Keith Thompson

4,371 reputation

1025

bio	website	keith-s-thompson.github.com
	location	San Diego, CA
	age	53
visits	member for	1 year, 7 months
	seen	May 9 at 14:35
stats	profile views	191

I'm a programmer and all-around nerd living in San Diego, California and working at JetHead Development Inc.

E-mail: Keith.S.Thompson@gmail.com

	4,371 reputation	bio	website	keith-s-thompson.github.com	visits	member for	1 year, 7 months
1025 badges		location	San Diego, CA		seen	May 9 at 14:35

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Apr 21	awarded	Nice Answer
Apr 15	awarded	Necromancer
Apr 3	revised	Is Feynman's explanation of how the moon stays in orbit wrong? added 470 characters in body
Mar 31	comment	What cosmic event would cause Sun rising from the west? A collision sufficient to reverse the Earth's rotation wouldn't just melt the surface it would disrupt the planet and create a new asteroid belt. (Quite possibly I'm wrong; feel free to do the math.)
Mar 31	comment	What cosmic event would cause Sun rising from the west? "In principle the tidal forces of the Sun will eventually slow the Earth's rotation so it always shows the same face to the Sun." -- Only given certain carefully chosen principles which ignore the existence of the Moon. The Moon's much stronger tides will eventually cause the Earth's rotation to become tidally locked to the Moon, not to the Sun. (Assuming our descendants or successors don't do something about it in the meantime.)
Mar 31	comment	Is Feynman's explanation of how the moon stays in orbit wrong? @mtanti: If you stay in the original frame of reference, the distance the ball moves "down" is larger. But the Earth is no longer straight "down"; it's now below and a little bit "behind" the Moon's new position. Over a short time span, the Moon's motion approximates the parabola it would follow in a uniform gravitational field; the Earth is at the center of the circle that's tangent to that parabola.
Mar 30	comment	Is Feynman's explanation of how the moon stays in orbit wrong? @MarkMitchison: Good point, I've updated my answer accordingly.
Mar 30	revised	Is Feynman's explanation of how the moon stays in orbit wrong? added 48 characters in body
Mar 30	answered	Is Feynman's explanation of how the moon stays in orbit wrong?
Mar 18	revised	How does space affect the human body (no space suit, no space craft) Link to YouTube video
Feb 27	comment	What's the surface area of a liquid? How does evaporation increase if the surface area of a liquid is increased? If you have a tall glass of water with a given fixed surface area, it will lose a constant amount of water per unit of time (in an identical environment); the deeper the water, the longer it will last. But for a given volume, the large the surface area that's exposed to air, the more quickly it will evaporate.
Feb 26	revised	What is this underground nuke test name and params? Grammar
Feb 26	comment	What's the surface area of a liquid? How does evaporation increase if the surface area of a liquid is increased? Why would having more surface molecules make the evaporation rate decrease?
Feb 26	comment	Density of stars near the center of the Milky Way @theJollySin: Not really. I've updated my answer with a link to a Wikipedia article that gives different figures.
Feb 26	revised	Density of stars near the center of the Milky Way Link is dead, add another
Feb 17	comment	Stresses in asteroid during close flyby Tide is the difference in (gravitational) acceleration over distance. It falls off with the cube of the distance from the primary, which is why the Moon's tidal effect on the Earth is stronger than the Sun's. For an asteroid near Earth, the (differential) force from the tide and the asteroid's own gravitational cohesion are both fairly small; within Roche's limit, the tide exceed's the asteroid's gravity. The net gravitational force on the asteroid is zero, since it's in free fall, so I don't think "jerk" comes into it, except perhaps as a second or third order effect.
Feb 16	revised	Stresses in asteroid during close flyby added 60 characters in body
Feb 16	answered	Stresses in asteroid during close flyby
Feb 15	comment	Is the moon a planet? If we discovered, say, a Neptune-sized body in a nearly circular orbit at 150 AUs, I think we should call it a "planet". And we've detected hundreds of "planets" orbiting other stars. If we're going to use the word, I think we should have a consistent definition for it.
Feb 12	awarded	Good Answer