Relativity And Simple Algebra

[OceanBreeze]

I'm trying to get my head around what I'm trying to prove. A train coming into a station has a proper length at velocity zero. I'm expecting the invariant length should remain the same from the platform's perspective no matter what the incoming speed of the train? I have to check if this is true and the significance of it being true. In Einativity, the formula for invariant length includes both length and time but in ralfativity length is already invariant so there would be a different formula for invariance. That formula would also need to calculate an invariant length of the train no matter its velocity. I'm not sure if any of this makes sense yet. Maybe I need to check that the invariant length must be the same from any perspective velocity of the train. I can check this last point by doing some calculations on my train in the station example to get me started but I don't know what I'm looking for yet.

 

You lost me on this one.

 

What do you think is an invariant length in SR?

[ralfcis]

c²t² - x² =c²t'² - x'²

 

each side of the equation is the invariant length of the spacetime path.

 

So if Alice goes out 3 ly at .6c, her coordinates of (ct', x') are (4,0). Bob's coordinates of that same point are (ct,x) = (5,3)

 

So Bob's invariant length = sqrt (25 - 9) =4 which should equal Alice's invariant length  of sqrt(16-0) =4.

 

So the spacetime path = 4ly from both perspectives. I don't know what the significance of this is.

 

This is from Greene's video on invariants. https://www.youtube.com/watch?v=AJs7rk3QGD4&list=PLj6DWzIvBi4PFDXCCV1bNhVUgDLTwVbFc&index=54&t=0s

 

I'm trying to work out what this all means for the pole in the barn scenario. In relativity, Alice's time dilates and the distance she travels contracts. So Bob says she travelled 3 ly in 5 yrs and Alice's clock says she travelled 4yrs so her distance must have been 3/Y = 12/5 = 2.4ly. But what this all has to do with the invariant length of 4ly and what's the length of the pole and the barn or train in the station I don't know yet. Is the invariant length somehow related to proper length? Does this somehow solve my dilemma of treating the pole as endpoint time coordinates (between which I have no real definition of spacetime length) instead of a contractible physical object. I'm trying to determine if relativity uses invariant length as what I'm looking for. This will take some time to sort out as i don't know what I'm trying to define.

 

In my train in the station example, my train is always the same proper length. I don't join the coordinate times when the back of the train sees the light to when the front of the train sees the light and call that the length of the train. This is exactly what you're doing when you say relativity of simultaneity of the endpoints does not preclude some sort of physical length variation.  Einativity does join those points and calls them the new length of the train. I'm trying to see if these varying train lengths are somehow made invariant to get this craziness under control. Invariant spacetime paths must have been invented for a reason but I don't yet see it.

Edited July 14, 2020 by ralfcis

[sluggo]

AnssiH;

 

Agree on basic ideas of mental constructs as models that mimic behavior of the physical world. Am noting differences.

 

speed of light:

 

"In the first place it is clear that the equations must be linear on account of the properties of homogeneity which we attribute to space and time."

1905 paper, par.3

 

[There is no reason to assume otherwise.]

 

1-way speed of light isotropy, smallest variations:

 

Cialdea, Lett. Nuovo Cimento 4 (1972), pg 821.

Uses two multi-mode lasers mounted on a rotating table to look for variations in their interference pattern as the table is rotated. Places an upper limit on any one-way anisotropy of 0.9 m/s 

 

Ragulsky, “Determination of light velocity dependence on direction of propagation”,

Phys. Lett. A, 235 (1997), pg 125. A “one-way” test that is bidirectional with the outgoing ray in glass and the return ray in air. The interferometer is by design particularly robust against mechanical perturbations, and temperature controlled. The limit on the anisotropy of c is 0.13 m/s.

 

[in SR, the measured speed of light is always c. This has been verified by years of experiment.]

 

[Physics of the Newtonian era and earlier, assumed an instantaneous light speed.

In the 1600's astronomical observations revealed light had a finite speed.

This fact, the anomaly of induction, and the failure to detect absolute motion (MM), was the motivation for Einstein's theory built on the 'principle of relativity'. He believed there was no need for an absolute ether rest frame, as proposed by Lorentz. The observer would be free of any restraints imposed by such a system, and any inertial ref. frame would be sufficient.

The definition of 'time of event' is the reading of a local clock that is simultaneous with the event. In the process of describing motion via coordinate systems, the problem of comparing the time of a local event with the time of a remote event appears.

This requires a system of coordinate transformations from one event to another. Lorentz had developed his own, but Einstein developed his using the two postulates of SR, to find they were identical.]

