From Leonard Susskind to Everyone:
A number of years ago I became aware of the large number of physics enthusiasts out there who have no venue to learn modern physics and cosmology. Fat advanced textbooks are not suitable to people who have no teacher to ask questions of, and the popular literature does not go deeply enough to satisfy these curious people. So I started a series of courses on modern physics at Stanford University where I am a professor of physics. The courses are specifically aimed at people who know, or once knew, a bit of algebra and calculus, but are more or less beginners.
The response was overwhelming and it was suggested that Stanford put them up on the internet. You can find them at
http://www.learnoutloud.com/Catalog/Science/Physics/Modern-Theoretical-Physics/23022
Since the videos went up, I have received many emails with good questions. Some are about the material in the courses. Some are more broadly about physics and science. Here is the place to ask them. If I know the answer to your question I will post it. If not perhaps someone else can answer.
Leonard Susskind
636 comments:
«Oldest ‹Older 601 – 636 of 636A position travelling mat ne considérés as an électron travelling un thé past. As gravity is attractive for ordinary matter, is it not predictable that anti matter would behave repulsively ( because of time reversal).?
Dear Professor Susskind,
In talk show World science festival:- A thin sheet of reality : The Universe as hologram you talked about how much information can fit on surface of black hole.
Here you talked about bit of information on one plank length.
My question is if that instead of bit if there is qbit per plank length and all of them entagaled with each other..
Kindly waiting for answer
Thanks and regards...
Good Day Dr. Susskind,
I write to you today with a sense of both excitement and urgency as I look at the journey which lies ahead. I have been helping people heal with my bodywork for 20 years. I was struggling to articulate how my work differs from the other massage on the market... Totally stumped I decided to see if I could find any new science videos online to distract me... I am very intrigued with vibration and energy and plasticity... I looked for theories which took fragmented chaos coexisting with organized chaos and explaing the effect of applying 2 external forces (1 predictable and 1 random) that are both specifically in sync with the 2 internal systems in differentiated chaos. I FOUND IT! I have figured out how to provide those 2 external forces with consistently predictable results. I have developed a theory based on this model and have watched hours of your online lectures from stanford...facscinated with how I can explain entropy and the bose-einstein type effect using human body as the universe and explain it all with numbers.
Johnny Vos
1 (647) 515-6277
Professor I have a doubts that as complex no have no meaning but imagine if it have some physical interpretation then it may make some important discussion with physics
Dear Leonard,
I just wanted to thank you amd Stanford sincerely for all of your lectures. I have been totally immersed in them for 6 months now. They are incredibly useful for someone like myself-a scientist how has not done physics since university. They are by far the best lectures I have ever watched and have given me a real love for physics again.
Sir if langrangian is frame independent but it has kinetic energy term and is frame dependent please clear my doubt.
Dear Prof. Susskind,
I hope you enjoy this comment. I am a studious of mathematics and theoretical physics and I found, deepening the mathematics of S. Ramanujan, different and, in my opinion, interesting connections with various sectors of particle physics and black holes.
In particular, with regard the Riemann zeta-function, from the value of zeta(2) = 1.6449, can be obtained interesting mathematical connections with some developements of the Ramanujan’s Mock Theta Functions, in turn connected with some sectors of Particle Physics, Cosmology and some expressions concerning the Black Hole entropies and the hypothetical mass of Dark Matter particles. The link to one of my papers which concerns these mathematical results, also including zeta(2), is:
http://vixra.org/pdf/1906.0253v1.pdf
Thank You for your availability and best regards
Michele
Respected sir
I wanted to know if there are some mathematical formulations like Lorentz transformations and 4 vectors that led to the discovery of unruh effect or was that just experimental
I think I have found(maybe it's already done)a way to amplify the effect of time dilation without having to move faster through spacetime. I call it compounding effect.
Dear Dr. Susskind
I feel blessed to be in the space-time where legends like yourself make the most dreadful and complex concepts look so beautiful and appealing. I am literally addicted to your lectures. Currently I was going through your lectures on 'Basic concepts on Particle Physics' where you have also introduced quantum field theory.
Sir can you suggest me some books on Quantum field Theory and Particle Physics that I can follow as a beginner.
