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Double slit in time experiment. http://physicsweb.org/articles/news/9/3/1/1?rss=2.03Cbr20/E This surely is experimental evidence that that matter/energy is not just quantised over spatial dimensions (as shown by the classical double slit experiement) but over the time dimension as well. ie: spacetime does have a quantum nature.
Examples of use of spacetime:
Examples of use of space-time:
Since Wikipedia is not a dictionary, it should stick to one spelling. Thus I removed the comment "(alternatively, space-time)". Space-time already redirects to Spacetime, so all is well. — Herbee 20:31, 11 Nov 2004 (UTC)
The space-time four vector is:
[x y z ct]
the use of the vector as:
[x y z ict]
was common about 40 years ago or so, but it is now considered archaic and the former notation is prefered.--BlackGriffen
However, there are certainly physicists who prefer the i notation, including Dr. Jack Sarfatti.
The Wikipedia should present the mainstream state of a field as much as possible, presenting relevant dissenting views as such when they arise. The use of the i is just a lazy way to make finding the "length" squared of a four vector feel like finding the length of any other vector (dot product the vector on to itself). It is, however, just as easy to define a new "length" operator for four vectors that doesn't require complex numbers.
And if bandying about names is the game, a quick look at the Feynmann Lectures on Physics explanation of four vectors shows nary an i, even though he had a discussion of using c=1.--BlackGriffen
I concur: both 'space-time' and the 'i' notation appear to be common early usage, and physicists everywhere seem now to have standardised on both 'spacetime' and the 'i'-less notation -- The Anome
1: Is there a free 3d prog that does nice, uniform renderings of some of this math?
2: Might it be a good idea to use a sidebar (can even use a msg tag for multiple article consistency) which describes some of the core foundational concepts, required for laymen learners like myself to have related study materiale at hand. Finding links in the text lacks structure that a weeded list would have. - SV (talk)
We can read in this article:
"Strictly speaking one can also consider events in Newtonian physics as a single spacetime. This is Galilean-Newtonian relativity, and the coordinate systems are related by Galilean transformations. However, since these preserve spatial and temporal distances independently, such a spacetime can be decomposed unarbitrarily, which is not possible in the general case." - is that right? Is unarbitrarily or arbitrarily? I've some difficulties with english but I'm trying to translate this to portuguese and I can't understand this... Is it an error?... Say something, please. -- Manuel Anastácio 20:29, 15 Jun 2004 (UTC)
GPS?? WTF?? - Omegatron 03:38, Dec 16, 2004 (UTC)
I've heard quite a few article discussions mention the expansion of spacetime. IT'S JUST AS PREPOSTEROUS AS TIME DILATION! How can something that is NOT a physical entity be expanded? Scorpionman 02:14, 20 May 2005 (UTC)
Knowledge Seeker is comfortable with analogies of two-dimensional rubber sheets as four-dimensional spacetime. Isn't it relaxing to have such closure?
Take Knowledge Seeker's rubber sheet. Stretch it high. Stretch it wide. Now you have a four-dimensional rubber sheet. "It doesn't seem very strange to me." Closure.
Whilst editting spacetime symmetries, I remembered that a spacetime can (in principle) have dimensions other than 4. Most people use 4D spacetimes, but many researchers use 10D spacetimes etc; it even makes sense to talk of 3 dimensional spacetimes (2 space dimensions + 1 time). I think we need to redefine spacetime to accomodate these common uses - I don't know why I never spotted this before. Roughly, isn't an n-dimensional spacetime a manifold etc... with n-1 space dimensions + 1 time dimension ?
