carl23 Posts: 8, Reputation: 1 New Member #1 Aug 17, 2012, 05:03 PM
Astronomy
How far from the sun would you need to be, to receive no light at all.
 ebaines Posts: 12,132, Reputation: 1307 Expert #2 Aug 20, 2012, 05:48 AM
The intensity of a star light decreases as the square of the distance, and so the further away the star is the dimmer it appears. To receive "no light at all" would theoretically require an infinite distance - asuming there is no intervening dust or gas to absorb all the light. But if what you mean is "how far away would you need to be so that the sun is so dim as to not visible with unaided eyesight" then we can estimate that distance to be about 80 light years. At the distance the sun would appear as a magnitude 6.5 star, which is about the dimmest that human eyesight can discern.
 Stratmando Posts: 11,188, Reputation: 508 Uber Member #3 Aug 20, 2012, 04:14 PM
If you could get far enough from Our Sun, You would just have some other Sun to deal with. Its like everywhere.

ebaines, is their a Planet or Moon that half is always in the shadow of the sun, Just like Our moon to our earth?
 ebaines Posts: 12,132, Reputation: 1307 Expert #4 Aug 21, 2012, 06:00 AM
Originally Posted by Stratmando
If you could get far enough from Our Sun, You would just have some other Sun to deal with. Its like everywhere.
If you are in interstellar space you would see stars all around, but in general none would be close enough to be as bright as our sun appears from earth. The mean distance between stars is in the order of several thousand times the size of the solar system, so most of space is interstellar void.

Originally Posted by Stratmando
ebaines, is their a Planet or Moon that half is always in the shadow of the sun, Just like Our moon to our earth?
You're asking if any planet has a period of rotation exactly equal to its orbital period, so that one side of the planet always faces the sun (much as one face of the moon always faces earth), correct? Not in our solar system, although Venus is close to doing this. It's "day" is 243 earth days long, and its "year" is 225 days, so the sun would appear to rise in the west and move very slowly across the sky towards the east. In act if you were to walk across the surface of Venus at a mere 4 MPH you could keep up with the planet's rotation so that the sun would be perpetaually overhead (although you wouldn't be able to see the sun because of the thick clouds).
 Stratmando Posts: 11,188, Reputation: 508 Uber Member #5 Aug 21, 2012, 08:11 AM
Interesting.

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