 

length contraction:

 

[in the 1905 paper, par.4, 'physical meaning', he describes a moving sphere 'viewed' as an ellipsoid, when measured from a system with synchronized clocks, per par.1. This is open to interpretation as an apparent or measurement effect.]

[sluggo]

simultaneity and length contraction required for reciprocity

 

SR requires both ends of an object be located simultaneously.

A is black, B is green, each ship is length d, g=gamma.

The near end of both ships are at 0 for all measurements.

left:

A measures location of far end of his ship at d, on his axis of simultaneity Ax.

A measures location of far end of green ship at d, on his axis of simultaneity Ax.

B ship length/A ship length =1.

B measures location of far end of his ship at f, on his axis of simultaneity Bx.

B measures location of far end of black ship at e, on his axis of simultaneity Bx.

A ship length/B ship length =1/g^2.

Measurements are not reciprocal.

right (with length contraction):

A measures location of far end of his ship at d, on his axis of simultaneity Ax.

A measures location of far end of green ship at d/g, on his axis of simultaneity Ax.

B ship length/A ship length =1/g.

B measures location of far end of his ship at f, on his axis of simultaneity Bx.

B measures location of far end of black ship at e, on his axis of simultaneity Bx.

A ship length/B ship length =1/g.

Measurements are reciprocal

 

[ralfcis]

Anssih, I came up with a one way speed of light determination on the physics stack exchange. All other tests are flawed. The measurement is done from two colocated clocks slowly separated at constant relative velocity. All other tests stop the motion of the clocks which induces a twin paradox permanent time diff which does not happen if you maintain constant velocity during the test of 1 light beam fired between clocks. The results are measured from the Loedel reference frame which allows one to peer into the universal instantaneous present as if the clocks were again colocated despite their separation. This is not philosophy or history but mathematically proven if there was anyone on the planet to look at the proof. There is no proving a negative like saying it can't be done is a universally accepted truth. I thought I had blocked Sluggo. I'll fix that.

[OceanBreeze]

c²t² - x² =c²t'² - x'²

 

each side of the equation is the invariant length of the spacetime path.

 

So if Alice goes out 3 ly at .6c, her coordinates of (ct', x') are (4,0). Bob's coordinates of that same point are (ct,x) = (5,3)

 

So Bob's invariant length = sqrt (25 - 9) =4 which should equal Alice's invariant length  of sqrt(16-0) =4.

 

So the spacetime path = 4ly from both perspectives. I don't know what the significance of this is.

 

This is from Greene's video on invariants. https://www.youtube.com/watch?v=AJs7rk3QGD4&list=PLj6DWzIvBi4PFDXCCV1bNhVUgDLTwVbFc&index=54&t=0s

 

I'm trying to work out what this all means for the pole in the barn scenario. In relativity, Alice's time dilates and the distance she travels contracts. So Bob says she travelled 3 ly in 5 yrs and Alice's clock says she travelled 4yrs so her distance must have been 3/Y = 12/5 = 2.4ly. But what this all has to do with the invariant length of 4ly and what's the length of the pole and the barn or train in the station I don't know yet. Is the invariant length somehow related to proper length? Does this somehow solve my dilemma of treating the pole as endpoint time coordinates (between which I have no real definition of spacetime length) instead of a contractible physical object. I'm trying to determine if relativity uses invariant length as what I'm looking for. This will take some time to sort out as i don't know what I'm trying to define.

 

In my train in the station example, my train is always the same proper length. I don't join the coordinate times when the back of the train sees the light to when the front of the train sees the light and call that the length of the train. This is exactly what you're doing when you say relativity of simultaneity of the endpoints does not preclude some sort of physical length variation.  Einativity does join those points and calls them the new length of the train. I'm trying to see if these varying train lengths are somehow made invariant to get this craziness under control. Invariant spacetime paths must have been invented for a reason but I don't yet see it.

 

I guess what is throwing me off is your use of the term “length” when referring to a spacetime interval.

 

It may be that your way of thinking about this is more advanced than mine since I have never considered that a spacetime interval can be a length.

 

Probably the reason for that is that it contains quadratic terms, forcing me to think in terms of an area, not a length.

 

I do know, for example, that the area of a light-rectangle is frame invariant in SR.

 

Another way to think of it is as a displacement in spacetime, which would still be an area rather than a length as I understand it.

 

But I am working from memory. I will look for a source on exactly what a spacetime interval is, in a geometric sense.

I don't believe it can be a length or a vector as I am fairly sure a vector can not be frame invariant, in the direction of motion.

