this post was submitted on 02 Oct 2025
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Science Memes

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[–] mumblerfish@lemmy.world 107 points 2 months ago* (last edited 2 months ago) (4 children)

In the top one you will never actually kill an infinite number of people, just approach it linearly. The bottom one will kill an infinite amount of people in finite time.

Edit: assuming constant speed of the train.

[–] ivanafterall@lemmy.world 56 points 2 months ago (2 children)

I'm going bottom.

NOT LIKE THAT. Not like sexually. I just mean I want to kill all the people on the bottom with my train.

[–] ConstantPain@lemmy.world 43 points 2 months ago

Too late! Now bend...

[–] a_person@piefed.social 12 points 2 months ago

So still sexually

[–] buffing_lecturer@leminal.space 10 points 2 months ago (9 children)

Limits still are not intuitive to me. Whats the distinction here?

[–] NoneOfUrBusiness@fedia.io 25 points 2 months ago

If people on the top rail are equally spaced at a distance d from each other, then you'd need to go a distance nd to kill the nth person. For any number n, nd is just a number, so it'll never be infinity. Meanwhile the number of real numbers between 0 and 1 is infinite (for example you have 0.1, 0.01, 0.001, etc), so running a distance d will kill an infinite number of people. Think of it like this: The people on the top are blocks, so walking a finite distance you only step on a finite number of blocks. Meanwhile the people on the bottom are infinitely thin sheets. To even have a thickness you need an infinite number of them.

[–] turdcollector69@lemmy.world 7 points 2 months ago

Different slopes.

On top you kill one person per whole number increment. 0 -> 1 kills one person

On bottom you kill infinity people per whole number increment. 0 -> 1 kills infinity people

You can basically think of it like the entirety of the top rail happens for each step of the bottom rail.

[–] mrmacduggan@lemmy.ml 7 points 2 months ago* (last edited 2 months ago) (4 children)

For every integer, there are an infinite number of real numbers until the next integer. So you can't make a 1:1 correspondence. They're both infinite, but this shows that the reals are more infinite. (and yeah, as other people mentioned, it's the 1:1 correspondence, countability, that matters more than the infinite quantity of the Real numbers)

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[–] magic_lobster_party@fedia.io 61 points 2 months ago (4 children)

Bottom.

Killing one person for every real number implies there’s a way to count all real numbers one by one. This is a contradiction, because real numbers are uncountable. By principle of explosion, I’m Superman, which means I can stop the train by my super powers. QED

[–] rooroo@feddit.org 18 points 2 months ago

Wait until your league of super heroes is up against the axis of choice.

[–] plinky@hexbear.net 6 points 2 months ago

plus uncountable infinity implies there is uncountable supply of humans, which is nice.

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[–] pruwybn@discuss.tchncs.de 41 points 2 months ago* (last edited 3 weeks ago) (1 children)

Use the fact that a set of people corresponding to the real numbers are laying in a single line to prove that the real numbers are countable, thus throwing the mathematics community into chaos, and using this as a distraction to sabotage the trolley and save everybody.

[–] NoneOfUrBusiness@fedia.io 10 points 2 months ago

Hey, maybe they're infinitely thin people, in which case you can (and necessarily must, continuum hypothesis moment) have one for every real number.

[–] tiredofsametab@fedia.io 34 points 2 months ago

First, I start moving people to hotel rooms...

[–] stupidcasey@lemmy.world 33 points 2 months ago (2 children)

I pull the lever, if the cart goes over the real numbers it will instantly kill an infinite amount of people and continue killing an infinite amount of people for every moment for the rest of existence.

If I pull the lever a finite amount of people will die instantly and slowly over time tending twords infinity but due to the linear nature of movement it would never actually reach Infinity even if there are an infinite number of people tied to the track a finite amount is all that could ever die.

[–] dharmacurious@slrpnk.net 14 points 2 months ago (4 children)

So you're going to let those infinite people on top stay tied to the track and starve to death slowly‽

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[–] OhNoMoreLemmy@lemmy.ml 29 points 2 months ago (1 children)

Bottom has infinite density and will collapse into a black hole killing everyone, and destroying the tram and lever.

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[–] ssfckdt@lemmy.blahaj.zone 21 points 2 months ago

The first one, because people will die at a slower rate.

The second one, because the density will cause the trolley to slow down sooner, versus the first one where it will be able to pick up speed again between each person. Also, more time to save people down the rail with my handy rope cutting knife.

[–] Sunsofold@lemmings.world 19 points 2 months ago (4 children)

I ignore the question and go to the IT and maintenance teams to put a series of blocks, physical and communication-system-based, between the maths and philosophy departments. Attempts to breach containment will be met with deadly force.

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[–] aeternum@lemmy.blahaj.zone 19 points 2 months ago (1 children)

I think it was numberphile, or maybe vsauce, who did a video on infinities. It was really interesting. I learnt a lot, then forgot it all.

