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Sam (cc)

If the distance betwen us and the sun is millions of miles, how does that energy reach us from so far away? thank you...

Hi Sam,

Solar energy comes in a form of radiation from the Sun (part of this radiation is visible light). Radiation can propagate at very large distances even in the empty space. Solar radiation will get less intense when the distance from the Sun increases, but the total solar energy intercepting the Earth in a year  is much more than the global energy consumption (http://home.iprimus.com.au/nielsens/solrad.html).

Hi Sam,

You can actually calculate how much dimmer the light from the Sun, or any other bright light source, is as you get further away from it. The light from the Sun radiates out in all directions, so you can think of it as being spread out over a spherical shell of radius R. The surface area of a sphere is proportional to R², so the intensity, or brightness, of the light from the Sun falls off as 1/R². This basically means that if you double your distance away from a light source like the Sun, the light appears 1/(2x2)=1/4 as bright as it did at the source. If you triple your distance away, it appears 1/(3x3)=1/9 as bright.

Kris