Edited July 15, 2020 by OceanBreeze

[ralfcis]

Popeye, here's how ralfativity handles the train in the station/pole in the barn scenario. It's very different from how Einativity does it. First Einativity since you're familiar with it:

 

https://photos.app.goo.gl/gswbA72uqG7Rjq9N9

 

The train is depicted as the red lines of simultaneity which are also the Minkowski rotated x-axis. Since they follow Einy's clock sync method, the train clocks are the same value at the endpoints. The train and station both have a proper length of 2 ly which is reciprocally contractible from a 2.5ly spacing between where the light signals hit the ends of the train simultaneously. The proper length of the train is distorted by the Minkowski rotation of the x-axis to make the x'-axis which is also called the train's perspective line of simultaneity created by Einy's clock sync method. The train fits into the platform at t'=0 and a light signal will hit the ends of the train at t'=1.25 simultaneously from the train's perspective and at t=.625 (back) at t=2.5 (front) from the platform. So what's simultaneous for the train is not for the platform.

 

What Einativity does is join the two endpoints of the train with a line of length that is compressed by physical length contraction to fit into the station's rest length. Relativity of simultaneity is explained by this length contraction instead of vice versa.

 

In ralfativity,

 

https://photos.app.goo.gl/L63Hvd9iAxfSu11K9

 

the train's length is invariant at 2 ly. There is no Einy's clock sync method so the train's ends are not subject to being sync'd. The clock values are set by other rules I outlined in this thread. The light hits the back of the train at 1.25, the train moves on and the front is hit at 1.25 much later from a universal present perspective but simultaneous from the train's perspective because both times are labelled the same. There is absolutely no need to join these two points and say that's the length of the train when those points indicate a differing duration of time from different perspectives. Just because Einy's clock sync method or my rules make the clocks say the same time, it does not mean 0 time has passed between the light hitting the back and front of the train and the extended length of the train accommodates when its ends catch the light signals. I say the extended time the difference in the start of the the train and platform stopwatches is what gives the endpoints of the length invariant train to catch the light signals. Potato/tomato.

 

The true significance of what is happening can be seen from the Loedel half speed perspective which gives us a window into the instantaneous universal present.

 

https://photos.app.goo.gl/R3XFLfSqUjQVpLPK7

 

I spent a lot of time describing how this perspective works in this thread but what it does is allow the light signals themselves to reveal time and compensate for the diagram's corruption of the light signals' depicted lengths. In a Loedel depiction, the pink and yellow light signals have the same length and all spacetime diagrams must contain the same information independent of depiction. That's all unimportant to this specific question right now and so is the invariant spacetime interval which maybe one day I'll find some use for. The final answer I've found is I don't draw some fake line between time points and call it physically contractible length and declare that perspective has the power to contract it because we can measure that under the circumstances that create it and which disappears once those circumstances disappear. To me, that viewpoint is pure insanity no matter how symmetrical and spacetimey it makes Einativity's math. If you don't understand what I'm saying, read this over and over until you can ask specific questions. I wrote this fast so I may have been imprecise in some wording. This will be impossible to grasp or even see if you can only follow the prophet and his teachings. The scales have fallen from my eyes but everyone else is still walking around with them.

Edited July 15, 2020 by ralfcis

[ralfcis]

Popeye, the invariant "length" of the spacetime interval comes from the video I posted. This line is like a 4 dimensional straight line as it has both time and distance components. I haven't been able to gleen any significance from its existence (except that it's a reciprocal form of relativity's prime equation from which I derive all my equations) and have discounted its relevance to this discussion.

Edited July 15, 2020 by ralfcis

[Mutex]

c²t² - x² =c²t'² - x'²

 

each side of the equation is the invariant length of the spacetime path.

 

So if Alice goes out 3 ly at .6c, her coordinates of (ct', x') are (4,0). Bob's coordinates of that same point are (ct,x) = (5,3)

 

So Bob's invariant length = sqrt (25 - 9) =4 which should equal Alice's invariant length  of sqrt(16-0) =4.

 

So the spacetime path = 4ly from both perspectives. I don't know what the significance of this is.

 

This is from Greene's video on invariants. https://www.youtube.com/watch?v=AJs7rk3QGD4&list=PLj6DWzIvBi4PFDXCCV1bNhVUgDLTwVbFc&index=54&t=0s

 

I'm trying to work out what this all means for the pole in the barn scenario. In relativity, Alice's time dilates and the distance she travels contracts. So Bob says she travelled 3 ly in 5 yrs and Alice's clock says she travelled 4yrs so her distance must have been 3/Y = 12/5 = 2.4ly. But what this all has to do with the invariant length of 4ly and what's the length of the pole and the barn or train in the station I don't know yet. Is the invariant length somehow related to proper length? Does this somehow solve my dilemma of treating the pole as endpoint time coordinates (between which I have no real definition of spacetime length) instead of a contractible physical object. I'm trying to determine if relativity uses invariant length as what I'm looking for. This will take some time to sort out as i don't know what I'm trying to define.

