5,392 reputation
1631
bio website keith-s-thompson.github.com
location San Diego, CA
age 55
visits member for 3 years, 2 months
seen 17 hours ago

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

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


Dec
8
answered How does space affect the human body (no space suit, no space craft)
Dec
7
comment Why can there be fire in space while there is no oxygen?
@PatrickRitchie: Edited.
Dec
1
comment What is the official difference between a planet and a dwarf planet?
Pluto's orbit crosses Neptune's only in the sense that it comes closer to the sun than Neptune does. Pluto's orbit is tilted enough that it never actually comes very close to Neptune. In fact, Pluto's closest approach to Uranus (11 AU) is closer than its closest approach to Neptune (17 AU) according to this Wikipedia article.
Nov
30
answered Why can there be fire in space while there is no oxygen?
Nov
30
asked How plausible is a subsurface ocean on Pluto?
Nov
30
comment 2012: Is there some astronomical event happening?
Correction, my comment was on this blog post (regarding Julian vs. Gregorian calendars).
Nov
25
comment Most accurate ways to find the average distance between stars in Milky way galaxy
How do you define "average distance"? The most straightforward definition is, I'm sure, not what you mean: the average distance between X and Y for each pair of stars X and Y in the galaxy. That would be some tens of thousands of light-years. Do you mean the average, over all stars in the galaxy, of the distance to that star's nearest neighbor (e.g., about 4.3 light-years for the Sun)? How do you handle multi-star systems? How do you define multi-star systems? How do you define "star"? And the core is going to skew the results quite a bit, as are clusters.
Nov
19
comment If neutrinos travel faster than light, how much lead time would we have over detecting supernovas?
Typos: Meanwhile, the core collapse and rebound emits energy in forms that are absorbed by the body of the star, causing it to heat up.
Nov
18
answered Why does the “Troll-Mobile” not work?
Nov
18
comment How does a mobile phone vibrate without any external force?
For those who want to Google it, it's "eccentric drive".
Nov
18
comment If neutrinos travel faster than light, how much lead time would we have over detecting supernovas?
(ran out of characters) The bulk of the star isn't significantly transparent at all. We don't see the light from the blast until most of the star is blown away -- which happens in a matter of a few minutes or hours.
Nov
18
comment If neutrinos travel faster than light, how much lead time would we have over detecting supernovas?
Is scattering really the answer? My understanding is that the core collapse is a quick event that generates a blortload of neutrinos; the neutrinos travel through the material of the star (and anything else in their path) and reach us without delay. Meanwhile, the core collapse and rebound emits energy in forms that's absorbed by the body of the star, causing it to head up. We don't see the visible light until that energy (1) reaches the surface of the star, causing it to glow more brightly, and/or (2) blows away most of the star's mass, exposing the bright core.
Nov
18
awarded  Nice Answer
Nov
18
answered How does a mobile phone vibrate without any external force?
Nov
18
comment Can a photon passing by an open space barycenter of a system of masses be modeled as if all the system's mass is at the barycenter?
Actually, the barycenter of the Sun-Jupiter system is above the Sun's surface, at 1.068 solar radii from the Sun's center, according to Wikipedia. (It might dip below the surface when Jupiter and Saturn are at opposition; I haven't crunched the numbers.)
Nov
18
comment Can a photon passing by an open space barycenter of a system of masses be modeled as if all the system's mass is at the barycenter?
@user1003469: The Earth is a special case. Any spherically uniform body is gravitationally equivalent, for any object outside the surface of the sphere, to a point source at the sphere's center.
Nov
16
comment Best time of the year to see the star Alpha Centauri in Chile, Santiago
Two hours later than midnight is 2AM, yes? Or am I missing something?
Nov
14
comment What makes matter “solid”?
The idea that glass is really a liquid is controversial.
Nov
13
awarded  Autobiographer
Nov
12
comment Why is this radio telescope's reflector spherical and not parabolic?
A paraboloid would probably be better if the telescope were aimed only in one direction, straight up. Most radio telescopes steer by moving the entire dish until the axis and receiver are aligned directly with the target. But Arecibo's dish is immovable, and to aim at targets off the vertical, only the receiver is moved. A spherical shape gives uniform reception over the entire range to which it can point. (A 1000-foot steerable dish would probably be a paraboloid.)