Mpatel 10:50, 10 Jun 2005 (UTC)
It's probably better to stick to the 4D definition, and then mention that other uses of the word can accomodate things like 3D spacetime diagrams and higher spacetime dimensions in other theories. ---
Mpatel
(talk)
11:57, 19 October 2005 (UTC)
It might also be reasonable to consider space as being a single dimension, one that requires three coordinates in order to accurately describe the position of a point, rather than three seperate dimensions. Nothing tangible in our universe can be located in either one or two but not three spacial dimensions, which suggests that the dimension is not logically divisible into three. Moreover, length, width and depth are not distinguishable from each other without mutual reference, unlike the distinction that can be easily drawn between space and time dimensions. We commonly use the word 'dimension' in a non-scientific sense with reference to length, width or depth, but there would seem to be no need to define 'dimension' identically with reference to spacetime. By this logic there are then two common dimensions, space and time, and not four, time, length, width and depth. The word 'spacetime' may then be retained and need not be superceeded by the politically correct 'lengthwidthdepthtime'. Professor Krepotkin ( talk) 20:44, 2 June 2008 (UTC)
Physicist Itzhak Bars' 2006/2007? theory describes a four-dimensional space, two-dimensional time model. Will try to synthesize this information into the article according to the suggestions/comments above. Known Latitude 02:42, 18 October 2007 (UTC)
The first sentence of the article asserts that a space-time continuum is "time and three-dimensional space treated together as a simple four-dimensional object." If it is an object, one wonders if this object has a location. Where is this object?
This article is disappointing. Spacetime is not a subject that requires a great deal of knowledge to understand, but the text treats it as if it is. I would expect the average reader to feel vaguely lost by the end of the second paragraph, and then completely lost upon scrolling past the table of contents to be confronted by dense and mostly unexplained mathematical jargon. ‣ᓛᖁ ᑐ 09:31, 21 September 2005 (UTC)
My comment about the definition being incorrect was that it was incomplete (I was thinking of the technical details too - i.e. spacetime being a manifold). I was hoping for something like, 'Spacetime is a concept that views space and time as interrelated rather than as separate entities. The concept was formulated by Hermann Minkowksi soon after Albert Einstein developed the theory of special relativity.' As far as the basic idea of spacetime is concerned, that's about all we need for an introduction (I think). Later in the article, we need to mention the maths of spacetime, the physics of spacetime etc. --- Mpatel (talk) 13:10, 23 September 2005 (UTC)
I know; I didn't say (or suggest) that it should. --- Mpatel (talk) 13:53, 23 September 2005 (UTC)
What I'm saying is this: your definition of spacetime is ok for a layperson (and this is what should be at the start), but not for a specialist (who will be satisfied by the manifold stuff later on in the article). I mentioned the historical bit only to indicate what I think should also be at the start. --- Mpatel (talk) 15:42, 23 September 2005 (UTC)
From any physical theory that contains a set of elements called space and a set of elements called time, one can create the Cartesian product of space and time and this product is called spacetime. An element of spacetime is called an event. Hence, an event is an ordered pair (where,when) where where represents an element in space (a point in space) and when represents an element in time. Two events in spacetime are called simultaneous if they have the same element of time as the second element in the ordered pair. Two events in spacetime occur at the same place if they have the same element as the first element of the ordered pair.
In Newtonian physics, space has the additional structure of a three-dimensional Euclidean space, and time has the structure of a one-dimensional Euclidean space. Newtonian spacetime is the Cartesian product of the three-dimensional Euclidean space and the one-dimensional Euclidean space. However, one does not make the product into a four-dimensional Euclidean space, one keeps the three-dimensional Euclidean structure on space, and the one-dimensional Euclidean structure on time. The three-dimensional Euclidean space structure on space allows one to identify points in space with ordered triples of real numbers by choosing some (not unique) coordinate system. Given a unit length, this coordinate system may be chosen so that the square of the distance between any two points and is
Similarly, the one-dimensional Euclidean space structure on time allows one to identify elements in time with the set of real numbers by choosing some (not unique) coordinate system. Given a unit time duration, the identification of time with the real numbers may be chosen so that the square of the time difference between events occuring at times and is given by
In Newtonian spacetime, the distance D and the time duration between the events and is not combined to produce the product metric (which would give the square of the spacetime distance as ). and are considered separately.
In special relativity, Minkowski spacetime (the spacetime of special relativity) is determined by the property that the set of events (the elements of the spacetime) can be specified by an ordered quadruple and the existence of a spacetime interval between any pair of events and whose square is given by
In both Newtonian spacetime and Minkowski spacetime events can be specified by four real numbers. However, in Newtonian spacetime, the spacetime consists of a product of space and time (and all observers agree with the splitting of the spacetime into its space component and it time component). In Minkowski spacetime, each observer can choose to split the spacetime into a space component (a three-dimensional Euclidean space) and a time component (a one-dimensional Euclidean space). Different observers split spacetime into different space and time components, but they all agree that spacetime has four dimensions and that the square of the spacetime interval between a pair of events has a fixed value (once a unit interval has been selected).
