# Relativity and simple algebra II

Discussion in 'Alternative Theories' started by ralfcis, Feb 6, 2021.

1. ### Neddy BateValued Senior Member

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2,332
It seems you still can't wrap your head around the triangular shape. We assume from the beginning that in the reference frame of the light-clock, the light pulse travels up and down, hitting the mirrors over and over, like this || for lack of better graphics.

Now, considering a different reference frame that is moving horizontally with respect to that very same light clock, (like you are driving past it at constant speed in your car). If you naively think the light still travels a vertical path like this || then the light pulse will miss the mirror, because in your car reference frame the mirror moves to the right by the time the light arrives there. So, as he indicates in the video, we know that vertical path || cannot be correct, because then you have created a contradiction. Think about it, if a light clock is working perfectly in its own reference frame, and you drive past it in your car, it must continue function properly. So we know the light pulse cannot miss the mirror, and the path must be something like this /\/\/\/\ obviously.

This should be as easy to understand as if you dropped a ball on a uniformly moving train. You would say the ball drops straight down, and bounces back up, like this ||. But someone watching from the train station would say that the ball also has motion in the direction the train is moving, so the path is more like this \/\/\/\/ (although there would actually be a parabolic shape in that case, due to gravity causing the ball to accelerate, rather than move at a constant speed as the light pulse does. I hope this helps, even if I am not on your list of approved posters.

Last edited: May 9, 2021

3. ### ralfcisRegistered Senior Member

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Wow I can't believe you think I'm stuck at this simple part. Can you not read my posts at all? Can you not see my Md's? Surely there's someone on here besides Queerus' sock puppet who understands some SR. I'm not going to engage with you Neddy at all, ever. Ok maybe if you have something interesting to say that I haven't already said.

Did I not write this in post 408 and you're acting like you're informing me of something I didn't already know?
"What relativistic phenomenon causes the light to bounce off the top and bottom plates at an angle? Greene suggests it must be so due to the principle of relativity, that if the photon is hitting the plates in the stationary reference frame, it must also hit them in every other frame. Since the mirrors are moving from the stationary perspective, the light has to leave one plate at an angle to meet up with the other one. Sure but how does this principle enact this physically? Greene suggests the photon acts like a ping pong ball when he knows that the speed of light can't be altered by the speed of the source like a ping pong ball being hit sideways by a racket. I've seen other explanations that length contraction affects the angles of the flat mirrors. There is no physical angle, it's all due to relativity of simultaneity. The position and time the photon hits the plates differs from each perspective. The speed of c remaining constant is dependent on length contraction and time dilation working together. He never mentions any length contraction in his derivation and he proves time dilation by assuming time dilation."

Remember when you arrogantly stated the angle theta was due to the aberration of light and then provided no math to support that. My math showed where theta came from but you probably didn't read that either.

Last edited: May 9, 2021

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7. ### ralfcisRegistered Senior Member

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I thought you said there was no comedy on this comedy show. Is that Qreeus's sock puppet?

8. ### Michael 345New year. PRESENT is 72 years oldlValued Senior Member

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I try to put some in

I can name it such but prefer to keep generic to use in other situations

9. ### Q-reeusBannedValued Senior Member

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Forcing me to respond to a stupid and wrong guess. I NEVER resort to sock-puppetry and despise those that do. ENOUGH.

river likes this.
10. ### ralfcisRegistered Senior Member

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My apologies to Q-reeus.

river and Q-reeus like this.
11. ### originHeading towards oblivionValued Senior Member

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It doesn't bounce at an angle off the plate. Do you not realize the frame is moving? The ball of light in the moving frame is always directly above the center of the plate, it is not moving at an angle to either plate. This is pretty basic to the whole analysis.

12. ### ralfcisRegistered Senior Member

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That's right. Thank you. I definitely missed that. There is no angle between the light and the plate.

13. ### SsssssssRegistered Senior Member

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That would be a very good idea. You should also try to do the exercises, and then you could find out if you really understand relativity.
Look: I already pointed out that your interpretation of what he said is stupid. Or do you have an answer to "is six feet equal to thirty miles per hour"? Either I'm a competent physicist and Greene is a competent physicist and you should listen to my clarifications of what's basically a decent video let down by a little laziness, or we're both idiots and you should ignore us. You can't have it both ways.
Not really. I've read your posts before and I can see the way you treat Neddy Bate and Q-reeus, both of whom appear to understand this a whole lot better than you do. Your problem is that you want someone competent to talk to but you also want them to agree that you're right and you understand relativity better than anyone else. So I already know you're going to ignore everything I have to say. I only asked who were the other 2.5 people to see if perhaps you'd actually taken on board some of what I've said before, in which case it might be worth trying again. Apparently not. Apparently I'm going to try anyway.
Um... no.
You don't need to care at this point. All Greene is developing is relativistic kinematics. Basic sanity requires that the light come off the mirror at an angle in the moving frame. Greene just works out the implications of this, assuming that the speed of light is $c$ in all frames. The result is time dilation.

