This discussion is about a regular, pretty useless, and embarrassing, confusion at RG. If there is no spacetime, special and general relativity do not include time dilation or length contraction, there is no fusion of space and time, and SR and GR do not apply to arbitrary motion. But these things happen, experimentally. Of course, one can use a kind of "inverse Wick rotation", as done in STA and Cl(1,3), but the predictive power reduces.
It is well-known that the `contraction of length´ is real, as is time dilation, both can cross a barrier, and produce thermodynamic work. They are not illusions or apparent, for non-comoving observers. Views to the contrary are a misuse of the resources offered by RG, in detriment of valid opinions.
Space is practically empty. Space and matter are different. Space and time may be 3+1 dimensions, but evidence, empirical and mathematical, point to 4 dimensions, hence treated as fusion -- there is no unique way to separate them. This is well referenced in physics, see below. Philosophy is not physics, it is subjectively defined. As an experience of the self, time is not the same as in nature.
The 3D gimbal suffers a lock on the way to the Moon. The Earth moves, and travels around the Sun. The Sun moves, and circles the Via Lactea. The satellite moves, and passes the Solar system. The galaxies send us their light, billions of years ago.The Big Bang I hear, the CMB I measure, the Hubble flow I sense. In all of that, the constancy of the speed of light in vacuo, the Lorentz transformation, and spacetime, I'd measured. [1-7] Now, what do we understand?
On September 21, 1908 Hermann Minkowski, an already famous mathematician, began his talk at the 80th Assembly of German Natural Scientists and Physicians with the now well-known introduction:
"The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality."
One question has remained. How can one use special relativity to have some kind of union of space and time -- to “fuse” different things, experimentally and theoretically, and as they are even measured in a different way? Or, what does to "fuse" space and time mean?
This discussion attempts to clarify this common question. We are all cooperating (see below *). For example, as we see by attempts to use STA and Clifford(3,1) in special relativity. Also, in the original formulation of special relativity, that does not use the concept of spacetime. Both fail to work, as we see in the literature.
Note that comoving and non-comoving, as well as length contraction and time dilation, are not just words or optical illusions -- what they denote can cross a barrier, can produce thermodynamic work. They define different physics, different truth-conditions, not just different truth values [6]. And they manifest, or not, always in the same conditions. Length contraction and time dilation only exist for non-comoving observers, and do not exist for comoving observers. In cosmology, there is the non-conflicting addition of the Hubble Flow, which allows comoving observers to separate.
In all cases, there is only some sort of union we cannot separate -- or "fusion" -- between space and time. In other words, this "fusion" happens so that there is no unique way to split spacetime into space and time.
Otherwise the experimental data do not fit, the above sentences do not fit, life qua experience does not fit. Such as the experience of gimbal lock, which is well-known in 3D rotations at any speed, but becomes easy to avoid in 4D [7].
Globally, we can separate space and time, as we see, locally we cannot, as we also see. Like separated long wires, fused at a point, spacetime. Maybe even more wires, maybe even more dimensions exist. But, at least, we have a reality of 4D.
No ontological question is possible either, no philosophy (subjective mode) is possible, on what could be painful to one's prior convictions, like PEMDAS in middle school maths, maybe, but plain to see objectively, and forward looking. Not even words are important anymore, by themselves, but also what they mean, what they denote (in linguistics, reference and sense).
One can skip a discussion on existence, and focus on the effects.
This is at least, certainly, scholarly, possible, as a path we can take by following with an IF and entertaing what may happen.
Thus, after the IF, there is no rational discusion possible on the existence of spacetime. We can focus on the effects, using the predicted effects themselves versus observations, to affirm or deny spacetime.
* In this work, we define -- Cooperation: different people, at different times, doing different things, for the same objective. The discussion is just asked to not include ad hominem attacks, they do not advance any argument.
Even those who may seem NOT to cooperate, below, are cooperating. That way, we hope that the space in RG can be seen as more open and welcome for real effects, and where one's creativity can be useful to others.
REFERENCES
[1] H. Minkowski. Space and Time: Minkowski's Papers on Relativity. 2012. Online at: http://rgs.vniims.ru/books/spacetime.pdf
[2] C. P. Burgess. General Relativity: the Notes. 2009. Online at: http://www.physics.mcmaster.ca/~cburgess/Notes/GRnotes.pdf
[3] While the original but limited formulation of special relativity is still taught at various college-level textbooks, such as
Article Physics: For Scientists and Engineers J. .W. Jewett and R.A. Serway. Physics for Scientists and Engineers with Modern Physics. Thomson Brooks/Cole. 2012
[4] In another version of the SR, by Mashhoon, an accelerated observer is in effect replaced — on the basis of the hypothesis of locality — by a continuous infinity of hypothetical momentarily comoving inertial observers. Here, the accelerated observer and the otherwise identical instantaneously comoving inertial observer have the same velocity and position. In SR, two observers comoving are defined as having the same velocity and position. Cited by 36 references, with 14 occurrences of "comoving", Mashhoon paper at arXIv may further his treatment of accelerated motion in SR, and illuminate the use of "comoving" in SR:
at https://arxiv.org/pdf/0805.2926
[5] For the spacetime formulation, also this book:
Taylor and Wheeler. Spacetime Physics. . W. H. Freeman and Company. 1966.
