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Does time exist?
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But in the specific instance of determining whether both observers will read the same measurement on the track ruler what we are interested in is not how much the light has travelled with repsect to Observer 1, but rather how much the light has travelled with respect to the track, to see how much of the track has been illuminated by the light.Yes. So the track ruler is moving in one frame of reference, and therefore not accurately measuring the distance light travelled with respect to observer 1. The ruler is stationary in another frame of reference, and therefore accurately measuring the distance light travelled with respect to observer 2. The train ruler, likewise, accurately measures the distance light travelled with respect to observer 1, but not observer 2.
"passing through reference frames" may be the wrong way to phrase it, but Observer 2 makes up part of Observer 1's reference frame, just as the rods do, and vice versa.There is no passing through reference frames. This would only happen if observer 3 adopted the same velocity of observer 1.
with regard to the sphere(s), if it is the same sphere, with different centres, then it won't necessarily be a sphere - I picture it to be somewhat like how a wormhole is traditionally depicted.The sphere has two different "loudnesses", and sphere of light has different centres. The rod, in other words, has two different locations. Just as your computer is "near" in your frame of reference, but "far" in my frame of reference.
Also, to say that the computer (or the rod) has two locations is somewhat of a misnomer, I think, because it blurs the lines between what is meant by "location"; just because we are standing different distances from it, it doesn't mean it has two locations. If you superimpose a theoretical, mathematical co-ordinate system on reality, and I do likewise, then we might argue that it has two locations, but that isn't actually the case because neither of us owns the "true" co-ordinate system.
I'm inclined to put more trust in your own mathematical ability - simply because I am familiar with my ownYes they would. They would both also agree on what the train ruler says. Observer 2 would say the track ruler is correct. Observer 1 would say the train ruler is correct.
The above is incorrect because you are conflating the two rulers. We will only consider the track ruler.
Observer 1 passes the 0 mark on the ruler (The midpoint) at t' = 0 and meets the light at t2' = ɣt2(1 - v^2/c^2) (This was derived in post # 54).
t2' = ɣt2(1 - v^2/c^2) = t2/ɣ = 5L/18cɣ
In this time, the track has travelled a distance of
5L/18cɣ * v = 5Lv/18cɣ = 5L/18ɣ(c/v) = 5L/18ɣ(4/5) = 4L/18ɣ
But since the track is contracted, it will measure the larger distance of ɣ4L/18ɣ = 4L/18.
This is in agreement with observer 2.
A similar calculation can be performed to show that both observers will agree with what the train ruler says.
but my initial impression, and this could quite easily be down to an error in my reasoning, is that saying that Observer 1 passes the 0, mark on the ruler at, t'=0 looks like a bit of a red herring - not in the sense that you are deliberately trying to mislead, but because when Observer 1 passes the 0 mark both the light and the track have already been travelling.
In Observer 1's reference frame, with the rod following behind the light, at 4/5 of its speed, the light will only ever have moved ahead of the rod by 1/5 of the overall distance travelled by the light, thus it will only have illuminated a length of track measuring 1/5 of that distance, and hence that graduation on the track - by the time it reaches Observer 1.
On the other hand Observer 2 will see a sphere of light centred on the rod, and so it will illuminate 5/9 of the distance by the time it reaches Oberver 1. Even allowing for contraction, it appears as though they will see different lengths of track illuminated.
All that being said, with respect to the derivation in post #54, the conclusion appears to be assumed in saying that t' = ɣ(t - vx/c^2). The derivation of ɣ as per the video you posted is something which the author also challenges.Your first birthday is a present event of a reference frame. You typing a response yesterday is a present event of a reference frame. You reading this is a present event of a reference frame. If you accept that all these events are real (not just you reading this), then there is no major dispute.
In this reference frame none of those events are real any longer, but that would just be in this reference frame. My first birthday, with respect to this reference frame, is now an abstraction; but if that reference frame actually exists then it has it's own present i.e. if me as a one year old exists, the [he] is currently having [his] first birthday (according tho him). So if the entire universe is paused then the present is made up of all those present reference frames.
