It’s hot outside. Really hot. But is it hot enough to fry an egg on the sidewalk? It’s only a matter of time before you will see someone on TV trying to make this happen. Most likely they will not be successful.
The problem is that an egg needs a temperature of 158°F to become firm. In order to cook, proteins in the egg must denature (modify), then coagulate, and that won’t happen until the temperature rises enough to start and maintain the process.
A sidewalk presents several challenges to this. According to an experiment reported in Robert Wolke’s book, What Einstein Told His Cook: Kitchen Science Explained, sidewalk temperatures can vary depending on the composition of the sidewalk, whether it is in direct sunlight, and of course, the air temperature. Dark objects absorb more light, so blacktop paving would be hotter than concrete. More often than not, sidewalks are concrete. Wolke found that a hot sidewalk might only get up to 145°F. Once you crack the egg onto the sidewalk, the egg cools the sidewalk slightly. Pavement of any kind is a poor conductor of heat, so lacking an additional heat source from below or from the side, the egg will not cook evenly.
Something closer to the conditions of a frying pan would be the hood of a car. Metal conducts heat better and gets hotter, so people actually have been able to cook an egg on a car hood’s surface.
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