Anybody want to listen to Richard Feynman for 9 hours explaining the laws of nature? Guessed so!

I’ve found very rare Richard Feynman’s lectures on Physics for all physicists and amateurs!

The following are a collection of rare lectures by the man himself (MP3 Sound):
V1 Ch07 Theory Of Gravitation – 51:42 (20.4 MB)
V1 Ch08 Motion – 53:46 (23.3 MB)
V1 Ch09 Newton’s Laws of Dynamics – 54:42 (23.9 MB)
V1 Ch10 Conservation of Momentum – 53:44 (23.4 MB)
V1 Ch11 Vectors – 52:41 (23.2 MB)
V1 Ch12 Characteristics of Force – 59:36 (26.1 MB)
V1 Ch13 Work and Potential Energy 1 – 55:45 (24.4 MB)
V1 Ch14 Work and Potential Energy 2 – 52:15 (22.8 MB)
V1 Ch15 Special Theory of Relativity – 50:00 ( (25.6 MB)
V1 Ch16 Relativistic Energy And Momentum – 54:57 (24.7 MB)

You can download all from RapidShare for free. The lectures are stored in RAR files, and can easily be unpacked using the free tool 7-Zip (for Windows and Linux):

RapidShare – Feynman Lectures 7-9.rar (66.2 MB)
RapidShare – Feynman Lectures 10-12.rar (71.3 MB)
RapidShare – Feynman Lectures 13-15.rar (71.6 MB)
RapidShare – Feynman Lectures 16.rar (24.3 MB)

Each of the first three RAR files has three lectures in them, and the last one has lecture 16 alone.

Enjoy!

“I agree that photons don’t accelerate LOCALLY. But at cosmological distances, their travel speed relative to both the observer and emitter MUST change. Otherwise, how could distant galaxies have been receding at superluminal velocities at the time of emission, yet the photons approach us at exactly c today?”

You grasp the math better than me, but I think you have got trapped in the same “logical confusion” as me. It’s probably “over bold” for an amateur like to tell you how to think, but after debating this topic over the last weeks, the logic finally make sense:

* We cannot visually see anything that has moved toward us at superluminal speed, including redshift or photons.

* We can calculate, using comoving distance and cosmological time, that the objects that emitted light towards us 700 million years after the big bang, *NOW* should be accelerating at superluminal speeds, at physical distances further than 13,7 light years. BUT please observe – we cannot physically see these objects *NOW*.

Take a good look at this picture of the embedded Lambda-CDM geometry

The brown line on the diagram is the worldline of the Earth (or, at earlier times, of the matter which condensed to form the Earth). The yellow line is the worldline of the most distant known quasar. The red line is the path of a light beam emitted by the quasar about 13 billion years ago and reaching the Earth in the present day. The orange line shows the present-day distance between the quasar and the Earth, about 28 billion light years.

Here is very basic and helping information from good old Wikipedia – Understanding the expansion of space

Speedy

> “Sigh – this is a coordinate dependent quantity and so there is no single “correct” answer.”

So much sighing and groaning… I feel like the foolish Kung Fu Grasshopper at the knee of the great master.

I have agreed that there are an infinite number of coordinate systems which yield an infinite number of different perspectives. BUT, I think there is at least one coordinate system in which the relationships I proposed might be correct.

What’s important here is not the *absolute* values of distance, speed and acceleration, it’s the relationship of relative values as a function of time and density as perceived in the distinct frames of the emitter and observer. Surely one or both of those frames has some special logical relevance to the issue of observed redshift.

Geraint, your papers refer frequently to superluminal recession velocities, which you say are inevitable and open ended at large distances in both the FLRW and conformally Minkowski metrics. You also apply Gauss’ Law in your radar ranging paper in the same manner I do, and you specifically apply it to round-trip velocities in your two selected coordinate systems. You also specifically state that redshift is a result of a discrete transformation at the observer’s frame rather than an accumulation of infintesimal redshifts en route. The terminology I’m using and the points I’m trying to make are similar to those in your papers, although the particular redshift mechanism is original.