What would be the case thought if one of the presents was chosen as the moment to pause the universe; where that present is "the past" of another reference frame?
Oberver in motion
This is related to the point above about the "true present"; it might appear to be going back over old ground, but, through my own fault, there was an inherent assumption which was never addressed; the assumption relates to the notion of "past" and "future" reference frames.
Yhe point raised was:
and the reply:The crux of the issue, as far as I can see, isn't the relative motion of either Observer with respect to the earth, the sun, or our solar system; it is that Observer 1 is moving relative to Observer 2, as well as both rods, A and B, while Observer 2 is at rest relative to the rods.Then what is the absolute "present"? What must we be stationary with respect to in order to determine the true present?
The notion of the "universal pause button" was raised after this, while allowing the assumption of "past" and "future" reference frames; "past" and "future" reference frames are however challenged by the notion that Observer 1 would conclude that it is he that is moving relative to the rods and the "beam" of light.
To address the issue: "What must we be stationary with respect to in order to determine the true present?"
Our ability to determine the true present has no bearing on its existence, but in the context of Observers 1 & 2, if Observer 1 correctly [in my opinion] concludes that it is he that is in motion, with repsect to the rods and Observer 1, then he would come to the same conclusion - that the lightning strikes occured at the same time - as Observer 2.
Again, the issue of how Observer comes to the conclusion might need to be addressed, but you would imagine that if he arrives to the train station before his train departs and instead of boarding the train immediately he stands on the platfrom and watches the train start to pull out before boarding it, then he would conclude that it is, in fact, he that is in motion relative to the rods.
Alternatively, if he were to wait with Observer 2 until the train was approaching and then walked a distance to get picked up by the train (using it's sophisiticated device for picking up passengers while in motion), which allowed him to reach the inertial velocity of 0.8c before reaching the rods, he would surely conclude that it was he that was in motion and not the passing countryside.0 -
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But in the specific instance of determining whether both observers will read the same measurement on the track ruler what we are interested in is not how much the light has travelled with repsect to Observer 1, but rather how much the light has travelled with respect to the track, to see how much of the track has been illuminated by the light.
And as I have shown, light and observer 1 will cross at the 4L/18 mark. Meaning observer 1 travelled 4L/18 with respect to the track, and light travelled L/2 - 4L/18 = 5L/18 with respect to the track. Light will be 1/5 ahead of the pole only according to the train ruler.with regard to the sphere(s), if it is the same sphere, with different centres, then it won't necessarily be a sphere - I picture it to be somewhat like how a wormhole is traditionally depicted.
I have a football. It is effectively a sphere. In my frame of reference, the centre is "near". In your frame of reference, the centre is "far". Hence, it has two locations assigned to it. So long as there is one centre per reference frame, there is no issue.Also, to say that the computer (or the rod) has two locations is somewhat of a misnomer, I think, because it blurs the lines between what is meant by "location"; just because we are standing different distances from it, it doesn't mean it has two locations. If you superimpose a theoretical, mathematical co-ordinate system on reality, and I do likewise, then we might argue that it has two locations, but that isn't actually the case because neither of us owns the "true" co-ordinate system.
Exactly. A co-ordinate system is just a set of labels we place on all events. If we talk about the light without respect to any co-ordinate systems, which is what physicists often do, then there is no issue. There is no intrinsic centre of the sphere.
But interestingly enough, if we look at the light sphere in the context of space time, there is indeed a centre to the light "cone" that all observers will agree on. I.e. All observers will agree that lightning struck the pole.I'm inclined to put more trust in your own mathematical ability - simply because I am familiar with my own but my initial impression, and this could quite easily be down to an error in my reasoning, is that saying that Observer 1 passes the 0, mark on the ruler at, t'=0 looks like a bit of a red herring - not in the sense that you are deliberately trying to mislead, but because when Observer 1 passes the 0 mark both the light and the track have already been travelling.
