"Order-of-Magnitude" Physics Workshop

Synopsis

Estimates and order-of-magnitude thinking have been one of the centerpieces of science and mathematics for thousands of years.  Archimedes famously estimated pi by trapping the area of the unit circle between inscribed and circumscribed polygons. Newton estimated the distance “fallen” by the moon and compared it the distance fallen by a mass at the surface of the Earth and found them to agree “pretty nearly,” lending credence to his ideas about the inverse square law.  Perhaps most impressively of all, Maxwell derived a wave equation for the electromagnetic field and found a wave speed given by 1/sqrt(mu_0 espilon_0) and when he plugged in the numbers, found to his astonishment, the speed of light!   In this hands-on jam session, we will perform some of these classic estimates and then turn to more modern examples such as what sets the size limit of bacterial cells and blue whales, the farm land it takes to feed each of us, and the amount of fertilizer used worldwide compared to the missing poop from whales removed from the oceans in the 20th century.  We will spend 5-10 minutes each working on various estimate problems and I will close the discussion with reflections on the past, present and future of order-of-magnitude thinking in science and society.