In 1962, Leonard Susskind earned a B.A. in physics from City College of New York after transitioning from his plan to get a degree in engineering. He earned his Ph.D. in 1965 from Cornell University.

Dr. Susskind worked at Yeshiva University as an Associate Professor from 1966 to 1979, with a year at University of Tel Aviv from 1971 to 1972, before becoming a Professor of Physics at Stanford University in 1979, where he remains to this today. He was awarded the Felix Bloch Professorship of Physics since the year 2000.

## String Theory Insights

Probably one of Dr. Susskind's most profound accomplishments is that he's credited as one of the three physicists who independently realized, back in the 1970's, that a certain mathematical formulation of particle physics interactions seemed to represent oscillating springs ... in other words, he's considered one of the fathers of string theory. He has done extensive work within string theory, including the development of a matrix-based model.

He's also responsible for one of the more recent discoveries in the exploration of theoretical physics, the holographic principle, which many, including Susskind himself, believe will provide great insights into how string theory applies to our universe.

In addition, in 2003 Susskind coined the term "string theory landscape" to describe the set of all physically possible universes that could have come into being under our understanding of the laws of physics. (At present, this could contain as many as 10^{500} possible parallel universes.) Susskind is a strong proponent of applying reasoning based upon the anthropic principle as a valid means to evaluate which physical parameters its possible for our universe to have.

## Black Hole Information Problem

One of the most troubling aspects of black holes is that when something falls into one, it is lost to the universe forever. In the terms that physicists use, information is lost ... and that isn't supposed to happen.

When Stephen Hawking developed his theory that black holes actually radiated an energy known as Hawking radiation, he believed that this radiation would be insufficient to actually resolve the problem. The energy radiating out from the black hole under his theory would not contain enough information to fully describe all of the matter that fell into the black hole, in other words.

Leonard Susskind disagreed with this analysis, believing quite strongly that the conservation of information was so important to the underlying foundations of quantum physics that it could not be violated by black holes. Ultimately, the work in black hole entropy and Susskind's own theoretical work in developing the holographic principle have helped to convince most physicists - including Hawking himself - that a black hole would, over the course of its lifetime, emit radiation that contained the full information about everything that ever fell into it. Thus most physicists now believe that no information is lost in black holes.

## Popularizing Theoretical Physics

Over the last few years, Dr. Susskind has become more well-known among lay audiences as a popularizer of advanced theoretical physics topics. He has written the following popular books on theoretical physics:

(2005) - This book presents Susskind's view of how string theory predicts a vast "string theory landscape" and how the anthropic principle can be applied to evaluate the various physical properties of our universe against all of the assorted possibilities. This is described above in the string theory section.*The Cosmic Landscape: String Theory and the Illusion of Intelligent Design*(2008) - In this book, Susskind describes the black hole information problem (described above), framed as an intriguing narrative about a disagreement within the theoretical physics community ... one which has taken decades to resolve.*The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics*with George Hrabovsky (2013) - A math-based introduction to the fundamental concepts within classical mechanics, such as conservation of energy and symmetries in physical laws, which is intended to lay the groundwork for what someone would need to know to proceed to the next level in physics. This is based on lectures that are available online, as described below.*The Theoretical Minimum: What You Need to Know to Start Doing Physics*

In addition to his books, Dr. Susskind has presented a series of lectures that are available online through both iTunes and YouTube ... and which provide the basis of *The Theoretical Minimum*. Here is a list of the lectures, in roughly the order that I would recommend viewing them, along with links to where you can view the videos for free:

- Classical Mechanics (YouTube) - A 10-lecture series focusing on the fundamentals of classical mechanics
- The Theoretical Minimum: Quantum Mechanics (YouTube) - A 10-lecture series that tries to understand what physicists know about quantum mechanics
- Special Relativity (YouTube) - A 10-lecture series explaining Einstein's theory of special relativity
- General Relativity (YouTube) - A 10-lecture series that lays out the modern theory of gravity: general relativity
- Particle Physics: Standard Model (YouTube) - A 9-lecture series focusing on the Standard Model of particle physics
- Cosmology (YouTube) - A 3-lecture series focusing on what we know and understand about the history and structure of our universe
- String Theory and M-Theory (YouTube) - A 10-lecture series focusing on the fundamentals of string theory and M-Theory
- Topics in String Theory (YouTube) - A 9-lecture series focusing on the fundamentals of string theory and M-Theory

As you may have noticed, some of the themes repeat between lecture series, such as the two different lecture sets on string theory, so you shouldn't need to watch them all if there are redundancies ... unless you really want to.