Who knows forty-three?
Please cite/link your sources, if possible. At some point in the next few days, I will:
Upvote all interesting answers.
Accept the best answer.
Go on to the next number.
43 are the degrees Celsius for R' Moshe Feinstein's lower threshold of yad soledes bo (Igros Moshe OC IV:74).
Yes, I can and will shamelessly switch units of measurement in search of a convenient number. No, I don't honestly think this will beat Alex's awesome answer.
43 are the thousands in the tribe of Reuben at the final census in the desert. (Numbers 26:7).
43,730 specifically. In the first census (Numbers Ch. 1), only one tribe, Gad, has a number that's not an even hundred. In this census, again only one tribe, this time it's Reuben.
Did different tribes round differently? Did only values very close to 50 (or 30?) round to that? Do we know?
Oh right, the answer to everything was yesterday.
1) זבחים מב ב
אבל דמים הניתנין על המזבח הפנימי כגון ארבעים ושלש של יום הכיפורים
There were forty-three "sprinkling" of blood onto the inner altar on Yom Kippur.
2) The amount of פתוחות in ספר בראשית. (The amount of "paragraphs" in a Torah scroll for the Book of Genesis.)
4) The amount of times the name יששכר appears in תנ"ך. (Try it here: http://www.snopi.com/ToraSearch/torasearch.asp)