RE: When plants align
March 14, 2015 at 9:31 am
(This post was last modified: March 14, 2015 at 9:46 am by Smaug.)
(March 14, 2015 at 9:18 am)Chuck Wrote: The answer depends on how precisely do the planets have to line up for you to consider them to be "lined up".
If you require a single straight line to pass through all planet, that almost certainly has never happened, nor will ever happen. The reason is the plane of each planet's orbit is slightly different. The planes of different planetary orbits intersect along lines of different orientation, so even if all planets seem to align when viewed top down from above the solar system - in itself an extremely unlikely event - they won't be aligned when looked at edge on.
On the other hand, if you relax your definition of aligned to mean, for example, all 8 planets occupying the same 45 or 90 degree slice of arc around the sun when viewed top down, then yes, it has happened many times before and will happen again many more times.
To add to what you've said, the relaxed case is called an Appulse or Parade of planets. It's such a case when all the planets appear in a narrow sector (with an angle of 10 to 40 degrees) of the celestial sphere. There are different kinds of appulses depending on how and how many planets are aligned. An appulse of all the planets happens with a period of about 170-200 years as far as I remember.
As for the conjunction of all the planets, it's mathematically possible but is extremely unlikely indeed. Speaking of inclinations of orbits, it's possible that due to precession and deformation the orbits align in such a configuration when the conjunction is possible in a rigorous sence. But due to the chaotic nature of Solar system's behaviour such an event is technically impossible to predict.