[6] "Paraphrasing one of Frege's examples, if I tell you "I will photograph the Morning Star" or if I tell you "I will photograph the Evening Star" then, clearly, the two phrases have the same reference (i.e., the planet Venus) but one describes it as the last celestial body to disappear at dawn and the other as the first one to appear at dusk -- thus, they have different senses or meanings."
and following paragraphs, In Ed Gerck, 1998, Technical Report Toward Real-World Models of Trust: Reliance on Received Information
[7] https://www.researchgate.net/post/Is_gimbal_lock_a_proof_at_any_speed_of_an_underlying_4D_spacetime
At `consciousness´ I gave the following answer:
Sorry but in the paper of Minkowski there also isn´t any 4th dimension. Also no `vice versa´. When Minkowski multiplies time by velocity (c) he only had shown that there is a relationship of the unit `distance´ (measure: [m]) and the unit `time´ (measure: [s]) — coming by the unit `velocity´ as the proportion of both [m/s]). So, if one multiplies time by velocity, the result is distance, not time! At this point, and following, Minkowski failed. His double-cone has at least two big errors: 1. There isn´t depicted (shown as diagram) any space; z-axis gets exchanged by ct. 2. ct isn´t time. If ct-axis has to show distance (time in another scale, as Minkowski thought) then light produces spheres, no cones! The origin of the em-wave doesn´t move. The cone-diagram makes sense by right understanding. Outside is beyond our horizon in detection. But therefore the hidden z-axis of space has to stay for time (time and nothing else). For different times em-waves are depicted at the x-, y-plane as circles. From bigger radius to radius zero at the path past to present; reverse at the path of the time from present to future. Time may be depicted everywhere, it has no place. One may show it tabular or in different pictures (film e.g.). Also as picture in picture, different times have to be interpreted. I think about the problem whether by the Minkowski-diagram all involved must have the velocity c.
Let´s go on here.
You don´t gave an answer. Again Minkowski.
If you would stay at the assertions of him, you should be able to explain what I asked for.
Don´t take it personal, Minkowski isn´t alive any more and you want to argue on his paper. By that I think you are a good partner in discussion. Maybe you help me to understand or I will do it for you.
Where is the third dimension of space in the Minkowski cones?
Why could the origin of the em-wave move (to produce the cones)?
Have you read the file (German) which I added as pdf?
[Okt. 26.2018: Equation (24.3) has to be corrected, x2 – y1 => x2 – x1]
Time is determined by a (short) cycle in relation to another (longer) one or ever going on until stopping to count the cycles which are used to measure.
Distance only then stays in proportion to time if the velocity is constant!
Lorentz-Tranformation only is created for a constant speed, special for the speed of light of em-waves.
If i may add to the interesting discussion Peter , your clear search for truth is very appealing. From Ed's nice explanation , connecting a puzzling connection of time and space ,I obtained a simple intuitive conception (may be naive) as follows ( assuming there is a horizon beyond which we do not know anything):
1. From Theory of Relativity we have that length(space ) shrinks depending on velocity.
2. Time is a measure of duration
3. Now if velocity v is assumed we can measure and connect
distance and time i.e. the distance traveled tells us how much time has elapsed.
4. From 3 , to my mind , I am now able to "see"length(space)shrinks with increased velocity. The dimensional units are a problem in the pure accepted sense.Perhaps normalizing would help. Similarly Entropy connects Information theory , Chemical reaction , System states etc and also Time ,I think.
Cheers
Hello Narasim: Length does not shrink for comoving observers, nor time dilates. But length contraction and time dilation was somehown seen as an expectation in the original form of special relativity, in 1905. Then, the Lorentz transformation played the central role, leading to these results for non-comoving observers.
This has been abandoned for +100 years, also by Einstein, including relativistic mass, no longer in use because it is not real. We cannot make any scientific valid assumption from this history.
Thanks Ed , would like very much to use your knowledge. Is there an explanation for why speed of light is constant ?
Cheers
Narasim, thanks for your valuing my work. The search for truth comes by the way to understand research in opposite to an only repetition — as it was necessary for to study.
”… a horizon beyond which we do not know anything ”
Yes, that´s what the cones stay for. But read my explanation very exact.
” 1. From Theory of Relativity we have that length (space) shrinks depending on velocity ”
No, if velocity would shrink length, then — by the relation of length and velocity, time constant — velocity would increase. And so: v = f(v) which couldn´t be true.
” 2. Time is a measure of duration ”
Here you have differentiate between the philosophical question what time is and how we measure it.
Time is not the measurement of it. But we do measure it by (short) cycles of what ever latest is valid.
Time is the duration of reason and effect which is not reversible.
Every axis of matter (energy) could rotate (x, y, z). That only comes by time.
Rotation of an axis means to exchange the orientation of the two other axis.
Rotate something 180° axis after axis and you will get the original situation. This is why space is secluded by itself. Don´t believe other explanations. They are stupid.
By that, time couldn´t be bundled to any axis of space. It has it´s very own quality.
” 3. … connect distance and time … ”
Please follow the common declaration: That´s only valid for constant velocity.
The first formula teached in physics at school is that of velocity (v), length (s) and time (s):
v = s/t
” 4. … length (space) shrinks with increased velocity … ”
No, all what Einstein found was a correction of a measure. If one measures a length of anything which is in relative motion to him (another frame) by signals of light, he has to use the correction. The `length with it´s own velocity´ would be measured unchanged by that one which is in the same velocity as the measured length (same frame).
The shrinking space is nonsense. Space is nothing (in the material-sight), an ideal which couldn´t be bent because there is no reaction on matter or energy.
For the phenomenon of constant speed of light there is no explanation as I know. Only the verification by experiments. But nowadays it stays in hard discussion.
There we have the EPR-Paradoxon also the Michelson-Experiment.
But EPR is solved by me. For redshift I am not shure at all. It may have two reasons.
Narasim and all: Speed of light is constant in vacuo for all inertial observers. It is true for the reason that the laws of physics do no change for inertial observers. This is included in the text above, as a result of the spacetime understanding, and it is physics, not mathematics only:
"The requirement that all inertial observers agree on the interval ds2 therefore includes as a special case the condition that all such observers agree on the speed of light in vacuo."
Now, there is a movement that uses scientific terms, such as doubt, to deny science. But doubt, in science, is a technical term, just as "steam cleaning". There is no steam in "steam cleaning", it is just hot water.
