How Far Can the Human Eye See?
The Earth’s surface curves out of sight at a distance of 3.1 miles, or 5 kilometers. But our visual acuity extends far beyond the horizon. If Earth were flat, or if you were standing atop a mountain surveying a larger-than-usual patch of the planet, you could perceive bright lights hundreds of miles distant. On a dark night, you could even see a candle flame flickering up to 30 mi. (48 km) away.
Read the rest at: http://www.livescience.com/33895-human-eye.html
As things get darker out there, let’s keep our little candles burning. ~ TD