It isn't mathematical ability that is the issue. The issue is conceptually grasping what is happening. 5L/18cɣ is the time interval between the observer passing the 0 mark and the observer intercepting the light. Therefore the track, in that time, must have travelled from a state of the 0 mark being at observer 1, to a state of the mark 4L/18 being at observer 1. If you want, you can consider the entire travel time, and you will get the same answer since observer 1 starts before the 0 mark. But the calculation would be more convoluted.
And remember, the (1/5)(ɣL/2) is what his own ruler will report. I.e. His ruler will tell him the light travelled ɣL/2, so the real location of the pole must be a distance ɣL/10 away from him, according to his own ruler. You keep telling me you want to discuss the track ruler, but you keep using the train ruler. The pole is stationary with respect to the track ruler.In Observer 1's reference frame, with the rod following behind the light, at 4/5 of its speed, the light will only ever have moved ahead of the rod by 1/5 of the overall distance travelled by the light, thus it will only have illuminated a length of track measuring 1/5 of that distance, and hence that graduation on the track - by the time it reaches Observer 1.
Thus, 1/5 of "That distance" (ɣL/2 according to his own ruler, not according to the track ruler).On the other hand Observer 2 will see a sphere of light centred on the rod, and so it will illuminate 5/9 of the distance by the time it reaches Oberver 1. Even allowing for contraction, it appears as though they will see different lengths of track illuminated.
Again, you are conflating two rulers. The section of the track that will be illuminated will be from the 4L/18 mark to the L/2 mark. Similarly, both observers will agree that the train ruler has been illuminated from the ɣL/2 mark to the 0 mark. It is very straightforward if you just take time to methodically work from the lorentz transformations.
Observer 1 will say that, since the track is moving, and since different portions will be illuminated at different times, the overall reading cannot be trusted, meaning the image of the track's illuminated section, if we use correct markings, will actually be ɣL/2. Observer 2 will say it is the train's ruler that is moving and hence incorrect, and the track ruler is giving the correct reading.All that being said, with respect to the derivation in post #54, the conclusion appears to be assumed in saying that t' = ɣ(t - vx/c^2). The derivation of ɣ as per the video you posted is something which the author also challenges.
It is not assumed. It follows from the Lorentz transformations.In this reference frame none of those events are real any longer, but that would just be in this reference frame. My first birthday, with respect to this reference frame, is now an abstraction; but if that reference frame actually exists then it has it's own present i.e. if me as a one year old exists, the [he] is currently having [his] first birthday (according tho him). So if the entire universe is paused then the present is made up of all those present reference frames.
What would be the case thought if one of the presents was chosen as the moment to pause the universe; where that present is "the past" of another reference frame?
Oberver in motion
This is related to the point above about the "true present"; it might appear to be going back over old ground, but, through my own fault, there was an inherent assumption which was never addressed; the assumption relates to the notion of "past" and "future" reference frames.
The notion of the "universal pause button" was raised after this, while allowing the assumption of "past" and "future" reference frames; "past" and "future" reference frames are however challenged by the notion that Observer 1 would conclude that it is he that is moving relative to the rods and the "beam" of light.
To address the issue: "What must we be stationary with respect to in order to determine the true present?"
Our ability to determine the true present has no bearing on its existence, but in the context of Observers 1 & 2, if Observer 1 correctly [in my opinion] concludes that it is he that is in motion, with repsect to the rods and Observer 1, then he would come to the same conclusion - that the lightning strikes occured at the same time - as Observer 2.
Again, the issue of how Observer comes to the conclusion might need to be addressed, but you would imagine that if he arrives to the train station before his train departs and instead of boarding the train immediately he stands on the platfrom and watches the train start to pull out before boarding it, then he would conclude that it is, in fact, he that is in motion relative to the rods.
