Department of Mathematics FAS Harvard University One Oxford Street Cambridge MA 02138 USA Tel: (617) 495-2171 Fax: (617) 495-5132

Open Neighborhood Seminar of October 23, 2019

Speaker: Marius Lemm

Title: Why doesn't an electron fall into the nucleus
Abstract: In physics class at school, we are taught that matter is composed of atoms. We learn that every atom has at its center a positively-charged nucleus, around which negatively-charged electrons orbit, just like planets orbiting the sun. However, we also learn that positive and negative charges attract. So, ... why doesn't an electron simply fall into the nucleus? This is no small question as the answer holds the key to the stability of all matter around us. It turns out that the answer lies in quantum mechanics. This lecture will give a crash course on the mathematics describing quantum mechanics and in particular pin down the notion of "uncertainty principle" mathematically. It will conclude with a proof that a quantum-mechanical electron does not fall into the nucleus, hopefully prompting a sigh of relief from the audience.