[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

It's all relative!




OK  Maggie and Tom,  I wanna play too!!!

I used to do this with my kids.  I called it how fast are you moving when 
you're standing still?

Tom has covered the earth's rotation on its axis and its motion around the 
sun, but there are at least two more interesting reference frames, and the 
speeds keep going up!!

The Milky Way galaxy is approximately 100,000 light years in 
diameter.   The sun is about 30,000 light years from the center. Thus, in 
one trip around the galaxy, the sun covers 60k * PI light years.  A light 
year is 9.46e12 km, so that's 1.78e18 km for the sun to orbit the galaxy once.
It takes about 226 million years (give or take a bit) for the sun to do 
that, and of course it pulls the earth and the rest of the solar system 
along for the ride.  Crunching the numbers shows that the sun / earth's 
speed relative to the center of the Milky Way is 250 km/s.  !!!   That's 
approximately 25 times AO-40's speed at perigee.

...and of course the universe is expanding such that the separation rate 
for two galaxies is directly proportional to the distance between them. So 
from the point of view of someone in a galaxy on the other "side" of the 
universe, the earth is retreating at nearly the speed of light, or about 
30,000 times the speed of AO-40 at perigee.



-- 
  _______________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.cstone.net/~w4sm/ham1.html
   Charlottesville, VA     PGP key: http://www.cstone.net/~w4sm/key
  _______________________________________________________________________

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home