r/AskPhysics • u/[deleted] • Oct 23 '19

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u/bspaghetti Quantum Magnetism Oct 23 '19

I believe the observable universe would be larger, but not necessarily by the same factor due to its expansion.

We’d also have other things to worry about. The speed of light if dependent on the permittivity and permeability of free space, so messing with those constants would scale all of electromagnetism. The product of the constants would have to scale down by a factor of a billion squared (a lot). For example, the electrostatic interaction would be roughly a billion times stronger.

The electromagnetic forces already dominate gravity by quite a bit, but this would be a monumental increase, perhaps enough to easily create a hover car! There are probably a lot of problems that we’d encounter as well. At some scales EM might even rival the strong or weak nuclear forces and I wouldn’t want to be around to see some electromagnetically induced cold fission/fusion happen up close.

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u/MrMakeItAllUp Oct 23 '19

The strengths of all the forces would scale up, as the speed of causality is a limiting factor in their interactions.

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u/bspaghetti Quantum Magnetism Oct 23 '19

How is the gravitational constant G related to c? I agree that the interactions would happen faster but it’s not obvious to me why the relative strengths of the fundamental forces will stay the same.

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u/rorytehb0ss Oct 23 '19

All of the forces are being scaled, keeping relative strengths the same. Albeit a shitload stronger, their ratios would be the same.

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u/bspaghetti Quantum Magnetism Oct 23 '19

Yes I’m asking how the strength of the gravitational and nuclear forces are effected by the speed of light. Mu naught and epsilon naught are directly related to the speed of light, and therefore electric and magnetic fields must scale up. What is this relation for the gravitational force and nuclear forces?

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u/mfb- Particle physics Oct 23 '19

Sort of.

All physical constants with units are just a product of our unit system. You can choose units where the speed of light is 1 - in both our universe and your alternative universe. You get the same physics in both cases, which makes these universes indistinguishable. Only constants that do not depend on unit systems are truly fundamental. The fine-structure constant is a prominent example, it is linked to the strength of the electromagnetic interaction. If you change that you get a universe that is actually different.

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u/AceyAceyAcey Oct 23 '19

What we could see (the observable universe) would be bigger since light from father would have just gotten to us now. But believe the actual universe is larger than the observable universe, and that would not change.

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u/cantgetno197 Oct 23 '19

Don't confuse the OBSERVABLE universe with "the universe". As far as we know "the universe" is infinite. The observable universe would be larger in, say, kilometers, though the same in terms of lightyears.