Alternatively, if he were to wait with Observer 2 until the train was approaching and then walked a distance to get picked up by the train (using it's sophisiticated device for picking up passengers while in motion), which allowed him to reach the inertial velocity of 0.8c before reaching the rods, he would surely conclude that it was he that was in motion and not the passing countryside.
Determining motion with respect to something else is easy, and there is no dispute over this. Both observers will agree that the rods are moving with respect to observer 1, and stationary with respect to observer 2. But the observers would not be able to determine whether the train is moving absolutely, or whether the earth is rotating, and hence moving the tracks, and the train is stationary. Motion with respect to something doesn't indicate which frame of reference is more correct. This can be seen with a slight modification of the thought experiment.
Let's put the rods on both the train and the track. Call the new rods rod A' and rod B', and get rid of lightning. In observer 2's frame of reference, the passing of A and A' happens at the same time as the passing of B and B'. They are simultaneous. In observer 1's frame of reference, rods B and B' will pass before rods A and A'. Both observers are stationary with respect to one set of rods. Which represents the true present?0 -
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but couldn't we also extend the grid system from the sphere such that it covered both observers and resulted in just one grid reference system?
What what is stationary and what is moving? Do we set up a grid system where the rod is stationary, or a grid system where the rod is moving? This will define whether or not the rod stays at the centre of the sphere of light.I know, but what I am saying is that that is just a consequence of applying two imaginary reference systems to the same thing, where one reference system would do.
But which one imaginary reference system do you assume?Here is a brief outline of the experiment, which is continued in more detail on the section of the site linked below.
Experimental section
I can email him and ask him if he has a more detailed procedure - I presume the details of an experiment would usually be more formal. He is quite open to email, so if you wanted to ask him the specifics I'm sure he would be delighted to oblige - you would probably know the right questions to ask.
What I meant was I could not find the article for the experiment. The details he gives are nowhere near comprehensive enough for me to review the experiment. Not making references available is a big no no in science.
Put it in perspective. The neutrino experiment is gathering huge attention from the scientific community. Scientists rushed to get their name on the famous article. The level of detail in the article is of a scientific standard.
http://arxiv.org/pdf/1109.4897v1
The author of the website is presenting an equally astounding violation of relativity. But he presents no article. Does this mean he did the experiment himself? If he presented the detail needed to repeat the experiment, then scientists would presumably rush to repeat it.Just to be clear, if you and I get the train from Dublin to Cork tomorrow morning, we can't know if it is the train that is moving, or the rotation of the earth that is causing cork to move towards us; do you genuinely believe that to be the case? What about the engines in a train and the work that has gone into designing vehicles that can move? Isn't there something to do with the energy gone into powering a train that means it has to go somewhere which wouldn't be accounted for by simple carbon emissions?
We know the rotation of the earth, with respect to the solar system, is in an easterly direction. But with respect to the galactic super cluster, our solar system, and hence earth, could be rotating in such away that travelling from north to south means you are stationary with respect to the galactic cluster.
The moral of the story is any time we are talking about motion, we are always talking about it with respect to something else.
As for the energy powering the train, it would still be expended, just as you must expend energy to balance yourself on a rotating log.What if we change the "dilemma" somewhat, and install a superhero instead of an observer on a train; a superhero who can travel up to, but not including the speed of light. The superhero would know that it is they that is moving, and not the rotation of the earth that is causing them to move, because they have to move their limbs.
We can even assume he can travel the speed of light if we like. Let's say he leaves the earth and travels across the universe at some arbitrary speed. How would he know if it is he that accelerated, and travelled through the universe, or if he is stationary and the universe accelerated in the opposite direction, and is travelling past him? Relativity says he would have no way of knowing, as the laws of physics are the same in all reference frames.I'm sure it shouldn't be too difficult to show that it is the engine of the train which is causing the train to move and not the rotation of the earth causing the track beneath to go past. Otherwise all the science behind lokomotive transport could be discarded, no?
