18 nautical miles (~almost 21 statute/land miles)
19 miles
At least as far as ancient Greece
How far should headlights shine?
Lighthouses were a great help for Roman shipping or any other Mediterranean shipping for that matter. As storms would frequently occur, the lighthouses gave sailors a direction as to where a port was located. In calm weather, the lighthouses acted as a nautical roadmap, as every experienced captain knew where they were located, and how far away from his destination they would be.
Lg shine by far!
The light itself has no limit, unless it runs into something on the way that absorbs it (soaks it up). The main question is not "How far can the light go ?" The main question is "How far away from the source is your equipment good enough to detect the light ?" With current astronomical equipment, we can detect and measure light coming from 13 billion light years away.
A "light year" is a measure of distance, derived from "how far light can travel in one Earth year". Thus, if you shine a torch for the amount of time it takes the Earth to orbit the sun exactly once, that light would have travelled the distance of a "light year".
The sunlight travels through the vacuum of space until it reaches an object to be reflected or absorbed. This can include objects like planets, moons, asteroids, and spacecraft. The light from the sun can reach objects as far as the outer reaches of our solar system.
"Lighthouses of the sky" are the Cepheid Variables. These are stars that periodically change in brightness, somewhat the way a rotating beam from a lighthouse would as it fell on an observer. The brightness of a Cepheid is proportional to the period of its variance. So if we know the period (how long it takes the beam to come around), we know how bright the star should be. Comparing that to the observed brightness tells us how far away it is (if it's one-quarter as bright as it would be at a standard distance - 32.6 light years - then it's twice as distant (65.2 light years).)
the answer is approx, 350 feet. if they are standard head lights.
Smeaton's 24 candles on the Eddystone Lighthouse could be seen up to 22 miles away due to the design of the lighthouse lens and the height of the structure, which maximized the reach of the light. This was a significant improvement in visibility compared to previous lighthouses.
As far as light can travel