5,352 reputation
1531
bio website keith-s-thompson.github.com
location San Diego, CA
age 55
visits member for 3 years, 2 months
seen yesterday

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


Oct
17
comment Is dark matter around the Milky Way spread in a spiral shape (or, in a different shape)?
Does that mean that spiral galaxies are disk shaped (as opposed to spherical) because of non-gravitational interactions? Wouldn't a spinning mass of gas and dust form a disk even without self-interaction?
Oct
17
comment Is dark matter around the Milky Way spread in a spiral shape (or, in a different shape)?
Wild guess: Probably not. As I understand it, the arms themselves aren't all that much denser overall than the gaps between them; they're just richer in young bright stars. I wouldn't expect the mechanism that creates and maintains the arms to affect dark matter.
Oct
17
comment Which way do spiral galaxies rotate?
@SachinShekhar: The article says "Astronomers suspect that NGC 4622 interacted with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it." I can't judge whether that's accurate, but it seems plausible.
Oct
16
comment Get time from sun Azimuth
A sundial? 8-)}
Oct
12
comment What is the current status of Pluto?
@CarsonMyers: It isn't, according to the link in the answer.
Oct
12
comment What is the current status of Pluto?
Is Ceres a planet in your book? What about Haumea, Makemake, and Eris? The real question is, would Pluto have been called a planet if we'd known what we know now about the bodies that exist int the Solar System?
Oct
12
comment What is the current status of Pluto?
@CarsonMyers: The Earth-Moon barycenter is barely inside the surface of Earth; it's about 1000 miles below the surface, and would be above the surface if the Moon were about 35% farther away, or if were about 35% more massive.
Oct
12
comment Two planets in same orbit - not planets?
The magic hexagon is called a Klemperer Rosette. And yes, it has been used in science fiction. Alas, apparently it's not dynamically stable. (In Niven's novel, presumably the Puppeteers had more than sufficient technology to keep their planets where they wanted them.)
Oct
12
comment Collision of Phobos
Since Phobos is within the Roche Limit, that implies that there can't be any loose material on its surface, at least not near the points pointing directly towards and directly away from Mars. Any such material would be pulled off the surface by the tide. It also means that the local effective gravitational acceleration is negative. (But it appears to be covered with at least 100 meters of regolith, which is a bit of a mystery.) Reference. It would be fascinating to see a plot of the local acceleration over the surface.
Oct
12
comment Tropical year is 27s/year off from Gregorian year?
Right. In other words, leap seconds correct for amount by which a solar day differs from 24 hours; leap days correct for the amount by which a solar year differs from 365 solar days. (And "24 hours" is defined as 86400 seconds, where the second is defined as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom" (reference).
Oct
12
comment What could this very dark planet be made of?
Unobtainium, obviously!
Oct
11
comment Why do rockets need a cosmic ray detector?
Um, maybe it's to detect cosmic rays? 8-)}