Oh my! What a bargain!So we've traded Write4U for Ralf, evidently.
Oh my! What a bargain!So we've traded Write4U for Ralf, evidently.
Thing about discussion fora is that you can't willy-nilly go back and correct things people have already responded to - for obvious reasons. (I say "Yay for Science!" and then you respond with "I agree" and then I change my post to say "Yay for Nazis!")...the greatest failing of this forum is you can't go back and correct mistakes in past posts because they don't trust the users enough to be honest. That's what I miss about my previous forum which was the only one that allowed unlimited corrections.
It's not broken. Your old forum was.It's ridiculous. Don't bother to reply, just fix it or not please.
Thanks, ralfcis.Ok so I'm going to finish off my last post before I tackle the questions which are legit and am grateful James R took the time to ask them.
Something is wrong, then. It doesn't matter who is measuring the speed of light. They should always measure it to be c, in any reference frame. If you think Alice is measuring the speed as 1.25c, then you've made a mistake somewhere - on your diagram, in your calculations, or maybe in both.The results of my last Md are shocking to anyone who thinks they know relativity.
The pink light signal, from Bob's perspective using his own clock, takes 3 yrs to travel 3 ly but if he was going according to a simulation of Alice's watch it would be 3ly in 2.4yrs.
You've got a different speed of light there for Alice, again. This time it is 2c. Again, without spending more time trying to track it down, I don't know where your error is, but there's no doubt there's an error. Alice's speeds of light are not even consistent in two different calculations you have made, let alone consistent with special relativity.From Alice's perspective, using her watch and her star charts (which were drawn on Earth using various techniques like the parallax view to measure distances), her thin red line of perspective simultaneity points to the signal starting at 2.5 yrs her time and ending 1.5 of her yrs later. So the pink light signal travelled 3 ly in 1.5 of her yrs. If she used Bob's simulated time, it would be 3 ly in 3 Bob yrs. I'm not including how length contraction handles this because in this math, I don't need it to.
I don't know what you mean by "proper years". A time interval for a light signal cannot be a "proper" time, because a proper time is, by definition, the time measured between two events that happen at the same location in space (in a particular reference frame). Light is always travelling, so the sending and receipt of a light signal never happens at a single location, in any frame of reference.But I've introduced a new perspective, the Loedel perspective that allows one to peer into proper time without the hysteresis of other perspectives. From that perspective, Alice and Bob both agree the 3ly were travelled in 2 proper years.
Yes! See above.But, but, those unfamiliar with what the true meaning of "c being the speed limit from all perspectives" would complain that my perspectives involve super-luminal speeds and they're all different values..
What's "perspective"?They confuse the clocks you use with perspective.
I don't know what you mean by "the relative velocity to c".They also confuse an absolute velocity c with the relative velocity to c.
What is this "gamma velocity", physically? Your use of v' and v is reminiscent of a transformation between two different reference frames, but velocities don't transform that way between frames, as you know.If I choose to say Alice's gamma velocity v'=Yv...
You seem to be saying that Alice is travelling faster than light, in some frame. Relativity doesn't allow that.This can't mean light doesn't beat her to her destination using her clock (and relativity of simultaneity of when the light signal started).
Define "the proper perspective". Who has "the proper perspective"?The answer is my math doesn't care about individual perspectives but only the proper perspective (which is an oxymoron).
I don't understand what you mean by "true simultaneity". Simultaneity means that two events happen at the same time. Two spatially-separated events that are simultaneous in one frame can never be simultaneous in a different frame. That is a result of special relativity.The true simultaneity of when the signals were sent was when both proper times were 2 and received at 4.
Yes. Length contraction is a standard, derived, result of special relativity in the special case where the length measurement in one of two reference frames is a "proper length" (i.e. a length measured in a frame where the object is at rest).Relativity goes to great lengths to maintain c is the relative velocity limit in any direction by keeping all slopes at c but it also reacts to relative velocities by altering the length of the light lines (pink is twice the length of yellow).
Special relativity limits the speed of information transfer to c.(Without c as a limit of information, there would be no such thing as causality in this universe.)
I commented on that formula in a previous post, which you have not responded to.$$Y_u/Y_w=DSR_v$$ as Y_u approaches infinity causing Y_w to approach infinity but the ratio approaches a finite value because the infinities cancel out as they must in physics.
Please explain why TEX is a great failing of this forum.I think besides TEX, the greatest failing of this forum ...
You can, but only for a limited time after you post them....is you can't go back and correct mistakes in past posts...
That may be a small part of the reason, but there are many other considerations....because they don't trust the users enough to be honest.
Can't you go back there? Did they ban you?That's what I miss about my previous forum which was the only one that allowed unlimited corrections.