Love from India
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Thank you Dr. Susskind!
I recently watched your YouTube video-"ER = EPR, 1/2", posted by "Stanford Institute for Theoretical Physics", and wrote some questions that occurred to me while I watched. I paused the video while I typed into my cellphone. If my question is unclear I thought a reference to the time in the video might clarify. The time is indicated in Minutes and Seconds, divided by the total Minutes and Seconds, for the full video.
I have a BS in Physics from 1984, but GR wasn't taught at Cal Poly Pomona then. I did get to Differential Equations and have been looking for more math on YouTube. Here are my questions:
A1) How do you know that every two spatial points in a vacuum are entangled without measuring them?(30'53"/107'53")
A2) How do you collect two sets of entangled particles, sufficiently numerous to create two black holes, without measuring the entanglement and thereby disentangling the particles? T=33'35"/107'53"
A3) Is the "Firewall" created by time stopping at the event horizon (nothing happens because time has stopped, except that the gravitational field persists!)? T=34'39"/107'53"
A4) The "Kruskal" coordinates used in the EPR paper before Kruskal was born, are they unique in envisioning the "wormhole" (per Wheeler) to explain "dual entanglements", from outside the event horizon of "A" to inside the event horizon of entangled blackhole "B"? Specifically are the "Kruskal" coordinates unique for revealing wormholes or do any of the other coordinate systems that remove the event horizon singularity also show the wormholes? T=54'14"/107'53".
A5) Since messing around inside Alice's blackhole might cause a disturbance to be created inside Bob's blackhole, could this ever be measured, since it is inside the horizon? T=62'59"/107'53".
A6) How does time go forward in the wormhole, from the time of the origin of the wormhole (the point in time where the two blackhole event horizons are touching)? My understanding is that the passage of time stops at the event horizon, is this incorrect? I found an equation on the internet for calculating the redshift of frequencies in a gravitational field, between a radial start point and a radial endpoint. Fiddling with this equation on a spreadsheet I found a result of the frequency going negative at the endpoint, for a startpoint inside the event horizon. Does time start going backward inside the event horizon? T=77'43"/107'53"
A7) The statement, or paraphrase, "There is no sharp division between particles and black holes", does this refer to the increasing gravitational field at the particle's "surface", associated with heavier and heavier particles? T= 96'54"/107'53".
Dear Professor Susskind,
many thanks for your superlative lessons and your book on quantum mechanics!
I would have a couple of question on the Born Rule.
1) I understand this rule gives you the probability to get an eigenvalue while measuring a given spin. After you have got a value and you repeat the measure the value is then determined and no more probabilistic and you get always the same repeating the measure?
2) when I measure a given spin and I get a value for it, is the measure the same also for other people who measure it?
Thank you so much for your time,
Regards
Fabio
The site can't be reached
I recently read a book by Richard A. Muller titled “NOW - The Physics of Time” and it motivated me to watch your (Leonard Susskind) first lecture on General Relatively on Youtube. Einstein’s Theory predicts that spacetime is so severely bent at the surface of a Black Hole, due to the intense gravity caused by the extreme mass of the Black Hole, that time virtually stops at the Event Horizon. This extreme time dilation or the stoppage of time, at the Event Horizon may be caused by a local cancelation of the expansion of the universe and spacetime at the Event Horizon described in Muller’s book. In other words, if time is a consequence of the expansion of the universe, and if the expansion is stopped, so is time. This observation seems to indicate that Muller’s Theory of “NOW” is consistent with General Relativity and may be correct. In fact, it helps to explain why time stops at the Event Horizon, which has always been an enigma to me. I was wondering if anyone thought of this or heard of this idea before. I am a big fan of Professor Susskind lectures and books and I hope he keeps producing them.
PLC on 02/01/2021
Professor Susskind,
My question relates to your first lecture on special relativity. You drew a picture of the coordinate system (x,t) in which you drew the trajectories x=vt (x'=0) and t=vx (t'=0). When I use the lines t'=0 and x'=0 as axes of a new coordinate system (x',t') and transform the coordinates of a point in space-time from the (x,t )basis to the (x',t') basis, I don't get the Lorentz transformation. I get the Lorentz transformation multiplied by a factor sqrt(1+v square)/sqrt(1-s square). WHERE AM I THINKING WRONG? Is it incorrect to take the two lines x'=0 and t'=0 as axes of the new (x',t') basis and why?
