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1d
accepted What is the angular diameter of Earth as seen from the Moon?
2d
comment What is the angular diameter of Earth as seen from the Moon?
@LocalFluff: Gives me a thousand results of angular size of the Moon as seen from Earth.
2d
asked What is the angular diameter of Earth as seen from the Moon?
Oct
20
comment Are ascending node of sun, the point of intersection of prime meridian and equator and center of earth all collinear?
@barrycarter: In fact, I meant the momentary celestial equator for given equinox day - the moment when the point on Earth where the Sun is in zenith crosses the Earth's equator.
Oct
19
awarded  Revival
Oct
18
comment Are ascending node of sun, the point of intersection of prime meridian and equator and center of earth all collinear?
@barrycarter: Could you explain? The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. That seems to imply they are always in sync, since one is defined by the other. Did you mean the ecliptic plane? In that case, it intersects the equator plane, and during equinoxes the intersection line happens to pass the Sun (or, if you nitpick at inexactness of the Ecliptic - the Sun passes the Earth equator plane twice a year.) At these moments Earth center, the Equator and the Sun are colinear, but the meridian is entirely random.
Sep
25
awarded  Yearling
Sep
24
awarded  Autobiographer
Sep
5
answered Are ascending node of sun, the point of intersection of prime meridian and equator and center of earth all collinear?
Sep
3
accepted What is the ultimate fate of a cluster of galaxies?
Jul
22
comment Are these facts about moon true?
@StanLiou: Nevertheless, Moon doesn't reverb as if it was hollow.
Jul
22
comment Are ascending node of sun, the point of intersection of prime meridian and equator and center of earth all collinear?
@SalmanAzmat: Not exactly. During either equinox there is a moment when the line between center of earth and the sun aligns with the equator (as opposed to just crossing it twice daily), and if it happens the sun is in zenith above prime meridian at that moment, your conditions will be satisfied. But depending on precision you allow, that may be a very short time window. It's all about how precisely you want that to be. Each equinox the line crosses the prime meridian within about 0.25 degree of latitude, or about 27 kilometers from equator. Some years it's less, some - more.
Jul
22
answered Are these facts about moon true?
Jul
2
awarded  Curious
May
4
comment Do moons have moons?
Well, 'boulders up to several decimeters in size' within Rhea's ring aren't exactly 'moons' but I wouldn't hesitate to call them 'natural satellites', so, yes, this is clearly a case of a planet's satellite with own natural satellites.
Mar
23
comment What limits the usable focal length of telescopes currently?
I wonder, radio waves, optical waves, that's all electromagnetic radiation, just different wavelengths. What's with optical waves that prevents radio waves tech to be adapted to that spectrum?
Mar
19
accepted What limits the usable focal length of telescopes currently?
Mar
11
accepted When did the Moon stop?
Mar
10
comment Why are most lunar maria on the visible side?
while Earth itself may obscure 4 degrees of Lunar sky, its gravitational field covers substantially more.
Mar
10
accepted Why are most lunar maria on the visible side?