On 6/22/2004 06:16, beavith wrote:

On Tue, 22 Jun 2004 06:32:23 GMT, Odysseus
wrote:

beavith wrote:

[snip]

ceebee mentioned that the Hubble Constant is figured to be 74km/s/Mpc
where km is, of course, kilometers, s is seconds and Mpc is
megaparsecs.

my old HS physics teacher would always admonish us to "watch the
units." our old grade school math teachers would also tell us to
reduce our fractions.

here's the conundrum: if Mpc is roughly 3.25 million parsecs, and km

Light-years, not parsecs.

thanks. typo. i was in the groove.

is another distance, if you reduce the Hubble constant to its basic
terms, won't you get a number with a unit of km^2/s?

Umm, no. Speed, distance-per-time, divided by distance is just
inverse time, here s^-1. Unless I've fouled up my arithmetic H = 74
km/s / Mpc = 2.4 * 10^-18 /s. This is a proportional rate, the
quantity that changes over time being dimensionless -- very like an
interest rate (percentages being dimensionless quantities in disguise).

hertz or cycles per sec for example. got it. and what you are saying
is what i had originally thought, too. however, give me a quick
primer in fractions...

does x/yx = x/y/x ?

x divided by y times x gives you 1/y, as x and 1/x factor each other out.