Doubt is necessary in science, until you have proof. You should, then, question the proof, in the process, but nature is the arbiter in natural science, and intellect in maths. After that, one has to have the mental discipline to follow beyond the proof, to where it may go. There is no "constant doubt" to what is proven twice, by nature and mind, in physics.
It may happen that a factor is overlooked, a result is wrong. But, exactly by forging forward we can find the future inconsistencies, which we do not condemn, or the people. We value them as a door, even as a small keyhole, that let us see what is beyond the door, the wormhole that links different realities, and we find new proofs, go further.
It happened with Einstein, Minkowski, then Einstein. IF (big IF) spacetime were not discovered, by anyone yet, there would be no general relativity. Science cannot prove truth, but helps everyone get closer.
Dear Ed,
SR is built on the Lorentz Transformations and the concept of the
space-time simply derives from a trival fact:
in the simplest form at the first order
t'=t-v*x/c2 (found by Poincare')
x'=x-vt
it is a relation between IRF and IRF' for EM waves, in which the Einstein-Poincare' sync procedure is applied and valid only within IRFs.
and in the first equation the x appears mixed with the time, exclusively due to the sync procedure adopted.
IT is easily understood from what quickly reported above that the space-time or the Minkowski metric based on the LT is a machinery artifact necessary to make certain calculations of how some systems appear if signals are exchanged and time gets mixed due to how these calculations are arranged.
Always in the idealization of the Inertial reference frame which is in some cases are a non applicable idealization/approximation.
At the same time to affirm that SR is generally valid in between accelerated frames is not an accurate view point at all.
@ all
Did you know that there is a difference if the source or the reflection-shield for a signal is in motion which is near or equal to the velocity of the signal?
Einstein only postulates a single term, but that is not true.
This result was an insight coming by a long discussion around this topic with O. E. Roessler.
You will find a precise depiction to this topic next weeks on my homepage.
In short I then will give it here too.
Space and time are different things, measured differently. They do not fuse in SR,
only mix differently , for different inertial transformations, between frames that are inertial.
In SR you avoid accelerated motion (which lead to non inertial system of reference), situations equivalent to some field such as centrifugal or gravitational.
These fields are refered to as non inertial forces. The abscence of non inertial forces is what characterizes an inertial frame of reference.
Stefano, You wrote, "At the same time to affirm that SR is generally valid in between accelerated frames is not an accurate view point at all." This is incorrect, blinds a great realization, but we do not need to argue here. This is a false controversy, as some people like in RG. It has been decided +100 years ago, search online, suggest Burgess of the Perimeter Institute. Peace and joy.
>
we need to argue here instead...because it is incorrect what you said and the reason is also in the overriding of the definitions of LT themselves which I reported..
what is the reason of your questions?
Worshipping the current theory??
Stefano, Burgess summarizes, "The geometry of flat space captures equally well the relativistic kinematics of particles that are not moving at constant speed."
You have to use spacetime, the original Einstein formulation will not do. This is well-known, for +100 years. It is not a matter of scientific doubt. Look for Burgess, online at GRNotes, for the phrase.
As reported in ResearchGate by Janusz Pudykiewicz, according to Ungar (online source) , we departed from the original formulation of Einstein in our interpretation of special relativity towards the reformulation based on Minkowski's four-dimensional geometry.
In the transition process, the Einstein's formulation in terms of the addition law of the relativistically admissible three-velocities has been replaced by the Lorentz transformation. Based on the information provided by Ungar, “Einstein considered Minkowski's reformulation of his theory in terms of four-dimensional spacetime to be no more than superfluous erudition". Einstein accepted, though, the concept later because it was an essential basis for the formulation of general relativity, the spacetime formulation.
Ed
there is no original formulation, there is a derivation and it is unique.
Actually the first to admit (arbitrarily and inaccurately) that SR was suitable also for accelerated frames was Einstein himself, although he did not push SR to work into rotational motion...
I'm waiting for the exact reference then.
I'm not starting at all from what Einstein said, because as you say is 100+ but from the LT and the Lorentz Group, the Pillar of SR.
Stefano, The suggested references are:
H. Minkowski. Space and Time: Minkowski's Papers on Relativity. 2012. Online at: http://rgs.vniims.ru/books/spacetime.pdf
C. P. Burgess. General Relativity: the Notes. 2009. Online at: http://www.physics.mcmaster.ca/~cburgess/Notes/GRnotes.pdf
while the original but limited formulation of special relativity is still at various college-level textbooks, such as
Article Physics: For Scientists and Engineers
J. .W. Jewett and R.A. Serway. Physics for Scientists and Engineers with Modern Physics. Thomson Brooks/Cole. 2012
For the spacetime formulation, also this book:
Taylor and Wheeler. Spacetime Physics. . W. H. Freeman and Company. 1966.
"The scholar is always studying, always ready and eager to learn. The scholar knows the connections of this specialty with the subject as a whole; he knows not only the technical details of his specialty, but its history and its present standing; he knows about the others who are working on it and how far they have reached. He knows the literature, and he trusts nobody; he himself examines the original paper. He acquires firsthand knowledge not only of its intellectual content, but also of the date of the work, the spelling of the author’s name, and the punctuation in the title; he insists on getting every detail of every reference absolutely straight. The scholar tries to be as broad as possible…These are the things, some of the things, that go to make up a pro."
—Paul Halmos, I Want to Be a Mathematician
Peter . would you like to consider wrt your observations the following.
1. We may only be living in 3 dimension whereas the "reality" may be higher dimension. As an example , a sphere in 3d as it passes through a plane(say xy plane ) would appear as a changing disk ..zero to max to zero .
2. Rotation . example say a disk( say iron) in xy plane.To rotate we need to move it . Then we have the notion of time , which leads to how fast we rotate it. Let us assume we are able to do this fast (so v=w*R ) . I suppose it will have a max radius beyond which the edges will disintegrate. Now imagine(difficult cognitively) space itself rotating . It seems reasonable, to suppose, there might be an upper limit on radius R . This is where , perhaps we have ,I think, only "Information " and no space! . this might be why in the thread there are allusions to "Information as Absolute". This seems how views have changed from " conservation of mass" to "conservation of energy " (E = mc^2) and finally to conservation of information ie Entropy . I have the notion Entropy has all possible states(material and non material) in its definition and if Time is viewed as a unidirectional phenomena , we may be passing through "Information space" and acquiring new insights.
