Richard Feynman’s Big Mistake About Einstein

[@alanbarnett6993]

I'm sure that Feynman understood the paradox and its resolution, as opposed to Maudlin, who understands the physics but doesn't seem to understand the paradox. The paradox involves the following thought experiment and the accompanying analysis. A spaceship carrying an astronaut travels to a distant star and returns, while her twin stays on Earth. First analyze the situation from a reference frame fixed to the Earth. In that reference frame, the Earth is stationary and the spacecraft is moving, so because of time dilation, the clocks on the spacecraft appear to run slower, and the twin who returns is younger. Now analyze the situation in the reference frame of the spacecraft. In this reference frame the spacecraft is stationary and the Earth is moving, so because of time dilation, the clocks on Earth appear to run slower, and the twin who stays on Earth is younger. To resolve the paradox, you have to find the error in the reasoning, not merely state that when formulated differently the paradox disappears.

[@surendranmk5306]

Only the astronaut had undergone the acceleration and gained the relativistic mass. Did you consider that?

[@brianmcdonald7233]

I was and remain confused. He asserts that there is an absolute space time structure to get out of this relative space time paradox. The twins are moving apart at the same rate simply depending on the frame of reference. Like Feynmann, this has always baffled me. If there is an absolute space time structure PLEASE explain this. Where is it located ? Can we measure all motion compared to the space/time structure AND relative motion separately. I'm sure that's thr case but no one ever explains Minkoski's the none variant space/time structure.

[@surendranmk5306]

@@brianmcdonald7233 Space time never can be invariant. It includes three fundamental quantities not two. Space, energy and time because time is inseperable from energy. Energy density of space is varying in both cases, according with gravitation and motion through space. Increase in energy density slow down time flow rate and vice versa. Nothing in this universe is at rest. Important thing is it is not possible to detect or measure uniform motion within the frame of reference where only relative measure can only possible. But we can measure exactly the acceleration in free space because it produces weight. So accelration and spin is not relative motions in free space but gravitational acceleration is not detectable directly. Earth allready have motion through space which we never can exactly calculate. Now one rocket is accellrated from the earth up to close the velocity c where it gains relativistic mass which slow down it's time flow. This happens only in the rocket no way in the earth. After it gained the maximum speed, shutting down the burning rocket it is in uniform motion now then the weight of every thing wiill disappear that we can have only mutual relative speed measurement which is unidentifiable with in our frame. Measurement is only possible during the acceleration. (Regret for my poor language)

[@rogerphelps9939]

Just use relativistic Doppler. Assume the Earh observer and the spacecraft observer have very powerful telescopes so that they can always see each oher's clocks. What they see is dependent on both the Lorentz transform and their varying separaion.Once this is done there is absolutely no paradox.

[@alanbarnett6993]

The resolution of the paradox is actually quite subtle, and involves understanding the meaning of time dilation and the applicability of the Lorentz transformation. Time dilation is usually derived from the Lorentz transformation, which in special relativity describes a coordinate transformation that is valid between two unaccelerated cartesian coordinate systems in the absence of gravity. Two obvious questions are, "unaccelerated relative to what?" and "under what circumstances are the effect of gravity small enough to be negligible?". General Relativity supplies the answers to these questions; an "unaccelerated coordinate system" is one that is in freefall, and gravity can be neglected if either 1) the gravitational field is weak enough, or 2) the coordinate systems are restricted to a region of space over which the gravitational field doesn't vary substantially. At some level, the resolution of the twin paradox is that Lorentz transformations are not valid since neither coordinate system is freefalling; the spacecraft is obviously accelerating, and the observer on the surface of the earth is not in freefall either due to the electro-magnetic force exerted by the surface of the Earth. But is one twin biologically younger than the other, and if so, which one? To answer this question, we can analyze the problem in a reference frame at rest with respect to the sun. Since non-gravitational forces on the sun are small, this is an excellent approximation of a free-falling system. With respect to this coordinate system, the time dilation in the frame of reference attached to the twin who stayed on Earth is negligibly small, while the time dilation in the reference frame attached to the twin in the spacecraft can be substantial, so we conclude that the twin who took the space journey will be younger. This is not a completely satisfactory resolution of the paradox. We have basically analyzed the system in a frame of reference attached to the twin on Earth. A completely satisfactory resolution of the paradox would be to also analyze the problem in a frame of reference attached to the spacecraft. Since Special Relativity isn't valid in that reference frame, this involves the study of arbitrary coordinate transformations, which will lead us to the Principle of General Covariance and is essential in the derivation Einstein's gravitational field equations. We first have to define an (accelerated) coordinate system attached to the twin in the spacecraft and computing the elapsed time on Earth in that coordinate system. Defining such a coordinate system is not trivial, but since proper time is invariant under a general coordinate transformation, we know we will get the same answer. Problems in physics in general are much easier to solve if you choose the appropriate coordinate system

[@bozo5632]

I'm pretty sure he's mischaracterizing what Feynman actually said.