Why? Locomotive transport is perfectly legitimate when we are talking about motion with respect to the surface of the earth.The true present would then be represented by the infinite number of reference frames, at say, t=0.
Let my try and illustrate my point. Let's push the pause button at some t=0, according to two reference frames. I.e. Let's look at two reference frames that agree when the pushing of the button occurs. Below is an illustration of the first frame.
The black line is the present. Dots on the black lines are events that occured during the present. (Let's say the event in the centre is the "pushing the pause button event".) Dots above and below it are future and past events, and are therefore not real according to you.
But now let's look at it from the perspective of both reference frame.
The blue line is the present from the perspective of the 2nd reference frame. Notice that all the blue dots are now real, and the back dots (bar one, the pushing of the pause button) are in the future or past, and are hence imaginary. So we have two reference frames that agree with when the pause button was pressed, but have different "presents". My question to you is, when we push the button, which events are real? All of them? None?0 -
I would say a grid system where the rod is stationary, becuase I would question the assumption of the sphere with two different centres.What what is stationary and what is moving? Do we set up a grid system where the rod is stationary, or a grid system where the rod is moving? This will define whether or not the rod stays at the centre of the sphere of light.
that would be a matter of choice.But which one imaginary reference system do you assume?
I think the comparison with the OPERA experiment is a little off; I'm sure when it comes to independent researchers (assuming this guy is legit) then I can imagine trying to get someone to read past the extract, of a paper which challenges the well established MMX & SR, without letters such as OPERA or CERN attached, would be quite difficult. Through no major fault of anyone's - afterall, if every crackpot theory were to be peer reviewed that would lead to a lot of wasted time; but I'm sure you can appreciate that that might lead to some genuine research slipping through the net.What I meant was I could not find the article for the experiment. The details he gives are nowhere near comprehensive enough for me to review the experiment. Not making references available is a big no no in science.
Put it in perspective. The neutrino experiment is gathering huge attention from the scientific community. Scientists rushed to get their name on the famous article. The level of detail in the article is of a scientific standard.
http://arxiv.org/pdf/1109.4897v1
The author of the website is presenting an equally astounding violation of relativity. But he presents no article. Does this mean he did the experiment himself? If he presented the detail needed to repeat the experiment, then scientists would presumably rush to repeat it.
I've emailed him again to see how he submitted it for peer review, and see if he has a more comprehensive outline of the experiment.
I understand that, but it is the below which i think is the case.We know the rotation of the earth, with respect to the solar system, is in an easterly direction. But with respect to the galactic super cluster, our solar system, and hence earth, could be rotating in such away that travelling from north to south means you are stationary with respect to the galactic cluster.
The moral of the story is any time we are talking about motion, we are always talking about it with respect to something else.
with respect to the train, we are talking about locomotion with respect to the surface of the earth, though.Why? Locomotive transport is perfectly legitimate when we are talking about motion with respect to the surface of the earth.
but if it was the train that was in motion and the brakes were applied, wouldn't the direction of momentum be different than if it was the earth that was causing the movement?As for the energy powering the train, it would still be expended, just as you must expend energy to balance yourself on a rotating log.
If Observer 1 applied the breaks, wouldn't the direction of momentum let him know if it was the train that was moving, or the ground beneath him. I'm thinking along the lines of the difference between running on a treadmill and running on the road; if you stop suddenly on a threadmill you will be thrown backwards, but if you stop suddenly on the road your momentum would take you forward.
but if we take it back to the surface of the earth, he would know from the fact that he was moving his limbs that it was he that was moving, wouldn't he?We can even assume he can travel the speed of light if we like. Let's say he leaves the earth and travels across the universe at some arbitrary speed. How would he know if it is he that accelerated, and travelled through the universe, or if he is stationary and the universe accelerated in the opposite direction, and is travelling past him? Relativity says he would have no way of knowing, as the laws of physics are the same in all reference frames.Let my try and illustrate my point. Let's push the pause button at some t=0, according to two reference frames. I.e. Let's look at two reference frames that agree when the pushing of the button occurs. Below is an illustration of the first frame.
