Not Going Anywhere
Back in September last year, Jupiter was suddenly in the news. It was coming close to Earth! Wouldn't be this close again until 2022! Newscasters told you how to look for it, and breathlessly told you that at present it was the brightest object in the sky, except for the moon! And maybe the sky would be clear tonight, and you'd be able to observe it!
This was all very entertaining to the sort of person who knows Jupiter by name and pals around with him nightly. Because while all this was technically true, it was quite silly. In the first place, Jupiter didn't look much brighter on September 17th than it ever does. It's often the brightest object in the night sky: only the Moon and Venus are brighter (well, and very occasionally Mars.) But the really amusing thing was the sense of urgency, as if Jupiter might suddenly dart away again: as if you might miss it, as you might miss, say, the Perseid meteor shower. Jupiter is very big and very far away, and from our viewpoint here on Earth, it doesn't move very quickly at all. In fact, it's been in roughly the same part of the sky ever since September, and when I began writing this post this morning I could still see it through the window at Tom's, blazing away in the pale blue dawn, off to the southeast. Your chances of missing it were very small indeed.
This animation by Brad Goodspeed is terrific for showing how big Jupiter is: he tried to give you a sense for how big different planets would appear to us if they were as close as the moon. Of course, if Jupiter were this close, our little Earth would drop -- plop! -- into it, like a pebble into a pond, and that would be the end of government health care, and Mubarak's presidency, and a number of other things.