The detailed mechanism requires Maxwell's equations, but in short the light induces currents in the surface of the mirror and the electric and magnetic field of those currents is the reflected light. Roughly speaking. In the stationary frame the electrons move back and forth, but in the moving frame they move in a zigzag because as they move back and forth they move sideways along with the mirror. Back and forth currents induce vertical radiation, zigzag currents induce diagonal radiation.
The speed of light is not altered. Its direction is different in the two frames - aberration, as Neddy Bate already told you.
He does not. He derives time dilation assuming consistency between the frames (what I called basic sanity above) and the invariance of the speed of light.
How are you drawing Minkowski diagrams without assuming the Lorentz transforms and all that goes with them, including the relativistic aberration phenomenon you claim to be deriving?
It does bounce at an angle in the moving frame, exactly the angle necessary so that the horizontal component of its velocity is equal to the velocity of the mirror and it remains between the mirrors. That angle is Greene's $\theta$, and obviously it must satisfy $c\cos\theta=v$ (the bit ralfcis thinks means that lengths are velocities).

14. ### ralfcisRegistered Senior Member

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I appreciate the help and realize I have a long way to go. I'll devote as much time as I can to this. You can't be hyksos. I've spent less time talking to hyksos than I did with Don Lincoln and that was maybe 3 posts.

15. ### originHeading towards oblivionValued Senior Member

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I never said it didn't.

16. ### ralfcisRegistered Senior Member

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What?????? Now I can't read. Please tell me what you meant there because I was sold hook line and sinker. I remember having a lengthy discussion with phyti on the relativistic law of reflection on my old forum. He believes length contraction is a real physical phenomenon where atoms actually contract in the direction of motion. Now if I don't accept length contraction as real then I can't accept time dilation is real and I can't accept that that light is absorbed by atoms and then reflected at a real angle on moving plates because I'd have to deny the principle of relativity to do so. In my Md, I have two separate identical light clocks. You don't know which one is actually moving because they are engaged in relative motion. The light is bouncing straight up and down in both. The apparent angle is due to one frame's perspective of the other, not some real phenomenon induced by relative velocity. This is the crux of my apparent problem in understanding SR. I don't see perspective as reality even though it's measurable. I don't even see the reality of electricity being expressed as magnetism in a moving frame as being due to length contraction but can be equally explained as due to a perspective of time dilation. This is the battleground with me. Fix this and all these other misconceptions on my part will just melt away and we won't need to argue each one separately.

17. ### ralfcisRegistered Senior Member

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If you've read my posts you'd see my agenda is learning the truth, I have dropped my ideas many times when they are faced by the truth (usually the truth arises from the math itself). Experts have answers to questions they've seen a hundred times before but they don't recognize mine are not those questions and try to shoehorn me with answers that are not relevant. That's frustrating because I wonder why they can't understand what I'm saying.
Yes six feet equals 30 miles per hour in .0000378 hours.
Great explanation but you've just moved the light clock down to the electron level. It's still the same problem of where the zig zag angle comes from when in each frame there is no zig zag angle. It only exists as a perception from one frame to another as Origin didn't apparently say.
Ok I do need to study aberration as I have no idea about it.
Are they wrong? As I explained, they do not contain length contraction. The x'-axis is replaced by the lines of perspective simultaneity. I replace v and c with Yv and Yc which is the Brehme concept of your proper space in my "moving" time. Relativity of simultaneity is used instead of length contraction/time dilation and the Loedel half-speed perspective allows me to deal in a pseudo proper time and proper space which doesn't need perspective time dilation or length contraction. Everything was going just fine until my last Md which had the hiccup of length contraction showing up between the plates. You gave an answer to why this is happening but I have not yet understood it.

Last edited: May 11, 2021
18. ### ralfcisRegistered Senior Member

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I'm not a religious man, I don't bend over to the edicts of any higher authority.

