A Century of Gravity: 1901--2000 (plus some 2001)

Abstract

This lecture consists of two parts. The first is a (totally unsystematic) survey of some of the high points in the evolution of gravity and its successors, primarily in the course of the past century. The second summarizes some new work on surprising properties of higher $(> 1)$ spin fields in cosmological backgrounds: the presence of $\L$ gives rise to discrete sets of massive models endowed with gauge invariances, that divide the ($m^2, \L$) plane into unitary and non-unitary phases. The unitary region common to fermions and bosons shrinks to flat space ($ \L \to 0 $) as their spins increase.