Mysteries of Modern Physics: Time

Rated 1 out of 5 by from I bought this for a grandson in college. He is delights with it. I am considering The 30 Greatest Orchestral Works for myself. You seem to have courses for everyone. I still enjoy those I already have.
Date published: 2020-03-06
Rated 5 out of 5 by from Very interesting but challenging This course was very interesting. It tackled the fascinating subject of the arrow of time. I am a trained experimental physicist but found some of the theoretical aspects and ideas challenging at times but overall I am pleased I listened to the whole course. Professor Carroll is an excellent lecturer and he led me through a difficult, but interesting, subject. Without his valuable guidance I would have given up early in the course.
Date published: 2019-12-20
Rated 1 out of 5 by from failed to resume I saw only one lecture and it failed to resume. I wish a refund.
Date published: 2019-10-20
Rated 5 out of 5 by from I found this course very interesting and informative.
Date published: 2019-10-02
Rated 4 out of 5 by from slow build, but eventually and interesting course The lecturer takes a while to get into the discussion of how time affects our everyday lives. I enjoyed the lectures relating to biology and astronomy. He spent a bit too long on thermodynamics and particle physics.
Date published: 2019-08-05
Rated 4 out of 5 by from Is relevant to the title. I recomend to translate in spanish. Should be more blackboard graphics and demostrations as in classroom.
Date published: 2019-07-29
Rated 5 out of 5 by from This is the third teaching company course I have had with Professor Carrol. It was excellent
Date published: 2019-07-27
Rated 5 out of 5 by from This is an appropriate title for this course. I've read several books and watched other presentations about this topic, but kudos to Sean Carroll for giving us one of the best explanations I've heard. Taking an arcane subject like the physics of time and trying to explain it in a popular fashion is no easy task, but he choses appropriate examples and keeps focused and on topic. His careful editing and selective repetition of the material helps you stay on track. While I wouldn't recommend this to someone who is very unfamiliar with this topic, those who have an interest and who put the effort in, will be well rewarded. I also appreciate that he does add some equations to help support the material. I am ranking this course a five. It is one of the best ones I've bought.
Date published: 2019-06-14
Rated 5 out of 5 by from Masterful Teacher The professor teaches without reliance on visible notes. He has a great grasp of the subject and presents it in a manner that holds your attention. I am truly enjoying his lectures.
Date published: 2019-05-30
Rated 3 out of 5 by from Format problem I purchased this item reluctantly because I prefer to listen to the courses while driving. Although, in this case, I was so interested in learning more about “time” at additional expense, I bought the visual format. However, when playing course, I saw no reason for that format! Very disappointed.
Date published: 2019-04-14
Rated 5 out of 5 by from Mind Stretching This course is based on physics, philosophy, mathematics, cosmology, astronomy, and enhanced self awareness. I have gone through all twenty four lessons and am now starting over. The content is so extensive that I think it will take another pass to begin to remember everything and that might not be adequate. The characteristic of the course is that there are many difficult topics treated fairly comprehensively but the range of topics is equivalent to more than a few college courses.
Date published: 2019-04-07
Rated 5 out of 5 by from Stimulating With and academic background in history and political science, I want to explore disciplines beyond my comfort zone. I found this series by Dr. Carroll fascinating. While I don't pretend to understand all that was presented, I thoroughly enjoyed the intellectual stimulation and piqued my interest for further courses in physics and cosmology
Date published: 2019-04-02
Rated 5 out of 5 by from Great Course in Demystifying the Mystery of Time Initially mundane with discussions of the engineering aspects of thermal energy, focusing on19th Century steam engine technology, and smattering of History topics, Professor Carroll delved into various modern topics in Physics such as Thermodynamics, Quantum Mechanics, Elementary Particles, Relativity, etc., and the lectures became considerably more stimulating and interesting. Professor Carroll has the unusual ability to explain difficult Physics concepts with clarity, organization and insight, but would not "talk above the heads of the audience". The caveat for some viewing the course lectures without basic understanding of college science is that one should have some basic requisite scientific knowledge to be capable of understanding Professor Carroll's lectures, i.e., preferably college-level Physics but not anything more advanced such as upper-division or graduate studies. Courses in Chemistry or Engineering involving Heat, Thermodynamics, Classical Mechanics (Dynamics, etc.), Molecular Science/Modern Physics and Electrical Energy/Electricity would be extremely helpful. All in all, this is an excellent course taught by an outstanding Caltech faculty member - an advanced and abstract subject such as Time would require a brilliant mind to deliver the lectures and offer explanations accessible to those who are not research physicists. BTW, Professor Carroll's lecture style enabled me to complete viewing of all of the lectures on the DVD disks on "Time", a matter I admit I have yet to follow through with many other DVD ones I purchased from Great Courses! How about a follow-on course based on more advanced concepts on related Physics taught by Professor Carroll?
Date published: 2019-02-24
Rated 4 out of 5 by from Time, Is There a Question? This course spends a great deal of time answering the question of why there is an arrow of time. The course tries to answer this using the second law of thermodynamics. In fact, half the course wanders around the discovery of the second law. This course was interesting and it did hold my attention although I don't think I actually learned anything I didn't know.
Date published: 2019-02-05
Rated 4 out of 5 by from Time: Still a Mystery Professor Carrol is a great mind and the concept of time is really difficult. If the question is "Why is there and arrow of time?", that implies looking for a cause. I think spending so much effort on the second law of thermodynamics showed a correlation, but not a cause. That key question wasn't answered. Having said that, I learned a great deal in the course and was pleased by the information. It's not his shortcoming that we haven't yet figured out what time actually is. My own uneducated idea is that time has more to do with the fact that the speed of light is not infinite. Light takes time.
Date published: 2019-01-02
Rated 5 out of 5 by from Mysteries of Modern Physics: Time A great course, easy to understand, interesting topics, well prepared and professional presentation. Highly recommend to those who are interested in Science and Physics but without in-depth knowledge of these subjects. You will learn a lot from this course, good value (knowledge) for money.