In general relativity, the spacetime is curved. Minkowski spacetime is flat and the spacetime of general relativity is curved. In a manner that is analogous to the way that a sphere in three-dimensional Euclidean space can be approximated by a tangent plane near the point of contact between the plane and sphere, the curved spacetime of general relativity has the same type of relation to flat Minkowski spacetime as does the sphere to a tangent plane. The difference between the curved spacetime of general relativity and the flat spacetime of Minkowski spacetime is reflected in the (Riemann) curvature tensor.
In general, spacetime represents the part of a physical theory that is supposed to correspond to the common sense notion of space and time. After the ideas of relativity, space and time do not appear to be independent of each other and independent of other physical entities. What space and time are (and what spacetime is) is not known. In classical physics, spacetime is Newtonian spacetime. In special relativity, spacetime is Minkowski spacetime. In general relativity, spacetime is a curved four-dimensional space satisfying Einstein's field equations. Each physical theory has its own version of spacetime.
Ref: Newtonian Mechanics, Special Relativity, General Relativity, etc.
I've reorganised the article to bring out the relativity ideas more clearly. The maths section still needs a lot of work. Perhaps some more on the concept of spacetime in non-relativistic theories is needed. --- Mpatel (talk) 08:52, 22 October 2005 (UTC)
Hi RaulMiller.
Actually, I didn't change 'model' to 'object'. I changed 'coordinate system' to 'object', because spacetime is definitely not a coordinate system - spacetimes are independent of any observers and hence coordinate systems: nature doesn't care whether we measure the properties of a spacetime (e.g. time intervals) with clocks and rulers; all that matters is that spacetime exists independently of anyone who chooses to measure it's properties or not. The word 'model' is still there in the first sentence. Perhaps 'object' could be changed to 'entity' or maybe something better. --- Mpatel (talk) 08:37, 29 October 2005 (UTC)
The word 'solution' is in the opening paragraph and has not been explained (getting from manifold to solutions of the Einstein field equations is not exactly a trivial route). Non-specialists will not necessarily understand what 'solution' means (at least not without explanation or further clarification). I think the word 'solution' in that paragraph should be replaced with 'spacetime(s)'. Also, the word 'unitary' could be confused for something more technical ! - maybe 'unified' is better here. I'll try these and see if they are better. MP (talk) 09:35, 5 February 2006 (UTC)
Firstly, this article is generally disappointing: Lack of clear structure, lack of clarity in use of concepts, and just vagueness in general. The section on quantized spacetime should make reference to the work of David Finkelstein, one of the first to suggest this idea, the mention of the chronons, and should mention at least some of the basics. --NYCSEAN 20:25, 10 March 2006 (UTC)
Refers in the body of the article to the date 1929. This is *somewhat* misleading, considering he that died in 1804. The date is of course of an English translation of his work. Adittionally, Kant is most famous for his work The Critique of Pure Reason (considered probably to be the single most important work in Western Philosophy) and his earlier work was largely an attentuation of errors towards his later work.
Thus the reference properly needs to refer to the original date of publication, and if it is prior to the CPR in 1781, then make a refence to the fact that it was during his formative stages (admittedly which are the first 50 odd years of his life). I will get round to doing this eventually if it is not done by someone who already knows, please anyone post disagreements if there are any. Tsop 11:52, 12 June 2006 (UTC)
Compared to some of the other complaints above, mine is minor, but the assumption that one cannot have a nervous system if one is relegated to 2 spacial dimensions was proven wrong long ago. The Macullogh-pitts (sp?) crossover circuit allows you to cross two wires in 2 dimensions and have them act as if they are separate. It makes me wonder how well researched the other claims about the uniqueness of 3+1 space are. Swestrup 05:55, 12 September 2006 (UTC)
The article states that extra dimensions would only appear to make a difference at the subatomic level. But isn't it right that some version of string theory predicts effects on gravity already at the mm- to micrometer-scale? Depending on the size of the compactification, of course. - 80.143.117.226 23:06, 19 January 2007 (UTC)
In the last section, "intelligent life manipulating technology" can be interpreted two ways which ironically both may be correct...
May be it my browser problem. Is this image linked properly?
