median
don steward
mathematics teaching 10 ~ 16

Wednesday 16 March 2011

how far away is the horizon?

when you stand on a beach, with your toes in the sea, how far away is the horizon?

it looks further away than it is - because light gets bent

worth asking students to guess first

it is surprisingly near














an exaggerated diagram shows that this is a simple enough application of the pythagoras rule

since the Earth isn't spherical, use the average radius: 6371km

for a 2m (0.002km) eye height the distance is a mere 5.1 km (3 miles)

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