3. In rotation also there is acceleration and it may lead to shrinking of space in the extremities.
Cheers
More precise question, Ed.
To be inertial observer you must have no acceleration relative to what?
Eugene and all: In the spacetime formalism, this question is answered in the absolute. The inertial observer has no worldline with curvature.
Note that, op. cit. Burgess *, absolute acceleration is geometric, a mere manifestation of the deformation of the worldline of an accelerating particle and does not imply some absolute space with respect to which the particle accelerates.
Exactly in the same way, absolute inertial motion reflects the straightness of the worldline of an inertial particle and does not imply some absolute space with respect to which the particle moves with constant velocity.
* Although it is not clear from its definition, Gauss’ Theorema Egregium states that the Gaussian curvature can be determined purely in terms of lengths and angles measured within the surface — that is, in terms of the induced metric and its derivatives — and so is a property intrinsic to the surface itself (as opposed to an extrinsic property that depends on how the surface is embedded into an external R3).
“…Now imagine(difficult cognitively) space itself rotating …”
that isn’t so. It is rather easily for any normal human to understand that the space cannot rotate.
More see at least last SS post [the other are useful also] in https://www.researchgate.net/post/What_is_the_actual_physical_meaning_of_the_Lorentz_Transformations?view=5bcc82f084a7c12063181457
The SS post in https://www.researchgate.net/post/Why_are_there_lightspeed_particles_in_the_universe
can be useful here as well, though.
Cheers
So, we have priveleged (inertial, not defined by observations!) frame, Ed.
About geometry.
We can not measure empty space.
Ed, what is intrinsic geometry?
By the way, inertial - it is not about gravity, in principle.
Ed Gerck,
geometry is just a description of something, and this something does not exist, since geometry does not have an ontology by itself... something has seriously derailed in several circumstances...
https://www.researchgate.net/post/Is_Nature_based_on_a_perfect_hyperfluid_an_active_background_the_unique_responsible_of_all_the_interactions
Stefano and al: I replied in the context of spacetime theory, as I specifically wrote "In the spacetime formalism, this question is answered in the absolute." -- this is a false controversy, common in RG, but it ends here.
You are free to solve an age old problem, of what is an accelerate movement and if t is relative, like all measurements in physics. You can follow the Newton route, and remain relative. You can also understand Gauss theorem on curvature.
Vasyl: You ask, "what is intrinsic geometry?" I suggest Wolfram and online to search for that answer that satisfies you. Trust no one, is my suggestion, and the efforts will be compensated by your results. Btw, I never wrote that inertial is about gravity, must be someone else.
Ed: what is trivial to understand is that space-time is only a tool of calculation, nothing else, based on the Lorentz Ttransformations.. does not have an ontology.
This discussion is defined to be about the fusion of space and time in the current formulation of special relativity, and general relativity as well. Inertial reference frame questions always appear, and I suggest that subject is not well understood in several discussions in RG. For example, that special relativity applies also for accelerated motion. Lorentz is a consequence of spacetime, not the cause, and that makes a difference.
Of course, physically, length contraction or time dilation are not shut-off by acceleration. Equations can become more complicated, at first, but the beauty of the spacetime formalism is that it does not change in either case, or any case we can think of. Just the Christoffel symbols of the second kind, zero in special relativity, not zero in general relativity. Flat versus curved spacetime.
There is an easy way to detect pseudo-science, or mathematical models gone astray, at any natural science area, such as physics. No wrong explanation provides a large number of correct results. By the coherency of the results, compared to nature, not other minds, the objectivity asserts itself.
This has happened with the spacetime approach, compared to the orignal, first, approach by Einstein. Anyone familiar with the history of science can understand the process. Einstein did, and created general relativity out of the ashes of his beloved special relativity, using the same spacetime.
It may seem a contrasense to understand special relativity from general relativity, as we suggest, and the route is indeed steep, but the vista is beautiful. The work (op.cit.) by Burgess is particularly modern and helpful in his insights on intrinsic geometry. Surprisingly, it also helps in cyberspace, cybersecurity, where there is no actual reference at all, and intrinsic geometry meets its deep needs.
Ed, I wanted to hear the answer, but it will come down like that.
Just keep in mind that this "intrinsic" geometry is a thing based on self-reference - implies an entity of other geometry on which the concept can be existed. It is also tautology.
Komarov, I suggest you read about intrinsic geometry before talking about it. It will remind you of Polanyi. For example, with Michael Polanyi, in his idea of self-coordination of independent initiatives. Different channels may measure distance differently, but what matters is leading to a joint result which is unpremeditated by any of those who bring it about. That, more than the sum of its parts, is given by intrinsic geometry.
Narasim, no complete repetition of hole the thread for one person. Please read with the attempt to understand.
But to 1. : Geometrical figures are abstract ideals in thinking. None of them goes anywhere!
To 2. and 3. : Knowledge comes by studying physics.
Philosophical: `Space itself rotates.´
I don´t think so. Space is no thing (nothing). Only the existing phenomena may rotate or do anything.
`Different measure´ about the same length/distance:
The rule of Einstein only is a factor of correction (mistake of measurement in principle).
But we don´t know how to correct because there are two different results.
One for measuring signal is in relative motion, one for measured object is in relative motion. The third observer defines `relative motion´.
Stefano: The Lorentz transformation is not at the start of spacetime, it starts as above in the discussion, not based on Lorentz at all. We can ignore it.
Different worlds, different tautologies. The question is: which world do we live in? A 3D world where time flows one only way, or a 4D world, where there are multiple times as there are multiple places? Are we seing a slice of a 4D world? Can the slice change?