Why not address my specific questions and ideas rather than reciting broad mantras: “There are no absolutes my son … everything is relative… ”

Jon

Lawrence B. Crowell

Sigh – this is a coordinate dependent quantity and so there is no single “correct” answer.

> “Again something is amiss. SNI data tells us that the recessional velocities of galaxies in increasing, not decreasing.”

Dark energy is causing recessional velocities to increase in late times (e.g., since about 7Gy), but it will be many Gy before the are as fast as they were shortly after the inflation era ended. Gravity caused recession speeds to slow dramatically during the first 7 Gy before they turned around and started increasing again.

> “Photons don’t accelerate! Null geodesics might be curved and the photon red or blue shifted, but there is no acceleration of a photon.”

I agree that photons don’t accelerate LOCALLY. But at cosmological distances, their travel speed relative to both the observer and emitter MUST change. Otherwise, how could distant galaxies have been receding at superluminal velocities at the time of emission, yet the photons approach us at exactly c today?

GR terminology such as “spacetime curvature” is all well and good, but we should not slavishly constrain ourselves to use terminology which obscures the fact that something real and tangible is occuring out there. Terminology is here to help us communicate, not to get in the way. When I talk about photons accelerating, I am simply referring to the distance they relocate over some elapsed period of time, as measured from a particular frame of reference. Let’s focus on the substance rather than the terminology.

Jon

Well I can’t say the absorber theory is definitely wrong, but I think it is a fundamental principle of the scientific method that all possible approaches should be exhausted that rely on close-to-conventional physics before radically exotic “new” physics is accepted. Time travel is just inherently too radical, and is not used in any other mainstream physics theory. And the concept of time travel is known to have many theoretical impediments. For example, both the emitter and receiver will move substantial distances during the wave travel period. I don’t see how there’s anything in the theory to accomodate that spatial relocation angles between the past, present and future.

In my humble opinion the closer a cosmology theory is to purely kinematic (with GR gravity of course) the more likely it is to be correct.

Jon

Why do you think your “common sense” in anyway is a good predictor of the way the universe works?

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Again something is amiss. SNI data tells us that the recessional velocities of galaxies in increasing, not decreasing.

Lawrence B. Crowell

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Photons don’t accelerate! Null geodesics might be curved and the photon red or blue shifted, but there is no acceleration of a photon.

Lawrence B. Crowell

I submit that, rather than applying Gauss’ Law to a cosmic sphere centered on EITHER the observer or emitter, it should be applied to BOTH such cosmic spheres, at every point along its path, and then netted, to yield a combined “forward and backward” figure for gravitational influence at each point. This set of effects can then be integrated to calculate the geodesic across the entire path.

Intuitively, early in the photon’s travel the gravity of the sphere centered on the observer will dominate, because the radius of that sphere is enormously larger, and during this historical epoch the cosmic mass/energy density is also relatively very high. So the initial acceleration toward the observer (which causes blueshift) is very high. Late in the photon’s travel the sphere centered on the emitter will now dominate, because the radius of that sphere is enormously larger. So the net effect of cosmic gravity will be to decelerate the photon. However, this deceleration will be milder than the early acceleration, even though the sphere’s radius is larger, because the cosmic density has decreased by much more proportionally than the propoprtion by which the late observer sphere’s radius exceeds the early emitter sphere’s radius.

The math remains to be done, but I am encouraged by the logic. I believe that the cosmic gravity field MUST provide the sole explanation for the photon’s early acceleration and late deceleration. In the absence of accumulated SR time dilation (which seems to be ruled out by the FLRW metric), the photon can’t self-accelerate just because it is “required to” in order to pass every galaxy at exactly 1c.