Date published: 2018-12-14
Rated 5 out of 5 by from Brilliant Attempt to Understand the Arrow of Time! Mysteries of Modern Physics: Time presented by Dr. Sean Carroll is OUTSTANDING! Sean is unleashed at the start of each lecture and never misses a beat. It is obvious he is sharing his lifetime work in physics and cosmology and there is no script. I had purchased the lecture set to casually review and gain some insights into the arrow of time, but was I wrong! Dr. Carroll is mesmerizing and eventually found myself wanting to become a cosmologist. He is brilliant in a matter of fact way as he discusses entropy and it relationship to the arrow of time. I have now purchased over 300 lecture sets and this is in the top 5! I highly recommend this lecture set and especially Dr. Sean Carroll. I am going to purchase every other set he had produced!!
Date published: 2018-12-07
Rated 5 out of 5 by from Time An excellent explanation of time, mostly from the viewpoint of physics, especially the notion of entropy. It did make me realize the full impact of Newton, wherein the philosophers thought they had beat the arrow of time with the advent of a fully mechanistic and hence predictable universe. That euphoria is long gone.
Date published: 2018-12-01
Rated 5 out of 5 by from Mysteries of Modern Physics: Time One of the best of the Great Courses, and I have quite a few. Sean Carroll is an excellent teacher. He does not talk down to the viewer but at the same time uses language that non-physicists can understand. An exceptional course.
Date published: 2018-11-28
Rated 5 out of 5 by from Mysteries of Modern Physics : Time Sean Carroll is a gifted lecturer and writer. All of his Great Courses projects are first-class.
Date published: 2018-10-22
Rated 5 out of 5 by from My BA is in general education and MA in educational counseling (background) and other than "general" science courses I have little background in advanced physics nor concepts of relativity. Having stated this I was quite pleased with this course (although there was more than one "rewind" to review/understand certain concepts and ideas) and tout the gateway foundation to delve deeper into quantum physics (now that I've retired I plan on eventually attempting to truly understand Rodger Penrose's writings) and how the universe actually functions on all levels. I have already ordered and received the course on Chaos, partly due to the way the present course was setup and presented. HIGHLY recommend this course to anyone not already versed in the space/time aspects of quantum physics.
Date published: 2018-09-22
Rated 5 out of 5 by from Lifes big questions I've just finished watching this for the second time. I have many of these courses and all of the professors are excellent. Professor Carroll is probably my favorite. He has a way of discussing the most complex subjects in a way I can understand even though I have virtually no formal education in physics, cosmology, and the rest. I also have the other two courses of his which I plan on watching multiple times. My fervent hope is The Great Courses will bring him back for more courses in the future.
Date published: 2018-08-26
Rated 1 out of 5 by from Repatative course, I didn't learn much This is my first review. I think it only fitting that I warn others that this course, unfortunately is a dud. Professor Carrol does not just physics in this course. He tries to take journeys in the history of clocks, and other non-physics disciplines - which in my opinion makes the title of the course inaccurate. It should be re titled. A better presenter, I think would be Dean Buonomano the author of the recent book "Your Brain is a Time Machine" - or even better MULTIPLE presenters with fields in philosophy, neuroscience and physics... All I learnt was that entropy is correlated with the passage of time, that the past has less entropy, (the past hypothesis) and that the 2nd law of thermodynamics is correct in predicting more entropy. We don't know why the early universe had less entropy, because we do not know how the big bang happened. I was thrilled in the first 3 lectures or so because I thought I was going to get some sort of physics of time, but what I got was a lot of waffling on the point. Professor Carrol should review his remarks and make them concise and to the point, with better titles for the sections. I would like to see a purely physics presentation with a more concise structure next time in a second edition, which I would consider purchasing.
Date published: 2018-08-25
Rated 2 out of 5 by from tries to cover too much and can't pull it off I was expecting this to deal with time primarily from the perspective of science but obviously science is not clear on this topic and/or the presenter seems not to be. So rather than focus down on maybe the history of our scientifically evolving understanding of the phenomenon we call time he unfortunately jumps from philosophy to psychology and literature to science and back in what seems to be a haphazard manner. I plowed through but found it generally unsatisfying and did not feel at all enlightened about time.
Date published: 2018-06-23
Rated 1 out of 5 by from don't buy it I have bought 74 courses through "great courses." I've generally liked them. Some have been too basic. "Time" was a total waste of my time and money. With each lecture, I thought...what did I learn from this? Very little.
Date published: 2018-06-21
Rated 1 out of 5 by from mysteries of modern physics:time Too simplistic,shies away from math too much to give good context. Too repetitve-it seems like he thinks I do not hear what he has already said.
Date published: 2018-06-16
Rated 4 out of 5 by from Somewhat disappointed Some portions were interesting but entropy discussion ignore current approach to describing entropy with less emphasis on Boltzman
Date published: 2018-05-24
Rated 5 out of 5 by from Excelent course Very interesting and well presented. Both people with some background in physics and those who lack the basic knowledge but are interested in the subject can benefit from the course.
Date published: 2018-04-14
Rated 5 out of 5 by from Interesting and addictive Of all the Courses I have bought from the Great Courses, this is the first CD (audio only) one I have bought. I thought I was getting the DVD and was somewhat disappointed. However, the CD forces me to pay more attention to the course material and I find myself imagining what the DVD would be like at that time. Not sorry at all.
Date published: 2018-04-06
Rated 1 out of 5 by from Too Speculative The lecturer is trying to deal with a difficult subject, and I give him great credit forthis. However, the style at times appears ad lib or more like a rant than a carefully reasoned thesis. The only solid point he appears to make- and he does this over and over again- is that entropy increases with time and the changes cannot be readily reversed. The remainder of the course, through no real fault of his own, is speculation. Hence, the amount of solid information you will garner from this course is not great.
Date published: 2018-03-19
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Mysteries of Modern Physics: Time
Course Trailer
Why Time Is a Mystery
1: Why Time Is a Mystery