[@zemm9003]

I dunno. Feynman did say a lot of nonsense. Also I never respected him for not clearing out that the sum of paths approach comes from Dirac and he barely changed anything about it.

[@KipIngram]

Part of why people get confused about this is because a path that results in a smaller amount of proper time (that the inertial observer) will necessarily involve acceleration. There will BE acceleration. But as Dr. Maudlin points out, it's not the "root cause" of the result. As he notes, one can adjust the experiment so that the Earth twin has a motion profile that can have the same overall acceleration content as the traveling twin (just "arranged" in a different way in time), and will still wind up older. The acceleration alone is just not enough to yield the result.

[@alexgoldhaber1786]

Feynman is still right. Acceleration in this particular example is the reason. Let's just say the observer taking the geodesic is the one with most time. The accelerating observer is going on a non-geodesic path.

[@jayantamajumder9014]

Prof Maudlin is spot on, IMHO. The presence of an absolute time is inescapable, and what we measure as time (i.e. the chronometric mechanism) is impacted by motion. The odometer analogy runs counter to intuition since in relativity the "longer" path accrues a lower measurement, a better analogy is a device that must juggle between spatial movement and measured-time accrual - so that the more it does the former, the less it gets to do the latter.

[@dansantos3027]

I think Tim Maudlin mischaracterized Einstein twin paradox by saying that the paradox is the same thing as describing the difference between vector quantity and scalar quantity. If a car has to travel straight from point A to point B, then that's a vector quantity; but if a car has to curve around a straight line between the same point A and point B, then that's a scalar quantity, because a curved path is longer than a straight line between point A and point B. Einstein twin paradox is a lot more complicated than that.

[@ozzy6162]

I'm more confused than ever - thank you Tim.

[@sistajoseph]

In mathematics there is an established principle called the least action. This is supposed to be a physical principle, not quite certain at this point about its physics. There is also a maximum action principle. It was proposed in, A Short Treatise on the Space Time Continuum by Piankh- 2020. Let us apply it to clocks. A clock is a time-keeping machine, that means it is doing something, carrying out an action. If it is then forced to carry out some extra action, the time keeping slows down. This is obvious and we experience this all the time on our computers. Why is it a puzzle. Take note, in this experiment, time does not slow down, the clocks slow down. Time itself, is a different debate.

[@guyejumz6936]

I agree that the approach of explaining time dilation by integrating along the spacetime interval is the best way to explain it; and of course, the twin paradox isn't a paradox; it's simply that the result of such integrations are not independent of path (but why would they be, anyway?) The analogy with length intervals in ordinary geometric space is also good, but I have some reservation about using the term "Euclidean" to describe the definite-ness of the metric space, because Euclidean can also refer to flat curvature, and curvature is not at play in this case (Minkowski space is also flat.) This imprecision can create a lot of confusion. However, the statement about acceleration regarding twin A and B, while it's not the best explanation of spacetime, is still technically correct, since an unaccelerated frame of reference will always span the greatest spacetime interval between two events.

[@matsogren7143]

Without a reference to Feynman's discussion of the so-called twin paradox, it is hard to judge whether he made a mistake or not, but I think that it is very unlikely that he did. As the difference between the twins is that one of them changes velocity with respect to an inertial system and the other does not, it is correct to say that the difference is due to the fact that one twin accelerates and the other does not. Still, that does not really explain anything. However, the narrator of this video does not really explain anything either. He does not even address the "paradox", which is that both twins observe that the other twin's clocks are slower than his own. In order to understand the twin "paradox" (and some other relativistic "paradoxes") one has to consider the role played by the relativity of simultaneity. In this case, the heart of the matter can illustrated by a thought experiment where a single clock at rest in one inertial system moves with constant velocity between two synchronized clocks at rest in another inertial system. Then, the relativity of simultaneity ensures that observers in both systems agree that the single clock will measure a shorter elapsed time between the passages than that measured by the two synchronized clocks. (and agree on how much shorter). Thus we have asymmetric situation. We use two clocks in one inertial system, and one clock in the other. This is the core asymmetry between the twins. Thus, when a rocket accelerates from earth towards a distant star, an observer on the rocket will find that an earth synchronized clock at that star will rush forward in time, because the change in velocity makes the event that a clock on earth shows a certain time simultaneous to the event that the distant clock shows a later time, according to his notion of simultaneity. The observed time difference is proportional to both the distance between the clocks and the relative speed of the rocket with respect the earth and star. Thus, even though the observer on the rocket observes that the clock at the distant star ticks slower than his own clock, the clock at the distant star has, so to speak, got a head start that more than makes up for this. The relations between the relativity of simultaneity, time dilation, and length contraction are directly expressed in the Lorentz transformations and thus belong to core of special relativity.