I have no idea what that means. Are you just saying that no observer sees clocks in his own frame as ticking at anything other than the "normal rate"? That would just be the same as saying that all inertial frames are equivalent, approximately. Is that what you're saying, or are you saying something different?
I don't know what you mean by an "imbalance of relative velocities". How do we "balance" relative velocities? By "balance" are you just saying that two relative velocities are different from one another, or are you saying something else?
- What is a "participant"?
- What quantity is being changed?
- What kind of change causes a permanent slowing of time?
- Does that permanent slowing of time apply to all "participants" everywhere, or only to one of the "participants"?
- Can time ever speed up again, once it has been permanently slowed down? (The word "permanent" suggests it can't.)
- Does that mean that the entire universe is constantly slowing down, every time any "participant" makes the relevant change?
- Why does the permanent slowing happen only when the participant "initiates" a change, and not at any other time during or after the change?
- Please define "Doppler Shift Ratio" for me. What it is a ratio of
Think of a clock 3 ly away that is broadcasting its clock face. You would see the time on that face 3 yrs in the past. If the clock was moving, the delay in clock info would be affected by the motion. But the motion would also affect the underlying time you are observing which the clock is recording. So the apparent rate of the clock info and the real time dilation affecting the clock you are observing is the apparent rate and the time rate that combine to make up DSR. So DSR can be written with gammas or (c-v), (c+v) terms. I'm going to lay out all my formulas for DSR and explain the significance of each. Note: time dilation is not due to time slowing but to the relativity of simultaneity of when the clocks are stopped and started but I'm trying to answer all these questions before I explain how that works mathematically.If it is only "partly" an "apparent rate", what is the other part?
I hope you understand this now because you seem stuck on units. Like I said, the DSR is like a slow motion or fast forward on your DVD player and the normal rate of time is your play button. I've explained how v_t is also a rate of time ct'/t and is related to the gamma factor, v_t=c/Y so v_t is not dimensionless.At this point, I don't understand how either a "permanent slowing of time", or a "Doppler shift ratio" can be a "rate". Moreover, I don't see how vtvtv_t, which appears to be a dimensionless quantity, can be a "rate through time".
That doesn't comport with my understanding of what a reference frame is. In standard texts on relativity, a reference frame can be conceptualised as being like a literal 3-dimensional "frame" of rulers in a 3-d cubic lattice (it is actually imaginary, of course). At each intersection of the lattice, we can imagine there is a clock. For a single reference frame, all the clocks at all points of the lattice can be synchronised so that, no matter where they are in space, they all tick at the same rate in that frame and read the same time.Yes all inertial frames are equivalent and every inertial frame moves through time at the normal rate of v_t=c and the units of time are proper time.
I don't understand what t, x and t' are in that equation. Are they time and space coordinates for a particular set of events? If so, which set of events? I'm also puzzled as to why x' does not appear in that equation. Is it a special case in which x'=0 for some reason, rather than being a more general equation?The main equation:
$$(ct')^2 = (ct)^2 - x^2 $$ is of hyperbolas bound by +c and -c (timelike region of the light cone) that intersect all velocity lines at the same proper time.
That seems sort of okay to me. When you talk about the "proper time", here, you mean the proper time of the "moving" spaceship (i.e. the observer who has v=3/5c in the "stationary" frame)?Here is an Md showing the hyperbola that intersects all velocity lines at proper time =2. The green Loedel half-speed perspective or line of simultaneity intersects the same proper time for v=0 and v=3/5c.
I'm still not certain what your "Doppler Shift ratio" is. You most often seem to write it like this:As I explained when Alice and Bob, the two participants, are engaged in constant relative velocity, their Doppler Shift Ratios are the same value and their time dilation is reciprocal.
Are you saying that people in different frames of reference do not always agree on the value of the "DSR"? You seem to be saying that Alice can change the DSR, while it doesn't change for Bob, or something like that.At v=3/5c (separating so v is positive) , DSR = 1/2 and Y=5/4 (or as I say v_t=4/5c). When Alice makes a change in velocity, let's say to -4/5c, her DSR =3 and Y changing to 5/3.
When you say "relativity velocity" here, which reference frame is measuring those relative velocities? Are you using Bob's frame, Alice's frame, the "average" frame which sees both Bob and Alice moving, or what?But this is not reciprocal due to the delay of c. Bob's relative velocity remains at +3/5c indicated by his DSR of Alice still remaining at 1/2 and his Y at 5/4.
Here, you talk about what Bob "sees", which brings in issues of light signalling delays. Maybe what you're saying about what Bob sees is correct, but that doesn't raise any issues for me in terms of relativity, as far as I can tell.This is an imbalance of relative velocity and if Alice has travelled out 3ly before she makes the velocity change, Bob won't see the balance restored until t=8 when the info of the change reaches him at c. At that point, his DSR and Y will match Alice's.
