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Originally Posted by Jerry
What is most startling to me though, is our failure to detect gravity waves. When you read the latest proposals of the LIGO team, it is easy to assume that we have not detected gravity waves simply because we do not have the necessary instrumental sensitivity. It is a misconception that this limit is theoretically driven: The observational constraints placed upon current tests for gravity waves are based upon prior constraints from less sensitive experiments.
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Again, see
Giovanni Santostasi's thesis. The calculation of the integration time required by ALLEGRO to detect the SN1987A remnant directly is in chapter 12, beginning on page 110. That calculation is clearly based only on theoretical GR expectations for a rotating neutron star (not the core-collapse event itself, but something that should be detectable for millions of years after the event). The results of the calculation are
then compared to ALLEGRO's sensitivity limit.
What has been done in the case of supernovae events (rather than remnants) is to place upper limits on the
total number of core-collapse supernova within the galaxy assuming GR is correct. Currently the limits are uninteresting, being in the hundreds per year level (things will get more interesting with LIGO-II, after 2005). They wouldn't be able to quote such a number at all if your interpretation was correct, because all that would be known in that case would be that we hadn't see any detections yet. As it is, having a way (from GR) to calculate the strength of gravitational waves produced by a supernova allows a numerical limit to be quoted. Of course, if GR is wrong then so is the limit, but the limits are not yet anywhere near tight enough to conflict with what we know (that there have been about six supernovae in the galaxy in the past millenium). If all we had was the sensitivity of past experiments, and no theoretical model for gravitational wave strengths then nobody would be able to quote such limits at all.
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2) Neutron stars were predicted using General Relativity and Quantum physics. They have been observed, confirming the prediction, but when they are found in binary pairs winding into each other they emit intense radio pulses. This pulsing was not predicted and is proving difficult to model. What is predicted is a very powerful gravity wave that we should be able to detect in binary neutron stars we observe winding into each other. (The mass loss necessary to create this wave IS observed, but not the gravity wave.)
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They emit radio pulses when not in binaries, as well. There are more known pulsars outside binaries than there are in binaries, which is not really surprising when you consider the events that create neutron stars.