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- S1 E1 - Why Time Is a MysterySeptember 27, 201233minBegin your study of the physics of time with these questions: What is a clock? What does it mean to say that "time passes"? What is the "arrow of time"? Then look at the concept of entropy and how it holds the key to the one-way direction of time in our universe.#Science & MathematicsFree trial of The Great Courses Signature Collection or buy
- S1 E2 - What Is Time?September 1, 201230minApproach time from a philosophical perspective. "Presentism" holds that the past and future are not real; only the present moment is real. However, the laws of physics appear to support "eternalism"--the view that all of the moments in the history of the universe are equally real.Free trial of The Great Courses Signature Collection or buy
- S1 E3 - Keeping TimeSeptember 1, 201231minHow do we measure the passage of time? Discover that practical concerns have driven the search for more and more accurate clocks. In the 18th century, the problem of determining longitude was solved with a timepiece of unprecedented accuracy. Today's GPS navigation units rely on clocks accurate to a billionth of a second.Free trial of The Great Courses Signature Collection or buy
- S1 E4 - Time's ArrowSeptember 1, 201229minEmbark on the quest that will occupy the rest of the course: Why is there an arrow of time? Explore how memory and aging orient us in time. Then look at irreversible processes, such as an egg breaking or ice melting. These capture the essence of the one-way direction of time.Free trial of The Great Courses Signature Collection or buy
- S1 E5 - The Second Law of ThermodynamicsSeptember 1, 201231minTrace the history of the second law of thermodynamics, considered by many physicists to be the one law of physics most likely to survive unaltered for the next thousand years. The second law says that entropy--the degree of disorder in a closed system--only increases or stays the same.Free trial of The Great Courses Signature Collection or buy
- S1 E6 - Reversibility and the Laws of PhysicsSeptember 1, 201230minIsaac Newton's laws of physics are fully reversible; particles can move forward or backward in time without any inconsistency. But this is not our experience in the world, where the arrow of time is fundamentally connected to irreversible processes and the increase in entropy.Free trial of The Great Courses Signature Collection or buy
- S1 E7 - Time Reversal in Particle PhysicsSeptember 1, 201231minExplore advances in physics since Newton's time that reveal exceptions to the rule that interactions between moving particles are fully reversible. Could irreversible reactions between elementary particles explain the arrow of time? Weigh the evidence for and against this view.Free trial of The Great Courses Signature Collection or buy
- S1 E8 - Time in Quantum MechanicsSeptember 1, 201231minQuantum mechanics is the most precise theory ever invented, yet it leads to startling interpretations of the nature of reality. Probe a quantum state called the collapse of the wave function that may underlie the arrow of time. Are the indications that it shows irreversibility real or only illusory?Free trial of The Great Courses Signature Collection or buy
- S1 E9 - Entropy and CountingSeptember 1, 201231minAfter establishing in previous lectures that the arrow of time must be due to entropy, begin a deep exploration of this phenomenon. In the 1870s, physicist Ludwig Boltzmann proposed a definition of entropy that explains why it increases toward the future. Analyze this idea in detail.Free trial of The Great Courses Signature Collection or buy
- S1 E10 - Playing with EntropySeptember 1, 201232minSharpen your understanding of entropy by examining different macroscopic systems and asking, which has higher entropy and which has lower entropy? Also evaluate James Clerk Maxwell's famous thought experiment about a demon who seemingly defies the principle that entropy always increases.Free trial of The Great Courses Signature Collection or buy
- S1 E11 - The Past HypothesisSeptember 1, 201229minBoltzmann explains why entropy will be larger in the future, but he doesn't show why it was smaller in the past. Learn that physics can't account for this difference except by assuming that the universe started in a state of very low entropy. This assumption is called the past hypothesis.Free trial of The Great Courses Signature Collection or buy
- S1 E12 - Memory, Causality, and ActionSeptember 1, 201230minCan physics shed light on human aspects of the arrow of time such as memory, cause and effect, and free will? Learn that everyday features of experience that you take for granted trace back to the low entropy state of the universe at the big bang, 13.7 billion years ago.Free trial of The Great Courses Signature Collection or buy