19. ### SsssssssRegistered Senior Member

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Then I guess I don't understand what you meant by what you posted.
That isn't a problem understanding SR, that's a problem understanding any physics at all. This kind of observation goes all the way back to Galileo.
That's not what's happening. What's happening is that you talk some nonsense based on a failure to understand Newtonian physics, not even relativity, and start arguing with people who try to help you instead of thinking about what they are telling you.
In other words, a velocity is not a distance and equating them is idiotic. This will go a lot quicker if you just admit when you're wrong instead of trying to finesse your way into thinking that you were really right, which is what you're doing by multiplying the velocity by a time as if that were some kind of counter argument to velocities not being distances.
I thought your problem was with understanding how light reflects off a moving mirror, but it is much more fundamental. Of course the path is a zigzag in one frame. Neddy Bate explained why in #501 and Greene even drew it out in the video: if the pulse is to remain between the mirrors and the mirrors are moving laterally then the pulse must also be moving laterally. Steady lateral motion plus a repeating up and down motion is a zigzag. Trying to claim that this zigzag is "just a perception" but the straight up and down motion in the mirror rest frame is not "just a perception" is the same as claiming that the principle of relativity is grossly wrong. You will not get anywhere attempting to understand any physics if you want to claim that.
No idea. I haven't looked. But if you are drawing them correctly then you are assuming special relativity is correct and hence that the principle of relativity is correct and the zigzag motion of the light is just as real as the straight up and down motion. If you deny all those assumptions and implications while drawing correct Minkowski diagrams then you are contradicting yourself. If you are drawing them wrong, you are drawing them wrong.

The rest of that paragraph reads like nonsense to me. You are, at the very least, misusing the term "proper time". Even if you have somehow done things correctly and are just explaining it badly you haven't got rid of length contraction or time dilation. You've just disguised it, and as a side effect forced Alice and Bob to use non-orthogonal coordinate systems. That requires them to use most of the machinery of general relativity if they want to do something as simple as measure up for a carpet.

20. ### ralfcisRegistered Senior Member

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I'll say whatever you want me to say. I was so stupid for assuming Greene was serious about equating distance with velocity when anyone else would know it was just carelessness on his part for saying it. There, can we move on to more important things now?

21. ### originHeading towards oblivionValued Senior Member

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I said this:
Ss said this:
And I of course said this:
The point is does the ball of light move at an angle when viewed from a stationary frame? Of course it does.
But the question by ralfcis was, "What relativistic phenomenon causes the light to bounce off the top and bottom plates at an angle?" I was simply saying the light does not bounce off the mirrors at an angle. Draw a line from the ball of light to the top or bottom mirror at any time from either frame and the line will be straight up and down, no angle. Does the ball of light move at an angle when viewed from the stationary frame, absolutely, does the ball of light hit or leave the mirror at an angle? No.

22. ### phytiRegistered Senior Member

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Ralf;

I was following this to see if your attitude has changed. Maybe a little, but not enough.

The teacher-student relation is supposed to transfer knowledge from the teacher to the student. How can the student know if the knowledge is truthful. He can't, unless he applies the things learned and gets similar results.

Rule 1. The truth of a statement is in the statement, not who states it.
Eg. The sum of interior angles of a triangle are 360°, but not because Euclid said so.
(If he didn't say it, someone else would have.)
When Brian Greene talks about 'moving through time', that's poetic license, a metaphor not to be taken literally. The source of that idea originated with Minkowski, when he generalized the coordinates, making time a 4th dimension. Making 'time' another line on paper, thus removing its identity, is similar to removing gender by classifying male and female as people, i.e. more abstraction. Greene's metaphor allows students to interpret the space-time graphics as you would a road map, when in reality all motion occurs horizontally on the x axis. Any line extending upward at any angle is a history of positions, thus not something that can be observed in its entirety at one time.

Anyone indoctrinated into Minkowski Relativity is required to think in terms of 4-vectors, which do have an advantage in terms of mathematical efficiency. That does not eliminate the use of algebra for typical space and time problems.

As an 'old school' student, it seems explaining the behavior of the physical world in terms of physical processes has been replaced with an explanation in terms of the abstract representations of the theory.

So what's new, and how is your health?

23. ### ralfcisRegistered Senior Member

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All my formal knowledge comes from those Greene videos and while I reject most of what he says, that part about the faster you are observed to move through space, the slower you are observed moving through time, I almost totally accept except since I don't believe length contraction has a form of persistent reality like permanent time difference due to the twin paradox, then I don't believe time dilation is time itself slowing but a difference of the relativity of simultaneity when the start and end of events are timed. This latest hiccup where my math shows the distance of the vertical plates in the light clock is subject to perspective length contraction is the first indication I've seen where my ideas go wrong. I want to explore that because the extent of my wrongness might go all the way back to rejecting length contraction as real. My attitude is not to accept and believe in the edicts of higher authority but to be shown reasonable arguments of where my math goes wrong. Is that really so unreasonable to expect or an indication of a bad attitude? SR has had 116 yrs to sharpen its teaching game yet for almost everything I object to from Greene I get excuses that he wasn't feeling well that day so don't take him literally.

Oh yeah, my dad died of Covid at the end of 2020, I got a heart attack a week later which seems to make me tired, my mom seems to have contracted dementia from her bout with Covid and made me quit my first job in over 3 yrs to take full time care of her but then changed her mind. I decided to devote all my time to making the house liveable for her anyway. Other than that I'm just peachy.

Last edited: May 12, 2021