Lecture 2 | Modern Physics: Special Relativity (Stanford)

Рет қаралды 133,472

Stanford

Күн бұрын

Пікірлер: 50

@joabrosenberg2961 3 жыл бұрын

Classical Field Theory 8:00; Reviewing classical mechanics 11:30; Wave on a string 33:00; The Wave Equation 1:08:00

@boldsign 12 жыл бұрын

This video makes me want to go to Stanford University just to take classes from this dude!!!

@franklinenfor9592 Жыл бұрын

Wow Brilliant lectures by Leonard Susskind. The one who breaks down complicated things even to the understanding of a norvice. Wish I came across this earlier enough. Kudos prof.

@Chaos7703 16 жыл бұрын

I particularly like 1:00-1:06 where he's talking about the differences squared in positions resolve to first derivatives (velocities) and the differences of those being second derivatives (accelerations). It gave me some cool visualizations of the interactions going on.

@NeoGenus1 16 жыл бұрын

This stuff is helpful, I've only got this class 2x a week so any extra lecture I can get is just great!

@TheBobathon 14 жыл бұрын

@SuperSpinor Yes... the "stretch" is not √(Δφ²+ε²); it should be this minus the natural length of the string. To do it properly, you need to bring in a tension, T. Each spring is stretched by an amount T/k even at rest, so the natural length is (ε-T/k). The "stretch" is ε√(1+Δφ²/ε²) - ε + T/k. If you do a series expansion, drop the higher order terms in Δφ²/ε², and drop the constant term (because it doesn't affect the equation of motion), you get U=TΔφ²/2ε.

@zphuo 6 жыл бұрын

@8:00 Field theory. @1:28:00 Important about action is history!

@murtaza6642 11 жыл бұрын

love the lectures you give

@plutopulp 11 жыл бұрын

I hear you that there is always a certain part of visual memory that enters with learning and this changes from person to person. In the long run however if you really want to understand this stuff, i think you need to be able to construct it all and try it for yourself without relying too much on memory, and becoming aware of the assumptions you make when you do rely on memory is very important also i feel. It demands alot of attention though! If you're just learning to use it that's different.

@M00Nabove 12 жыл бұрын

I came across this video by watching some popular physics stuff. And I am soooooooooooo frustrated that I was so lame in physics at school and then I didn't continue in that area and now I cannot enjoy these lectures! Argh! Enjoy, you, who can. I am jealous! :D

@drb_physix 13 жыл бұрын

Professor Susskind rocks!

@TheFratmanbootcake 13 жыл бұрын

@canceodgr8 There is no mistake. He is working in units of c=1... It's what most people do when working with relativity. For example, measure time in years and distance in light years, then the speed of light is 1.

@fjolsvit 12 жыл бұрын

The constraints on the vibrating violin string are the bridge and the nut. Not the bridge and the peg.

@tnguyen318 12 жыл бұрын

How to write physics Law in Space: 1. Testing objects in space and how they move. 2. Testing Objects on the moon and writing them down. 3. Lighting up (construction lights) the entire sky (area of space) to see what it is.

@aactipo 11 жыл бұрын

well you were right..i did it for 7 and it worked..i can see the pattern now

@SKCSK792 14 жыл бұрын

Fantastic lecture

@nathanbolingo9 11 жыл бұрын

I'm looking for the demonstration of the michelson morley experiment by Einstein's relativity

@fazeelayaz941 12 жыл бұрын

thank u very much susskind ur great ur lectures are great too

@mashuharada8637 4 жыл бұрын

he is so good

@asilvescu 13 жыл бұрын

He already mentioned that he is using units where c=1. so no mistake.

@lsbrother 12 жыл бұрын

It's me - I am responsible for writing the laws in Space. I have not yet been given credit.

@binaryblade2 14 жыл бұрын

I'm curious how the principle of least action could produce a lossy wave equation.

@bartkwezelstaart9306 10 жыл бұрын

How can dx^2 + dy^2 be invariant and dt^2 - dx^2 not?

@0xpatrakar 8 жыл бұрын

someone answered that

@nicolasrodriguez9946 2 жыл бұрын

It’s the other way around

@ggankinboon 14 жыл бұрын

I want to ask that why actual time= dt-dx??? According to the Twin Paradox... the traveler will have a slower time... if it is minus...then it will have a shorter time!!!!