 

In my train in the station example, my train is always the same proper length. I don't join the coordinate times when the back of the train sees the light to when the front of the train sees the light and call that the length of the train. This is exactly what you're doing when you say relativity of simultaneity of the endpoints does not preclude some sort of physical length variation.  Einativity does join those points and calls them the new length of the train. I'm trying to see if these varying train lengths are somehow made invariant to get this craziness under control. Invariant spacetime paths must have been invented for a reason but I don't yet see it.

 

I don't want to hijack this thread, but this is getting interesting!

 

For me at least, the only way all this time 'dilation' and space 'contraction' makes sense is in understanding (for me) that we are talking about 'space length' and 'time length'. (this is going to sound really simplistic, but I expect the universe works from very simple fundamental principles that always apply).

 

So instead we can just agree that time and space have a length property (duration for time, and distance for space), and that property is variable.

 

The length of time and space is variable:

 

Because the length of time is the same as the length of space (at any point, or reference frame), the length of time it takes light to go unit length of distance will be constant: The speed of light is constant. 

 

The speed of light is constant, and the length of time and length of space is variable relativity speaking.

 

The issues with things like the twins paradox, or determining the length of time or distance travelled relative to someone other reference frame can only be understood if you accept that time and space is a length property and it is variable. 

 

If you know the variation in that relative length you can agree on a simultaneous event and understand that even though the clocks will display different numbers.

 

(I know I'm not going to explain this very clearly, so sorry, but I would love for you to get your head around it, and see if it makes any sense to you).

 

I assume that space is just a distance, length, gap between two points (in space), and nothing more, It has a fundamental scalar property of length at any point. You would define that length of that space where you are to be your reference frame (or reference length). 1 meter is always going to be 1 meter regardless of that basic property.

 

Time is just the distance, length, gap between two events, time length is an emergent property of space length (we would refer to that as space length derived time, or spacetime). 

 

The speed of light is constant, so at any point the: Length of space / length of time = 1.

 

Anything that exists over space (so matter but not energy) has it's size vary as a function of that length property. 

 

If we start with general relativity, we can say that time is longer at the center of the earth and shorter as you move away from the earth, So a clock on the ISS will measure a shorter time than the same clock at the surface of the earth. (disregarding SR measuring longer time).

 

But on the ISS if you use your local clock to measure out 1 meter (by using light), obviously your 1meter will be shorter than the same 1 meter on the surface of the earth.. if you measured its length from the surface of the earth.

 

The length of time is shorter on the ISS relative to the surface of the earth, so length must also be shorter relative to the surface of the earth. 

It is impossible to directly measure that very small length difference, but we can accurately measure the length of light from the ISS, and we can measure the length of time on the ISS, and both the length of light (wavelength) and the length of time (faster clocks) both show that length to be shorter (blue shifted light, and fast clocks).

 

Also the reverse is true, if you are on the ISS, you look at earth you see light length to be longer (red shifted) and you see clocks tick slower (longer time).

Everyone agrees that the speed of light is the same though. The length of space and of time are relatively variable, and locally constant.

 

length of space / length of time = 1

 

SR is a variation of the same principle, but a little harder for me to get my head around.

SR is a velocity (speed) that is a function of the length of space over a length of time. It is using speed to 'interact with' or 'experience' more or longer space over time. 

 

So a stationary object has sees one unit of space over any unit of time, but a moving object sees greater than one unit of space over a unit of time. 

A stationary 1 meter ruler will exist over 1 meter over 1 second, but a moving 1 meter ruler will exist over greater than 1 meter over 1 second because it is moving through space.

 

Seeing longer space, means you are in longer space, and because you are in longer space you are larger so to keep the speed of light constant you need longer time. We observe this as 'time dilation', or for me, just longer time, because longer space.

 

So for me there is no 'proper' path, or time, there is just an acceptance that the length of space itself varies, and anything in that space (but not energy), varies with it, there is no need for the clocks to agree on a particular time. 

 

This is a non-geometrical treatment of space and space length derived time (spacetime), instead of trying to justify numbers on different clocks that start and stop at the same local time disagreeing, by a geometrical (worldline, path, geodesic), I think of it as a linear function with different lengths of space (and time). I don't have to curve the higher value to fit start and stop points. 

 

So one clock reads 5 and one reads 10, they started and stopped at the same time, the 5 clock is in the longest time it counted only 5 seconds (longer seconds) than the 10 clock that counted 10 (shorter) seconds. You just cant agree on how long the second is (it's variable).

