eli5: why isn’t it possible to cook e.g. cookies at twice the temperature for half the time? obviously i know it isn’t possible, but *why*? what’s the physics behind it?
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Food cooks by transferring heat from a source (e.g. oven, skillet, boiling water, etc.) to the interior of the item being cooked. The speed of cooking is limited by the capacity of the food to conduct heat. The heat conducting capacity changes very little regardless of the heat source. Raise the temperature of the heat source, the food simply cooks faster at the surface, but not at its interior. The result is that the surface of the food is done much faster than the interior. This is good if you want a very rare steak, i.e. crispy brown surface with cool, red center. On the other hand, if you’re going for medium rare, it’s best to start with very high heat to brown the surface, then lower the heat to allow the interior to warm slowly while remaining moist and juicy. The same is true in baking. If you set the oven too high, the surface of your cake will char while the interior is still raw dough.
The energy from the heat can’t make it into the center of the cookie in half the time, and at the same time you’re causing unwanted reactions in the outer part of the cookie by heating it too high (burning it).
When you put something in the oven, the outside heats first, and then the inside slowly absorbs heat from the outside.
If you raise the temperature, the outside heats way faster but the inside still lags behind.
In the most extreme scenario, the outside is burnt while the inside isn’t even warm.
The amount of time it takes heat to penetrate the cookie is always the same. So when you cook higher for less time, the inside doesn’t get the heat before the outside burns
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