So Hot, You Could Fry an Egg
| Published: July 11, 2010 – 8:05 pm
Can it be so hot you can fry an egg on the sidewalk? Is a hot sidewalk evidence of global warming?
This week, I was asked to comment on the big heat wave along the east coast of North America and the resolution of the scandal that came to be called “Climategate.” Along with these serious subjects, an egg got fried on a sidewalk.
As you may know, I strongly believe humans are making our world warm. The egg on the sidewalk provided me with a chance to talk about the fundamentals of heat transfer and about our changing climate.
I commented briefly that indeed Climategate was much ado about very little. The scientists were proven to not be hiding anything, and so on. Unfortunately it nearly derailed the real climate conference in Copenhagen. Several minutes later at the end of her show, journalist Campbell Brown showed some video of one of her CNN producers taking a shot at cooking an egg on a New York sidewalk. He had a bit of trouble, but I think he got the idea across. It’s hot back east, very hot.
Using my radiant thermometer (pyrometer, such a word!), I satisfied myself that an egg on a griddle cooks well if the griddle is around 125 Celsius (260 Fahrenheit). Doing a bit more messing around, I found that an egg will cook on a surface that’s only 55 Celsius (130 Fahrenheit). It just takes time – almost 20 minutes. So indeed, it can be hot enough to fry an egg on the sidewalk.
The little hand-held radiant thermometer is upside down, but it shows around 53.8 Celsius. This took about 22 minutes to cook under ideal cast iron skillet sidewalk temperatures. Along with the temperature, we need the pavement to hold a lot of heat (high thermal capacity). Sometimes the sidewalk isn't hot enough through and through; it depends on the pavement. Sure; try it...
I can tell you from experience in the airplane electronics industry that you can, for just a moment, put your hand on a metal surface that’s around 65 Celsius, about 150 Fahrenheit. Much above that, and you can’t leave your hand there for more than an instant. You may have found yourself walking on a hot sidewalk or on hot sand, and you can just barely stand it (pun intended). That’s the temperature we’re talking about.
If you want to try this, please do. Post a picture on my Facebook page. Some more advice: use a little olive oil or butter on the sidewalk or street. This allows more heat to flow into the egg. This is “conduction” of heat. Then, use an egg “ring” to keep things under control while the egg gets hot. You get your egg rings (if you don’t already have ‘em) in the gadget section of a grocery store or cooking specialty shop.
The science to discover or keep in mind is that the sidewalk can get hotter, much hotter, than the air. The air this week was around 40 C (a little over 100 F). But the egg cooking area was a bit hotter than that because it’s not only heated by the air, it’s heated by sunlight, or sun-heat. It was heated by convection with the air, and by radiation of the sun. Black surfaces do indeed get hotter than not-so-dark surfaces. Asphalt gets hotter than cement. Hot enough to fry an egg. Oil helps conduct heat into the egg.
For me, this has everything to do with climate change. Everyone should keep in mind that if we made every black street a pale color, like white, or close to white, the world would indeed cool off. If we did indeed embrace solar hotwater systems for our houses and buildings, we would pump out much smaller amounts of greenhouse gasses.
If you’re a young or young-at-heart engineer or entrepreneur, consider coming up with an economical pale pavement material and getting rich! Same with a standardized solar hot water system. Rich! I tell you!
Two more good ideas. Think about it over fried egg, your poached egg, your egg salad sandwich, and your soufflé.
Let’s change the world,
Bill
Brilliant! We live in Doha Qatar and have definitely had some egg frying temps lately! I tried it today just out of curiosity but it didn’t work. I did not use oil, nor did we use the hotest spot. I’ll take my boys out tomorrow afternoon and give it another try! Thanks Bill! We love you and as homeschoolers own so,so, so many of your Dvd’s!
Great post Bill. Love the idea for the young-at-heart entrepreneur. Keep up the great work.
Hi, I think there is going to be a time when men are going to have to build tunnels for us humans to just walk outside from one building to another! you all may think I am nuts but if the world keeps getting hotter, humans will not be able to stand the heat so, instead of us being able to go out into a bright beautiful sunny day we are going to have to hide from that bright and hot sunny day. It may not be in the next twenty years but if the world is around long enough this will come to pass, I probably will not be alive but remember these words that you may think are coming from a crazy lady at the moment. and may God have mercy on us all!
I’ve so done this in Iraq took 5 minutes! and it didnt taste so bad either..
I\’ve so done this in Iraq took 5 minutes! and it didnt taste so bad either..