Expert: Jayendra Upadhye - 2/9/2007

Question
How does heat reach us from the sun?

Answer
Hi,
Odhran!

If i were to say the conventional thing, i would be saying.."Elementary my dear watson!" and no more!!

But there is something more interesting and fundamental to know in this, if you are interested.

You see, the heat we recieve starts off as Gamma radiation and streams of nutrinoes in the heart of the sun. It is the product of the hydrogen fusion reaction going on there.

The heart of the sun is actually a Dark EXTREMELY DENSE place. Dark, because the radiation is in the gamma region.
(not in the visible range).

The nutrinoes stream out close to the speed of light, thru all that dense and dark core as though it was simply non-existent. they do not interact with matter most of the time.

However the gamma radiation is buffetted about as it is absorbed by the dense matter and re-radiated! It looses energy to the matter in the core, thus heating it up, and itself loosing energy in the process. (compton effect).

The scattered gamma radiation ultimately emerges after a million years (no jokes) as visible light and reaches us in just 8 minutes!! [refer sagan's Cosmos].

The reabsorption and re-radiation within the sun is what contributes to the pressure within that keeps the sun from imploding under its own monstrous weight!!

Now isnt that interesting?
Jayen