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 close




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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