week ago (2 children)

That just moves the problem, what happens if I put a piece of paper between them? Unless they don't interact with anything they still face the same problem.

[–] JcbAzPx@lemmy.world 1 points 6 days ago

That's pretty simple, if there is any matter they could both interact with in the way, it would be converted to energy and either expelled to the side or shunted to another dimension.

[–] Cocodapuf@lemmy.world 5 points 1 week ago (1 children)

I mean we have these in the universe, one example of an unstoppable force is neutrinos. These tiny particles certainly seem to contain a whole lot of energy, moving close to the speed of light. But just try to stop one.

[–] humorlessrepost@lemmy.world 1 points 6 days ago

But just try to stop one.

Fiiine. BRB, I need to build a giant underground cave.

[–] SkunkWorkz@lemmy.world 21 points 1 week ago (1 children)
[–] iAvicenna@lemmy.world 11 points 1 week ago (12 children)

so if god creates rock so heavy that it can't lift it, its hand just passes through the rock? makes sense.

[–] Cocodapuf@lemmy.world 10 points 1 week ago* (last edited 1 week ago) (2 children)

I think if God creates a rock so heavy he can't lift it, it's probably a black hole. By definition we can't know what happens inside a black hole, because no information escapes the event horizon. As it's now consistent with known physics that we can't know many aspects of this interaction between God and the black hole, I think this paradox is basically solved. We don't know any more about the interaction, but it's no longer a paradox, it's consistent with physics.

[–] ripcord@lemmy.world 1 points 6 days ago (1 children)

But black holes have finite mass. By "heavy" you're implying it's infinitely heavy or something.

You can definitely also lift a black hole.

[–] Cocodapuf@lemmy.world 1 points 6 days ago (2 children)

Well I don't know about any objects more massive than black holes. I think a black hole is really the only viable form a body can take once there's enough matter in one place, like there's an upper limit for the size of stars and after that anything larger collapses into a black hole.

An object of infinite mass is a contradiction, a universe can't exist with a single object of infinite mass, it would consume everything instantly.

[–] ripcord@lemmy.world 1 points 6 days ago (1 children)

OK, but being very massive is not the same as what was being discussed.

You can also "lift" a finitely massive black hole with anything else massive.

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[–] Snazz@lemmy.world 1 points 6 days ago

It may be worth it to decide how we define ‘unstoppable force’ and ‘immovable object’.

An Immovable Object has 0 velocity:

v = 0

Acceleration is the time derivative of velocity:

a = d/dt(v(t))

a = d/dt(0)

a = 0

And we know that

a = F~net~ / m

An object with infinite mass would satisfy this equation, but an object with no net force would too. We could add a correction force that will satisfy the constraint of 0 net force.

|F~net~| = 0

∑F~i~ = 0

F~correction~ + … = 0

To satisfy Newton’s 3rd law, we would need a reaction force to our correction force somewhere, but let’s not worry about that for now.

A physics definition of ‘Unstoppable Force’ is:

|F~unstoppable~| =/= 0

In this case the gravitational force fits this description, given a few constraints

F~g~ = Gm∑ M~i~ / x~i~^2^

As long as the gravitational constant G is not 0, our object has mass, and

∑ M~i~ / x~i~^2^ =/= 0, then

|F~g~| > 0

But this does feel kinda like cheating because it’s not really what people mean by ‘unstoppable force’. the other way to define it is just immovable object in a different reference frame.

a = 0, |v| > 0

I’m gonna stop here because this is annoying to type out on mobile

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[–] Saleh@feddit.org 6 points 1 week ago (2 children)

God is distinct from the creation and has no physical shape inside the creation so the idea of "object too heavy to lift" is already conceptually nonsensical.

But also in the scope of our physics: What would an object be that is too heavy to "lift" for anyone and anything? It would be the heaviest object in the universe. So what will happen with the heaviest object in the universe? It would be the main center of gravity for everything else. In the same way you cannot "lift" the earth, but rather lift yourself from it as your force will just propel you away from the earth rather than the earth away from you, while you are inside the area dominated by earths gravitational field.

[–] Cocodapuf@lemmy.world 7 points 1 week ago* (last edited 1 week ago) (1 children)

When you jump you are pushing the earth away from yourself a little bit, and then some of your gravity pulls the earth back toward you. You have moved the earth, and for a brief moment your jump has in fact altered Earth's orbit.

