Meanderings Of Mars

Press, Volume CII, Issue 30044, 31 January 1963, Page 7

Meanderings Of Mars

AU of the superior planet* (tboae wboae oebita Ito outride that of tite earth) continually alter their partitions against the backdrop of fixed stars with a rather peculiar motion when viewed from the earth. For the greater part of a year they appear to move in the direction of their orbital motion, but for a few mouths they reverse and move in a retrograde manner—just as it they had turned around in their orbits. The motion of Mars, which is retrograde at the moment, is a good examjde: it ia moving to the left, away from tbe constellation Leo (see diagram). On March 18 it win start moving forward again and will pass through Leo next Jim# The explanation for this

behaviour is quite simple, but difficult to explain without a lot of diagrama We will try, anyway. Think of a fairground merry-go-round. If you stand on the edge of the meny-go-round as it rotates, an onlooker severti yards away win appear to move sideways back and forth against the background of tents and stalls « you go round and round. If the onlooker then walks around the merry-go-roupd in the same direction as its rotation he will appear to move forward quite a way, then back a little, then forward again, the actual amounts depending on his walking speed compared with the rate of your rotation on the merry-go-round. Think about this a moment, then it will

be quite dear why the outer isra,“BSfi.«*j! parent motion of Mars, m shown in the diagram, stems directly -from the fact that the eerth and Mam move in approximately circular paths centred on the sun.