Really enjoyed Mike Johnson's "A Hubbling Experience" (Mar 97) I had to run his numbers and then redo it using the correct solid geometry formula to convince myself his method gave a good approximation at 75 billion. However, he claims that "a more precise calculation with a calculator gives 74.3 billion." When I run Mike's numbers precisely, I don't get 74.3 billion. However, when I do it "right" (i.e., using the cosine of the subtended angle) I do get 74.3 billion. So Mike does too know some solid geometry.
More interesting, perhaps, is the difference between this 75 billion and the 100 billion estimate that Carl Sagan and company have estimated for 15 years or so. As I recall, the television show about this Hubble picture said that they purposely aimed the Hubble at the "darkest" spot in the sky, where they expected to see nothing. That is, where no telescopes had seen anything before. That means they were intentionally looking past all the stars and galaxies in the nearfield to see what was way out there. Given that this view extrapolates to 75 billion, it's real easy to assume that the other 25 billion (and probably more) are easily accounted for in the brighter regions of the heavens.
By the way, my wife (the LocSec) told me, "You might be a Mensan if you spend two hours figuring out how another Mensan approximated a cosine function using a radian conversion."
Dennis Lenahan,
Editor, HMMmm
High Mountain Mensa, Colorado