Jon

>”These calculations of the comoving velocity for z =~ 1100 by Jon strike me as off the mark. Given the Hubble rule (FRW cosmology etc) that

1 + z = exp(v/c)

and for z = 1100 indicates that v/c = ln(1100) = 7, or an apparent velocity of 7c. Things are not moving nearly as fast as is being presumed here.”

I believe you are looking at the instantaneous recession velocity of the EMITTER as measured in the OBSERVER’S (Earth’s) frame of reference. According to my spreadsheet and the Wright and Morgan online cosmic calculators, an emission source at z=1089 had a recession velocity of 56.6c then and 3.3c now, as measured in the observer’s frame of reference. Not sure why your equation calculates a different number.

The figure I gave of 1048c is measuring something quite different: the average TRAVEL SPEED of a PHOTON during the SEGMENT of its trip between z=1023 and z=511, as measured in the EMITTER’S frame of reference.

Jon

“This theory says that when you push on something, it creates a disturbance in the gravitational field that propagates outward into the future. Out there in the distant future the disturbance interacts with chiefly the distant matter in the universe. It wiggles. When it wiggles it sends a gravitational disturbance backward in time (a so-called “advanced” wave). The effect of all of these “advanced” disturbances propagating backward in time is to create the inertial reaction force you experience at the instant you start to push (and cancel the advanced wave that would otherwise be created by you pushing on the object).”

This travel back and forward in time is right up there with string theory and colliding branes on the wacky scale. I understand that a lot of brilliant people contributed to these theories, and the math really does work. But there is no guarantee that a theory supported by valid math is itself physically valid. I like many people think we need to apply more common sense to evaluating these far out theories.

Jon

Geraint, thanks and of course you are absolutely right. Those last posts from me only prove what a complete nutcase I am in physics!

I have to explain something though (to save my face ). English in not my native language and I’m not a physicist, so if everyday talks runs pretty okay, I’m completely lost in space when pros start talking about “null geodesics” and “gauge condition” etc, and I have to run thru half the Internet before I get the picture. And then add “hieroglyphic” equations to that and you got the picture of a totally confused amateur very late at night!

Lawrence B. Crowell is of course also absolutely right when saying; “People should maybe exercise the discipline to use that marvelous multi-media machine we have had from our evolutionary roots.”

Law No. 1: There is only one way to learn – use your brain.

Sorry guys, I’ve been rambling on too much about “it must be something wrong”, and I take it back.

Have a read of the Wheeler-Feyman absorber theory (or transaction theory).

Speedy – that’s really no different to what we’ve been saying.

Universal Expansion
The expansion of the universe causes distant galaxies to recede from us faster than the speed of light, if comoving distance and cosmological time are used to calculate the speeds of these galaxies. However, in general relativity, velocity is a local notion, so velocity calculated using comoving coordinates does not have any simple relation to velocity calculated locally. Rules that apply to relative velocities in special relativity, such as the rule that relative velocities cannot increase past the speed of light, do not apply to relative velocities in comoving coordinates, which are often described in terms of the “expansion of space” between galaxies. This expansion rate is thought to have been at its peak during the inflationary epoch thought to have occurred in a tiny fraction of the second after the Big Bang (models suggest the period would have been from around 10^-36 seconds after the Big Bang to around 10^-33 seconds), when the universe may have rapidly expanded by a factor of around 10^20 – 10^30.

Astronomical Observations
Apparent superluminal motion is observed in many radio galaxies, blazars, quasars and recently also in microquasars. The effect was predicted before it was observed by Martin Rees and can be explained as an optical illusion caused by the object partly moving in the direction of the observer, when the speed calculations assume it does not. The phenomenon does not contradict the theory of special relativity. Interestingly, corrected calculations show these objects have velocities close to the speed of light (relative to our reference frame). They are the first examples of large amounts of mass moving at close to the speed of light. Earth-bound laboratories have only been able to accelerate small numbers of elementary particles to such speeds.

From Wikipedia

This of course doesn’t deal with redshift, as this webpage do.