Take the sunlight which falls on an ordinary magnifying glass at the surface of the earth, and calculate its intensity at the middle of the focused bright spot. Realize that the rest of the area in the glass's geometric shadow is much darker than if the glass weren't there.
I don't understand the problem.
________________________________
From: "Folkerts, Timothy J" <FolkertsT@bartonccc.edu>
To: "Phys-L@Phys-L.org" <Phys-L@Phys-L.org>
Sent: Monday, August 12, 2013 7:45 PM
Subject: [Phys-L] Sunlight Brighter Than The Sun???
Here is a link to Nature that seems to claim to be able to focus sunlight on the earth *even* *brighter* than the sunlight leaving the sun (72 MW/m^2 vs 64 MW/m^2. This would seem to me to be a violation of the 2nd Law of Thermodynamics.
It comes from the University of Chicago, which is is pretty reputable place. Any thoughts?