Henry Baker <hbaker1@pipeline.com> wrote:
Physicists talk about the expansion of the universe.
Wouldn't it be equivalent to talk about the compression of time?
No. Distances in space are increasing, but the sizes of objects are not. The original definition of the meter was pegged to the size of the Earth. Later it was defined as the length of a specific metal ruler. Still later, in terms of a wavelength. And today, in terms of the speed of light. Under all those definitions, the size of the Earth and of the things on it are not changing. Similarly with other planets and other solid objects in space. It's possible that the expansion exerts a force on solid objects to make them get larger. But if so, their internal cohesion easily resists this force. (Any such force is much too weak to directly detect or rule out with today's technology.) You could devise a system of measurement such that the size of the universe is constant, but the speed of light is slowing down and the sizes of atoms are shrinking. But most people would find that less intuitive and less useful. Anyhow, to make it work I think you'd also have to have some or all of the charge of the electron, the permittivity of space, Planck's constant, and the gravitational constant changing in sync, but I haven't worked out the details. If you're willing to have the sizes of atoms and the speed of light vary, not with time, but with location, you can devise a system in which the Earth is inside out. In that system, most of empty space seems distant only because as objects get closer to the center they shrink and slow down, Earth's surface seems to curve the "wrong" way only because light curves due to its varying speed with altitude, the cosmological horizon is located at the center and is smaller than an Earth-surface-atom, and the infinite volume of rock that fills almost all of space has a finite mass because it gets less dense as it gets more distant.