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Re: [Phys-L] Sunlight Brighter Than The Sun???

In order to stay in an orbit that keeps it along the line from earth to sun, it would have to be very close to the earth. To double the energy reaching earth, it would have to have twice the area of the earth. Do we have enough sand to create such a glass lens? A better approach might be to have a huge mirror at the same distance as earth from the sun that reflects energy to us at a roughly 90 degree angle. It would totally screw up earth based astronomy - but hey - we're physicists - not astronomers.

Bob at PC

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Folkerts,
Timothy J
Sent: Tuesday, August 13, 2013 12:05 PM
To: 'Phys-L@Phys-L.org'
Subject: Re: [Phys-L] Sunlight Brighter Than The Sun???

But as you focus the light, the "best" you should be able to do is to
effectively have sunlight coming from the angle subtended by the
magnifying glass -- looking back you would see the surface of the sun
everywhere over the surface of the lens. No matter what sort of lenses &
mirrors you had, you would get light as bright (or dimmer) coming from (less
than or equal to) the entire upper hemisphere. This would produce a net
flux less than the flux coming directly from the photosphere.

Or put another way, if you can get 72 MW/m^2 by focusing sunlight, then
you could heat a blackbody placed in that light to ~ 5970 K. This would be
heat flowing from a "cool object" (the sun @ 5780 K) to a warm object (the
surface @ 5970 K) -- a clear violation of the 2nd Law of Thermodynamics.


-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of curtis
osterhoudt
Sent: Tuesday, August 13, 2013 12:58 AM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] Sunlight Brighter Than The Sun???

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.

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