Re: Explanatory Power

Kevin O'Brien (
Fri, 12 Mar 1999 05:12:15 -0700

Neal Roys wrote:

>I'm looking for something that has a falsifiability scenario that parallels
>the "no-red-shift-is-discovered" scenario that Einstein described for
>falsifying general relativity (i.e. if light from distant galaxies is
>blue-shifted, then general relativity is falsified)

Actually, that wasn't the test. In Appendix III of his book _Relativity_,
Einstein wrote that as of 1920 it had already been established that the
light from stars (not galaxies) was red-shifted. The question for Einstein
was whether this red shift was caused by the gravitational potential (in
which case it would confirm general relativity) or by some other mechanism
(in which case it would render general relativity "untenable", to use
Einstein's description). In other words, since the red shift of light from
other stars had already been established, finding a blue-shifted star would
not have falsified relativity. However, if it was discovered that the
observed red shift was caused by something other than the gravitational
potential, then relativity would have been falsified even though the red
shift had been observed.

As an aside, Einstein does briefly discuss galaxy red shift in Appendix IV,
but states that that shift was due to the expansion of the universe, so
galactic red shift has very little to do with general relativity (and some
nearby galaxies are blue-shifted because they are moving towards us).

Kevin L. O'Brien