 

From basic optics you can see how lensing would work, it also explains why clocks run slower towards the center of the earth and faster further away (from GR).

It explains Shapiro time delay, and the space is longer due to 'gravity' or space length from matter/mass (from GR).

 

It explains gravitational shift of light, it also shows that potential energy is matter in shorter space, it takes energy to get into and stay in shorter space.

 

The longer the space (and therefore time) the lower the energy state of matter in that space length, that means the light from that longer space will be distributed over a greater length of space, it will have a longer waveLENGTH, we observe gravitational shift (or Einstein shift), even in a high rise building.

 

This model also means that space is not curved or warped (matter does not curve space, it just makes it longer), and to me that makes more sense, how can NOTHING (space, only has a length) have a geometry?

 

Sure you can go in any direction you like (and not just 3), but you always have to go a length or distance.

 

Anyway, you might want to give it some thought when you are trying to deal with time dilation and space contraction, I find that just going back to first principles and looking at what we actually know to be the case, is a good way to go, as opposed to trying to reverse engineer the finished model and it's assumptions.

[ralfcis]

A lot of words but all you've said is for c to be constant, time and space must compensate. That's what Einy said, that's not what I say, hence the length of this thread. I'm not entertaining other theories, just here to answer any questions on my own theory. Do you see a problem with it or are you offering alternatives. I've listed the problems I see with Einativity and people continually ignore that list.

[Mutex]

A lot of words but all you've said is for c to be constant, time and space must compensate. That's what Einy said, that's not what I say, hence the length of this thread. I'm not entertaining other theories, just here to answer any questions on my own theory. Do you see a problem with it or are you offering alternatives. I've listed the problems I see with Einativity and people continually ignore that list.

 

I dont have a theory, this is just relativity, or at least what we observe that we attribute to relativity, time and space does not 'compensate' I don't know how you got that out of what I said. 

 

My post was specifically addressing one of the problems you see, and I gave an alternate way of looking at that problem. I do see a problem with what you explained as your problem, the solution to a problem is not another problem, it is a possible solution, I provided a possible solution for you to consider.. (or not).

 

As for a lot of words !!!!! Oh my  :shocked:. The speed of light is constant, we know from observation that the length of time is not constant, speed is distance over TIME!!! How does that work??? you tell me? (it's that simple). 

[ralfcis]

Yes it's 75 pages of simple so far. But for your specific question, c may be constant  for v=x/t but Yv is the amount of invariant space you travel in the time on your ship's clock. So if you travelled 4ly to proxima centauri in 3 yrs according to your clock, your Yv is 4/3c using invariant space in your time. If you think I'm breaking c by saying this then you haven't been paying attention.

 

As for the rest of what you said, you do have a theory, it's called relativity and in that theory c is kept constant  for observed frames  by time dilation being compensated for by length contraction. What problem were you addressing? You did not provide a possible solution, you told me to find it myself by adopting an alternate way of looking at the problem. We do not know from observation that time is not constant. In fact both participants clocks tick at the same rate in their own frames and each one sees the others clock exhibit 2 different rates of "slowing" of which neither is an actual slowing of time itself because that would contradict both seeing their own clocks tick at the same rate. You read some Wiki articles and you repeat them without applying critical thinking. You needn't take it personally, I give people a chance and if they offer me nothing thought provoking I turn them off by being rude and then I wait usually way too long to put them on ignore. This is the only forum that tolerates my bad behavior.

Edited July 15, 2020 by ralfcis

[OceanBreeze]

Popeye, here's how ralfativity handles the train in the station/pole in the barn scenario. It's very different from how Einativity does it. First Einativity since you're familiar with it:

 

https://photos.app.goo.gl/gswbA72uqG7Rjq9N9

 

The train is depicted as the red lines of simultaneity which are also the Minkowski rotated x-axis. Since they follow Einy's clock sync method, the train clocks are the same value at the endpoints. The train and station both have a proper length of 2 ly which is reciprocally contractible from a 2.5ly spacing between where the light signals hit the ends of the train simultaneously. The proper length of the train is distorted by the Minkowski rotation of the x-axis to make the x'-axis which is also called the train's perspective line of simultaneity created by Einy's clock sync method. The train fits into the platform at t'=0 and a light signal will hit the ends of the train at t'=1.25 simultaneously from the train's perspective and at t=.625 (back) at t=2.5 (front) from the platform. So what's simultaneous for the train is not for the platform.

 

What Einativity does is join the two endpoints of the train with a line of length that is compressed by physical length contraction to fit into the station's rest length. Relativity of simultaneity is explained by this length contraction instead of vice versa.