I don't really understand what you mean by "effects of any velocity ...". Which physical effects are you trying to "recognise"?Relativity doesn't recognize the effects of any velocity that does not result in a re-unification of Bob and Alice because of its definition of spacetime paths and proper time (proper present to be more precise) only exists during co-location ( the two clocks can't be separated).
I'm not seeing a flaw.The flaw appears if Alice stops.
I don't understand what "infinite return time" means.It's obvious using math you can extrapolate infinite return time results in Alice ages 1 yr less than Bob as a result of her stop.
Okay. Your "participant" seems to be roughly equivalent to "observer", but sometimes you seem to use it for "reference frame" (as when you refer to the "background grid"). I think it is important to distinguish the two, because a single observer can only ever be at a single position in space at a given time, where a reference frame is a system of coordinates that covers the whole of space and time.1. Bob, Alice, Earth or the background grid can be participants.
Actually, the acceleration during the turnaround in the "twin paradox" scenario causes an effective "time gap" as the moving observer's notion of simultaneity shifts around due to her change of velocity.3. Acceleration which in my math is nothing but a sequence or average resultant change to the relative velocity or a handoff of clock information between an outgoing and incoming ship with no acceleration involved. Also called a frame jump by some.
That would suggest that it is temporary, not permanent. Just a matter of language; not that important, I guess.5. The change is permanent until another change is made.
I don't think so. I think the issue comes not from signalling delays, but from the change of reference frame during acceleration. If Alice turns around in her spaceship, then her "outgoing" frame (when she has velocity +v relative to Bob) is obviously different from her "return" frame (when she has velocity -v relative to Bob). At the turn around point, Alice must alter her frame from one to the other. In reality, she must pass through an infinity of frames in between as she does that (with velocities in the range from +v to -v). In the process, her notion of which spacetime events are simultaneous in her frame changes continuously.This has to be done when the participants are separated because the permanent change is dependent on the delay of information between them.
Relativity doesn't define "reality" or "perspective present", to my knowledge. Those are not terms I have seen in any standard text on relativity.When I say information it's like this. If the sun magically disappeared (in the god's eye proper present), we would be orbiting nothing and getting light from nothing in our perspective present for 8 minutes until reality caught up with us. Relativity, unfortunately, defines reality as the perspective present and has no concept, except in the hyperbolas Md, of a god's eye proper present separated by distance.
No, I'm not implying that. There is no absolute motion or absolute standard of rest in relativity, and no "absolute present". You and I appear to agree on the relativity of simultaneity and on relative motion, so far at least.6. No, you are implying absolute motion and a universal present with the words you used.
I think it is best to be specific and talk about events in spacetime. Those can be "changes", but they are changes that have specific space and time coordinates in every frame. Talking about "changes" in the abstract risks leading to ambiguity.7. If more changes occur before the imbalance reaches Bob, they accumulate and propagate from their origin in the same way the first one propagated (from its origin at 3 ly e.g.)
I'd say your graphs show how time progresses. One of the axes is time! You can draw a graph in whatever reference frame you need. The only problem with the "twin paradox" scenario is that if you're going to draw a Minkowski diagram for Alice, you're going to need two - one for each of her two frames, before and after the turnaround.Relativity does not allow you to show how time progresses during a relative velocity imbalance.
I agree. This is consistent with special relativity that says that when Alice and Bob are travelling at constant relative velocity, each sees the other's clocks (whatever they are) as running slower than their own, in this case by a factor of 2.The interval between the light lines is how much time interval is broadcast and how much time interval is received. So the Bottom two pink light lines show Bob broadcasts 1 year but Alice receives it over 2 years so she observes Bob's TV broadcast at half speed slow motion or DSR = 1/2. The bottom two yellow light lines show Alice also broadcasts 1 year of her life and Bob sees it over two years so their DSR is reciprocal as is their Y because their relative velocity is reciprocal.
Yes.After Alice makes her velocity change she immediately receives Bob's year at twice the speed (in only half of her year) according to the spacing of the pink light lines.
Alice immediately knows about her own change in velocity because she is on the spot when it happens. Bob, on the other hand, has to wait for information about Alice's change of velocity to reach him, because he's far away from her when she changes velocity. In other words, there is a light signalling delay that Bob has which does not apply to Alice.But the spacing of the Yellow light lines shows Bob still receives Alice's broadcast at DSR=1/2 until t=8 when Alice's change of velocity reaches him.
You're not being specific enough about reference frames and times.Because the DSR's are different, Bob's relative velocity to Alice is .6c but Alice's relative velocity to Bob is -.6c hence a period of imbalance.
t=8 is the first time Bob has information about Alice's new state of motion at t=5, which allows him to calculate a new DSR (if he wants to do that). There's no problem with that.Then Bob's DSR of Alice changes from 1/2 to 2 at t=8 which means their relative velocity is the same at -.6c.
