Main Question or Discussion Point
Would a nearby Gamma Ray Burst (GRB) cause the Sun to cast a shadow on Earth if it were to shine from behind it?
The Sun is bigger but farther, and Chronos said it is 30 arc minutes in diameter.To a very good approximation, indeed.
What do you know about the relative size of sun and earth?
30 arc minutes?Yes, but what size is the shadow of the sun on the surface of the earth?
Ok. So what I basically want to know is if the visible luminosity of a GRB is powerful enough to cause the Sun to cast a shadow on Earth. I use GRBs as an example, but I guess a supernova could do it, too, right?As a plasma ball, the sun is a very efficient gamma ray shield. The sun moves across the sky an apparent 60 arc minutes per day. It's apparent diameter is about 30 arc minutes. You should be able to figure out from this about how long the sun could shield us from a GRB [a point source] occurring on a line of sight behind the sun.
How big is the earth in arc minutes? How much of the earth does that cover...?The Sun is bigger but farther, and Chronos said it is 30 arc minutes in diameter.
30 arc minutes?
Gamma ray bursts aren't very bright visibly. So it wouldn't be much of a "shadow"Ok. So what I basically want to know is if the visible luminosity of a GRB is powerful enough to cause the Sun to cast a shadow on Earth.
Yes, and much brighter than a GRB. But still not much of a "shadow".I guess a supernova could do it, too, right
I don't know..How big is the earth in arc minutes? How much of the earth does that cover...?
It's a trick question; That doesn't translate into a size on earth. For this situation, the angular diameter of the sun doesn't matter, only the fact that its real diameter is much larger than earth. All of earth will be in "shadow"I don't know..
No. Those events are nowhere close to as bright as the sun (er - perhaps a GRB from within our galaxy would be, but they are rare events and so far are only seen from far away). It depends on distance of course, but a supernova in our galaxy might shine as brightly as Venus.I'm trying to picture what the sky would look like if the Sun were to 'eclipse' a GRB or a supernova. It seems that the glare from either of those two events could overwhelm the visible brightness of the Sun by several orders of magnitude, no?
Not in the normal sense of the word, no.Are you saying the Sun wouldn't cast any shadow on the Earth with that much light in the background?