From: Hal Finney (hal@finney.org)
Date: Fri Feb 21 2003 - 12:52:50 MST
BillK mentions the paper which Serafino found here:
http://arxiv.org/abs/astro-ph/0301184
> "If time moves along like business as usual even at Planck scales,
> however, you have to reconcile the Big Bang model with an event that
> isn't just off the scale, it's infinite!"
The real issue here is that this is supposed to be a test of quantum
gravity. According to that theory, uncertainty in space and time is
present at the smallest scales, giving the universe a somewhat granular
nature. This can be reflected in principle in the propagation of light
over galactic distances. Lieu and Hillman claim that this should destroy
interference patterns on such photons, in contrast to observations.
However I found a Usenet post which pointed to two papers which deny
this conclusion,
http://xxx.lanl.gov/abs/astro-ph/0302333
http://xxx.lanl.gov/abs/astro-ph/0302372
Both claim that the authors made a mistake. (I just read the abstracts.)
The first argues that the "kind" of interference is relevant, that
what you see through the telescope is wavefront-based and will not
be destroyed by quantum gravity, rather you need an amplitude-based
interference detector like a Michelson interferometer. The second paper
makes a similar point, arguing that the authors "vastly overestimated"
the destruction of phase coherence in this system.
I suspect that the critics are right. I recently read Lee Smolin's
book, Three Roads to Quantum Gravity, and he mentioned some possible
tests of the theory based on long-travelled photons. They are subtle
effects, though. If the bare existence of interference fringes was that
sensitive a test of quantum gravity, people would have figured it out
a long time ago.
Hal
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