Ed:
>
this is the invariance of the EM waves in between inertial observers which is nothing else but the actual reason why the LT were invented by Lorentz and Poincarè and derived by Einstein.
for sure not in a space-time since
a) the foliation requested by the IRFs in SR is just an artifact which divides artificially in infinite separated domanis.
b) recent theories of quantum gravity relegates the time as an external parameter. but 3D+T is not sufficient, since the degrees of freedom are not enough.
We need a prinicple of integration and not principle of dissociation like the foliation in SR.
Stefano: You are welcome to your interpretation of my words, but they are not what I wrote. You are projecting, a common personal phenomenon. The Lorentz transformation does not appear, as you can plainly see. It could, rest assured, make an appearance later on, but not as a prerequisite, only as a consequence. We do not need to talk about Lorentz Transformation in this discussion.
Stefano and all: Going further than the personal note above, I would like to address the rest of your comments. Yes, 3D+T as in Cl(3,1) is not sufficient, as said in the dicussion text.
Theories of quantum gravity may relegate the time to an external parameter, but none is successful -- so, it should be considered an academic exercise, at best, maybe a proof by absurdum. It does not work, not this way.
A principle of dissociation? What you call "foliation in SR", others could call fusion, as in the discussion. It is possible that time is not what flows, and the flow of time is actually reversible, as in quantum mechanics, and spacetime is showing another picture: That we can visit different times, as we can visit different places. That would make time reversible, and we can already use current time-machines to go the past, billions of years, in EM waves, using telescopes.
Philosophy could be of great help here, because we may not be sensitive to see it in physics. A multi-disciplinary approach, diversity with redundance and variety, may see what is hidden. It seems to be out there, just not quite in focus to everyone.
We already found that there is no gravity force, it curves the existing spacetime, it can be measured by the curvature and transmitted. Previously, we found that there is no magnetic source, just charge in motion. The fusion of spacetime offers new perspectives, in the gauge transformations.
@ Stefano
Sorry to say `wall´. A wall is ordered well by (useful) bricks.
To all (off topic). Other people's emotions and irritation are easy to ignore, if you do not pay attention to it (-;
To Ed. Discussion about authorization and trust is very interesting to me, despite the fact that I have a different set of thoughts about this (another look at old question of finite automation and incoming spontaneity/will). You asks sometimes really interesting questions, discussions about which lead sometimes to interesting personal conclusions for other participants.
Understanding that a publicly created topic can provoke third-party dialogues not in the key of the topic’s creator is the only thing that lacks. You just have to accept it (or not) as this... and be happy because the topic attracts people and not silent initially. Any controversy is good, since it is dialectics for all, not only for you.
NB: I also sometimes look who is voting for a particular answer. But I silently looked through the topic, I didn’t even have the desire to engage in controversy here, because I have other understanding of the dynamics (respectively, time too) and the limitations of a particular model by the parameters taken into account (inertial concept).
We all here are examples of absence of truth to hundred years authority, and we want to change protocols, same as you.
Hello Komarov and all: thanks for the support. In mining the gold of truth in public dialogues, it is important to keep the focus, collaborating with unpremeditated third-party dialogues also in the sense of leading to conclusions, not dispersing into a divergent nozzle before the topic can clarify it.
An example of this point is offered here, in not going into Lorentz Transformation as I know we do not need to talk about it for this discussion topic, it is badly understood, gives a sensation of accomplishing something, it is one more thing that (for example) a social scientist is asked to understand, and will by its absence prove that it is not needed here. Less is more.
The Lorentz Transformation further besets special relativity, by introducing what no one can see in their own world, comoving, such as my mass or momentum fluctuating widely all of a sudden, which does not change everytime a neutrino flies by at 0.9c, my height, ditto, or my age, ditto. We better leave this topic, which is not needed in this discussion, on the fusion of space and time, and what it means, and how it it is actually measured.
The definition of inertial reference frame, acceleration, or geodesic motion, do NOT need to include Lorentz Transformation either, and its absence may clarify this discussion, thinking of what comes ahead, in curving the spacetime we defined by ds2. There is no intent to stop any side discussion, or effect, just to postpone or direct it to other places, while we entertain what will make a difference in dealing with the topic of spacetime fusion.
It is an experiment, but a prescient one. It has guidance, not just flow. The guidance is the trust, the many ways of knowing, that cohesion can bring. We do not have to always hit the bullseye, all the time, just being close enough to the target, the rest of the discussions will bring to the target (Lyapunov), wherever it is. A way to measure prescience, the fact of knowing something before it takes place, as pre-science.
Why have we only second derivative in Newton's law? Because with more than second derivative equations have no solution in common case. More than second derivative means more than two dimensional phase space where chaos begins.
The main Newton's secrete, coded by him in anagram was:
"It is usefull to solve differential equations"
An inertial observer enclosed in a box would not feel drawn to any of the walls,
but just float around.
Let's have some fun. Below, in parenthesis and bold, I hopefully tell a message of deeper significance on the topic of spacetime fusion, but avoid readers from falling off the proverbial chair, in tight curves.
When Gauss defined the curvature of a surface, for example, he (Gauss) made explicit use of the way the surface sits in space. Evidently, this (i.e., the way the surface sits in space, not Gauss, not his celebrated and well-understood theorem, we are not wet behind our ears here, not anyone or anything else) is an extrinsic “curvature as bending” rather than the intrinsic “curvature as stretching” that he (Gauss) also measured (yes, he measured many different things, the old man).
The latter is in the basis of spacetime, the geometry of special relativity (avoiding Einstein first approach) and general relativity (both use the same spacetime, one flat and the other curved). Notice that this metric is not positive definite (I mean what I say), unlike the metric considered when thinking about the geometry of three-dimensional space. But distance is positive (excludes zero, all is fine...so far...) and agrees with our notion of distance in flat space if (Big IF) it is restricted to a purely spatial interval.