[–] filcuk@lemmy.zip 7 points 2 months ago

Ah yes, I remember my eyes glazing over as things got too complicated to fit through my thick skull

[–] helpImTrappedOnline@lemmy.world 14 points 2 months ago

The second one. It'll be a bit rough, but overall should be a smoother ride for the occupants.

[–] Honytawk@lemmy.zip 13 points 2 months ago (3 children)

The top one, because time is still a factor.

Sure, infinite people will die either way, but that is only after infinite time.

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[–] BilSabab@lemmy.world 12 points 2 months ago (3 children)

Is there a way to take both routes?

[–] ours@lemmy.world 11 points 2 months ago (2 children)

Hit the hand brake and drift that sucker.

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[–] Harvey656@lemmy.world 12 points 2 months ago (3 children)

I mean, the bottom. The trolley simply would stop, get gunked up by all the guts and the sheer amount of bodies so close together. Checkmate tolley.

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[–] Tiger_Man_@szmer.info 11 points 2 months ago (5 children)

Considering that there's a small but non zero chance of surviving getting ran over by a train some of them are gonna survive this and since there are infinite people that will result in infinite train-proof people spawning machine

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[–] missfrizzle@discuss.tchncs.de 8 points 2 months ago* (last edited 2 months ago)

you know, I'm not sure you can have an uncountably infinite number of people. so whatever that abomination is I'll send the trolley down its way. it's probably an SCP.

[–] LadyAutumn@lemmy.blahaj.zone 8 points 2 months ago* (last edited 2 months ago)

In the top case has it been arbitrarily decided to include space in between the would-be victims? Or is the top a like number line comparison to the bottom? Because if thats the case it becomes relevant if there is one body for every real number unit of distance. (One body at 0.1 meter, and at 0.01 meter, at 0.001, etc)

If so then there's an infinite amount of victims on the first planck length of the bottom track. An infinite number of victims would contain every possible victim. Every single possible person on the first plank length. So on the next planck length would be every possible person again.

Which would mean that the bottom track is actually choosing a universe of perpetual endless suffering and death for every single possible person. The top track would eventually cause infinite suffering but it would take infinite time to get there. The bottom track starts at infinite suffering and extends infinitely in this manner. Every possible version of every possible person dying, forever.

[–] sgtlion@hexbear.net 8 points 2 months ago (6 children)

Bottom. No matter what your "real" number assignation in the queue is, theres an infinite number of people before the train gets to you. Therefore every single person will live a full life before the train reaches them.

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[–] dontbelievethis@sh.itjust.works 8 points 2 months ago

Bottom. Greater probability that it gets stuck in the corpses.

[–] BeatTakeshi@lemmy.world 7 points 2 months ago (3 children)

Top case is not the smallest infinite; going for prime number would save a lot of time for a lot of people before they die

[–] Schadrach@lemmy.sdf.org 16 points 2 months ago

The set of all primes is the same size infinity as the set of all positive integers because you could create a way to map one to the other aka you can count to the nth prime. Reals are different in that there are an infinite number of real between any two reals which means there's no possible way to map them.

[–] kadu@scribe.disroot.org 9 points 2 months ago

The set of primes and the set of integers have the same size, you can map a prime to every integer.

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[–] BenLeMan@lemmy.world 7 points 2 months ago* (last edited 2 months ago)
  1. I lay some extra track so the train runs over the perverts that come up with these "dilemmas" instead. Problem solved. 👍
[–] chunes@lemmy.world 7 points 2 months ago (1 children)

Good to know there are roughly 6 real numbers for every integer

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[–] Daft_ish@lemmy.dbzer0.com 7 points 2 months ago* (last edited 2 months ago)

Getting killed by a train is apparently just an inevitability in this universe. Either choice is just the grand conductors plan.

[–] trxxruraxvr@lemmy.world 6 points 2 months ago (3 children)

Doesn't matter, there are not enough people to try this anyway

[–] SpaceNoodle@lemmy.world 7 points 2 months ago

Not with that attitude

[–] Thedogdrinkscoffee@lemmy.ca 7 points 2 months ago

Depends on the speed of the trolley.

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[–] InvalidName2@lemmy.zip 6 points 2 months ago (11 children)

Some infinities are bigger than other infinities

Is this actually true?

Many eons ago when I was in college, I worked with a guy who was a math major. He was a bit of a show boat know it all and I honestly think he believed that he was never wrong. This post reminded me of him because he and I had a debate / discussion on this topic and I came away from that feeling like he he was right and I was too dumb to understand why he was right.

He was arguing that if two sets are both infinite, then they are the same size (i.e. infinity, infinite). From a strictly logical perspective, it seemed to me that even if two sets were infinite, it seems like one could still be larger than the other (or maybe the better way of phrasing it was that one grew faster than the other) and I used the example of even integers versus all integers. He called me an idiot and honestly, I've always just assumed I was wrong -- he was a math major at a mid-ranked state school after all, how could he be wrong?

Thoughts?

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[–] nuko147@lemmy.world 6 points 2 months ago (3 children)

I thought that the correct answer to these was making a loop on the right, merging the lines.

[–] Noodle07@lemmy.world 7 points 2 months ago

The answer is multi track drifting

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