Live data from Hacker News

Conterintuitive facts in mathematics, CS, and physics

axisofordinary.substack.com

231–240 of 335 posts

Re: Conterintuitive facts in mathematics, CS, and physics

#231

Is there a joke or double entendre to the misspelling of 'counterintuitive' in the HN title (the article title is correct) that I'm missing?

I'm pretty sure it's just a typo. The actual title is "The most counterintuitive facts in all of mathematics, computer science, and physics", which is slightly too long for HN and a bit click-baity. No need to retype or abbreviate CS though.

Re: Conterintuitive facts in mathematics, CS, and physics

#232

> 16. If you let a 100g strawberry that is 99% water by mass dehydrate such that the water now accounts for 98% of the total mass then its new mass is 50g: https://en.wikipedia.org/wiki/Potato_paradox I really like this one. It's a perfect combo of intuitive from one perspective and mind bending from another. > 18. A one-in-billion event will happen 8 times a month: https://gwern.net/Littlewood This one, on the other…

#16 is something video games taught me, particularly Path of Exile. In PoE resistance are a flat multiplier to incoming damage. Eg monster does 100 damage per attack and you have 60% resistance then you take 40 damage. The interesting thing is that the higher your resistances the more effective each additional percentage point of resistance is. Let's say a monster does 100 damage per attack. If you have 0% resistance…

A similar example with league of legends:

One point of resistance gives 1% effective extra health no matter how much you already have.

100 armor give 50% reduction (100/100+100) while 200 armor give 66% (100/100+200)

The percentage 50 -> 66% is shown ingame and players often think the value per point of armor drops.

What does actually happen is your effective bonus health changes from +100% to +200% and every additional point will be worth the same

Re: Conterintuitive facts in mathematics, CS, and physics

#233

Earlier quoted context omitted.

> Both the stellar day and the sidereal day are shorter than the mean solar day by about 3 minutes 56 seconds. This is a result of the Earth turning 1 additional rotation, relative to the celestial reference frame, as it orbits the Sun (so 366.25 rotations/y). https://en.wikipedia.org/wiki/Earth's_rotation

So we would need 367 unique date identifiers … but we’ve only got 366 (Feb 29th being the non-annual one). I get I may be being unintelligent, but isn’t the author confusing the rolling coin paradox with an obscure astronomical reference system and coming up with a ‘mistakenly technically correct’ result that doesn’t match experienced reality?

It matches experienced reality if you look at the stars rather than the sun, or if you use something like a Foucault pendulum to measure the rotation speed.

Re: Conterintuitive facts in mathematics, CS, and physics

#234
post #181

Earlier quoted context omitted.

I don't get what thought that picture is supposed to provoke.

The earth has "holes" and as such the proof of that statement for a sphere does not apply to the earth.

Thank you, something about this didn't make total sense to me.

Re: Conterintuitive facts in mathematics, CS, and physics

#236
post #99

Earlier quoted context omitted.

Wait, how is 95% effective twice as effective as 90%?

just as going from 98% effectiveness to 99% effectiveness halves your risk (you go from 2% chance of falling ill to 1%) its a common concept in games in which armor follows a linear formula (each point of armor is more effective than the last when calculating effective health)

Then there's the polynomial wizard.

Re: Conterintuitive facts in mathematics, CS, and physics

#237
post #150

Number 19 is a clinker. Banach-Tarski applies only to objects in real-number space, but there are no such objects. For that to work, objects have to be infinitely divisible, but all of our objects are made out of atoms. Real-numbered space is a good enough approximation to our experience that we hardly ever encounter a model failure like this one.

I'd deny that our objects do not live in a real space. Spacetime is real-valued. The issue isn't the reals, but that "solid object" isn't defined properly, ie., the sets under question don't have well-defined volumes. As soon as you fix that problem, via measure theory, the paradox resolves. You dont need to ditch real numbers.

Sqrt(2) is a real number yet I bet you to properly measure up to the last point the diagonal of a square.

Re: Conterintuitive facts in mathematics, CS, and physics

#238
post #204

> 15. Two 12-inch pizzas have less pizza than one 18-inch pizza. That is surprising, because it's not true. Any calculator will confirm that 2 (2 π×6) > 2 π×9. Or am I missing something?

it's true but really what they're missing is the number and variety of toppings on these pizzas.

Variety maybe, but surely number is also proportional to area (and presumably it's worse because "crust width" doesn't scale with diameter?)

Re: Conterintuitive facts in mathematics, CS, and physics

#239
post #103

Earlier quoted context omitted.

16 is like the money hall problem. I understand the answer, the answer makes sense to me. And yet but when I think of it how I think of it initially ... it still makes no sense.

The way to make sense of this is not to think about the water weight but the solid matter. By changing the proportion of water from 99% to 98%, you're also doubling the proportion of solid mass from 1% to 2%.

> you're also doubling the proportion of solid mass from 1% to 2%.

And the final step is then, that the solid mass didn't change and therefore the liquid must be halved, instead of the solid doubled.

Re: Conterintuitive facts in mathematics, CS, and physics

#240
post #6

> Knowing just slightly more about the value of your car than a potential buyer can make it impossible to sell it: https://en.wikipedia.org/wiki/The_Market_for_Lemons From that Wikipedia page: > This means that the owner of a carefully maintained, never-abused, good used car will be unable to get a high enough price to make selling that car worthwhile. This is bullshit-- the word "enough" was sneaked in there without…

Can make it, but I believe there is likely a point where sellers and buyers utility value considerations cross. That is seller considers price of car to be same as buyer considers this. As these two values are not necessarily tied together. Maybe needs of both parties are different.
Post reply on HN