I'm removing the paragraph on this theory because I've never heard of a theory like this and I couldn't find any references when I googled it. I'm no specialist, though, so if someone can find a good reference please feel free to revert my edit and add the reference. —Preceding unsigned comment added by 201.222.138.228 ( talk) 23:10, 17 May 2008 (UTC) Wow! Faster-than-light revert! I suppose I was wrong, then... Well, at least I tried. 201.222.138.228 ( talk) 23:38, 17 May 2008 (UTC)
I'm also removing this paragraph because don't find it serious. Googled it, and I found ANY, and that is, ANY REFERENCE ABOUT IT. So I'm sorry but I'm removing it, unless someone here could indicate a clear reference to this or the individuals who proposed this theory.
The original text appearing on the article, has been removed and placed here, where people can indicate sources talking about it, to do this "reliable". The text don't indicate who are the people behind the theory, also there are no references about "Jack-in-the-box" (name which sounds suspicious or almost peculiar).
The text says a group of scientists in Portland, Oregon... who? who exaclty? where are thouse scientist? (no source). And then "Jack-in-the-box"... I find this suspicious...
Spiralization and Compression Theory ---- A recent development in physics is the theory of the spiralization and compression of space time, also known as the "Jack-in-the-box" theory. This theory was first put forth in 2006 by a group of scientists working in Portland, Oregon. The theory speculates that over time, all the dimensions of space spiral inward until reaching a state of absolute compression. When complete compression is reached, space springs outward and expands rapidly, as with the big bang, before the cycle is begun again. The highlight of this theory is the independence of time from the spiralization and compression of space. The impact of this theory on relativity and attempts at a unified field theory are yet unknown. However, it has been predicted, using the spiralization and compression theory, that the Large Hadron Collider will produce micro-universes.
Anyway... I will copy the subject of the spiralization and compression theory here... to allow people research on this:
I found the following arXiv documents talking about spiralization theory:
astro-ph/0501170 - West-Side Story (On the History of Density-Wave Spiral Theories in the 1960s) astro-ph/0406143 - Title: Density-Wave Spiral Theories in the 1960s. II astro-ph/0406142 - Title: Density-Wave Spiral Theories in the 1960s. I cond-mat/9502097 - Title: The motion of holes on the triangular lattice: t-J model
—Preceding unsigned comment added by 88.12.170.8 ( talk) 23:55, 11 June 2008 (UTC)
This "spiralization theory" is not in the mainstream of physics and does not deserve front page treatment. 99.161.108.144 ( talk) 22:32, 16 June 2008 (UTC)
could someone please put this in english —Preceding unsigned comment added by 66.0.47.5 ( talk) 16:25, 14 July 2008 (UTC)
Everything is connected; by moving through dark matter time doesn't exist; dark matter is the space between atoms. —Preceding unsigned comment added by 135.196.87.114 ( talk • contribs)
anyone knows? —Preceding unsigned comment added by 70.236.117.86 ( talk) 08:49, 1 October 2008 (UTC)
I call BS. —Preceding unsigned comment added by 66.69.194.16 ( talk) 04:08, 9 October 2008 (UTC)
Could someone take a look at the second paragraph of the section "Privileged character of 3+1 spacetime" and either rephrase it to be more understandable, or remove it. I'll do it in a few days if noone else beats me to it. Cuardin ( talk) 15:01, 27 October 2008 (UTC)
This article reads fairly well and is not too stupid throughout most of its progression. Then we get to the last bit about the necessity of 3+1 in our universe (as circular as it sounds) with the bloated references to Tipler's Godly shenanigans. Somebody needs to do something about this abrupt drop in quality, coherence, and logic.