The possibility that distance (as would be measured by ds2, formally) can be zero or negative (Horror! Tight curve. Hang on! That is how bad it really could get. Heresy Warning!!) is the main reason (Reach Absurdum!) why the geometry of spacetime differs from the geometry of four-dimensional space (Don't go there, a fate worse than death awaits you).
More at (with proper context, this is a matter of ontological discussions, its nature may not exist -- but does.) the discussion text and NOTES, above.
Cheers, Ed Gerck
The box and the observer could be moving at the same constant speed with respect to another inertial system, but could not detect this motion.
If they were in a non inertial system, ie. car driving on a curve, the observer would be plastered against some wall.
If one takes the variable (i*t) instead of t, then the infinitesimal ds2 seems exactly the same in the two spaces, so insertion of time seems to not alter the fundamental structure of linear space.
It does change, though, because i2 = -1.
Some people tried to change it, and published (one can search), also in using Clifford algebra in Cl(3,1) and STA, in real algebra of multivectors, but it does not work physically, though mathematically. Baumgartner tried to filter it out after Cl(3,1) but you cannot filter out after the fact, the error goes through.
Time is a dimension and can transform into space in spacetime, and vice-versa, as we see in experiments and theory. Time dilation happens with length contraction - it is not one or the other.
Ed,
so time dilation and length contraction should be two faces of the same coin??
Time dilation is detectable and is detected daily also due to different positions in gravitational fields..
Do you think there is a length contraction also of objects closer to big masses?
Time dilation due to a transport along H at speed v is 1/2Hv/c2, , at the first order in a IRF. What is the length contraction(LC) in that case?
Since LC it is not cumulated, it depends only instantaneously by squared speed and goes back to 0 at 0 speed.. unlike time dilation.
What makes more sense to compare is not the time dilation and the LC but the period of the clocks and LC.
Yes, one can argue further, that is an ontological question. Some think that this is now unanswerable, but this very question, if posed, makes one realize that we live in, at least, a 5D world. Seems like a good enough approximation, to use 4D.
Besides, 3D does not fit the experimental facts, it's pseudo-ontological, because when one observes time dilation one must observe length contraction, and vice-versa, in fusion of space and time.
Dear Amrit, sorry for curiosity, tell me, did you re-create RG account on your own desire, or because of block your old by network?
Ed,
I think you did not read well enough what I said...never said that it occurs for comoving observers. An observer with speed v in regards to another is not a comoving observer.
An observer in a gravitational field is different..
Again time dilation is not the counterpart of length contraction, it is the variation of period of clocks which is a possible counterpart of length contraction.
I think I side with Stefano in sustaining that special relativity does not address
non inertial systems of reference, ie. acclerated systems. That is why something more general was needed.I particular gravity could not fit in...through the equivalence principle this is the same as introducing an accelarated frame.
Your brand of special relativity does not work with accelerated motion, OK, but spacetime is special relativity that is valid (works all the time) for accelerated motion, for non-inertial, ARBITRARY, reference systems. Read the discussion text, and references. It is all there. Do you need more?
One will not have all the answers in life when special relativity is correctly done, but one can have less empty doubts. Note that time dilation and length contraction are ALWAYS non-zero for non-comoving observers. You can complement that phrase too, that time dilation and length contraction are ALWAYS zero for comoving observers. There is no case left.
Let's start... hang on to your seat belts, curves ahead...accelerate motion...
Ed:
I was not saying that now!!! Are you able to follow what somebody says without putting in somebody else's mouth something which he did not say?
I was saying that although SR predicts time dilation and length contraction in the same context: non co-moving frames/observers
time dilation
a) is experimentally verified (twin effect/muon ring)
b) is due to different proper times of non comoving frames, clocks with different periods. it is a cumulated effect which becomes permanent in the twin effect, the offset between clocks when the clocks are at rest again and join, is detected in the same location.
c) is measured also as an offset between clocks
length contraction
although should manifest itself together with time dilation for non comoving frames
a) it did not receive a satisfactory experimental verification
b) it is not a cumulated effect and not a permanent effect, when sticks rejoin they are same length.
c) it is probably only an "apparent effect"
in addition SR predicts that co-accelerated clocks set at distance H, for v
If you are simply saying that accelerated motion HAPPENS in space time;
of course. Not easy to go out of space-time- Just dont count on SR alone to give you all the answers.
Special relativity works on the basis that there is no preferential inertial frame of reference. However and to pursue along the lines of Eugene Kislyakov, it can be argued that the cosmic microwave background is a a preferential frame in our universe.
Robert, Igael, and all: This is a misconception, a false controversy, and does not affect the discussion here, but can be illuminated by it.
The principle, which is due as far back as Galileo, is NOT that there are no special frames, such as the CMB or other, but that there are no frames where the laws of physics are different to inertial observers.
The original versions, by Einstein, and Galileo, are in the historic records. The current version is above, in the discussion text. Curiously, the current version is NOT a principle, without cause, but a condition on the cause -- now (since +100 years), the common metric of spacetime:
"The requirement that all inertial observers agree on the interval ds2 therefore includes as a special case the condition that all such observers agree on the free speed of light (free as in vacuo)." (above).
In other words, physical phenomena (such as the free speed of light) are the same in the CMB and all inertial reference frames because every inertial observer has his own space and time, and therefore describes the phenomena in their reference frame (i.e., in own space and time) in which is at rest.
There could also be a frame where the CMB is at rest but NOT the Universe, even if the Universe would be expanding perfectly radially regarding the CMB. And, for doing any physics experiment, any other frame is as good as the CMB.
It is also a misconception that in the CMB rest frame you measure no velocity with respect to the CMB photons.
Right
Any frame moving at constant speed with respect to an inertial one is also inertial.
what SR attempts to say is that the laws of physics are independent of which inertial frame you have, including the speed of light in vacuum.
