Re: [Utah-astronomy] Utah-Astronomy Digest, Vol 95, Issue 44 Beating the Dead Expanding Earth One More Time
This is just about worn out, but I must add the point (and give evidence) that it's all a matter of scale. Gravity works on the relatively small scale (i.e., within a few million light years) while the accelerating expansion of the Universe is seen on the really BIG scale (several billion light years). The Hubble Constant tells us that if we ignore the acceleration (easy to do, say, t 500 million light years distance) the expansion is about 70 km/sec/Mpc. In other words, every additional million parsecs (about 3 million light years) between objects,the velocity at which they move apart increases by about 70 km/sec. If we take this ratio, convert Mpc to kilometers, and see what the recessional velocity is for a distance of 6000 km (about the Earth's radius) we find that the expansion of space (don't forget that's what's really expanding), we find that the speed of expansion is about one TRILLIONTH of a meter per second! It's gonna take a lot longer than even the age of the Earth to see a measurable change. While you wait, the Sun's going to swell up and burn the Earth to a crisp. Get out yer marshmallows! John R.Peterson
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John R. Peterson