Hi in your section about space-time intervals. When defining time-like intervals, you've put when . Please correct me if i'm wrong, but this appears to be incosistent with your formula for the spacetime interval. Either the inequality needs flipping or a minus sign needs changing. Similarly for space-like intervals. —Preceding unsigned comment added by Father lent ( talk • contribs) 03:28, 24 March 2009 (UTC)
Is it just me, or does the space-like and time-like sections contradict themselves? For the space-like interval in big bold letters, , and in smaller letters in the text following. —Preceding unsigned comment added by 129.105.244.231 ( talk) 16:57, 3 August 2009 (UTC)
It seems to me that we still need to nail down the sign convention and ideally get something more set in stone across most other wiki pages. There are too many people trying to impose their own sign conventions on pages that it's starting to get a little ridiculous. Either they don't know that the signs can be interchanged at whim, as long as we are consistent, or they're being stubborn. I think this may be an area worth consolidating on. (Tough area to mod especially with some more crackpot ideas slipping in when it comes to relativity and other fields at the forefront of current research.) Perhaps consider 'stamping' pages as approved by people with the appropriate accredited degrees (i.e. Degree in Physics, Astronomy or Mathematics)? I think it would be good to try to provide some verification to pages (this goes beyond the relativity page). <Don't have an account yet> —Preceding unsigned comment added by 81.106.135.150 ( talk) 21:32, 11 August 2009 (UTC)
How people can so bastardize Einstein's works is beyond me, but I guess it's easy to butcher the man's theory when he's no longer around to defend himself. Thank you Michio Kaku and thank you Discovery Network for turning Einstein's Space-Time into a crock full of magical thinking, you couldn't have missed the point any further if you tried.
Can we PLEASE have Einstein's writings on this topic including amid all this sci-fantasy, so that people can actually read Einstein's thoughts and not simply be left to rely on second hand interpretations for speculatory astrophysicist like Dr. Kaku?-- 67.58.84.106 ( talk) 16:58, 18 June 2009 (UTC)
Isn't normal time just "earth time"? That is One Year is the time it takes for Planet Earth to go around the Sun. One day is the time for Earth to go around it's own axis. 364 "days" is the time the planet takes to go around the sun. 24 "hours" is just the arbitrary way we cut this up from there and from there it's cut into these arbitrary "minutes" and from there "seconds" which is both 60 units... From there we part "time" into new units like milliseconds etc. So for example MARS time would be completely different...
So my question is, how does this relate to the time talked about in "spacetime"? It's not just for me, it might add something to this wikipedia entry... Deathcreepscloser ( talk) 21:44, 19 October 2009 (UTC)
I have added a reference to to the Incas' concept of Pacha to historical section. This is a deep insight having no analogies in the other cultures. I guess, this may be worthy of more detailed explanation. Raoul NK ( talk) 06:57, 23 October 2009 (UTC)
I have removed the reference to "Pacha," since it is not related to the subject of the article. Spacetime, as it is being defined in this article, is a geometric object simplifying the mathematical representation of Einstein's theory of relativity. I would suggest that vague cultural notions of the wholeness of spatial and temporal experience are actually quite common throughout history, and that perhaps a new article or section be formed to treat philosophical or cultural concepts that bear some resemblance to the mathematical concept. I think there will be no argument that the "Inca" concept of "pacha," which has not been studied in a peer-reviewed publication as having any connection to that "ancient" empire (from the 1200s C.E.), has no historical link with western mathematics and the geometric object called Spacetime. —Preceding unsigned comment added by 204.69.190.75 ( talk) 23:23, 8 November 2009 (UTC)
Ok, great. That edit was removed and the "pacha" bullshit re-instated." I'm just going to come out and say that to have the first line of a section called "historical origins" of one of the most celebrated products of western culture be an assertion that an obscure 13th century South-American empire figured it out long ago downright insulting. That's like telling the world that some Englishman invented Kabuki Theater because there is some documented case of a play with white make-up pre-dating the Samurai Era in Japan. Spacetime is a mathematical object; its history has nothing to do with the Inca Empire, and that reference and the prominent picture of some Incan holiday should be immediately removed. —Preceding unsigned comment added by 204.69.190.75 ( talk) 23:38, 8 November 2009 (UTC)
Why is it stated thta "thus, all other cases except N=3 and T=1, from an anthropic and physical perspective are ruled out", when it is obvious this is a fallacy to start with. The arguments provided do not reach this conclusion at all.
