2006-12-19 07:58:40 · 2 answers · asked by budspaula1990 1 in Science & Mathematics ➔ Astronomy & Space
The orbit paths and speeds of the planets are now so well known, astronomers use software and computers to simply project into the future where the planets would be at any given day and moment, including looking for instances of planetary grouping, or alignment. It's not any different from predicting solar or lunar eclipses.
In the older days, mechanical orreys were used to make such predictions.
2006-12-19 08:13:18 · answer #1 · answered by Scythian1950 7 · 0⤊ 0⤋
It is basically a numbers game. They know exactly how long each planet takes to complete one orbit and where they all are now. So in a half year Earth will be half way around the Sun from where it is now, and Saturn will be only 1/60 of the way around the Sun from where it is now. And so on.
2006-12-19 08:53:03 · answer #2 · answered by campbelp2002 7 · 0⤊ 0⤋