From this it followed (perhaps unfortunately) that the Galilean(and newtonian) perception of
time and space as independent and absolute was wrong, The aproriate transformation was found by Lorenz, which coincides with the Galilean perception at low speeds
For those who never liked this mixture of space and time there perhaps remains
just one other option. This is to go back to the banished ether, say that it is static and everywhere, that bodies do move through it with zero viscosity, and that the speed of light depends on nothing else than the medium which it is in, in this case the ether. In another medium (glas) it is smaller and depends on frequency. In the ether it would not depend on frequency, and is a measured constant c.
Then those alert to the fact that the ether could not be proved, prefer to say there is no medium, and go back to the usuall SR version.
Those who do not like it propose a better theory!
Ed, "There could also be a frame where the CMB is at rest"...
It makes sense to clarify here that radiation according to all modern concepts cannot be at rest, in principle. So, with all the apparent proximity of the frame of reference which can be associated with the principally unitary cosmological singularity, it is impossible to grasp at it, since the radiation beause of speed limit is the edge that delineates the event horizon inside a coherent universe. This is the edge of non-violation of cause-effect relationships, and all the so-called here "inertial observers" can be only in the same subject relationship with it (radiation).
But if CMB as common coherent phenomenon exists and for the current Universe it does not, the continuity condition for the latter will be violated, which means that it will be impossible to extrapolate logically its structure into a cosmological singularity or to build any gravitational GR-like model. What is equivalent to the existence of tears (discontinuity) in causal relationships along the evolutionary path to the present. This is a very dubious prospect by many rational reasons.
As for SR vs GR (as you said earlier, "...both use the same spacetime, one flat and the other curved")...
It is not the same spacetime. The relationship of special and general relativity can be compared with the relationship of a straight line tangentially passing through a point on a curve. In a neighborhood of a point, linearization can be used as much as the first-order of Taylor expansion. These are just different sets of constraints selected to satisfy adherence to cause and effect relationships for models with different sets of parameters (SR and GR).
Continuity is not applicable to SR model framework because of linearization (as you said, every "inertial observer has his own space and time"). So, as I also said earlier, inertial - it is not about gravity (i.e. not about continuity, not about actual Universe), just some abstract model, useful in special case of parameters.
Komarov and all: The spacetime is, indeed, the same, in special relativity and general relativity, as (t,x,y,z). The metric is different, maybe that is what you mean, where the Christoffel symbols are zero in special relativity and non-zero in general relativity.
There is is an extrinsic “curvature as bending” and an intrinsic “curvature as stretching”. Intrinsic geometry is needed, it is not just mathematics, this is about the nature of things -- intrinsic is different nature from extrinsic. One can model that topology with a thin piece of dough, bending versus stretching, for curvature -- it is different. It is not just mathematics, the contrary is false physically.
The Gaussian curvature can be determined purely in terms of lengths measured within the surface — that is, in terms of the induced metric and its derivatives — and so is a property intrinsic to the surface itself, as opposed to an extrinsic property that depends on how the surface is embedded into an external R3, how it sits in space.
BTW, it may seem contrasensical to study general relativity in order to understand special relativity, but one can then more natutally seek to understand the correct place for curved spacetime, in terms of extrinsic versus intrinsic, before one inserts there the flat spacetime and differentiate from geodesics, which will be used to model accelerated motion and extend the idea of "straight lines" in the absence of external forces. The spacetime is the same, not the metric.
In my thought, since there is space bending and time distortion due to gravitation,
if you take some limited spatial enclosure and limit the time interval,so these effects are negible, then things reduce to SR over the limited space time enclosure, to understand the relationship between SR and GR. It is easier if not too close to some large mass.
The discussion text was updated, to reflect, and explain, the physical stance below, which Einstein, Minkowski, Poincaré and others pioneered more than 100 years ago, and now is studied in physics undergraduate courses all over the world, and one sees in all the universe. May it foster discussions, not limit, by setting boundaries that guide the flow, like Michael Polanyi and others said, in a collective effect.
FOREWORD: Time and space do not exist without the other, spacetime is the law of the universe. One can just discuss the acceptance of this fact, here on Earth, consciously, freely, openly, but without ontological questions left on the nature of the universe, as far as, literally, anyone can unbiasedly see, billions of years in the past. This universe, in all aspects WE CAN SEE NOW, including quantum mechanics, is at least 4D, but we can have slices of 3D here and 2D there, or 1D. Likely we can have more, in dimensions to infinity, and even beyond.
Globally, we can separate, as we see, locally we cannot, as we see, like separated long wires, fused at a point, spacetime + ...
Ed,
at first I did not understand your "accusation", but if you read well, I actually put what you accused me to neglect: "Yours" in my reply but RG "short view" took it away. It is RG fault to hide such thing not mine.
Stefano: If one works well, and waits long enough, the bodies of the enemies will float down by the river. The enemies are the enemies of Arjuna, such as Deceit, Avarice, Fear, and, above all, Egotism. The river is time itself. Thanks to Komarov, for citing the metaphor here, on RG. All fear is unfounded.
going back to the previous...
Time dilation
a) is experimentally verified (twin effect/muon ring)
b) the experimental fact confirm that (twin effect) is due to different proper times of non comoving frames, clocks with different periods.
c) It is a cumulated effect which becomes permanent in the twin effect, the offset between clocks when one clock moves in one direction and comes back is detected when the clocks rejoin.
d) it is measured as an offset between clocks
Length contraction
although should manifest itself together with time dilation for non comoving frames
a) it did not receive a satisfactory experimental verification
b) it is not a cumulated effect and not a permanent effect, when sticks rejoin they are same length.
c) it is probably only an "apparent effect"
in addition SR predicts that co-accelerated clocks set at distance H, for v
I used the quote from film in the narrow, humble context of waiting the statistics for estimation the value of speed of propagation of gravitational waves.
Or in a global sense I meant the accumulation of experience that kills unsuccessful hypotheses over time and reveals understanding, what can not be significantly accelerated.
