by neufer » Sun Nov 07, 2010 9:45 pm
Arrgy wrote:
That there are so many different theories as to how often we cross the plane (dark rift) shows that we don't have a clue.
No....
It is determined solely by the average density of stars in our neighborhood.
A periodicity of 56,000,000 years (i.e., an extinction every 26 to 30 million years)
corresponds to an average density of one solar mass per (56,000,000)
2 4π/3 AU
3
or one solar mass per (56,000,000)
2 4π/(3 x 64,240
3) cubic light years
or one solar mass per 49.55 cubic light years
or one solar mass every (3.673 light years)
3
which is probably a good estimate for the average density.
(The uncertainty here mostly involves the local density of dark matter.)
[quote="Arrgy"]
That there are so many different theories as to how often we cross the plane (dark rift) shows that we don't have a clue.[/quote]
No....[b][color=#FF0000]It is determined solely by the average density of stars in our neighborhood.[/color][/b]
A periodicity of 56,000,000 years (i.e., an extinction every 26 to 30 million years)
corresponds to an average density of one solar mass per (56,000,000)[sup]2[/sup] 4π/3 AU[sup]3[/sup]
or one solar mass per (56,000,000)[sup]2[/sup] 4π/(3 x 64,240[sup]3[/sup]) cubic light years
or one solar mass per 49.55 cubic light years
or one solar mass every (3.673 light years)[sup]3[/sup]
which is probably a good estimate for the average density.
(The uncertainty here mostly involves the local density of dark matter.)