[jstanley]

People say that 2-dimensional life is impossible because it's impossible to make a 2-dimensional digestive system.

But you just need to make it work like a zip. The two halves of the body have interlocking hooks, and they move out of the way to let food pass through, and then reconnect.

[s1mplicissimus]

I think 2-dimensional life is impossible because physical things exist in all dimensions. As spacetime is already 4 dimensions, no physical thing at all exists in 2 dimensions, thus no life either

[kragen]

Oh, that's just trivia about the contingent universe. You wouldn't say it was impossible for Carthage to have conquered Rome, would you? It just didn't, by chance, happen.

[s1mplicissimus]

I assume the contingent universe is where my existence happens and thus a potential thankfulness should be placed on. I'm for example not gonna be thankful we're not in a higher-dimension universe, because my experience would likely be unfathomably different and things might look very different from there.

As history shows, Rome did win, so I wonder just how you imagine Carthage could have won? Should they just have "tried harder"? (i imagine they did what was possible) Was there another universe where the first apes that would later become Carthagians found more bananas, thus had higher population and resources and won this way? Honestly curious how you set the rules of this counterfactual history :D

[kragen]

In our timeline, the Cunctator, having provoked the Second Punic War through diplomatic maneuverings in his old age, held Hannibal at bay in Italy for over a decade while weakening him, until Scipio forced Hannibal to return to Africa, where the Romans defeated him.

But, in another timeline, a mosquito stung the Cunctator shortly after war broke out, giving him malaria, which was then endemic in Italy. He would have recovered if not for another piece of bad luck: clumsy from the fever, he stumbled on the way to the latrine and cracked his skull on a rock, dying instantly. The Cunctator's friend and rival Gaius Flaminius was given command of the Roman forces, who attempted direct confrontation with Hannibal's forces, suffering a series of increasingly disastrous defeats until finally Hannibal marched his elephants into Rome and put the Roman Senate to the sword.

The same mosquito hatched in our timeline, but mosquitoes are not strong fliers, and the air currents were slightly different in our timeline, so it instead stung the Cunctator's slave, who got malaria but survived. Air currents are of course chaotic¹, and the divergence between the timelines has been traced to the thermal emission of a single photon from a warm rock thirteen years earlier in Karnataka, resulting in the rock being slightly cooler and producing an almost undetectably smaller thermal updraft that night.

How our universe could have ended up two-dimensional is a much more difficult question.

______

¹ https://npg.copernicus.org/articles/25/387/2018/npg-25-387-2... estimates the maximum Lyapunov exponents of well-regarded atmospheric models such as PUMA in the neighborhood of 0.02, i.e., a Lyapunov time of a few months. As I understand it, that means that the 10⁻²⁰ joules of an infrared photon emission creates atmospheric disturbances of about a joule in about six years and about 10²⁰ joules in about 13 years, which is a couple of milliseconds of solar irradiance.

[s1mplicissimus]

Air currents are highly complex and almost impossible to model in detail, that does not mean that they are not the outcome of conditions that preceded them (regardless of whether we know the formula).

So why were the air currents slightly different? Oh I guess because the surrounding weather must have been slightly different. And how did that happen? Because the surrounding climate was different. And how that? Because earths development facilitated that different climate. Maybe the moon was bigger? Earths mass smaller? Well that's a big ask for a historical event we know happened on our known earth surrounded by our known moon.

[kragen]

No, it wasn't because the surrounding weather was slightly different. The surrounding weather was exactly the same. The air currents were slightly different because a warm rock in Karnataka thermally emitted a photon 13 years earlier that it didn't emit on our timeline. (This happens, as far as we know, completely at random, without any cause; cf. https://en.wikipedia.org/wiki/Quantum_indeterminacy.) That was enough to cause the global atmospheric system to diverge enough that the mosquito stung someone else.

The findings of chaos theory are counterintuitive, but they are absolutely fundamental to how our universe works.

[fluoridation]

>You wouldn't say it was impossible for Carthage to have conquered Rome, would you?

Okay, but is space having 3 dimensions instead of 2 also an accident of history, or part of the fundamental structure of the universe?

For that matter, it's not obvious to me that history as it actually unfolded is not also part of the fundamental structure of the universe.

[schoen]

Although maybe https://en.wikipedia.org/wiki/Modal_collapse is real! I remember that Gödel may have thought so?

[kragen]

Maybe! In that case there would be no contingent universe, only the necessary one. You can see how this would appeal to theists like old Kurt. A buddy of his had a saying about dice...

[kragen]

Yeah, Dynomight suggested that in the article.

[jstanley]

Oops, I missed that!