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I'm not sure if you are kidding but just in case you are not this is very misleading and in fact misguided.

Refering to polynomials as exponential just results in confusion essentially removing any meaning from the word. Any function can be written as something involving exponents, so that statement becomes meaningless.


Ok I don't mean to be pedanntic but a sphere is just the boundary of a ball. If we are trying to capture volume we should be talking about balls of water.

Counter pedant: a ball is indeed what you get when, as in TFA, you put water “in a sphere”

I agree. It's a volume of water bounded by a sphere. I'm just being pedantic about the common use of the word in this thread.

I'm also somewhat surprised no one else was being pedantic about this. I expect better from HN :)


We know how to do this and have observed this tons of times at this point. This would not be novel in any way. This is about exciting the nucleus which is completely different.


It's essentially just the boundary of the Mandelbrot set which makes sense as that's where the calculation is the most unstable.


The theorem holds not for arbitrary dynamical systems but under two conditions: 1) The flow preserves volume 2) All orbits are bounded.

The second law of thermodynamics is in a sense a statement about evolution of probability distributions. As time goes on the dynamical system mixes any probability distribution such that entropy increases. Poincare recurrence is a part of this mixing phenomenon.


Your first requirement is part of the definition of a dynamical system. It is also satisfied for the evolution of the phase-space for any system in classical mechanics.

The second requirement is usually the case for systems with finite energy.

So as far as classical mechanics is concerned the Poincaré Recurrence Theorem pretty much always applies.


Dynamical systems definitely don't have to preserve volume!


Then your definition must be different from mine.

Which is possible. I mostly encountered them in the context of Ergodic Theory, in which case a preserved measure is very much non-optional.


Television typically runs ~7 minutes of unskippable ads for 23 minutes of content.


I'm sorry but how, other than colorful language, is it useful to consider every cell as a universe? And how does that put us at the center of the universe? Equating cell to universes here does nothing of value.


Reminds me of something I heard: AIs will be convincing long before they are smart.

Humans are wired to think that because a phrase is clever, that it must be true. For example, the Rhyme-as-reason Effect: https://en.m.wikipedia.org/wiki/Rhyme-as-reason_effect


AIs will be convincing long before they are smart

ELIZA and PARRY proved this all the way back in 1966 and 1972. ELIZA was a silly AI hack which mostly just repeated back what users said to it, turning users' statements into questions in the style of Rogerian psychotherapy. People could tell it was fake. But PARRY used the same technique but pretended to be a crazy asshole, repeating users' statements in the style of angry accusations, and people thought it was real.

Take a simple AI technique, add some element to make emotion overwhelm analysis, and you pass the Turing Test (because the Turing Test was only ever meant to be a thought experiment). PARRY convinced a lot of people, and Peter Norvig's AI book in Lisp shows you how to write ELIZA in the first couple chapters. It's trivially easy to make an AI which is more persuasive than smart.


Amusingly, the cell is about halfway between the radius of the observable universe (4.4 * 10^26 meters) and Planck length (1.6 * 10^-35 meters), at between 10^-4 and 10^-5 meters, or 0.1mm and 0.01mm.

About the size of a eukaryotic cell, in particular.

https://bio.libretexts.org/Bookshelves/Introductory_and_Gene...


You seem to be abusing exponential notation there. Halfway between 0 and 4.4 * 10^26 is 2.2 * 10^26, quite a bit larger than a cell. Halfway from Planck length should be just about the same given it's indistinguishable from 0 on that large of a scale. Even if you wanted to use logarithmic scaling, half of 4.4 * 10^26 would 4.4 * 10^13. Negative exponents are fractional. The Planck length isn't actually a negative number.


>Even if you wanted to use logarithmic scaling, half of 4.4 * 10^26 would 4.4 * 10^13

That's the geometric mean of 4.4 * 10^26 and 1. He took the geometric mean of the radius of the observable universe and the Planck length. That's a reasonable way to define "halfway" across orders of magnitude


Just eat some more edibles and it will all make sense to you.


And how does it put us at the center of the universe? What does it even mean that we should consider each "cell to be the unit"?


I actually like the thought, and ChatGPT totally misses the point. Cells don't have to be a universe to be the center of the universe. I think more to the point, each of us is the center of the universe, because the universe is relative.

ChatGPT is like that smooth sales guy that can use so many words to say so little. Everything sounds great, and then you walk out of the meeting, and you can't figure out what you just learned, if anything.


I don't think that having "universe" be a relative term is very useful. I prefer it as a topological one: If you're considering two universes, it's not just that they're very far apart, it's that there are no paths between them.