@williamwalker39 4 ай бұрын

The speed of light is not a constant as once thought, and this has now been proved by Electrodynamic theory and by Experiments done by many independent researchers. The results clearly show that light propagates instantaneously when it is created by a source, and reduces to approximately the speed of light in the farfield, about one wavelength from the source, and never becomes equal to exactly c. This corresponds the phase speed, group speed, and information speed. Any theory assuming the speed of light is a constant, such as Special Relativity and General Relativity are wrong, and it has implications to Quantum theories as well. So this fact about the speed of light affects all of Modern Physics. Often it is stated that Relativity has been verified by so many experiments, how can it be wrong. Well no experiment can prove a theory, and can only provide evidence that a theory is correct. But one experiment can absolutely disprove a theory, and the new speed of light experiments proving the speed of light is not a constant is such a proof. So what does it mean? Well a derivation of Relativity using instantaneous nearfield light yields Galilean Relativity. This can easily seen by inserting c=infinity into the Lorentz Transform, yielding the GalileanTransform, where time is the same in all inertial frames. So a moving object observed with instantaneous nearfield light will yield no Relativistic effects, whereas by changing the frequency of the light such that farfield light is used will observe Relativistic effects. But since time and space are real and independent of the frequency of light used to measure its effects, then one must conclude the effects of Relativity are just an optical illusion. Since General Relativity is based on Special Relativity, then it has the same problem. A better theory of Gravity is Gravitoelectromagnetism which assumes gravity can be mathematically described by 4 Maxwell equations, similar to to those of electromagnetic theory. It is well known that General Relativity reduces to Gravitoelectromagnetism for weak fields, which is all that we observe. Using this theory, analysis of an oscillating mass yields a wave equation set equal to a source term. Analysis of this equation shows that the phase speed, group speed, and information speed are instantaneous in the nearfield and reduce to the speed of light in the farfield. This theory then accounts for all the observed gravitational effects including instantaneous nearfield and the speed of light farfield. The main difference is that this theory is a field theory, and not a geometrical theory like General Relativity. Because it is a field theory, Gravity can be then be quantized as the Graviton. Lastly it should be mentioned that this research shows that the Pilot Wave interpretation of Quantum Mechanics can no longer be criticized for requiring instantaneous interaction of the pilot wave, thereby violating Relativity. It should also be noted that nearfield electromagnetic fields can be explained by quantum mechanics using the Pilot Wave interpretation of quantum mechanics and the Heisenberg uncertainty principle (HUP), where Δx and Δp are interpreted as averages, and not the uncertainty in the values as in other interpretations of quantum mechanics. So in HUP: Δx Δp = h, where Δp=mΔv, and m is an effective mass due to momentum, thus HUP becomes: Δx Δv = h/m. In the nearfield where the field is created, Δx=0, therefore Δv=infinity. In the farfield, HUP: Δx Δp = h, where p = h/λ. HUP then becomes: Δx h/λ = h, or Δx=λ. Also in the farfield HUP becomes: λmΔv=h, thus Δv=h/(mλ). Since p=h/λ, then Δv=p/m. Also since p=mc, then Δv=c. So in summary, in the nearfield Δv=infinity, and in the farfield Δv=c, where Δv is the average velocity of the photon according to Pilot Wave theory. Consequently the Pilot wave interpretation should become the preferred interpretation of Quantum Mechanics. It should also be noted that this argument can be applied to all fields, including the graviton. Hence all fields should exhibit instantaneous nearfield and speed c farfield behavior, and this can explain the non-local effects observed in quantum entangled particles. *KZbin presentation of above arguments: kzbin.info/www/bejne/qZazlX1tq7iErLM *More extensive paper for the above arguments: William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023: vixra.org/abs/2309.0145 *Electromagnetic pulse experiment paper: www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1 Dr. William Walker - PhD in physics from ETH Zurich, 1997

@lingarajpatnaik391 10 жыл бұрын

Dear Bart Kwezelstaart Your question: How can dx^2 + dy^2 be invariant and dt^2 - dx^2 not? Answer: According to the special theory, the interval “ds” is assumed to be an invariant if you go from one inertial system to another: dx^2 + dy^2 + dz^2 + (icdt^2) = ds^2 . [This is generalized from dx^2 + dy^2 + dz^2 + (icdt^2) = 0 i.e., dx^2 + dy^2 + dz^2 = dr^2 = (cdt^2) as dr/dt = c ]. Hope this clarifies. Lingaraj Patnaik

@MikeRoePhonicsMusic 12 жыл бұрын

Yeah, & I also wish his writing was cleaner. This stuff is difficult enough when typed out neatly. I'm trying to literally remember the equations as pictures in my mind, so when that 2 looks like a 1, it's hard to know for sure what I'm looking at unless I heard him say it as well. But the image stays on the whiteboard long after it is spoken. These things matter when expressing new concepts to students.

@nirdeshreddy92 13 жыл бұрын

thank u for the upload

@kendeb52 11 жыл бұрын

That doesn't bother me much, but I have wondered if he could function if you nailed his feet to the floor or took away his chocolate chip cookies and coffee :)