Halakhah su Salmi 137:7

As previously indicated, a Bet ha-Mikdash is not necessarily required for the offering of sacrifices. Yet any sacrifice must be offered on the precise location of the original altar. In Rambam's phraseology, "mekom ha-mikdash mekhuvan be-yoter—the site of the altar [is located] with extreme precision." This spot, hallowed through the ages, is pinpointed by tradition as the exact site of Adam's first sacrifice to the Almighty, of Noah's offering upon emerging from the ark and of the binding of Isaac. The difficulties in the task of locating this site with exactitude are such that the Gemara, Zevaḥim 62b, relates that at the time of the construction of the Second Temple, the location of the altar was revealed by a prophet who returned from Babylonia for this purpose. Kalisher maintains that this was necessary only because no remnant whatsoever remained of the First Temple, as was foretold: "Raze it, raze it, even to the foundation thereof" (Ps. 137:7). Of the Second Temple, however, there are yet extant sections of the walls; these, Kalisher asserts, may be utilized for purposes of determining the distance between the walls and the altar. In the previously cited responsum, R. Akiva Eger argues that we cannot rely on our measurements in order to determine the exact location of the mizbeaḥ since these measurements are based upon the tefaḥ, or handbreadth measuring four fingerwidths. These dimensions cannot be determined with exactitude at present since physical proportions have changed over the course of centuries. Although various halakhic standards dependent upon these measurements may vary according to the average physical proportions of mankind in each generation, standards derived in this manner cannot enable us to measure geographical distances and locate spatial points which are unvariable.