Some Light reading from Dr Math

for the answer.........

http://mathforum.org/library/drmath/view/55358.html

 

Solid angles are measured in steradians. The steradian is the solid angle which subtends a unit spherical surface area at unit radius of the sphere.
In much the same way that a radian is the angle that subtends a unit length circular arc at unit radius of the circle.
The angle of a full circle is 2 pi radians.
If memory serves, the solid angle of a full sphere is 4 pi steradians but don't quote me on that.

 

I'll take your word on it!

Don't know why, but it came up last night and I assumed it was probably something really obvious (360x360x360 or something).

 

Can't believe I actually remember this stuff. Haven't used it in years. Is solid angles 'O' Level or 'A' Level? Actually it's probably PhD level these days

 

I did A level further maths and we covered radians, but not steradians - i had no idea such a thing or 3d angles existed!

Chris

 

Must have covered it at Uni then

 

I went back to edit the post as I didn't quite express the definition of a steradian correctly. It is the solid angle which subtends a surface of unit area at unit radius. So for a sphere of radius 1m, one steradian will subtend an area of 1 sq. m on the surface of the sphere. Phew!

ps. and in twenty three years of engineering, I have never ever used steradians