The last several pages of Gemara have been dealing with preparing fuels used for burning on Yom Tov. As we have noted in our studies, burning fuel is permitted, as it is a prerequisite for cooking, which is permitted on Yom Tov. Nevertheless, according to the Mishna on our daf , we are only allowed to add fuel to an existing fire or flame, but not to light a new fire.
The Mishna teaches that a fire cannot be “brought out” (that is to say, lit) from wood, stones, dirt, tiles or water. Starting a fire with wood, stones and tiles would all be based on the same basic principles – the creation of heat or sparks by means of friction in the case of wood, or banging stones or tiles against one another (as is still done today in the case of modern cigarette lighters, for example).
Creating fire out of water means – as Rashi explains – using a water-filled glass instrument that works as a magnifying glass to create great heat by concentrating the sun’s rays on a particular spot.
There are a variety of explanations regarding how one can start a fire out of dirt. They include the possibility of pouring water on natural lime deposits in order to create a chemical reaction that produces heat, and using the heat created by decomposing organic matter.
One may not produce new fire on a Festival in any manner. The Gemara asks: What is the reason for this? The Gemara explains: Because he creates [molid] something new on a Festival. This is similar to an act of creation, and it is therefore prohibited.
The rishonim disagree as to the level of severity of such an activity. The R”iaz, for example, says that it is not truly an act of creation, but since something new is now here, it is forbidden by the Sages. The Rambam’s approach is to say that this is forbidden only because it could have been done before Yom Tov began.