I have seen discussions of universes with different numbers of spatial dimensions, universes without a strong arrow of time, universes with differing physical constants, etc. but I was wondering (here it comes, you are wondering) (LOL) would our universe be substantially similar with a drastically different speed of light? (and everything else the same, protons and gravity and such) For instance, if light propagated at 550 km/second ?? Or if light traveled at 90,000,000,000 km/second ?? And by substantially similar, would there be stars, and fusion, and planets and orbits, and galaxies ?