Why retrograde motion of the planets

From an observational standpoint, when the two planets are in opposition to each other on opposite sides of the sun the outer planet cannot be seen from earth. From a heliocentric perspective, then, retrograde motion is an illusion. The appearance results from observations made on a moving platform earth which 'laps' or overtakes the outer, slower moving planets. But this interpretation is only one of several possibilities.

The motion of the earth is not at all obvious to the observer. NASA is returning to Venus to learn whether the hot poisonous wasteland was ever habitable. NASA to return to Venus with two missions by What echoing radio waves taught us about Venus. Ask Astro : What would Earth look like from Venus?

Life in the clouds of Venus? Maybe not. Cosmos: Origin and Fate of the Universe. Astronomy's Moon Globe. Galaxies by David Eicher.

Astronomy Puzzles. Jon Lomberg Milky Way Posters. Astronomy for Kids. Sign up. Table of Contents Subscribe Digital Editons. A chronicle of the first steps on the Moon , and what it took to get there. Now you walk forward at a faster speed. Watch your friend and think about how they are moving relative to you.

At first, they move away, then as you pass them, they APPEAR to be moving backward relative to you - even though they are still walking forward. A site for ages 14 and up. Laura A. Whitlock Curator: J. Privacy Policy and Important Notices. Return to the StarChild Main Page.