Basketball backboard makes excellent magnifying glass

Originally published at:


Science is a real bummer sometimes.


Glass door knobs do too:


I melted the veneer on a bathroom cabinet from a magnifying makeup mirror; everything was fine until we cut down a tree outside the window and noticed mysterious burn marks a few months later.



nature’s revenge. gives a whole new meaning to the Gaia hypothesis ; )


Bah, that’s nothing compared to the London “Walkie-Scorchie” or the Las Vegas “Vdara Death Ray”…


I am confused by the backboard thing. I don’t think that’s anything to do with focusing sunlight– the “burned” area wouldn’t be a perfect rectangle, and also, you know, the glass isn’t curved. I guess it could be caused by reflected sunlight, but then it should be blurred by the movement of the sun.

Maybe there was a snowdrift piled up behind it at some point, and that caused moisture damage somehow?

ETA looking at the edges of the damage, it follows the tiles, which means it was probably caused by something underneath. I don’t think the sportball hoop has anything to do with it.


Plus, the sun moves across the sky, so any reflection or magnifying effect would be tend to be more spread out on the roof. Where was this, I wonder? Could this be due to the backboard keeping snow on the roof so that moisture caused the plywood to mildew and rot?


As a New Englander with some Ice Dam and Leaf Buildup experience, I concur.

I estimate several inches of leaves and a few seasons of freeze-thaw cycling. I bet the roof didn’t even leak yet, but it will eventually.


Shit, I have this exact same basketball hoop in my driveway. It’s flat plexiglass so it seems strange it would have any magnifying capabilities.

1 Like

Really, it looks too even and rectangular for the ice-dam hypothesis too…

Occurred to me that they may have been trying to obscure the bad roof using the basketball hoop. Image does come from a home inspection site and you home owners know people will do all kinds of things to hide defects. I like the idea of the magnifying glass effect but it seems unlikely. I am guessing that there was a bad stretch of asphalt tile or an inferior patch.

1 Like

I’m more concerned that the basketball hoop is installed above 2 large plate glass windows.


The sun would have to be below the level of the horizon to have caused that ‘burn’


Not pictured: The reflective, solid gold driveway.


I really hate when people attribute maginifying properties to flat glass. Almost as bad a trope as starting fires with eyeglasses.


I believe those are open garage doors.

And I agree with other posts above, this doesn’t quite make sense given the flat glass and the angle, not to mention this goal appears to be on a portable stand. It shouldn’t see enough light at the correct low angle, the flat material wouldn’t concentrate light enough, and the pattern from possible trapped leaves/ice wouldn’t be as linear.

Looks like a “portable” hoop that isn’t even attached to the building, so it wouldn’t cause any build-up…

1 Like

My guess is someone’s game is on fire and the probably set the backboard ablaze with a series of savage dunks. If you can’t stand the heat, get out of the lane and get ready to hose down that roof because it’s gonna get HOT up there.


I think this is being looked at backwards. The backboard didn’t magnify light passing through it, it reflected light hitting the back of it and that hit the roof–as well as the direct sunlight. This doubling of sunlight is likely what cause the premature weathering of that section of roof.

I would guess the narrowness of the aged zone has to do with the angle of the sun. It’s only above the roof enough to cause the double heating for a very small range of it’s movement. If not, we would expect to see a more V shaped ‘burn’.

Edited: Looking at it again, I think the trees in the background played a big part. There’s just that one narrow gap where the sun can hit it directly and indirectly. In winter, when there are no leaves to block the sun, I am guessing the angle of the sun is too low to cause mugh direct heating. Plus, the weather is cooler then.