Microscopic Reality in Halachah
There is a discussion among poskim whether viewing things through a magnifying glass or a microscope is considered “seeing” according to halachah; this question has bearing on numerous halachos. Many of the foods we eat, especially leafy vegetables, may be infested with bugs. If a person with good vision utilizes whatever means necessary (bright lighting and glasses, if needed) to carefully check the vegetables with the naked eye and sees no bugs, they do not have to resort to a microscope or magnifying glass. If, however, a bug is detected by the naked eye only upon careful scrutiny, even though it is not visible at first glance, it must be removed to make the vegetable edible. In case one sees only a black dot on a leaf, for example, but upon looking through a magnifying glass or a microscope they can tell that it is a bug, they must remove it. Poskim apply similar principles to two letters in a Sefer Torah that appear to be touching each other—but when looked at through a magnifying glass or a microscope it is obvious that the letters are not actually touching. Regardless, there is a still a problem with the Sefer Torah, since halachah is based on what people with good vision can see with the naked eye. There is also a discussion among poskim regarding an esrog: If there is a mark on an esrog, it is judged by the way it is seen with one’s eyes,which differs from the halachah of checking vegetables: the way the esrog is seen behashkafah rishonah (at first glance) is what counts, not how it’s seen upon intense scrutiny. #361