 

In ralfativity,

 

https://photos.app.goo.gl/L63Hvd9iAxfSu11K9

 

the train's length is invariant at 2 ly. There is no Einy's clock sync method so the train's ends are not subject to being sync'd. The clock values are set by other rules I outlined in this thread. The light hits the back of the train at 1.25, the train moves on and the front is hit at 1.25 much later from a universal present perspective but simultaneous from the train's perspective because both times are labelled the same. There is absolutely no need to join these two points and say that's the length of the train when those points indicate a differing duration of time from different perspectives. Just because Einy's clock sync method or my rules make the clocks say the same time, it does not mean 0 time has passed between the light hitting the back and front of the train and the extended length of the train accommodates when its ends catch the light signals. I say the extended time the difference in the start of the the train and platform stopwatches is what gives the endpoints of the length invariant train to catch the light signals. Potato/tomato.

 

The true significance of what is happening can be seen from the Loedel half speed perspective which gives us a window into the instantaneous universal present.

 

https://photos.app.goo.gl/R3XFLfSqUjQVpLPK7

 

I spent a lot of time describing how this perspective works in this thread but what it does is allow the light signals themselves to reveal time and compensate for the diagram's corruption of the light signals' depicted lengths. In a Loedel depiction, the pink and yellow light signals have the same length and all spacetime diagrams must contain the same information independent of depiction. That's all unimportant to this specific question right now and so is the invariant spacetime interval which maybe one day I'll find some use for. The final answer I've found is I don't draw some fake line between time points and call it physically contractible length and declare that perspective has the power to contract it because we can measure that under the circumstances that create it and which disappears once those circumstances disappear. To me, that viewpoint is pure insanity no matter how symmetrical and spacetimey it makes Einativity's math. If you don't understand what I'm saying, read this over and over until you can ask specific questions. I wrote this fast so I may have been imprecise in some wording. This will be impossible to grasp or even see if you can only follow the prophet and his teachings. The scales have fallen from my eyes but everyone else is still walking around with them.

 

I haven't been keeping up with the thread, so I have some catching up to do. 

[Mutex]

 

 

 it's called relativity and in that theory c is kept constant  for observed frames  by time dilation being compensated for by length contraction.

 

The speed of light is constant, that's not from relativity it is just an observed fact, I would say that space and time does not 'compensate' just to keep c constant.

 

So we have some known observations, the length of time varies from place to place (from GR) and as a function of velocity (from SR), we also observe that so we can say that is a fact.

 

So the facts are the speed of light is constant, and we measure time to be variable due either to gravity (GR) or velocity (SR). 

 

Length of space contraction does not account for time being relatively longer, it would only account for time being shorter, to keep c constant distance over time must also be a constant ratio.

 

So instead of saying 'dilation' and 'contraction', you can state that time AND space length are variables, but they vary by the same amount at that point in space.

 

This is not from relativity, this is from what we observe, they are however observations that show that space and time are relative, it has some relative property.

 

All I am saying, is that relativity the way it is treated now is considered as space being 3D and geometrical in nature. I am saying that you get the same observations if you consider this fundamental length property in a linear non-geometrical model. We get the same observations that we use to conclude that space is relative.

 

It's not my theory, it's Einstein's, I am just looking at it from what we observe from that theory (first principles).

 

 

 

What problem were you addressing? You did not provide a possible solution, you told me to find it myself by adopting an alternate way of looking at the problem.

 

I addressed the simultaneity issue, and explained and address that 'problem', I described why clocks do not agree after some observation or experiment, by showing that they do not have to agree, but you can still agree on when an event happened even though the apparent times are different.

 

 

 

We do not know from observation that time is not constant. In fact both participants clocks tick at the same rate in their own frames and each one sees the others clock exhibit 2 different rates of "slowing" of which neither is an actual slowing of time itself because that would contradict both seeing their own clocks tick at the same rate.

 

Time is only locally constant, as you said we see our own clock ticking at a constant rate (in our FOR), but relatively the length of time is not constant, we measure that variation all the time, we have to correct clocks in GPS satellites because of GR and SR time variability. 

 

But locally it is constant, because of how we define time, we define time by measuring the length of space, how much time does it take for something to go a certain distance through space, be it the earth around the sun, or how long it takes light to go a certain distance. 

 

So locally the length of space and the length of time are the same.  length of space / length of time = 1

 

But if you are observing a remote location what the length value is different, then you will observe a variation in that length of time, and therefore a variation in that length of space (because it's the same length). 

