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1h
revised Precision of geocentric gravitational constant
added 127 characters in body
1h
comment what is gravitational force?
"Rotation speed can create a centripetal (centrifugal??) force opposing gravity and making things lighter," Rotation also stores energy, and energy is mass, per $E=mc^2$. A body spinning sufficiently fast will exert higher gravity, e.g. a slowly-spinning neutron star will have a weaker gravitational pull than equivalent neutron star that spins very fast.
1h
answered Precision of geocentric gravitational constant
4h
asked Does earth's Umbra reach Sun-Earth L2?
Feb
1
comment Where's the Prime Meridian of celestial coordinates
@JeffY: Equinox (point) on equator, the meridian (line) anywhere. (in equatorial coordinates).
Jan
31
comment Where's the Prime Meridian of celestial coordinates
So - at (local) noon of the day of spring equinox the equatorial system prime meridian is directly above my head (accurate to precession since Jan. 1st, 2000, plus how much Earth has moved since the exact moment of equinox until noon.) Do I understand it correctly?
Jan
31
comment Where's the Prime Meridian of celestial coordinates
They cross in two places, on two sides of the celestial sphere. One is for Vernal Equinox, the other for Autumnal. Which is which?
Jan
31
asked Where's the Prime Meridian of celestial coordinates
Jan
30
asked What are the prerequisites for a meteorite to reach the ground?
Jan
28
awarded  Notable Question
Jan
22
asked What will eLISA be trying to observe?
Jan
22
comment Does the sun itself present the problem of global warming is it the main cause?
Well, IMHO this question is poorly phrased but on-topic. CAN the Sun contribute to global warming? Yes, in its cyclic radiation change it can periodically increase the global temperatures. DOES the Sun contribute to global warming currently? No, it's currently at a low of its cyclic change. And regardless, the Sun is definitely not the MAIN cause; its contribution (when it occurs) being one of lesser factors.
Jan
22
comment Does the sun itself present the problem of global warming is it the main cause?
The change seems to be around 0.2% between lowest and highest peaks. 0.2% out of Earth's average 289K is about 0.57K. Definitely not a negligible change, although luckily not cumulative. But considering 2015 was the warmest year in history of measurements and the Sun is at its low, we can expect its influence to impact the global temperatures quite badly rather soon.
Nov
20
comment Are objects in the universe moving away from each other at the same acceleration?
Note that this acceleration applies to objects that are not gravitationally bound: superclusters of galaxies. Two neighbor galaxies don't yield to space expansion because they are gravitationally bound to each other; they may move in relation to each other, including moving apart, even accelerating due to some other galaxies, but they are not accelerating due to space expansion. Two superclusters of galaxies do though.
Nov
19
comment How small a star can provide Sun-level illumination to its planets?
@Ricky: There's a bottom limit on size of a natural celestial body producing own light of sufficient intensity. Although a sufficiently big artificial satellite made from the right radioisotopes?
Nov
19
accepted How small a star can provide Sun-level illumination to its planets?
Nov
18
asked How small a star can provide Sun-level illumination to its planets?
Oct
12
comment What is the current routine of modern astronomy?
BTW, the question wasn't just idle curiosity. As a writer, I have (way too long by now) a story, with two of the protagonists being astronomers. While the modern astronomy itself doesn't play a big role, I wanted to get their "nightly activities" right before they are swept by the plot and cast into roles they are not really ready to fulfill.
Oct
12
comment What is the current routine of modern astronomy?
@JonEricson: The more unique answers there are the less "daily bread" they become. If it truly is that "there are nearly as many possible answers as there are working astronomers" then the last sentence of my question applies and should comprise the answer. Nevertheless, MBR's answer gives me a very good clue about what is to be expected.
Sep
25
awarded  Yearling