Information follows paths, so you end up with the "-verse" suffix regarding speech. The universe you're in is the one you can say things about and back those things up with evidence. Other universes, well there are no paths along which evidence about them can reach you, so you're limited in what you can say about them.


Also regarding the "center" of the Universe: the reason that "everywhere is the center" is because the Universe exists in higher than three dimensions. Asking "where is the center of the Universe" is like asking where the center of the surface of a balloon is. The center of the balloon is not on the surface in the 2D Universe.

The center of the Universe is the Big Bang, which is physically located at the beginning of time. Gravity is a depression on the surface of the Universe, which is why gravity and time are related: it literally brings us closer to the past :)

(Also note: physics is not my expertise, so take what I say with a giant grain of salt. I have just thought about this a lot over the years)


These are the properties of our universe, and of course we'll only ever have one to study. But words change, right? Atoms are no longer indivisible. Black holes are no longer fully black. So I'm really going for the properties that a thing must have in order to be considered a universe, so we don't end up with a change that's obnoxious. I'd hate it if "universe" eventually just meant "any old really big astronomical structure".

Perhaps the laws of physics would allow for different kinds, they just aren't ours (Lee Smolin's "Life of the Cosmos" is a fun exploration of this, recommended).

Overall I like your descriptions, but I'm going to have to do some thinking about the direction of a gravitational depression being one that points towards the past. I'm under the impression that many cosmologists reject the idea that something warped must be warped into some other dimension. The warping, I've read, can be intrinsic: Imagine a colored lens which is unevenly saturated with dye.

(I am also not a real physicist)


That’s silly. The center of the surface of the balloon is obviously the little part where you tie it off. I’m glad I could solve this universe paradox for you and all physicists in just a few seconds. Maybe I’ll get a Nobel Prize.


Consider a balloon with no tie. Like a basketball or something. The point is that the surface is elastic and the sphere is expanding. Balloons make the best metaphor for that imo. If you can think of a better one I'd be glad to hear it.

Only other thing I can think of is a "rubber bubble" which... is a balloon.


I often think of it as a soap bubble, but I have to stop and check myself: are we choosing spherical because that's simple, or because we have evidence? It could be toroidal or something even more bizarre.


I see it as a sphere because of the uniform expansion of the Universe. The Universe might just be so large that any measurable difference in the rate of expansion is outside the observable Universe, which could suggest a shape other than a hypersphere, but I don't subscribe to that school of thought.


A similar thing also happens in the modern formulation of the Stoke's theorem. Once you set up the machinery of differential forms it becomes almost a trviality which is just amazing.


There are simple practical reasons though. We don't do that to be fancy. There are simply not enough letters in the latin alphabet to not have common intersection in writing. We like to use the same letters for objects of the same type (like x,y for coordinates or i,j,k,l for indices) because that increases readability significantly. But it does mean that you run out quite quickly.

Adding another alphabet alleviates those issues somewhat but even with greek letters added in we still run into this issue somewhat commonly.


There are simply not enough letters in the latin alphabet to not have common intersection in writing.

Agreed. But yet... some of the approaches taken to deal with that can be wildly annoying. Actually, using the Greek letters is probably the best of the lot, since they are a completely different set of characters with known pronunciations.

OTOH, sometimes you'll see people use both upper-case and lower-case latin letters in the same problem, forcing you to read it in stilted language like "The derivative of Big X with respect to y, plus the integral of Little x ..." Aaarrgggh.[1]

And then you get the "stylized" letters, which are (mostly) just Latin letters, but have no obvious unique pronunciation or verbalization without going through contortions. I mean, what do you say for "𝔑" especially if there is also a "n" on the page? And who's even going to recognize these monstrosities unless you're already a mathematician: 𝔖, 𝔚, 𝖄? Aaarrggggghhh.

[1]: to be fair, you could have the same problem with mixed case of Greek letters, but I haven't seen that as a common problem. But maybe that's only because I'm not a mathematician. shrug


Well, you could use variable names longer than a single letter?


It's a trade-off between brevity and verbosity, some mathematics do that. Often longer variable names are in ALL-CAPS. Since ab = a*b, it's important to differentiate vars from multiplications.


Yes, it is. I just brought it up because it's an important factor when talking about the need for additional symbols.

Btw, even mathematicians don't mind writing out `sin` or `cos` or `ln` in their formulas. So they are certainly not completely averse to multiple letters.


At the very least they do not allow keychain to interact with browsers other than safari. This means that your autofill does not synchronize easily with your mobile devices.

That's a choice that is not based on technical conditions and is pure disrespect of user preferences.


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