- S1 E13 - Boltzmann BrainsSeptember 1, 201231minOne possible explanation for order in the universe is that it is a random fluctuation from a disordered state. Could the entire universe be one such fluctuation, now in the process of returning to disorder? Investigate a scenario called "Boltzmann brains" that suggests not.Free trial of The Great Courses Signature Collection or buy
- S1 E14 - Complexity and LifeSeptember 1, 201231minDiscover that Maxwell's demon from lecture 10 provides the key to understanding how complexity and life can exist in a universe in which entropy is increasing. Consider how life is not only compatible with, but is an outgrowth of, the second law of thermodynamics and the arrow of time.Free trial of The Great Courses Signature Collection or buy
- S1 E15 - The Perception of TimeSeptember 1, 201232minTurn to the way humans perceive time, which can vary greatly from clock time. In particular, focus on experiments that shed light on our time sense. For example, tests show that even though we think we perceive the present moment, we actually live 80 milliseconds in the past.Free trial of The Great Courses Signature Collection or buy
- S1 E16 - Memory and ConsciousnessSeptember 1, 201231minRemembering the past and projecting into the future are crucial for human consciousness, as shown by cases where these faculties are impaired. Investigate what happens in the brain when we remember, exploring different kinds of memory and the phenomena of false memories and false forgetting.Free trial of The Great Courses Signature Collection or buy
- S1 E17 - Time and RelativitySeptember 1, 201231minAccording to Einstein's special theory of relativity, there is no such thing as a moment in time spread throughout the universe. Instead, time is one of four dimensions in spacetime. Learn how this "relative" view of time is usefully diagramed with light cones, representing the past and future.Free trial of The Great Courses Signature Collection or buy
- S1 E18 - Curved Spacetime and Black HolesSeptember 1, 201230minBy developing a general theory of relativity incorporating gravity, Einstein launched a revolution in our understanding of the universe. Trace how his idea that gravity results from the warping of spacetime led to the discovery of black holes and the big bang.Free trial of The Great Courses Signature Collection or buy
- S1 E19 - Time TravelSeptember 1, 201231minUse a simple analogy to understand how a time machine might work. Unlike movie scenarios featuring dematerializing and rematerializing, a real time machine would be a spaceship that moves through all the intervening points between two locations in spacetime. Also explore paradoxes of time travel.Free trial of The Great Courses Signature Collection or buy
- S1 E20 - Black Hole EntropySeptember 1, 201230minStephen Hawking showed that black holes emit radiation and therefore have entropy. Since the entropy in the universe today is overwhelmingly in the form of black holes and there were no black holes in the early universe, entropy must have been much lower in the deep past.Free trial of The Great Courses Signature Collection or buy
- S1 E21 - Evolution of the UniverseSeptember 1, 201231minFollow the history of the universe from just after the big bang to the far future, when the universe will consist of virtually empty space at maximum entropy. Learn what is well founded and what is less certain about this picture of a universe winding down.Free trial of The Great Courses Signature Collection or buy
- S1 E22 - The Big BangSeptember 1, 201230minExplore three different ways of thinking about the big bang--as the actual beginning of the universe; as a "bounce" from a symmetric version of the universe on the other side of the big bang; and as a region that underwent inflationary expansion in a much larger multiverse.Free trial of The Great Courses Signature Collection or buy
- S1 E23 - The MultiverseSeptember 1, 201231minDig deeper into the possibility that the big bang originated in a multiverse, which provides a plausible explanation for why entropy was low at the big bang, giving rise to the arrow of time. But is this theory and the related idea of an anthropic principle legitimate science or science fiction?Free trial of The Great Courses Signature Collection or buy
- S1 E24 - Approaches to the Arrow of TimeSeptember 1, 201232minUse what you have learned in the course to investigate a range of different possibilities that explain the origin of time in the universe. Professor Carroll closes by presenting one of his favorite theories and noting how much remains to be done before conclusively solving the mystery of time.Free trial of The Great Courses Signature Collection or buy
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