הלכה על עבודה זרה 2:3

Rav Willig presents another potential distinction that may solve this problem. In a wide variety of halachic areas, we do not attach any significance to that which is not visible to the naked eye. The Chochmat Adam (Binat Adam 38:49), Rav Shlomo Kluger (Teshuvot Tuv Ta’am Vada’at 2 Kuntress Acharon 53), the Aruch Hashulchan (Y.D. 84:36), and Rav Ovadia Yosef (Teshuvot Yechaveh Da’at 6:47) rule that we need not be concerned about consuming bugs that can be seen only with the aid of a magnifying glass. Rav Moshe Feinstein (Teshuvot Igrot Moshe Y.D. 3:120:5) rules that we need not determine that tefillin are square using a microscope.⁹The Gemara (Menachot 35a) states that we have a tradition from Sinai that tefillin must be square. The Tiferet Yisrael (Avodah Zarah 2:3 in Boaz) rules that a fish whose scales are visible only when viewed with a magnifying glass is not kosher. He similarly rules that an animal with a hole in its lung that can be seen only with a magnifying glass is not a treifah. The Teshuvot Even Yekarah (2:33) rules that a Tanach whose tiny letters are visible only if viewed with a magnifying glass is not considered “written.” Rav Yosef Messas (Teshuvot Mayim Chaim 1:259) permits using an etrog whose blemishes can be detected only when examined with a magnifying glass. As such, we need not be concerned with the microscopic strands of DNA that suggest that a child is a mamzeir.