The black line is the present. Dots on the black lines are events that occured during the present. (Let's say the event in the centre is the "pushing the pause button event".) Dots above and below it are future and past events, and are therefore not real according to you.
But now let's look at it from the perspective of both reference frame.
The blue line is the present from the perspective of the 2nd reference frame. Notice that all the blue dots are now real, and the back dots (bar one, the pushing of the pause button) are in the future or past, and are hence imaginary. So we have two reference frames that agree with when the pause button was pressed, but have different "presents". My question to you is, when we push the button, which events are real? All of them? None?
Are those "timelines" an accurate representation of the possibilities, according to relativity? Does relativity provide for the possibility that the events in the present of one reference frame can be divided among the past and future of another?0 -
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I would say a grid system where the rod is stationary, becuase I would question the assumption of the sphere with two different centres.
But the "two different centres" are just the "grid with stationary rod" centre and the "grid with moving rod" centre. Again, this is no different to a ball having a "near" and a "far" centre. It's all just perspective.I think the comparison with the OPERA experiment is a little off; I'm sure when it comes to independent researchers (assuming this guy is legit) then I can imagine trying to get someone to read past the extract, of a paper which challenges the well established MMX & SR, without letters such as OPERA or CERN attached, would be quite difficult. Through no major fault of anyone's - afterall, if every crackpot theory were to be peer reviewed that would lead to a lot of wasted time; but I'm sure you can appreciate that that might lead to some genuine research slipping through the net.
I've emailed him again to see how he submitted it for peer review, and see if he has a more comprehensive outline of the experiment.
This might be true, but scientists have been testing relativity for a century, with plenty of modern experiments that contradict the author's results.
http://johanw.home.xs4all.nl/PhysFAQ/Relativity/SR/experiments.html
Here are specific references to Laser experiments.
http://johanw.home.xs4all.nl/PhysFAQ/Relativity/SR/experiments.html#modern-laser
Scientists have been very thorough with lasers and have not demonstrated any anisotropy in the speed of light.with respect to the train, we are talking about locomotion with respect to the surface of the earth, though.
It is with respect to the surface of the earth, not with respect to the train. Locomotion, with respect to the train, is non-existant. I.e. The train is always stationary with respect to the train. Engineers instead devised means of motion with respect to the surface of the earth.but if it was the train that was in motion and the brakes were applied, wouldn't the direction of momentum be different than if it was the earth that was causing the movement?
No.If Observer 1 applied the breaks, wouldn't the direction of momentum let him know if it was the train that was moving, or the ground beneath him. I'm thinking along the lines of the difference between running on a treadmill and running on the road; if you stop suddenly on a threadmill you will be thrown backwards, but if you stop suddenly on the road your momentum would take you forward.
If he applied the brakes, the ground would stop moving beneath him. He would interpret this as the ground slowing down.but if we take it back to the surface of the earth, he would know from the fact that he was moving his limbs that it was he that was moving, wouldn't he?
He would need to move his limbs to stay stationary just as you need to move your limbs to stay stationary on a spinning log.Are those "timelines" an accurate representation of the possibilities, according to relativity? Does relativity provide for the possibility that the events in the present of one reference frame can be divided among the past and future of another?
Yes. It is precisely the type of transformation relevant to special relativity. Here is the somewhat cluttered picture from youtube illustrating the lorentz transformation of space and time.
Or another that makes it more obvious
The x-axis is an instant in time according to one frame of reference. The x'-axis is an instant according to another. Notice they are not parallel, so the present in one frame of reference is smeared over the past, present and future of another.
