Is one permitted to fry an egg in direct sunlight?

One of the melachos of the Mishkan is Bishul – cooking. Chazal teach us that cooking prohibited by the torah is by fire and its derivatives, just as in the Mishkan. Consequently, heating a frying pan on a fire, removing it from the fire and cracking an egg into it would result in bishul d’oraisso, because the frying pan is hot from the fire. [1] Items heated on the fire are called toldos ha’ur.

What about electric grids?

Our sages compare electric heating elements to regular fire and make no distinction.

A source is the Rambam who writes [2] that one who heats steel in fire is liable for the melacha of mav’ir – making fire. The Maggid Mishne complements this saying that anything that turns into fire and burns is included in mav’ir. The gemora uses the term 'gachalat shel aish' - a coal of fire when referring to red-hot steel.

The filament or element in a bulb or heater turns red hot and has a status of fire. Accordingly therefore, cooking on electric hobs; gas flames; coals etc. are all bishul.

…and sunlight and sun heated?

The gemora Shabbos 39a writes that one may cook in sunlight on Shabbos and Rashi explains that this is not a regular cooking mode.

Chazal made a distinction between cooking in the sun and cooking in toldos hachamah – derivatives of the sun, which is rabbinically prohibited. [3] The reasoning is that toldos hachama and toldos ha’ur are indistinguishable. For example: a frying pan can be heated on a fire or in the sun. Cooking in the former violates an issur d’oraisso and the latter biblically prohibited. Chazal instituted a decree stating that one may not cook in toldos hachama lest one cooks in toldos ha’ur.

With respect to the above, Rashi was perturbed that if one cooks in direct sunlight one might cook on the fire. He counters this by saying that people will not mix the two and cooking in sunlight will not lead to cooking on a fire.

What about heating a frying pan in the sun and cracking an egg into it?

As stated, this is rabbinically prohibited. The problem is that a frying pan heats rapidly in the sun and it would appear that in order to cook an egg in the sun one would have to crack an egg into a frying pan inside the house and then take it back to sunlight when already in the pan. If the pan assists in cooking it would be a problem of toldos chamah.

Discussing this issue seems farfetched, as nobody really intends cooking in sunlight. However, this decision has many implications and understanding the fundamentals is crucial.

For example, soldiers fighting in the desert would crack an egg on a tank’s hull, hot from standing in the sun. On Shabbos this is prohibited on account of the above.

How would you categorize cooking in a microwave oven?

Rav Moshe Feinstein writes, [4] based on the Rashi mentioned above, where it is stated that cooking in sunlight is an irregular cooking mode, cooking in a microwave oven would be an issur d’oraisso of bishul, being that it is a regular cooking mode nowadays.

Rav Shlomo Zalman Auerbach disagrees and writes [5] that cooking with heat sources other than fire and toldos ha’ur is only ossur mid’rabanan. [6] (We are only referring to the actual cooking and not to other issues involved such as the light going on when opening the microwave door and the opening and closing of electrical circuits during the cooking process).

What about cooking with a magnifying glass?

Initially one might think that cooking with a magnifying glass is akin to cooking in the sun and permitted. However, the Sh’visas haShabbos writes that he is unsure as to whether heat produced with a magnifying glass is considered sun heat or toldos chama. This is because the sun’s rays are modified and producing heat and is not regular sunlight. [7]

And lighting a fire with a magnifying glass?

It seems that almost everyone agrees that it is mav’ir – lighting a fire is a d’oraisso. The abovementioned Sh’visas haShabbos writes that the fire produced from concentrating the sun’s rays is mav’ir because it is irrelevant whether fire is produced from water, wood, sulfur or a spark. The end result is what matters and a fire was created. [8]

Why make a distinction between mav’ir and bishul?

We see that the Torah prohibited cooking with fire and its derivatives and not with other means. One who salts or pickles meat or cooks it in the sun has not violated a biblical prohibition, which proves that the method in which the food is ‘improved’ or made edible is crucial in defining the issur of bishul. We can therefore state that the melacha of bishul does not merely define the end result rather the means to the end. The prohibition is in cooking food through fire and its derivatives.

The issur of mav’ir, on the other hand, is to create a fire regardless of the method. If done b’shinui all agree that it is a d’rabanan and creating a fire in a normal natural manner is a d’oraisso.