[–] Saleh@feddit.org -1 points 1 week ago (2 children)

Relative to the sun, which is the next center of gravity. As you go up the chain you end up with the heaviest object which you cannot move relative to anything, as it is the logical point of relative movement for everything else.

[–] Cocodapuf@lemmy.world 3 points 1 week ago (1 children)

You need to be thinking about n-body physics though, everything affects everything. If the earth moves, that moves the sun a little, if the sun moves, that moves the local cluster a little, etc. Why wouldn't that affect this heaviest object?

I mean, are you suggesting that this heaviest object is simply the center of the universe and that all coordinates are defined around it? Because while that seems practical, I don't think it's how matter and space interact.

[–] Saleh@feddit.org 1 points 1 week ago (2 children)

The universe is expanding everywhere all at once in all directions. So space itself is "moving". It is impossible to define movement except relative to another object made from matter.

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[–] iAvicenna@lemmy.world 2 points 1 week ago

nothing is distinct from xkcd, if it exists there is an xkcd about it

[–] PlexSheep@infosec.pub -2 points 1 week ago (3 children)

No that doesn't make sense. The thing you're alluring at is a classical thought experiment showing contradiction in allmightiness.

P1: God is Almighty, meaning he can do anything

Therefore he must be able to create a stone he can't lift. But then there is something he can't do: Either he can not lift the super stone, or he can not create a super stone that he can't lift.

[–] AA5B@lemmy.world 1 points 6 days ago

Easy to resolve that conflict. A creator would by definition be outside the universe since he predated it. However, if he went into the universe, his presence there would be subject to its laws

We can easily say the creator could make an immovable object, within its environment. If the creator went into the environment, he would be subject to its laws, and the front would fall off …. Er, the object would be immovable. However when his being s beyond the environment, creating an immovable object is just part of his plan

[–] iAvicenna@lemmy.world 6 points 1 week ago* (last edited 1 week ago) (2 children)

lol I am not alluring to anything I am just giving a xkcd twist to this well known paradox

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[–] RandomVideos@programming.dev 1 points 1 week ago

An omnipotent and omniscient being would have the ability to change words definitions or logic. They cant be stopped with a logical contradiction

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[–] WhiskyTangoFoxtrot@lemmy.world 6 points 1 week ago (1 children)

So who would win in a fight between the Juggernaut and the Blob?

[–] raltoid@lemmy.world 4 points 1 week ago* (last edited 1 week ago)

That has been debated to death before and it obviously depends on the writer and version of the characters, but in most cases neither are fully immovable or unstoppable. If they were, Juggernaut would probably just be redirected and keep going.

A little more practically speaking, Juggernaut wins easily:

  • The Blob is a mutant who can basically lock himself to the ground with a short distance around him and become immovable in relation to the ground while being able to absorb most impacts to effectively eliminate the force experience by him and thus the ground.

  • The Juggernaut is not a mutant, but an avatar of Cyttorak the Destroyer, the God/Demon ruler of the Crimson Cosmos dimension. He can tap into more and more of that power to the point where he can fight a somewhat angry Hulk on almost equal ground(he's even defeated him with some help).

Even if you let Blob be immovable and able to ignore all kinetic force, he still has a big weakness: He's not very superhuman when it comes to other forms of damage, or just pain in general. As demonstrated when he tried to go after one of the intelligent versions of Hulk. Hulk realized he couldn't move or hurt him, so he grabbed his stomach and started pulling. It quickly hurt so much that he instinctively stopped anchoring himself to the ground. At which point he basically became an invincible bouncing ball since he can't attach to the air. SoHulk treated him as one, until he sent him flying by using a big metal girder as a bat. And it's important to note that Blob is not very strong or good at fighting when it comes to superhumans, since he basically just relies on his powers.

And to expand on the Crimson Cosmos: It is so powerful that Doctor Strange taps into it to contain Hulk. It's even used to contain Thanos with most of the stones in the MCU(The red cloth strips that hold him is a spell called the "Crimson Bands of Cyttorak")

[–] schnurrito@discuss.tchncs.de 3 points 1 week ago (3 children)

Is Randall now just retelling YouTube videos from 2013? https://www.youtube.com/watch?v=9eKc5kgPVrA

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