Take our train example. If we hit the pause button at t = 0, both bolts strike in the present, according to observer 2, but one is in the past and the other is in the future according to observer 1.0 -
I don't think it's quite as simplistic as that though is it? It would be more like "grid with centre of sphere located above rod" and "grid with moving rod with centre not above rod"; in terms of a ball, it would be similar to the ball being beside a post in one grid and not beside the post in another.But the "two different centres" are just the "grid with stationary rod" centre and the "grid with moving rod" centre. Again, this is no different to a ball having a "near" and a "far" centre. It's all just perspective.
I don't think the author's experiment demonstrates any anisotropy in the speed of light eitherThis might be true, but scientists have been testing relativity for a century, with plenty of modern experiments that contradict the author's results.
http://johanw.home.xs4all.nl/PhysFAQ/Relativity/SR/experiments.html
Here are specific references to Laser experiments.
http://johanw.home.xs4all.nl/PhysFAQ/Relativity/SR/experiments.html#modern-laser
Scientists have been very thorough with lasers and have not demonstrated any anisotropy in the speed of light.
that is what we are talking about though, isn't it? the locomotion of the train with respect to the surface of the earth?It is with respect to the surface of the earth, not with respect to the train. Locomotion, with respect to the train, is non-existant. I.e. The train is always stationary with respect to the train. Engineers instead devised means of motion with respect to the surface of the earth.
But if you or I are travelling in a train and it slams on the brakes, we will be jolted forward initially - Is that something to do with us inhereting the momentum of the train?; if it were the earth that were moving the same effect wouldn't be felt, would it?No.
If he applied the brakes, the ground would stop moving beneath him. He would interpret this as the ground slowing down.
similarly though, if he were to stop suddenly wouldn't there be a discernable difference, which would help him to conclude that the log was spinning as well.He would need to move his limbs to stay stationary just as you need to move your limbs to stay stationary on a spinning log.Yes. It is precisely the type of transformation relevant to special relativity. Here is the somewhat cluttered picture from youtube illustrating the lorentz transformation of space and time.
Or another that makes it more obvious
The x-axis is an instant in time according to one frame of reference. The x'-axis is an instant according to another. Notice they are not parallel, so the present in one frame of reference is smeared over the past, present and future of another.
Take our train example. If we hit the pause button at t = 0, both bolts strike in the present, according to observer 2, but one is in the past and the other is in the future according to observer 1.
OK, I was getting a bit confused, I was thinking the blue dots (as per your initial diagram) corresponded to the black dots i.e. the blue dot "events" were the same as the black dot "events"; because that would have meant that events which were in the past of one reference frame were also in its present, while other events which were in its future were also in its present.
The "timelines", that are drawn there, only represent two reference frams of the infinite number of reference frames; the true present wouldn't consist solely of just those two reference frames, it would include all reference frames - how would that be graphed?
Using just the two reference frames above, the true present would consist of both lines. Sticking with the train example: at t=0 the lightning strikes would be in the present of Observer 2's reference frame and so those events would be real in Observer 2's reference frame; while the strike at B would have occurred already in Observer 1's referene frame so the lightning striking B is no longer a real event - in Observer 1's reference frame - it is in the memory of Observer 1.0 -
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I don't think it's quite as simplistic as that though is it? It would be more like "grid with centre of sphere located above rod" and "grid with moving rod with centre not above rod"; in terms of a ball, it would be similar to the ball being beside a post in one grid and not beside the post in another.
Which side of the post? It could be in front of the post with one grid, and behind the post in another. I do understand the counter-intuitive nature of this, and it is an effect that does not happen under Galilean transformations. But is happens because the speed of light is the same for all observers. Either you have the pole remain at the centre of the sphere in all reference frames, or you have a constant speed of light in all reference frames. Plus, as mentioned before, the lightning strike on the pole is at the centre of the hypersphere for all observers. I am surprised you have an issue with this, as you have agreed that co-ordinate systems are artifices.I don't think the author's experiment demonstrates any anisotropy in the speed of light either
The dot shifts from centre. This means it is inheriting more speed. If you are swimming across a river at speed v, and a current picks up, then you will inherit the speed of the current, making your total speed greater than v.that is what we are talking about though, isn't it? the locomotion of the train with respect to the surface of the earth?
