Tell me more ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.
up vote 1 down vote favorite

How far is the horizon, if a $r=2 m$ tall man watches to the sea?

I have calculated that it would be even just about 6 km. if R = radius of earth( $6370 \cdot10^3$ m ). By pythagorean theorem we get. $(r+R)^2 = x^2 + R^2$ => $\sqrt((r+R)^2 - R^2) = \sqrt((2+6370 \cdot 10^3)^2 - (6370x10^3)^2) = 5048$ m ~ $5$ km = x Is this right?

share|improve this question
1  
Seems correct to me. – Bernhard Sep 24 '12 at 10:57
But if you are looking at 100 m high hill, then you get that it disappears if you are 40 km away from it looking at the sea. $\sqrt((100+6370 \cdot 10^3)^2 - (6370x10^3)^2)+5000 = 35693 + 5000 = 40000 m$ – alvoutila Sep 24 '12 at 11:08
1  
Related to physics.stackexchange.com/q/29878/520. – dmckee♦ Sep 24 '12 at 12:31

Know someone who can answer? Share a link to this question via email, Google+, Twitter, or Facebook.

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.