Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Suppose, we know the length of the shadow of an object at some known time.

Can we use the this information to find position of the object (the longitude )?

share|improve this question
1  
I deleted some argumentative comments. –  David Z Nov 19 '11 at 1:28
add comment

1 Answer

Not without extra information...

If you know the length of the shadow and the time of day, you can't figure out the object's location. But you CAN narrow it down to a circle on the earth's surface, a circle with the sun at the center. If the shadow length happens to be exactly zero, of course, the circle reduces down to a point--the only point on the earth's surface where the sun is directly overhead at that moment.

If you know the length of the shadow and the latitude, then you can narrow down the longitude to two points.

If you know the length and direction of the shadow, you can locate the object (longitude and latitude) uniquely.

All this assumes the person is standing on a flat surface. If they might be on a slope, you can't infer anything.

share|improve this answer
    
Does anyone know any research paper or example of this being done? I remember somebody mentioning it the show, Numbers. They manage to pinpoint a criminal through a video he took –  Alexandre Cassagne Oct 27 '13 at 10:07
add comment

Your Answer

 
discard

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

Not the answer you're looking for? Browse other questions tagged or ask your own question.