What you want is an off-axis paraboloid, a segment of a paraboloid that does not intersect the axis. Then the target does not obscure the incident light. -- Gene
________________________________ From: Robert Baillie <rjbaillie@frii.com> To: math-fun <math-fun@mailman.xmission.com> Sent: Saturday, May 4, 2013 12:40 PM Subject: Re: [math-fun] Archimedean dog bowl causes fire in Santa Rosa
not that i want to try this, but what shapes would work?
bob baillie ---
Henry Baker wrote:
FYI -- So much for MythBusters... I wonder what Arthur C Clarke would say about this:
http://zebu.uoregon.edu/~probs/therm/sunstrok/sunstrok.html
http://sanfrancisco.cbslocal.com/2013/05/02/shiny-dog-bowl-blamed-in-santa-r...
Shiny Dog Bowl Blamed In Santa Rosa Fire
May 2, 2013 11:59 PM
SANTA ROSA (CBS SF) – A dog’s water bowl was being blamed for starting a fire at its owner’s Santa Rosa home, according to fire officials.
North Bay firefighters called it is one of the most unusual fire calls they’ve ever had.
Perry and Shay Weisbrich said they had to call 9-1-1 after their dog Toby’s metal bowl reflected a concentrated beam of sunlight onto the side of their house — a beam so powerful, the wood started to burn.
“I just looked outside a minute and saw what i thought was steam.” said Shay Weisbrich. “A big plume of it through the glass door.. So I went over there thinking, ‘that’s not right, not normal.’ And it was smoke!”
The Bennett Valley Fire Department responded before the fire got out of control.
As for Toby, the Weisbrichs said he’s getting a new dish: a plastic bowl.