 

The center of the earth has longer space and time, a GPS satellite, or a clock on Mt Everest has shorter space and time, we see light from longer space to be redshifted, and we see light from shorter space to be blue shifted. 

 

So it's not about dilation or contraction, it's about being relatively variable, it's the 'size' of space. 1 meter will always be 1 meter locally, but your 1 meter can be a different length to my 1 meter if I measure your 1 meter from my relative length.

 

 

 

You read some Wiki articles and you repeat them without applying critical thinking.

 

No need to starting getting snarky my friend, I can probably say that I have almost NEVER read a Wiki, certainly nothing about relativity or physics, I very much doubt there would be an interpretation about space length in Wiki at all.

 

Can you show me where I have not applied critical thinking, or are you just trying to be nasty and a POS ? Is that just a reflex action? 

 

 

 

You needn't take it personally, I give people a chance and if they offer me nothing thought provoking I turn them off by being rude and then I wait usually way too long to put them on ignore.

 

Really!! Oh OK, that's very mature of you.. It is also very narcissistic, I'm not interested in provoking your thoughts or pleasing you, it's not about you at all, I am interested in exploring what space and time is, how it works and how it explains what we observe. 

 

 

 

This is the only forum that tolerates my bad behavior.

 

Perhaps you need to address whatever issues you have that results from that. You seem to think a discussion of the scientific issues is a personal attack on yourself, makes you appear immature, that is why you would get banned from places, and I know from experience you would get nowhere in a scientific community with that huge chip of your shoulders. You ego is too big for the room.. 

 

But each to their own, it has (sort of) been interesting, best of luck with your model or whatever it is.. 

[AnssiH]

Wikipedia is the National Enquirer of world knowledge. The 1st sentence of that article was completely wrong so I didn't bother to read the rest.

You mean this sentence:

"When using the term 'the speed of light' it is sometimes necessary to make the distinction between its one-way speed and its two-way speed."

 

?

 

Can you elaborate in what way do you see it wrong?

 

If you don't assume time passes at the same rate within each inertial frame then you can't assume you are motionless relative to the clock right beside you.

Now that's certainly true in a subtle but very important way... I wonder if you are thinking what I'm thinking... :thinking:

Care to elaborate what makes you bring that topic up?

[AnssiH]

1-way speed of light isotropy, smallest variations:

 

Cialdea, Lett. Nuovo Cimento 4 (1972), pg 821.

Uses two multi-mode lasers mounted on a rotating table to look for variations in their interference pattern as the table is rotated. Places an upper limit on any one-way anisotropy of 0.9 m/s 

 

Ragulsky, “Determination of light velocity dependence on direction of propagation”,

Phys. Lett. A, 235 (1997), pg 125. A “one-way” test that is bidirectional with the outgoing ray in glass and the return ray in air. The interferometer is by design particularly robust against mechanical perturbations, and temperature controlled. The limit on the anisotropy of c is 0.13 m/s.

 

[in SR, the measured speed of light is always c. This has been verified by years of experiment.]

 

 

Anssih, I came up with a one way speed of light determination on the physics stack exchange. All other tests are flawed. The measurement is done from two colocated clocks slowly separated at constant relative velocity. All other tests stop the motion of the clocks which induces a twin paradox permanent time diff which does not happen if you maintain constant velocity during the test of 1 light beam fired between clocks. The results are measured from the Loedel reference frame which allows one to peer into the universal instantaneous present as if the clocks were again colocated despite their separation. This is not philosophy or history but mathematically proven if there was anyone on the planet to look at the proof. There is no proving a negative like saying it can't be done is a universally accepted truth.

Well I'm a bit surprised there's this much confusion about this topic. The reason I said this is a well known fact was not an attempt to convince anyone "by authority" - I'd rather have everyone think this through themselves. And it's not very difficult to think through.

 

Basically Ralfcis' method is fine, I'm just saying that it is also a convention, not an actual measurable fact.

 

The real reason I use the word "fact" is that this topic has got nothing to do with any experiments - it is true by definition, if you just manage to handle your definitions properly. So just think this through carefully;

 

First of all the "aether detection" experiments 100 years ago all assumed that "objects" and "space" have independent existence from each other, and thus signals between macroscopic objects could be simply measured as if the measurement devices are not part of reality themselves. Really naive idea considering that there's (so called) "electromagnetic information" about everything around you all the time - all of "space" is always filled with information from everything around it (since you can "see it"), in that sense there's no such thing as "empty space", and certainly "space" everywhere has got a very real dependence on everything around it.

 

It would be very mind boggling mystery if objects and space actually had fully independent existence, don't you think?

