Alternative versions of Physics

[Dr. Diaphanous]

Would it be possible for a universe similar to ours exist, with completely different rules of physics? I’m not talking about fiddling with universal constants such as the strengths of the four fundamental forces, leaving the rules the same. I mean, for example, what would chemistry be like if atoms were made of a solid nucleus of indivisible protons and neutrons, with electrons orbiting like planets around a star, and no quantum effects? Could life exist, if stars still somehow worked? Could we have a universe similar to this one if Einstein’s relativity was all wrong and it worked in a way more like the Newtonian rules?

And if there is only one possible way physics can be, that means that in theory you could, given sufficient genius, work it all out a priori without doing any experiments: “life exists, therefore this set of subatomic particles exists, matter must have wave/particle duality, et c.

[eSOANEM]

Assuming Maxwell's equations still hold in your non-quantum model universe, electron orbits are unstable as they lose energy by EM radiation and so you end up with the plum pudding model of the atom.

[broken_escalator]

No, the only other universe allowed is the cowboy universe؟

Spoiler:

[some_dude]

Also without quantum mechanics the ultraviolet catastrophe would occur so that a black body would emit radiation with infinite power. This would probably be a bad thing.

[Anaphase]

Another question would be if you could come up with a world that looks something like ours at the "human" scale (whatever "human" really means in that world), but is radically different at every other scale (maybe still following a QFT/GR framework but without retaining anything like the Standard Model or LCDM.) Could you make a geocentric solar system, or a flat Earth, or Philolaus's solar system* or something even weirder? Could you have phlogiston-based combustion?

_{*An inconceivably bright Central Fire with a flat Earth in orbit around it, always facing directly away. The Sun orbits further out and shines via reflected light.}

[Dr. Diaphanous]

I wonder what a flat earth would look like. For one thing there would be no time zones, the sun would rise in all places at once. I guess there wouldn't be a horizon in the same way, so you could see the whole world simultaneously with a telescope from a mountaintop, if the air was clear enough. Also, weather systems would be completely different, and I guess everywhere would have the same climate unless other factors come into play (e.g. if the edges are cooled by the ice cliffs encircling the Earth or something).

[thoughtfully]

Also without quantum mechanics the ultraviolet catastrophe would occur so that a black body would emit radiation with infinite power. This would probably be a bad thing.

Presuming Maxwell's equations are retained.

[bosonicyouth]

I wonder what a flat earth would look like. For one thing there would be no time zones, the sun would rise in all places at once. I guess there wouldn't be a horizon in the same way, so you could see the whole world simultaneously with a telescope from a mountaintop, if the air was clear enough. Also, weather systems would be completely different, and I guess everywhere would have the same climate unless other factors come into play (e.g. if the edges are cooled by the ice cliffs encircling the Earth or something).

If you consider Newtonian gravity, there would be a large ocean in the middle and people would be living on a very steep (hyperbolic?) hill around it, depending on the Earth's thickness. A gravity force that falls off more rapidly could be more comfortable, but then orbits wouldn't be closed. Unless you consider a gravitational force that increases linearly with distance, but then everything in the universe would be attached to everything else by virtual springs. I like this topic.

[Zamfir]

Could you make a geocentric solar system, or a flat Earth, or Philolaus's solar system* or something even weirder? Could you have phlogiston-based combustion?

This is how Discworld started out. Terry Pratchett wrote a parody of Larry Niven's Ringworld, called Strata. Instead of a ringworld, it has a machnically-constructed discworld, complete with miniature black holes for gravity and electric gohsts and flying carpets.

[doogly]

Oh look, there is an entire fictional science subforum. Get thee hence.

[WarDaft]

It's definitely not the only possible universe. It might however, be hard to find another universe conductive to naturally forming intelligent life.

[BobTheElder]

I wonder what a flat earth would look like. For one thing there would be no time zones, the sun would rise in all places at once. I guess there wouldn't be a horizon in the same way, so you could see the whole world simultaneously with a telescope from a mountaintop, if the air was clear enough. Also, weather systems would be completely different, and I guess everywhere would have the same climate unless other factors come into play (e.g. if the edges are cooled by the ice cliffs encircling the Earth or something).

Yeah (Terry Pratchett) just have the speed of light be something a bit slower than the speed of sound.... now you've got dawn / timezones / etc...

[quantropy]

The trouble with classical physics is that it doesn't really work. My impression is that if you postulate atoms with forces between them then its very difficult to arrange things so that you can build stable structures out of them. If you avoid this by assuming matter is continuous then all of the energy gets dispersed into ever higher frequencies.

In the end it comes down to your view of the second law of thermodynamics. You could postulate a universe obeying the laws of Conway's game of Life, but those laws aren't reversible in time, and so the second law of thermodynamics doesn't apply.

[PM 2Ring]

I agree with Doogly that this thread should be moved to the Fictional subforum. Please.

The trouble with classical physics is that it doesn't really work. My impression is that if you postulate atoms with forces between them then its very difficult to arrange things so that you can build stable structures out of them. If you avoid this by assuming matter is continuous then all of the energy gets dispersed into ever higher frequencies.

Yep. It's difficult to see how you could achieve stable solid matter without QM.

In the end it comes down to your view of the second law of thermodynamics. You could postulate a universe obeying the laws of Conway's game of Life, but those laws aren't reversible in time, and so the second law of thermodynamics doesn't apply.

I like this idea, but I have a soft spot for Conway's Life.

[reuben364]

It's definitely not the only possible universe. It might however, be hard to find another universe conductive to naturally forming intelligent life.

Varies greatly on your extrapolation of life and intelligence for these new beings. Try finding living, intelligent beings in cellular automata.

[Dr. Diaphanous]

Oh, I didn't notice that someone has recently invented an alternate reality in this very forum. http://forums.xkcd.com/viewtopic.php?f=59&t=73910.

Oh look, there is an entire fictional science subforum. Get thee hence.

Soooooorry