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Not hot enough to fry an egg on the sidewalk
By adamg on Fri, 07/22/2011 - 1:31pm
Uncooked eggs just sat there, attracting flies.
A few years ago, some co-workers and I went outside with some eggs at lunch one steaming hot day and cracked them open on the sidewalk, then watched as, well, nothing happened.
I later read you need some tin foil to concentrate the sun's rays, so went out around 12:45 today with two eggs and two "pans" - one flat and coated with Pam (just in case it did cook; I'd have to sample my work), the other an empty tuna can with tin foil shaped, sort of, into a heat funnel.
Didn't matter. Although I couldn't stand on the sidewalk next to them in bare feet for more than a few seconds, the only thing that happened after 20 minutes was some flies showed up. Also, I learned that if you look at a raw egg in tin foil in bright sunlight, you should really put some sunglasses on first. But I'm sure the spots will go away.
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Comments
I thought about that
The weather outside doesn't fell like a "hot sun" day where eggs could fry. It just seems like a "hot air" day, so it would be like putting eggs in an oven instead of a frying pan.
if eggs were frying on the sidewalk...
cars would be stuck to the road, don't you think? Vinyl siding--which can melt from the reflections of your neighbors windows--would be dripping off the sides of houses. People standing in line outside the RMV would similarly be stuck to the pavement...
An egg needs a temperature of 158°F to become firm. see http://www.loc.gov/rr/scitech/mysteries/friedegg.html
Interesting Side Note
About 10 days ago, during another 90+ degree day, my rear view mirror, mounted on my windshield, melted off during the work day. That is, the glue melted, and my mirror was hanging by the electrical connections when I came out to go home.
I've since reattached it and have been leaving a bit of vent in my sunroof to keep the temps from reaching such a hideous degree again.
Suldog
http://jimsuldog.blogspot.com
this is a great
this is a great experiment!
much more interesting than the ones im doing in the lab right now...
Try asphalt, not concrete
I suspect you will have a better shot if you put it on top of an asphalt sidewalk, not a concrete one. Black asphalt will absorb more of the sun's energy and heat up more, getting you closer to the urban frying pan.
Minimum temp required
Proteins have to be denatured and accumulate to be "cooked"...which is why you apply heat to cook meat. Egg proteins need to reach 158 F. I'm not sure how hot the air temperature would have to be but concrete doesn't really absorb or hold heat well (even though your feet might think so). So, even in the sun for a while, the concrete probably gets to about 130 F on a 100 F sunny day (my rough estimate). As my link also points out, as soon as the egg is on the concrete (the foil isn't doing much in either of your cases) it will help cool the concrete down making it even more difficult to cook the egg, particularly the center.
You could cook an egg with the sun if you can redirect enough of it to accumulate the energy on the egg (by using a convex lens or a concave mirror). But then again, you don't need it to be 100 F outside in order to focus enough energy to make a spot of light that reaches 160 degrees F either.
I was about to post that I
I was about to post that I successfully fried an egg on the sidewalk when I was a kid, and wondering why it worked. I think I now have the answer. The neighborhood I grew up in had slate sidewalks, which presumably get hotter than concrete, as the slate is dark gray. This goes along with how much hotter asphalt is on bare feet than concrete, or dark vinyl seats compared to light vinyls seats (why did they do the black vinyl in the 70s?).
Suggestion to Adam: get a cast iron frying pan, and set it out on the sidewalk for half an hour, then crack another egg on it. I bet it will fry up nicely.
This
Black cast iron frying pan, or some black cardboard on asphalt.
Intense Desert Sun does it Too
I vividly remember my mother frying an egg on the concrete patio outside our trailer when we first moved to a very arid area of Eastern Oregon, one prone to 110F days. This was her way of saying "yes, you DO have to wear shoes in the summer, damnit!"
It takes intense sun and an appropriate surface to pull this off. With the current 102F temp and humidity, we are in poaching territory ... but the sun just isn't so intense with so much water in the air.
Yep
The specific heat of slate is 0.76. Concrete is 0.96. That's the amount of energy (in kilojoules) it takes to heat 1 kilogram of those substances 1 degree Kelvin. So, it would take a decent amount more energy to heat the concrete than it would the slate just to reach the right temperature. Then, the question would be how easily the energy transfers out of those two materials and into the egg.
I am so glad
that you all geeked out for us so that now I don't have to. Thank you for the info and the chuckle!
Too bad
Too bad it's not hot enough to make french toast on the sidewalk, then you could activate the FTAS.
FTA
lol, great idea, very UHub.
Now that Adam's planted the idea, will one of the local stations try this trick on the 6:00 news?
You could always bake some
You could always bake some cookies in your car, instead.