[@Benjamin-The-Great]

What he describes as an additional problem from Feynman is the Twin Paradox itself. The paradox refers to the question of which twin aged given relative motion. It pre-dates Feynman. It was written about and resolved before Feynman was born. I'm confident Richard knew the resolution to the paradox, though perhaps he brought it up somewhere to help teach students.

[@stevenlloyd3899]

I believe Maudlin is incorrect & Feynman's explanation of the Twin paradox is correct due to acceleration that has been proven in far simpler experiments on earth & fast moving rockets with a synchronized clock in space as measured against earth bound clocks .. There is no getting around time dilation with velocity & the relative observer as opposed to the high speed object in comparison .... I admire a lot of philosophers in the realm of "thought experiments " , but I strongly believe Roger Penrose, Brain Greene & other contemporary physicists would side with Richard Feynman on this matter

[@JoshZeidner-j7g]

What was the mistake it's never explained

[@davidrandell2224]

SR wrong due to reference frame mixing and bad math. GR follows as incorrect. Physics- pukka- started in 2002. “The Final Theory: Rethinking Our Scientific Legacy “, Mark McCutcheon for proper physics including the CAUSE of gravity, electricity, magnetism, light and well..... everything. So,no.

[@quinnbremes621]

How can anyone sit on that couch?

[@mitchkahle314]

Very good explanation, Tim. Mahalo!

[@Viktor-i8g]

Time is just a mathematical ratio between the number of material changes in one system and the number of changes in another. In other words, the past doesn't exist cuz it passed. The future doesn't exist cuz it hasn't come in yet. And what is the present? Just a border point between the past and the future. The point is immaterial. It has no length, no width, no height. It is just an indication. A point. So the present is an immaterial border point. The present doesnt exist as we see it. It' just a point that moves ahead together with changes in, for example, us. So the theory of twins is just a bull. Independentely from their positions in space the changes in their bodies go with the same speed and he who had been in the rocket and returned to his brother would be the same age and looking completely as his bro does. Later we will speak about space, space time and the shitty fourth dimension that doesn't exist to understand that uncle Albert was a complete dork who was utterly bad at geometry😊

[@davidrennie8197]

He's not a physicist, he specialises in philoso-babble

[@voltydequa845]

Wow! Take the model of Flying Donkeys Circus, then present opposing interpretations of donkey's flight-time supposed difference paradox, and the gullible taking sides will implicitly absorb the utter nonsense premises as de-facto (given-for-granted) axioms. Not being that naive to bait into ever-shifting sophistry changing focus around math garb crumbs, much like circus-jugglers, we go for a model implementation. We almost all know that Newton's model is implementable and is implemented - be it on big scale, or be it on small limited-domain scale (engineering simulations), reality simulation. Let these sophistry tricksters implement a virtual world based on relativity postulates. They never did, and never will do, for the very simple reason that whatever implementation requires axiomatic coherence and self-consistency, while the SR is based on sophistry boxed inside some math garb. But Erhardt should already know that, since just a type & structure skeleton symbolic logic skeleton is more than enough to see that things do not add up. Tesla's on relativity were too polite. He said something like " people ... do not see the underlying errors", using the euphemistic "errors" instead of spade-for-spade "sophistry" or "utter nonsense". Promotion of nonsense resorting to conformism. And some dare to say that ignorant that have common sense are inferior to educated parrots that lack common sense. Seems like a test to recognize humans immune to Invasion Of The Relativistic Mind Snatchers.

[@aaabbb-ff1sp]

tokkok singsong

[@gorgig9136]

Richard Feynman was genius, this discusion is fake,

[@cookiecrumbles2948]

Who is this he you’re whining about?

[@RichardPepperman-kk9yb]

Your explanations are at times unnecessarily abstract. Then followed by a dizzying explanation because you cannot offer an understandable one. First and foremost you are mostly there to indicate that you're superior to Richard Feynman. I would laugh, but your host appears dead. Has anyone checked him lately?