2007-09-22 14:14:41 · 3 answers · asked by Lefty 2 in Science & Mathematics ➔ Astronomy & Space
They always line up -- its just that the line is very crooked.
Do you mean line up within plus or minus 180 degrees? 90 degrees? 1 degree?
2007-09-22 16:08:01 · answer #1 · answered by morningfoxnorth 6 · 0⤊ 0⤋
Partial line-ups are common. 'Line up' is usually a misnomer as a general allignment can mean anywhere within the same quadrant. Alignments of Mercury through Saturn are not that unusual. 1962, 2000, 2040,2438. The inner six planets are roughly alligned every 50-100 years.
Probability of ALL planets at same Right Ascension with respect to Sun at same time = once in 180 trillion years.
If we include the Moon in this calculation, that is, it being at either a solar or lunar eclipse during this time, we multiply its period onto this. For an exact alignment when all of the planets are inclined with respect to the ecliptic, we must factor this line-of-nodes precession into our calculations.
The calculated probability for an exact planetary alignment to occur is once in 86 billion-trillion-trillion-tril... years (86 followed by 45 zeros).
The odds strongly favor that an exact planetary alignment will NEVER occur throughout the entire history of the solar system.
2007-09-22 22:07:16 · answer #2 · answered by Troasa 7 · 5⤊ 0⤋
Depends what you mean by "line up". If you mean all on the same line, so that from the last one you'd see all the other ones as dot on the Sun, then it is extremely rare (maybe never happened in the last billion years).
The last "Great Alignment" meant that all planets were in the same 90 degree quadrant (not really in line), but even that is rare enough.
2007-09-22 21:47:51 · answer #3 · answered by Raymond 7 · 1⤊ 0⤋