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location San Mateo, CA
age 59
visits member for 8 months
seen Jul 16 at 14:38

Jul
16
answered Can two comets travel together as one?
Jun
27
awarded  Teacher
Jun
26
answered What is the physics of a gas mass subject to gravity in space?
May
22
comment How big would a disc have to be to blot out the sun covering 5% of the land mass of earth?
You would want the object to be at the earth-sun L1 point, about 1.5 E6 km away. This would need a bit of stationkeeping (it is an unstable point), but not much. That saves you a factor 2/7 in diameter, but the message doesn't change.
Dec
16
comment Why don't we have 2 Summers and 2 Winters?
The sun is at one focus of the elliptical orbit, not at its center. Perihelion is when the earth is at the end of the major axis nearest the sun, not (both times) the earth is at the end of the minor axis. There is only one per year. The 3% change in distance makes a 6% change in solar energy received. At San Francisco, the day is 14:45 long in June and 9:33 in December, an increase of 54% and we haven't accounted for the higher angle of the sun in the sky.
Dec
16
awarded  Supporter