It has been said in the article that because of all the instabilities created when taking into account more or less spatial and temporal dimensions that the universe AS WE KNOW IT might not exist. I fail to see how a universe that does not have electrons or atoms would not exist just because it is incomprehensible to us. It's as if you're saying God doesn not exist because we can't see it... 204.17.179.2 ( talk) 20:33, 4 November 2009 (UTC)
The article states that Weyl showed that Maxell's equations "don't work" in anything but 3+1. This is extremely vague and needs some sort of explanation. Even discounting current frivolous extra dimensional theories top physicists have been doing work in other D+1 dimensional theories (Schwinger in 1+1 QED, Wilczek w anyons in 2+1) and I find it hard to believe such a result would have been completely ignored by mainstream physics. —Preceding unsigned comment added by 128.230.52.206 ( talk) 17:29, 5 November 2009 (UTC)
I have removed the weasely phrase:
What we do find in the Time Machine (see for instance [4]) is the phrase
The words Viking or Vikings do not appear in "Time Machine", so I assume that the Viking thing is a mistake and should only be included if a hard source is found for it. DVdm ( talk) 21:12, 29 November 2009 (UTC)
An article about Quantized spacetime was uploaded today. There is also the article about quantum spacetime, a concept that is not mentioned in this article. It appears to me that these two concepts are different. This will have to be explained here. Andreas (T) 15:10, 12 January 2010 (UTC)
This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Double slit in time experiment. http://physicsweb.org/articles/news/9/3/1/1?rss=2.03Cbr20/E This surely is experimental evidence that that matter/energy is not just quantised over spatial dimensions (as shown by the classical double slit experiement) but over the time dimension as well. ie: spacetime does have a quantum nature.
Examples of use of spacetime:
Examples of use of space-time:
Since Wikipedia is not a dictionary, it should stick to one spelling. Thus I removed the comment "(alternatively, space-time)". Space-time already redirects to Spacetime, so all is well. — Herbee 20:31, 11 Nov 2004 (UTC)
The space-time four vector is:
[x y z ct]
the use of the vector as:
[x y z ict]
was common about 40 years ago or so, but it is now considered archaic and the former notation is prefered.--BlackGriffen
However, there are certainly physicists who prefer the i notation, including Dr. Jack Sarfatti.
The Wikipedia should present the mainstream state of a field as much as possible, presenting relevant dissenting views as such when they arise. The use of the i is just a lazy way to make finding the "length" squared of a four vector feel like finding the length of any other vector (dot product the vector on to itself). It is, however, just as easy to define a new "length" operator for four vectors that doesn't require complex numbers.
And if bandying about names is the game, a quick look at the Feynmann Lectures on Physics explanation of four vectors shows nary an i, even though he had a discussion of using c=1.--BlackGriffen
I concur: both 'space-time' and the 'i' notation appear to be common early usage, and physicists everywhere seem now to have standardised on both 'spacetime' and the 'i'-less notation -- The Anome
1: Is there a free 3d prog that does nice, uniform renderings of some of this math?
2: Might it be a good idea to use a sidebar (can even use a msg tag for multiple article consistency) which describes some of the core foundational concepts, required for laymen learners like myself to have related study materiale at hand. Finding links in the text lacks structure that a weeded list would have. - SV (talk)
We can read in this article:
"Strictly speaking one can also consider events in Newtonian physics as a single spacetime. This is Galilean-Newtonian relativity, and the coordinate systems are related by Galilean transformations. However, since these preserve spatial and temporal distances independently, such a spacetime can be decomposed unarbitrarily, which is not possible in the general case." - is that right? Is unarbitrarily or arbitrarily? I've some difficulties with english but I'm trying to translate this to portuguese and I can't understand this... Is it an error?... Say something, please. -- Manuel Anastácio 20:29, 15 Jun 2004 (UTC)
GPS?? WTF?? - Omegatron 03:38, Dec 16, 2004 (UTC)
I've heard quite a few article discussions mention the expansion of spacetime. IT'S JUST AS PREPOSTEROUS AS TIME DILATION! How can something that is NOT a physical entity be expanded? Scorpionman 02:14, 20 May 2005 (UTC)
Knowledge Seeker is comfortable with analogies of two-dimensional rubber sheets as four-dimensional spacetime. Isn't it relaxing to have such closure?
Take Knowledge Seeker's rubber sheet. Stretch it high. Stretch it wide. Now you have a four-dimensional rubber sheet. "It doesn't seem very strange to me." Closure.
Whilst editting spacetime symmetries, I remembered that a spacetime can (in principle) have dimensions other than 4. Most people use 4D spacetimes, but many researchers use 10D spacetimes etc; it even makes sense to talk of 3 dimensional spacetimes (2 space dimensions + 1 time). I think we need to redefine spacetime to accomodate these common uses - I don't know why I never spotted this before. Roughly, isn't an n-dimensional spacetime a manifold etc... with n-1 space dimensions + 1 time dimension ?
