An experiment was done with several lighthouses as well. The earth cannot possibly be curved. Both sides walked away in agreement. The tallest lighthouse in America is seen 27 miles out at sea. My gracious, there are so many false mariners in this website.

The Earth curves approximately 8 inches per mile. At 27 miles, you would have a drop of 18 feet. The tallest lighthouse in the US is 207 feet tall, so yes, you can see it at that distance.

Please be careful with the numbers. It might be true that Earth curves some 8 inches in a mile, but the accumulated effect of several miles is not linear. Anyway, 207 feet is a lot and I see no problem at all in seeing a 207 feet tall light house from a distance of more than 27 miles, if you are looking from the observation room of a large ship. It might start to be difficult to see if you are sitting inside a raft.

Good note. Let's redo the math, but instead of using 1 mile, use 27 miles.

I am not into miles, inches and feet, so I will redo the calculation using km, cm and meters (standard physic units)

1 miles = 1.609344 km. Therefore 27 miles = 43,45 km.

3963 miles = 6377,8 km radius

a^2 = 6377,8^2 + 43,45^2 = 40678220,74 km. so a = 6377,94 km.

6377,94 - 6377,8 = 0,14 km below your view point.

0,14 km = 140 m

The tallest lighthouse is 207 feet. 1 foot = 0.3048 meters, so 207 = 63 meters high.

I was unable to quickly find the height of an average container ship. However, I saw this picture in comparison.

I know the height of the A380 tail is 24,45. The A380 can almost stack 3 times up. It can be stacked up ~2.75 times on top. This means the bridge is at a height of 67 m.

63+ 67 = 130 m.

This means the lighthouse is actually 10 m further down from the viewpoint. So physically seeing the lighthouse would be impossible, even if you used a telescope. However, sailors could perhaps have seen the light of the lighthouse. Which is also the most important aspect of the lighthouse.

As illustrated in the following diagram.

http://imageshack.us/photo/my-images/855/shiptj.jpg/?sa=0