[ICR Creation Online] This argument comes from an article by Canadian young-Earth advocate Keith Davies (http://www.creation.on.ca/cdp/snrart.html), who claims that astronomers do not observe enough supernova remnants (SNRs) in our Galaxy to justify an age greater than 7,000 years. Davies assumes that SNRs will remain visible for 1 to 6 million years after the supernova event. In fact, although they may in fact continue to exist for that length of time, they become rapidly more difficult to detect as time passes. In the years following a supernova event, the remaining gases spread out, becoming thinner and thinner. They also become distorted by the interstellar medium (ISM), and become difficult to observationally distinguish from the ISM. So, even though SNRs can continue to exist for a few million years, most only remain detectable for 20,000 to 120,000 years, depending on the size of the supernova event and other factors. D.A. Leahy and Wu X. (Publications of the Astronomical Society of the Pacific, v.101, pp.607-613 (June 1989)) discuss the various effects limiting the detectability of SNRs. The remaining discrepency between observation and Davies' predictions is accounted for by various minor errors in Davies' paper. For a more detailed discussion of Davies' claims, see Moore (2000), http://www.valinor.freeserve.co.uk/supernova.html. Incidentally, Davies also notes that no third-stage SNRs (SNRs that have been expanding for more than 120,000 years) have been detected in the Galaxy. As stated above, this is because most SNRs are too spread out by that time to be detectable. However, some third-stage SNRs in other galaxies come from supernova events that were so large that the SNRs are still detectable. One known as SNR 0450-709, in the Large Magellanic Cloud, is 340 light-years across, and has been expanding for several hundred thousand years (see T.W. Jones et al, Publications of the Astronomical Society of the Pacific, v.110, pp.125-151 (Feb 1998)). The existence of such third-stage SNRs is inconsistent with the young-Universe hypothesis.