is the moon is moving away from us?....or is the universe just expanding? The 'measurement' of the radial expansion of the moon's orbit is 3.8 cm/yr http://curious.astro.cornell.e...uestion.php?number=124 [Broken] but that measurement is only slightly more than the hubble constant (the rate that the universe is expanding) Here is my calculation: Hubble expansion =70.8 km/sec / Megaparsec =70.8 km/sec / 3.08x 10^19 km = 2.3 km/sec / 1 x 10^18 km = 2.3 m/s / 1 x 10^18 m moon's radial expansion / dist to earth 3.8x10^-2 m/yr / 4 x 10^5 km yr=365x24x60x60 sec 3.8x10^-2 m/3.15x10^7 sec / 4 x 10^5 km 3.8x10^-2 m/s / 1.26 x 10^13 km 3.8 m/s / 1.26 x 10^15 km 3.02 m/s / 1 x 10^18 m The radial expansion of the moon was measured using the cube mirrors left by Apollo on the moon. Very simple. ---didnt they really just measure the Hubble constant? Isnt the moon really just moving away much more slowly than we measured because of the hubble constant? This calculation is posted in memory of the 40th anniversary of homo sapiens visit to the moon. ------------------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ sorry i dont have references for this basic knowledge at my fingertips, but i did read it somewhere and dont remember the source.