Begin 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.

33 min
What Is Time?
2: What Is Time?

Approach 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.

30 min
Keeping Time
3: Keeping Time

How 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.

31 min
Time's Arrow
4: Time's Arrow

Embark 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.

29 min
The Second Law of Thermodynamics
5: The Second Law of Thermodynamics

Trace 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.

31 min
Reversibility and the Laws of Physics
6: Reversibility and the Laws of Physics

Isaac 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.

30 min
Time Reversal in Particle Physics
7: Time Reversal in Particle Physics

Explore 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.

31 min
Time in Quantum Mechanics
8: Time in Quantum Mechanics

Quantum 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?

31 min
Entropy and Counting
9: Entropy and Counting

After 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.

31 min
Playing with Entropy
10: Playing with Entropy

Sharpen 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.

32 min
The Past Hypothesis
11: The Past Hypothesis

Boltzmann 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.

29 min
Memory, Causality, and Action
12: Memory, Causality, and Action

Can 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.

30 min
Boltzmann Brains
13: Boltzmann Brains

One 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.

31 min
Complexity and Life
14: Complexity and Life

Discover 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.

31 min
The Perception of Time
15: The Perception of Time

Turn 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.

32 min
Memory and Consciousness
16: Memory and Consciousness

Remembering 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.

31 min
Time and Relativity
17: Time and Relativity

According 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.

31 min
Curved Spacetime and Black Holes
18: Curved Spacetime and Black Holes

By 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.

30 min
Time Travel
19: Time Travel

Use 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.

31 min
Black Hole Entropy
20: Black Hole Entropy

Stephen 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.

30 min
Evolution of the Universe
21: Evolution of the Universe

Follow 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.

31 min
The Big Bang
22: The Big Bang

Explore 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.

30 min
The Multiverse
23: The Multiverse

Dig 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?

31 min
Approaches to the Arrow of Time
24: Approaches to the Arrow of Time

Use 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.

32 min
Sean Carroll

We need to push on our understanding of cosmology, particle physics, gravity, not to mention how complexity and entropy evolve through time, and eventually you'll be able to really understand what our theories predict.


Harvard University


California Institute of Technology

About Sean Carroll

Professor Sean Carroll is a Senior Research Associate in Physics at the California Institute of Technology. He earned his undergraduate degree from Villanova University and his Ph.D. in Astrophysics from Harvard in 1993. Before arriving at Caltech, Professor Carroll taught in the Physics Department and the Enrico Fermi Institute at the University of Chicago, and did postdoctoral research at the Massachusetts Institute of Technology and at the Institute for Theoretical Physics at the University of California, Santa Barbara. Professor Carroll is the author of Spacetime and Geometry: An Introduction to General Relativity, published in 2003. He has taught more than 200 scientific seminars and colloquia and given more than 50 educational and popular talks. In addition, he has written for numerous publications including Nature, New Scientist, The American Scientist, and Physics Today. Professor Carroll has received research grants from NASA, the U.S. Department of Energy, and the National Science Foundation, as well as fellowships from the Sloan and Packard foundations. He has been the Malmstrom Lecturer at Hamline University, the Resnick Lecturer at Rensselaer Polytechnic Institute, and a National Science Foundation Distinguished Lecturer. While at MIT, Carroll won the Graduate Student Council Teaching Award for his course on general relativity. In 2006 he received the Arts and Sciences Alumni Medallion from Villanova University.

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