Mpatel 10:50, 10 Jun 2005 (UTC)
It's probably better to stick to the 4D definition, and then mention that other uses of the word can accomodate things like 3D spacetime diagrams and higher spacetime dimensions in other theories. ---
Mpatel
(talk)
11:57, 19 October 2005 (UTC)
It might also be reasonable to consider space as being a single dimension, one that requires three coordinates in order to accurately describe the position of a point, rather than three seperate dimensions. Nothing tangible in our universe can be located in either one or two but not three spacial dimensions, which suggests that the dimension is not logically divisible into three. Moreover, length, width and depth are not distinguishable from each other without mutual reference, unlike the distinction that can be easily drawn between space and time dimensions. We commonly use the word 'dimension' in a non-scientific sense with reference to length, width or depth, but there would seem to be no need to define 'dimension' identically with reference to spacetime. By this logic there are then two common dimensions, space and time, and not four, time, length, width and depth. The word 'spacetime' may then be retained and need not be superceeded by the politically correct 'lengthwidthdepthtime'. Professor Krepotkin ( talk) 20:44, 2 June 2008 (UTC)
Physicist Itzhak Bars' 2006/2007? theory describes a four-dimensional space, two-dimensional time model. Will try to synthesize this information into the article according to the suggestions/comments above. Known Latitude 02:42, 18 October 2007 (UTC)
The first sentence of the article asserts that a space-time continuum is "time and three-dimensional space treated together as a simple four-dimensional object." If it is an object, one wonders if this object has a location. Where is this object?
This article is disappointing. Spacetime is not a subject that requires a great deal of knowledge to understand, but the text treats it as if it is. I would expect the average reader to feel vaguely lost by the end of the second paragraph, and then completely lost upon scrolling past the table of contents to be confronted by dense and mostly unexplained mathematical jargon. ‣ᓛᖁ ᑐ 09:31, 21 September 2005 (UTC)
My comment about the definition being incorrect was that it was incomplete (I was thinking of the technical details too - i.e. spacetime being a manifold). I was hoping for something like, 'Spacetime is a concept that views space and time as interrelated rather than as separate entities. The concept was formulated by Hermann Minkowksi soon after Albert Einstein developed the theory of special relativity.' As far as the basic idea of spacetime is concerned, that's about all we need for an introduction (I think). Later in the article, we need to mention the maths of spacetime, the physics of spacetime etc. --- Mpatel (talk) 13:10, 23 September 2005 (UTC)
I know; I didn't say (or suggest) that it should. --- Mpatel (talk) 13:53, 23 September 2005 (UTC)
What I'm saying is this: your definition of spacetime is ok for a layperson (and this is what should be at the start), but not for a specialist (who will be satisfied by the manifold stuff later on in the article). I mentioned the historical bit only to indicate what I think should also be at the start. --- Mpatel (talk) 15:42, 23 September 2005 (UTC)
From any physical theory that contains a set of elements called space and a set of elements called time, one can create the Cartesian product of space and time and this product is called spacetime. An element of spacetime is called an event. Hence, an event is an ordered pair (where,when) where where represents an element in space (a point in space) and when represents an element in time. Two events in spacetime are called simultaneous if they have the same element of time as the second element in the ordered pair. Two events in spacetime occur at the same place if they have the same element as the first element of the ordered pair.
In Newtonian physics, space has the additional structure of a three-dimensional Euclidean space, and time has the structure of a one-dimensional Euclidean space. Newtonian spacetime is the Cartesian product of the three-dimensional Euclidean space and the one-dimensional Euclidean space. However, one does not make the product into a four-dimensional Euclidean space, one keeps the three-dimensional Euclidean structure on space, and the one-dimensional Euclidean structure on time. The three-dimensional Euclidean space structure on space allows one to identify points in space with ordered triples of real numbers by choosing some (not unique) coordinate system. Given a unit length, this coordinate system may be chosen so that the square of the distance between any two points and is
Similarly, the one-dimensional Euclidean space structure on time allows one to identify elements in time with the set of real numbers by choosing some (not unique) coordinate system. Given a unit time duration, the identification of time with the real numbers may be chosen so that the square of the time difference between events occuring at times and is given by
In Newtonian spacetime, the distance D and the time duration between the events and is not combined to produce the product metric (which would give the square of the spacetime distance as ). and are considered separately.
