Three teachings of Rav Zutra bar Toviya: 1) don’t tighten loose stitches in a garment on Shabbos, 2) prohibited to learn from a “magosh” in order to do, 3) one who knows how to calculate astronomical movements must do so, and it’s a sanctification of God’s name. This suggests science is a holy practice when used to understand the wonders of God’s creation. Salting was replaced by drafting in the tally of 39 prohibited labors. Removing loose threads may be prohibited on Shabbos under the category of striking the final blow. Per Mishna 3 of Ch. 7, may we take out the garbage on Shabbos?