Expanding mass

[Enola Straight]

http://www.youtube.com/watch?v=bd-QqKmVyfU

What is the flaw in this theory?

[Darth Holbytlan]

The flaw? You mean beyond the fact that his "theory" is built out of complete handwavium lacking any of the detailed mathematical predictions that real physics makes?

I'll make one specific point: His central claim that expanding mass is equivalent to warping space is nonsense. First, he confuses warped space with space continually contracting over time, which would convert his "expanding matter" into "matter that is simply larger than we thought". Second, warped space is not interchangeable with flat space and expanded matter, since the former has capabilities the latter doesn't. For example, warped spaces is capable of producing geometries that flat space isn't, such as unbounded finite spaces like hyperspheres.

[Wyrm]

Another problem is that expanding matter formulation cannot have orbits or escape velocities.

The first thing revealed is that, in order for the Expanding Matter "theory" to produce acceleration like we see on earth with Newtonian mechanics on the 'real' coordinate system, the expansion has to be geometric. (This is because the length of your rulers is also changing — in order to ensure that the length of your ruler and the radius of the earth are always in the same ratio, the expansion rule has to be geometric.) BUT, an unaccelerated object moving away from the Earth at a constant speed (against this 'real', non-expanding coordinate system where rulers are expanding according to this expansion rule, as per our assumption) will always crash into the Earth eventually, no matter how far away it is, at what velocity it is traveling, because exponential growth will always overtake linear growth. Therefore, escape velocities cannot exist.

Furthermore, orbits cannot exist. If there's truly no force between objects or warping of spacetime to wrap worldlines about massive objects, then expansion of matter cannot create it. The fact that for any object will eventually crash into the Earth means that there's no stable orbits.

If we use the Earth's radius and gravity as a measure of how fast the Earth is expanding, the Moon ought to crash into the Earth in about 30 days.

We, of course, don't see this. On the other hand, warping space does allow there to be orbits and escape velocities.