Yes. And relativity is consistent with locomotion technology.But if you or I are travelling in a train and it slams on the brakes, we will be jolted forward initially - Is that something to do with us inhereting the momentum of the train?; if it were the earth that were moving the same effect wouldn't be felt, would it?
similarly though, if he were to stop suddenly wouldn't there be a discernable difference, which would help him to conclude that the log was spinning as well.
This is true. But, due to the principle of equivalence, we cannot say we are the ones who have slowed down. In relativity, gravity is merely an expression of the geometry of spacetime. In our reference frame, when the break is applied, the geometry of spacetime slows the earth, and is also the reason we experience a gravitational force towards the front of the train.OK, I was getting a bit confused, I was thinking the blue dots (as per your initial diagram) corresponded to the black dots i.e. the blue dot "events" were the same as the black dot "events"; because that would have meant that events which were in the past of one reference frame were also in its present, while other events which were in its future were also in its present.
The "timelines", that are drawn there, only represent two reference frams of the infinite number of reference frames; the true present wouldn't consist solely of just those two reference frames, it would include all reference frames - how would that be graphed?
When we consider all reference frames, we get the causal structure of the universe. The proper physics in other words. It looks like this.
The black dots are all random events. The black dot in the centre of the lines is the event "pushing the pause button". Any events that lie in the top white section are events in the future of the button push. If "pushing the pause button" were a normal, physical event, the future events would be all events that the "pushing" could influence. Similarly, if a dog barks and causes you to wake up, then the event "waking up" is in the future of "dog barks". Though since we are engaging in a thought experiment, and the pause button is instantaneously in effect, we simply say:
"The set of all events in the 'future' section are events that are in the future of the button push according to all frames of reference."
You would presumably therefore say they are not real. So far no issue. A similar thing could be said for the past section. These are all events that could have influenced the pushing of the pause button, such as the muscle movement of the finger, or the construction of the button itself. These causal events are in the past of the button push according to all reference frames, and hence not real any more.
But the next section is where your idea breaks down. The remaining sections are all events in the present of the button push. I.e. For all these events, there exists a frame of reference where the pushing of the pause button and the events happen simultaneously (i.e. In the present). So my typing this is "in the present", and you reading this is also "in the present".
There are two ways of interpreting these facts. The first, traditional approach is to insist that space time is necessarily four dimensional. Three space dimensions and one time dimension as described by relativity. The second approach, as discussed by Julian Barbour, is to consider all configurations of space, and to derive "change" and hence "time" as generated by special operators.
But either way, the newtonian, galielean notion of a "present" consisting of a single, classical 3 dimensional snapshot is no longer consistent. We can define a causal structure that exists at every event, but we cannot weave events into a single snapshot of the present.Using just the two reference frames above, the true present would consist of both lines. Sticking with the train example: at t=0 the lightning strikes would be in the present of Observer 2's reference frame and so those events would be real in Observer 2's reference frame; while the strike at B would have occurred already in Observer 1's referene frame so the lightning striking B is no longer a real event - in Observer 1's reference frame - it is in the memory of Observer 1.
But how can an event be both real and not real? Remember that reference frames are just co-ordinate systems. They cannot define what is real and what is not real.Just a further point on that: I'm not sure where Karl Popper's philosophy, with regard to falsification, ranks among the scientific community, but if applied in this instance then the author's observation would be sufficient, if not to falsify the theory, then to at least challenge it.
Is there a possible explanation for the alleged phenomenon, as outlined by the author?
If the experiment is confirmed it would definitely falsify relativity.
P.S. I forgot to answer your question about length contraction. We have witnessed the length contraction of electromagnetic fields. The electric field along the velocity of motion, making it stronger at right angles to the charge. But we have not been able to measure length contraction of, say, a train or a ruler due to the huge velocities we would need to obtain.0 -
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