597 reputation
211
bio website keith-s-thompson.github.com
location San Diego, CA
age 55
visits member for 1 year, 1 month
seen 6 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


6h
comment How do we know that the speed of the influence of gravity is instant?
If I understand this correctly, we appear to experience a gravitational force directed at the point where the Sun is now, not where it was 8 minutes ago (the latter is where we see it). But if the Sun's core suddenly collapsed, and we were able to detect the resulting gravitational waves, we'd detect them 8 minutes after the event, and from a direction matching the visible position of the Sun, not from the direction of the apparent gravitational force. Is that correct?
6h
comment Do extraterrestrial landscapes or planets count as nature?
Why would it not count as nature?
13h
comment What will happen to life on Earth when Andromeda and Milky Way galaxies collide?
I'm hoping we'll move Earth to a safe distance by that time, for sentimental reasons if nothing else.
1d
comment What would be the dynamics of a double-planet system, similar to Earth / Moon, but with both bodies nearly Earth-sized?
"Constellation" isn't the right word for this. A constellation is an apparent grouping of stars in the sky, or a region of the sky. I think replacing "constellation" by "system" would make your answer clearer. (For example, we already refer to the Earth-Moon system or the Jupiter system; the latter includes Jupiter and its moons.)
1d
comment How did the Mars satellites “take cover” from the recent comet flyby?
MAVEN, for example, orbits Mars every 4.5 hours. It can't just move behind Mars and stay there for a while. What it can do is slightly adjust its own orbit in advance so that, when the comet is at closest approach, its orbital motion carries it behind Mars. It's velocity would only need to be changed slightly, and it would still be on the side of Mars facing the comet 2.25 hours before and 2.25 hours after the closest approach. (I'm assuming this is how it was done.) I'm sure you know this, but I don't think it's 100% clear from your answer.
Oct
6
comment What scientific evidence is there to support or refute the Iron Sun Hypothesis?
I think the article is consistent with what I wrote. "At 3 billion degrees, the core can fuse silicon nuclei into iron and the entire core supply is used up in one day." So silicon-to-iron fusion produces energy, but only lasts about a day; once the silicon is depleted, the iron can't be fused any further without consuming energy. (The jump from Si, atomic number 14, to Fe, atomic number 26, does seem odd; I clearly don't entirely understand this stuff.) Elements lighter than iron can be fuel for fusion reactions; iron and heavier elements cannot.
Oct
6
comment Is Pluto still a dwarf planet?
Keep in mind that the debate is about the meaning of the English word "planet". Pluto itself quite literally couldn't care less. No perfectly consistent classification is possible anyway; is Mercury really more similar to Jupiter than to Ceres?
Oct
6
comment Is there any way a meteor can hit at less than escape velocity?
Meteors (actually meteorites) that hit the ground are typically slowed considerably by air resistance.
Oct
6
comment What scientific evidence is there to support or refute the Iron Sun Hypothesis?
I don't think that's correct. My understanding is that fusion reactions creating elements up to and including iron produce energy, and fusion reactions past that absorb energy (which is why elements past iron are produced mainly in supernova explosions). Thus a massive old star could be producing iron in its core. When the inputs to that process run out, the star collapses because fusion stops being exothermic.
Oct
6
comment What scientific evidence is there to support or refute the Iron Sun Hypothesis?
The Sun's spectrum only tells us about the composition of the visible surface. Hypothetically, if the core were mostly iron and the surface were mostly hydrogen and helium, that would be consistent with the spectrum we see. I don't take the "Iron Sun Hypothesis" at all seriously, but the spectrum isn't what refutes it.
Oct
1
comment What current evidence is there that disproves the Big Bang Theory?
The Big Bang happened everywhere -- but would it be accurate to say that the matter making up the currently observable universe expanded from an arbitrarily small volume? For example, the volume and mass currently making up the Milky way might have occupied, say, one cubic meter shortly after the Big Bang, and one millimeter before that, and so on.
Oct
1
comment What current evidence is there that disproves the Big Bang Theory?
If the estimated age of the Universe varies from book to book, you're probably reading some old books. Books published recently should, I expect, be reasonably consistent in giving an estimate very close to 13.8 billion years. What is the most recent book you've seen that gives an estimate outside, say, the range 13.7 to 13.9 billion years? Also, your question would be better if it were just a question. You state as a fact that "There is current evidence in our solar system that disproves this theory". There really isn't.
Sep
24
awarded  Yearling
Sep
3
comment Birthdate differences calculation relative to earths orbit duration
Yes, but the birth dates were expressed in calendar days. I've added a comment asking for clarification.
Sep
3
comment Birthdate differences calculation relative to earths orbit duration
It's not clear (to me, at least) just what you mean by "the real difference in our birthdates ... relation to how long earth orbits around sun". Are you trying to express the difference in sidereal years? If so, I'll delete my answer.
Sep
3
comment Birthdate differences calculation relative to earths orbit duration
The dates given are calendar dates, and there are no intervening leap days, so the 6 hours and 9 minutes doesn't apply. And by simplifying the question, you're not really answering it. If two people are born on the same calendar date and time in 1983 and 1984, then their ages differ by exactly 365 or 366 days, depending on whether the leap day 1984-02-29 is between their birth dates.
Sep
3
answered Birthdate differences calculation relative to earths orbit duration
Aug
22
comment Multiple apparent lunar eclipses last night
So something was blocking the moon as seen from your location. How sharp was the edge of the blockage? Was the edge straight or curved? (I can just about guarantee it wasn't a true eclipse; almost certainly something close to you, within a few miles, was blocking your view.)
Aug
12
comment How to polar align an equatorial mounted telescope when you are close to the equator?
Sounds like you need to figure out where due north is and aim about 4° below the top of the mountains. If I knew a good way to do that I'd post an answer, but a compass, a level, and a protractor might help. (Polaris is about 1° off the celestial north pole anyway.)
Aug
12
comment How to polar align an equatorial mounted telescope when you are close to the equator?
Polaris should be 16° above the northern horizon.