ethan@utastro.UUCP (Ethan Vishniac) (11/21/84)
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One thing I should have added to my discussion of Arp's article
was that the evidence Arp was citing to show that *some* galaxies
are less than 10^9 years old does not affect estimates of the
Earth's age. Nor did Arp think it did. The point he was
addressing is that it is generally thought (on the basis of
some fairly strong evidence) that galaxy formation is not
occurring at the present epoch. If galaxy formation is an ongoing
process in the universe then this raises the question of whether
it is fair to equate the age of the universe with the age of
our galaxy (which we tend to do, adding a little extra for the
formation epoch). The age of our galaxy might be considerably
*less* than the age of the universe if Arp were right.
In a similar manner one notes that ongoing star formation
shows that it is unreasonable to equate the age of the sun
(about 4 1/2 billion years) to the age of the galaxy (separately
estimated at more than 10 billion years).
"I can't help it if my Ethan Vishniac
knee jerks" {charm,ut-sally,ut-ngp,noao}!utastro!ethan
Department of Astronomy
University of Texas
Austin, Texas 78712