The entire "imbalance period" you refer to happens, in effect, at the turnaround point in Alice's journey. At that point, her frame of reference has to change from one moving at +0.6c to -0.6c (in Bob's frame). All other parts of her journey are constant velocity, relative to Bob, so signals are sent and received at regular intervals during those parts of the journey.You'll notice that during the imbalance period, Alice's proper time falls behind Bob's until the imbalance is over and she ends up 2 proper years behind Bob permanently.
That's not correct. We could, for example, draw lines of simultaneity for Alice on your graph, and see the "time gap" in her idea of simultaneity at the turnaround point.Relativity can only make this call at co-location and can't see how Alice's proper time falls behind.
Yes. That's the relativity of simultaneity. A standard, well-understood effect in special relativity. And we also have the signalling delays I talked about.It's because if the clocks are separated, different perspectives will read them differently...
I don't know what that is. It almost sounds like you believe this is some preferred frame of reference "underlying" Bob and Alice's perspectives. But special relativity has no preferred frames. I thought we agreed on that.....but the underlying proper time relationship...
I'm unfamiliar with the term "perspective reality"....is revealed by the Loedel perspective and any other perspective can be deduced from that. Relativity defines perspective reality and does not delve into the calculatable proper time reality that is the source of the perspective realities.
I think we're in agreement on this. You're just talking about the regular relativistic Doppler shift. Right?Think of a clock 3 ly away that is broadcasting its clock face. You would see the time on that face 3 yrs in the past. If the clock was moving, the delay in clock info would be affected by the motion. But the motion would also affect the underlying time you are observing which the clock is recording. So the apparent rate of the clock info and the real time dilation affecting the clock you are observing is the apparent rate and the time rate that combine to make up DSR. So DSR can be written with gammas or (c-v), (c+v) terms. I'm going to lay out all my formulas for DSR and explain the significance of each. Note: time dilation is not due to time slowing but to the relativity of simultaneity of when the clocks are stopped and started but I'm trying to answer all these questions before I explain how that works mathematically.
Okay. I can understand if you sometimes want to use units where c=1, in effect. The confusion only comes when you aren't consistent - putting factors of c into some equations, while assuming c=1 in others.I hope you understand this now because you seem stuck on units. Like I said, the DSR is like a slow motion or fast forward on your DVD player and the normal rate of time is your play button. I've explained how v_t is also a rate of time ct'/t and is related to the gamma factor, v_t=c/Y so v_t is not dimensionless.
I'm not really sure what this is about. In special relativity we haveWhen Y_t is 0, Y is infinite and vice versa. Zero in relativity is not a natural number, it is 1/infinity.
Where are infinities cropping up? Since no material object or reference frame can ever have v=c, Y should never be infinite.Since v and v_t are symmetrical, you can get around the infinities of the gammas if you consider the v_t version of an equation with the v version and vice versa. Relativity gives infinities a pass but by grouping Y with other variables, you can get all infinities to cancel out mathematically.
Can you please give me an example of where relativity would produce an infinite answer for any physical (i.e. measurable) quantity?This is why my math can derive finite answers that relativity can't because some of its results are infinite when they're really not.
I don't see a problem. For example, Alice can send signals to Bob at any time about what her clocks say, and vice versa. Why do you say that it is impossible to pass "proper time information" in standard relativity?I'd just like to add why I can have proper time as an underlying reality is because I have to math that allows light signals to pass proper time information while relativity does not.
No. The synchronisation of clocks in a single reference frame is something we assume has been done before we start using them for anything. The procedure is straightforward.It instead chose to incorporate light information into Einstein's clock sync method which generates perspective lines of simultaneity.
Well, yes. It is always possible to synchronise clocks in a single reference frame.All clocks on a line of perspective simultaneity are set to the same time using Einstein's clock sync method.
What? Sure they do. Two separated clocks that tick at the same rate can be used to define a "present". Events that happen at either clock at the same displayed time on the nearest clock happen simultaneously, assuming the clocks were previously synchronised.But this is an artificial present because 2 clocks separated by distance do not define any kind of present.
That's wrong. You're most likely on the opposite side of the world to me, but we can agree on what is happening "now", with reference to our separate clocks (as long as we account for time zone differences). There are no relativity issues (ignoring the rotation of the Earth and on on, which causes problems for reasons unrelated to special relativity). As long as we're effectively at rest with respect to one another, we can agree on anything that is happening "now", no matter where it is happening, or how widely we're separated. Our clocks are synchronised (in practice, our respective times are synchronised to Greenwich Mean Time, or Universal Time).Anyone separated from you does not share your present just because your clocks are synced to the same time.