My only enemies are uncertainty and entropy.
I used the quote from film in the narrow, humble context of waiting the statistics for estimation the value of speed of propagation of gravitational waves.
Or in a global sense I meant the accumulation of experience that kills unsuccessful hypotheses over time and reveals understanding, what can not be significantly accelerated.
My only enemies are uncertainty and entropy.
Stefano: Would you agree that:
a. Length contraction is zero transversally, always, but is non-zero longitudinally when it occurs?
b. Time contraction is always isotropic?
c. Length contraction proves the existence of magnetic fields exactly as measured, no monopoles necessary?
d. Length contraction can, always, when it exists, produce thermodynamic work? No thermodynamic work means no length contraction, always?
e. Time dilation is exactly reversible in all microscopic, quantum systems?
f. Length contraction is exactly reversible in all microscopic, quantum systems?
Vasyl
In your hope to end uncertainty, then you will have opposition for a long time.
Quantum theory carries INTRINSIC uncertainty.
Determinism has been dead for over 50 years now, except a tiny minority that was lead by Einstein (God does not play dice with the universe, he said)
An actual measurement of the speed of gravity waves would be usefull. The theorists are sure that it is c, but you cannot be too carefull.
The biblical quote (approximate) is
Just sit at the side of the road, and you will see the bodies of your enemies go by.
Of course no one means harm.
Regards, peace, Juan
Ed. What I think is that length contraction proves nothing about magnetic monopoles.
In (d) you should probably ask about mechanical work (not thermodynamic). A part of thermodynamic energy cannot be usefull work,
Otherwise the questions are reasonable
(a) is an easy yes.
Regards, Juan
Because one can write 4 equations - involving a trajectory and one to show the state of clock at each point of the trajectory assuming a synchronisation of each clock with one in the origin of an arbitrary coordinate system does not mean time exist in each point of a trajectory. More acuratelly while space is directly experienced time is just a useful abstraction. Combining real entities like apples and real oranges we have a set named Fruit. But you cannot eat fruit without eating apples or oranges.
Juan: Thanks. The definition of thermodynamic work that I like, is "Energy that crosses a barrier and can raise a weight against gravity". It is important to cross a barrier, and to raise a weigth as a simple expression of a conservative force acting without heat loss. There is nothing to lose to heat there, and thermodynamics does not conflate work with heat, but mechanics does. Mechanical work, as F.dr, can include friction and heat. There is no mandatory conservative force.
Andrew: By calling time an "useful abstraction" as you did originally, you are priming the subject -- it is a teleological fallacy, where tele is Greek like in telephone -- the distant end justifies the means, kind of thing. In your edited version of a minute ago, you deleted that, but now you joke about appletime and applespace. Clearly, you have thought hard about this. You can use this in another forum, this one is about physics. Do not use, please, this space for inconsequential jokes. Life is a school.
Ed,
>
I wrote it previously:
SR predicts that co-accelerated clocks, clocks which co-move, set at distance H, for v
Stefano: I will leave space to other comments and mainly say that "co-moving inertial observers do not see any change in physics" -- or, that "there are no special co-moving inertial frames where the laws of physics are different".
That is understood experimentally and mathematically, since Galileo. It applies to anything in physics, and Einstein made it his first principle, but in spacetime is not a principle "out of the blue" anymore, but a consequence (see text). The AJP article "jumped the shark." It does not need a reply and it is not an experiment.
Dear Ed,
I have deleted the exaggerated example as you have the right to request certain style of the discussion you have initiated.
By referring to time as a useful abstraction I mean that this is always an instance of a number derived from a complex procedure and generalized over the entire space. I agree with Ernst Mach's opinion:
" time is an abstraction, at which we arrive by means of the change of things". In the special relativity context as originally conceived it is an abstraction as well:
" Time is then defined as the ensemble of the indications of similar clocks, at rest relatively to K, which register the same simultaneously."
For me it means there is no tangible entity located in space. The fusion of the two - the spacetime is then a mathematical convenience that gradually gained an ontological status - unjustified in my opinion.
How does time behave in empty region of space? Is it there? When it changes continuously does it mean we have infinite sequences of events with no matter involved?
Ed,
Sure, the AJP is also aimed at a better understanding of the Physics (European Journal of Physics is devoted to teaching better the topics).
In that case the aim was to show you something well known which students are supposed to know and I hoped you knew as well!!
For SR such phenomenon is not a paradox in fact..
It simply disqualifies your thesis about how SR expresses time dilation and length contraction which are not supposed to manifest themselves always in the same situations, since the term vH/c2 should be detectable at low speeds and for co-moving bodies, which is not the case for length contraction.
And actually the fusion of space and time if occurs is right there also for accelerated frames, an outcome of the relativity of simultaneity inbuilt in the Minkowski space-time conception.
" I remember that one of the first things our lecturers explained, very wisely, was how in philosophy we should always criticise the theory and not the person. In undergraduate philosophy tutorials, especially in debates about applied philosophy, we would have to discuss contentious issues like abortion, animal rights, and nuclear weapons. We should strive to do that dispassionately, with philosophical objectivity, and without taking offence or attacking other people, even if we’d be shocked by the views they’re stating in the context of ordinary life.
There’s no other way to do philosophy. If we want to think rationally ourselves, we have to focus on the evidence for and against what people say, and forego criticism of the other person’s character. "
In https://donaldrobertson.name/2016/12/24/ad-hominem-arguments-and-the-principle-of-charity/
Most arguing scientists would define time as a quality been handled by physics.
But time is, what physics come from.
Universe wasn´t neither created by physics nor by time. That´s for belief.
For that you may think on anything, but be careful by thinking about the space!
Ed, a deeper thought at my answer will bring the relationship to the topic.
First help: If time – measured at different circumstances – ever will have another delay, one should try to exchange the view on the function.
And Ed, by three posts above I thought it was a discussion abpout pictures.