Originally posted by weedwhacker
The Apollo is orbiting the Moon very quickly....that series of photos I posted were taken within a matter of a few minutes, far less than one hour.
You just won't see the Earth rotate much in that short a timespan, now will you?
Number two, as to the photos from LEO...the ISS and Shuttle are moving rapidly, so the Earth isn't really rotating under them (well it is, but just
as slowly as always) they are moving quite rapidly over the Earth's surface...about 90 minutes per orbit.
[edit on 21 July 2009 by weedwhacker]
Mind if I add on a bit to further delve into your explanation?
If the ISS were simply rotating with the Earth, and not around it in its own trajectory, it would remain a stationary object in the sky, and therefore
we would be able to stand in one particular location upon the surface of the Earth and continuously keep our eyes on it. However, this is NOT the
case, as it in fact traverses the sky within a matter of minutes from viewable Horizon-to-Horizon, and therefore it moves considerably faster than the
speed at which our Earth rotates. The ISS moves at roughly 17,000 MPH, whereas the Earth spins around its own axis at roughly 1,000 MPH. If the Earth
rotated at the same speed as the ISS, our "Day" would cease to be 24 Hours Long, and it would instead be roughly 1.5 Hours Long.
If you want a tangible example, swing yourself around. Now note the speed. Then, take a modest length of line with a considerable amount of weight
attached to its end (Do not hit yourself though), and swing it as fast as you can, while rotating as quickly as you yourself can around your own axis.
Notice anything? The Weighted End of the line will very rapidly overtake your own rate of spin, and it will most likely rap around you multiple times
due to such. This is the same effect that we witness with Orbital Satellites, both Artificial and Manufactured ones. There are other variables, such
as the connection between Speed and Altitude, and Apogee and Perigee, but they are only necessary to explain if more technical aspects of such are
As for the Moon, it generally Orbits around the Earth at 2,000 MPH, which is all that is required (due to its Distance and Mass), for it to remain
within Earth's Orbit. The Moon itself rotates around its own axis at a speed of roughly 10 MPH. The CM's of Apollo orbited the Moon at roughly 4,600
-5,000 MPH (At 70 Miles above the Lunar Surface, which is between 1/2 and 1/4 of the Height/Distance of the ISS above Earth's Surface). It took 45
Minutes for the Apollo CM's to return from COMM Blackout once they initially entered it on the "Dark side" of the Moon (As it appears to us here on
Earth), and that generally covers half of their Full Lunar Orbital time/distance (90-110 Minutes in Total, over 6,700 Miles).
*Note: I have rounded many of the aforementioned calculations so as to provide the most simple numerical values possible.