Please don't ask me again to read W.L. Craig. He distorts physics.
This will be an oversimplification, but it drives the main points. What limits the amount of matter in the universe is the total energy of the universe, which is effectively 0. If space-time is infinite, you will sum up over an infinite volume and need an infinite amount of matter to maintain a total energy of 0. If space-time is finite, then the amount of matter is finite.
This will be an oversimplification, but it drives the main points. What limits the amount of matter in the universe is the total energy of the universe, which is effectively 0. If space-time is infinite, you will sum up over an infinite volume and need an infinite amount of matter to maintain a total energy of 0. If space-time is finite, then the amount of matter is finite.