Love your lectures. Following you on ER=EPR. Keep it up sir!
I recently read about the EPR paradox and John Stewart Bell's experiment to disprove it. I read that the experiment involved measuring the spins of particles in various orientations. My question is, if spin is an intrinsic property of quantum particles, how is it possible to measure spin?
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I have followed Professor Leonard Susskind's lectures for years, and though I am not a physicist, I've always been fascinated with the subject. In his first lecture on Special Relativity, he reveals a moment of respect and reverence for Albert Einstein (I often replay this segment), where though he hasn't read the paper in 50 years, he makes us feel like it was yesterday. It is the sort of moment a student lives for in the lectures of professors they admire.
It lead me to research something on the heart of the matter, and I found this article in the New York Times archive, where Hendrik Lorentz acknowledges Einstein's contribution to relativity, and I somehow thought Professor Susskind would appreciate it. Of course, he may already know of it.
(I found exhilarating as well Lorentz's description of how Einstein's formulas explained the 43 seconds/century that were unaccounted for in Mercury's orbit!)
Please let Professor Susskind know that he has a drawing and architecture professor in Boston as an admirer!
sandro
Sandro A. Carella, AIA
Crosstown Foundation for the Arts, Inc.
One North Square
Boston, MA 02113
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Telephone (001) 617.720.0100
https://sites.suffolk.edu/architecture/
You had asked in one of your lectures what came after acceleration and jerk. It is snap, crackle, and pop (like the cereal). I can't imagine when you would need them, unless 2 neutron stars are colliding - very stiff. It also seems to be a place where Einstein's equations could be modified - there is no extreme acceleration terms, as far as I can tell.
Prof. Susskind had a question -why is "B" used for the magnetic field. Best guess - the Biot-Savart Law.
Dear prof. Susskind
My qusetion is that there is any relation between the metric tensor of rindler coordinate and the metric tensor of einstein's curved coordinate?
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Dear All,
Why "B" is used for the magnetic field?
It is actually interesting. There is no special meaning of B. Maxwell used the letters A-H to name his vectors, and some of is still in use till this day. A as the vector potential, B as magnetic flux density, D as electric displacement field, E as the electric field, H as the magnetic intensity. Sadly, I could not find the vectors he denoted with letter C and G, but we do not use these signs anymore.
Relation between the metric tensor of Rindler coordinate and the metric tensor of Einstein's curved coordinates:
I do not fully understand this question. The metric tensor is the metric tensor. The values are different in different metrics, but the tensor has the same meaning everywhere. Maybe I am missing something here, and if so, please feel free to enlighten me!
Hope I could help! You are all great for learning these things and asking questions!
Balint
Is there any way to find problem sets that match these lectures and books??
Dear Unknown,
There is one great problem solving book on general relativity, even though it is hard. It requires deeper understanding, but solutions are also really informative. For first try I could almost solve nothing, read the solutions, went back in a few month, and I felt much more successful. It is called "Problem book in relativity and gravitation". Starts with special relativity, and slowly reaching the topic of general relativity.
And there is of course "Einstein gravity in nutshell", there are exercises at the end of every chapter, but there are no solution for each of them in the book. Also there is "An introduction to general relativity spacetime and geometry", it has excercises, no solutions though. You can find some solutions in the internet, but there are no official solutions for the problems.
I'm not sure about the other lectures, because I was focused on special and general relativity, but there are these series called A students guide for [insert your topic here], and there are many useful things there, Maxwell equations, tensors, etc. It also contains excercises with detailed solutions.
Hope I could help,
Bálint
Dear Professor Susskind
Reading the first chapter of Quantum Mechanics, a crazy idea suddenly crossed my mind.
Is it possible for an electron to spin in two directions, +1 and -1, AT THE SAME TIME?
Kind Regards
Anthony Tsang
Yale Patt is a brilliant computer science professor and someone who you should meet. He could give insight into computational complexity that no one else can. Ed Fredkin would also have been another suggestion, but unfortunately he has passed away.
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