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I'm in the process of fixing the text accompanying the links between the sections and their summaries. The Transhumanist 23:11, 19 August 2017 (UTC)
I don't know what you're doing, but if you need many call-outs for "mobile users do this to read the article", you're doing it wrong. Power~enwiki ( talk) 02:44, 20 August 2017 (UTC)
I feel that all the "See also: Section summary below" and "Return to Introduction" should be removed entirely. Having a separate "Introduction to Spacetime" article (if a page title can be agreed on) is a better way of solving the technical issues that you are concerned about. Simply shoe-horning mountains of device-specific text into the page is clearly not a good approach here. Power~enwiki ( talk) 16:01, 20 August 2017 (UTC)
Do we not have a method, such as {{ Selfref}} for example, by which we can automatically format all these self-references so that they won't show up in paper versions of articles? I think this may be a good compromise. -- œ ™ 00:56, 20 November 2017 (UTC)
The article says: "The fundamental reason for merging space and time into spacetime is that space and time are separately not invariant ..." Is there some reference for this?
Please, add new sections at the bottom, and, please sign your contributions.
According to Einstein the speed of an observer effects how time effects that observer. Then one can infer that because we are all move thru space at different speeds, time is relative to each observer. Then my question is "when is "Now" occurring ? Russcnj ( talk) 01:35, 24 November 2017 (UTC)
From the Explanation section: However, Albert Einstein's 1905 special theory of relativity postulated that the speed of light through empty space has one definite value—a constant—that is independent of the motion of the light source.
I think we should add independent both of the motion of the light source and of the motion of the observer. Independence from the observer's motion is the really striking and unintuitive part.
--
Arnaudf (
talk)
07:58, 8 January 2018 (UTC)
This symmetry of movement of source/observer is no consequence of the postulate, but of the relativity principle. The counterintuitivity lies in the postulate, exactly as it is formulated (without "moving observers"!) by Einstein, in that it denies the linear additivity of velocities (vobserved = vlight ≠ vlight ± vsource!). The ± covers an approaching and a receding source.
I think Arnoudf got Einstein's statement only incompletely. To talk about a "moving observer" (no observer anymore!) requires another "observer", since each observer is per definition at rest in his frame of reference. This leads to the misleading situation that the "observedly moving observer" (being not at rest!) is not an observer anymore, ... The constancy of speed of light is made up by all observers (at their respective rest!) agreeing on its value.
Since "moving (non!-)observers" are not relevant for the constancy of speed of light, it would be best to again get fully rid of them. I regret not having eliminated completely your effort to (additionally) answer Arnoudf's question, and you seem to have overlooked my rp to Arnoudf above. I do not want to get into some reverting frenzy, but the current phrasing is logically wrong.
My suggestion below is to essentially return to the status before introducing an inappropriate "moving observer", in an effort to explain a question that is better answered by "the difference between what one measures/observes versus what one sees", since genuine observers are constantly at rest. Other notions of being at rest are just confusing in SRT.
Einstein's equations describe important consequences of this fact: While the spatial distances and the temporal differences between two events, as measured by different observers, do not agree, there is a new invariant measure established, that connects the two events, the spacetime interval.
I am unsure whether to mention here the specs about inertial frames, which I omitted. Perhaps consensus should be achieved on this before moving on to Einstein/Minkowski. I hope you are OK with me splitting this. Purgy ( talk) 09:49, 3 April 2018 (UTC)
Until the turn of the 20th century, the assumption had been that the three-dimensional geometry of the universe (its description in terms of locations, shapes, distances, and directions) was independent and distinct from a one-dimensional time (the measurement of when events occur within the three-dimensional universe). However, Albert Einstein's 1905 special theory of relativity postulated that the laws of physics are the same in all inertial frames of reference (i.e. the principle of relativity), and that the speed at which light propagates through empty space has one definite value –a constant– that is independent of the motion of the light source.Because physics should not depend on different observers ( principle of relativity), this postulateThe combination of these two postulates has the counterintuitive consequence that theconstantspeed of light isalso independent of the motion of the observer.constant regardless of the frame of reference in which it is measured. Furthermore, the distances and times between pairs of events vary when measured in different inertial frames of reference.
Thanks, Prokaryotic Caspase Homolog ( talk) 20:56, 3 April 2018 (UTC)
I made a few changes. Feel free to add more or to undo anything that I've done. Prokaryotic Caspase Homolog ( talk) 12:09, 4 April 2018 (UTC)
More changes to work around your issue with moving observers. As before, feel free to make additional edits. Prokaryotic Caspase Homolog ( talk) 12:37, 4 April 2018 (UTC)
Until the turn of the 20th century, the assumption had been that the three-dimensional geometry of the universe (the where, as spatially perceived in terms of locations, shapes, distances, and directions) and the one-dimensional time (just measuring the temporal when of events within three spatial dimensions). However, Albert Einstein postulated 1905 in his special theory of relativity that the speed at which light propagates through empty space has one definite value –a constant– that is independent of the motion of the light source.
This postulate, upsetting the linear additivity of velocities, not only inseparably joins together the four dimensions, hitherto assumed as independent, of space and time, but also has many spectacular and counterintuitive consequences. Einstein framed his theory in terms of kinematics (the study of moving bodies) by devising fundamental thought experiments (trains and flashes) involving known lengths and signalling via light flashes. These showed that distances and even temporal ordering (simultaneity!) of pairs of events change, when measured in different inertial frames of reference. Einstein's theory was a breakthrough advance over ...
Because physics should not depend on different observers (principle of relativity), this postulate has the counterintuitive consequence that the constant speed of light is also independent of the motion of the observer.
... (separate vantage points that aren’t being subjected to g‑forces but have different velocities). Einstein's equations, derived from these experiments, describe the important consequences in detail, and establish a new quantity, the spacetime interval between two events, each described by its "where" and "when", as invariant with respect to change of observers.
Let's try this:
Until the turn of the 20th century, the assumption had been that the three-dimensional geometry of the universe (its spatial expression in terms of coordinates, distances, and directions) was independent of one-dimensional time. However, in 1905, Albert Einstein postulated in his special theory of relativity that (1) the laws of physics are the same in all inertial frames of reference (this is the principle of relativity), and (2) the speed at which light propagates through empty space has one definite value—a constant—that is independent of the motion of the light source.
A logical consequence of these postulates is the inseparable joining together of the four dimensions, hitherto assumed as independent, of space and time. Many other counterintuitive consequences emerge: in addition to being independent of the motion of the light source, the speed of light is constant regardless of the frame of reference in which it is measured; the distances and even temporal ordering of pairs of events change when measured in different inertial frames of reference (see relativity of simultaneity); and the linear additivity of velocities no longer holds true.
Einstein framed his theory in terms of kinematics (the study of moving bodies). Einstein's theory was a breakthrough advance over ...
I specifically excluded the following because there is no coverage in the main article of Einstein's thought experiments. The article is devoted to development of the geometric interpretation of relativity, not the kinematic. Perhaps this sentence should go into the Special relativity article, along with specific examples. Currently Special relativity gives no coverage of these thought experiments, which, although they never appeared in any of Einstein's formal publications, played a large role in Einstein's popular and semi-popular writings, as well as in his personal visualization.
by devising fundamental thought experiments (trains and flashes) involving known lengths and signalling via light flashes.
I also thought that words like "spectacular" and the use of exclamation points was non-encyclopedic. Prokaryotic Caspase Homolog ( talk) 03:00, 5 April 2018 (UTC)