I would guess that, if asked, most people would say that the Sun, Moon, stars and planets all rise in the east and set in the west. While it does appear that they do, they actually only appear to. In actuality the Sun is standing still, the Moon and planets are moving west to east, and the stars are going every which way. This apparent east to west motion is simply an illusion caused by the rapid rotation of the Earth. Similarly, if you’ve been paying attention to the planets this summer (and I know all of you have), from week to week they’ve all apparently slid slowly toward the west, getting closer to the setting Sun each day. Wrong again: this too is an illusion caused by the Earth’s motion; in reality, the planets actually move slowly west to east against the background stars, because all the planets orbit the Sun in a counter clockwise direction. Then, just when you think you have this figured out, about twice a year the planets stop and reverse direction for a few weeks or months before resuming their normal direction again. The original reason the planets did this was simply to confuse the ancient civilizations, especially the Egyptians, but once it was established that the Earth orbited the Sun, some European mathematician figured out it was but just another optical illusion caused by the Earth passing another planet in its orbit. We now call it ‘retrograde motion’. Well, it’s that time again. The planets have had a pretty quiet summer, but that’s all about to change. Jupiter is rapidly getting hard to see as it nears the horizon.
That’s too bad, not only because it’s my favourite planet, but because Venus and Mercury will be coming out to play over the next few days. The three will be getting uncomfortably close together, culminating on August 27th when Jupiter and Venus appear as a single planet.
Unfortunately, all this occurs virtually on the horizon just after sunset, and will be extremely difficult to see (so it’s only right that I try, of course). Mercury just came out a week ago, and can be found with difficulty barely above the western horizon 30 minutes after sunset. It will be gone again by September 1st. So, while Jupiter and Mercury will soon be out of the picture, all this retrograde stuff will have Venus rushing toward Mars in the southwest, which in turn is rushing eastward in a futile attempt to get away. Watch for it to pass beneath Saturn on the 24th.
What all this means is that over the next few months we will have a different set of planet interactions going on, something that would be quite rare if not for this incomprehensible ‘retrograde’ thing. New word, new show, all visible over the coming months from your own back yard.
