ABSTRACT
In the early to mid-twentieth century, physicists found that they could not describe the observed behavior of the electrons orbiting the nuclei of atoms by use of Newtonian physics. A new mathematical description of that behavior was developed. Called quantum mechanics, it has been tremendously successful in accounting for widely diverse phenomena at both the qualitative and quantitative level and is universally regarded as generally applicable to all matter. However quantum mechanics has some peculiar counter intuitive features and some aspects of its interpretation remain in dispute. This chapter focuses on how quantum mechanics changes the Newtonian picture of the past, present and future and of time itself. The mathematical apparatus governing the time dependence of the wave functions which describe states in quantum mechanics is completely time reversible, in a way closely analogous to the time reversibility of Newtonian mechanics, though the state descriptions are different.