 

Einstein doesn't explicitly mention one-way speeds because the impossibility of measuring them was well known at the time. This is why he starts off from defining a clock synchronization convention, and I suspect all physicists at the time would have understood him correctly. It's just the poor way relativity is taught as Minkowski space these days, that the important facts have become a bit hidden under the mud.

 

Once you have accepted that convention, you have effectively set one-way speed to C by convention. All the experiments that "measure it" simply use this convention to synchronize their clocks, and thus they have determined the end result before even starting. It is like saying "all experiments show that water always flows downhill", without realizing that your definition of "downhill" is determined by how water behaves on it.

 

Just imagine an experiment that has two spatially separated clocks, I'm sure you can easily convince yourself that you can't determine by light signals whether they are synchronized when you don't know about any possible bias in the speed of light.

 

Regarding the "moving the clocks slowly from one location", even if you move both clocks, again since you don't know the bias, you don't know which clock gets impacted more.

 

And btw the speed of the clocks is not relevant either - any motion will have an effect whose magnitude you can't measure because you don't know the bias.

 

It is certainly not valid to just assume there's no effect - if special relativity is valid, then there is an effect and we know exactly what type of effect. Furthermore we know the effect is such that natural observers can't measure it, for exactly the same reasons I've already discussed. (If we could measure this speed, we could very very easily establish universal simultaneity, and Minkowski spacetime would be completely viewed as a mental hack, nothing more, nothing less.) Also if Lorentz' aether theory is correct, the expectation is also the exact same effect on clocks (just plot oscillations with a bias and you see the same result).

 

Perhaps the easiest way you can convince yourself of this fact is to simply realize that if you plot this clock movement experiment on a spacetime diagram, you can plot how it would look like in terms of any arbitrary inertial frame, and you will get the same end result in terms of actually observable events (as long as you perform your frame transformations correctly). In each frame the speed of "C" against each clock is represented with different "bias", and the "world around" each clock is plotted in different state. The clocks cannot "measure" the bias on C no matter what inertial frame you plot the situation in, because they can only be in one spatial location at a time.

 

Just plot these experiments on spacetime diagrams yourselves if you feel the need. It's really not very difficult to see how your first assumptions are connected to how you end up seeing your "measurements".

 

I will also say that understanding this topic will allow you to understand special relativity in much deeper way that most people seem to grasp it. The whole idea works on the basis that one observer cannot receive information from anywhere "instantly", and thus it is mathematically trivial to represent reality with a convention of isotropic C.

 

It's just that if you take that mathematical fact too seriously, you also throw away the assumption of "dynamic universe". :shrug:

 

length contraction:

 

[in the 1905 paper, par.4, 'physical meaning', he describes a moving sphere 'viewed' as an ellipsoid, when measured from a system with synchronized clocks, per par.1. This is open to interpretation as an apparent or measurement effect.]

If you understand special relativity you should understand he is talking about how a different definition of simultaneity impacts a definition of space. It's not "apparent" (it's not even visually possible to "see" because we only "see" the finite speed signals from events), nor is it "measured" without first defining what type of simultaneity are we using.

 

Basically ralfcis is talking about a different convention for clock synchronizatoin / simultaneity. With different convention you also impact a definition of space and time. It's trivial to show that it is possible to create a fairly simple model with universal simultaneity, by using appropriate conventions.

[AnssiH]

I guess what is throwing me off is your use of the term “length” when referring to a spacetime interval.

 

It may be that your way of thinking about this is more advanced than mine since I have never considered that a spacetime interval can be a length.

 

Probably the reason for that is that it contains quadratic terms, forcing me to think in terms of an area, not a length.

 

I do know, for example, that the area of a light-rectangle is frame invariant in SR.

 

Another way to think of it is as a displacement in spacetime, which would still be an area rather than a length as I understand it.

 

But I am working from memory. I will look for a source on exactly what a spacetime interval is, in a geometric sense.

I don't believe it can be a length or a vector as I am fairly sure a vector can not be frame invariant, in the direction of motion.

It is best understood as length. In fact the reason there's quadratic terms in there is that it's just a pythagorean equation (with a negative component).

 

You can just write it as

 

[math] s^2 = x^2 + y^2 + z^2 - (ct)^2 [/math]

 

For more info:

https://en.wikipedia.org/wiki/Spacetime#Spacetime_interval

 

This trick is not useful for everything because it gives you somewhat ill-defined coordinates along the light cones. Basically the last term being negative means you get 0 length interval along light cones. Meaning, an event on earth gets the same exactl coordinate as some event on mars. That kind of sucks for some use cases :D

 

See;

http://foundationsofphysics.blogspot.com/2015/03/towards-quantum-gravity.html

 

-Anssi