In special relativity, Minkowski spacetime (the spacetime of special relativity) is determined by the property that the set of events (the elements of the spacetime) can be specified by an ordered quadruple and the existence of a spacetime interval between any pair of events and whose square is given by
In both Newtonian spacetime and Minkowski spacetime events can be specified by four real numbers. However, in Newtonian spacetime, the spacetime consists of a product of space and time (and all observers agree with the splitting of the spacetime into its space component and it time component). In Minkowski spacetime, each observer can choose to split the spacetime into a space component (a three-dimensional Euclidean space) and a time component (a one-dimensional Euclidean space). Different observers split spacetime into different space and time components, but they all agree that spacetime has four dimensions and that the square of the spacetime interval between a pair of events has a fixed value (once a unit interval has been selected).
In general relativity, the spacetime is curved. Minkowski spacetime is flat and the spacetime of general relativity is curved. In a manner that is analogous to the way that a sphere in three-dimensional Euclidean space can be approximated by a tangent plane near the point of contact between the plane and sphere, the curved spacetime of general relativity has the same type of relation to flat Minkowski spacetime as does the sphere to a tangent plane. The difference between the curved spacetime of general relativity and the flat spacetime of Minkowski spacetime is reflected in the (Riemann) curvature tensor.
In general, spacetime represents the part of a physical theory that is supposed to correspond to the common sense notion of space and time. After the ideas of relativity, space and time do not appear to be independent of each other and independent of other physical entities. What space and time are (and what spacetime is) is not known. In classical physics, spacetime is Newtonian spacetime. In special relativity, spacetime is Minkowski spacetime. In general relativity, spacetime is a curved four-dimensional space satisfying Einstein's field equations. Each physical theory has its own version of spacetime.
Ref: Newtonian Mechanics, Special Relativity, General Relativity, etc.
I've reorganised the article to bring out the relativity ideas more clearly. The maths section still needs a lot of work. Perhaps some more on the concept of spacetime in non-relativistic theories is needed. --- Mpatel (talk) 08:52, 22 October 2005 (UTC)
Hi RaulMiller.
Actually, I didn't change 'model' to 'object'. I changed 'coordinate system' to 'object', because spacetime is definitely not a coordinate system - spacetimes are independent of any observers and hence coordinate systems: nature doesn't care whether we measure the properties of a spacetime (e.g. time intervals) with clocks and rulers; all that matters is that spacetime exists independently of anyone who chooses to measure it's properties or not. The word 'model' is still there in the first sentence. Perhaps 'object' could be changed to 'entity' or maybe something better. --- Mpatel (talk) 08:37, 29 October 2005 (UTC)
The word 'solution' is in the opening paragraph and has not been explained (getting from manifold to solutions of the Einstein field equations is not exactly a trivial route). Non-specialists will not necessarily understand what 'solution' means (at least not without explanation or further clarification). I think the word 'solution' in that paragraph should be replaced with 'spacetime(s)'. Also, the word 'unitary' could be confused for something more technical ! - maybe 'unified' is better here. I'll try these and see if they are better. MP (talk) 09:35, 5 February 2006 (UTC)
Firstly, this article is generally disappointing: Lack of clear structure, lack of clarity in use of concepts, and just vagueness in general. The section on quantized spacetime should make reference to the work of David Finkelstein, one of the first to suggest this idea, the mention of the chronons, and should mention at least some of the basics. --NYCSEAN 20:25, 10 March 2006 (UTC)
Refers in the body of the article to the date 1929. This is *somewhat* misleading, considering he that died in 1804. The date is of course of an English translation of his work. Adittionally, Kant is most famous for his work The Critique of Pure Reason (considered probably to be the single most important work in Western Philosophy) and his earlier work was largely an attentuation of errors towards his later work.
Thus the reference properly needs to refer to the original date of publication, and if it is prior to the CPR in 1781, then make a refence to the fact that it was during his formative stages (admittedly which are the first 50 odd years of his life). I will get round to doing this eventually if it is not done by someone who already knows, please anyone post disagreements if there are any. Tsop 11:52, 12 June 2006 (UTC)
Compared to some of the other complaints above, mine is minor, but the assumption that one cannot have a nervous system if one is relegated to 2 spacial dimensions was proven wrong long ago. The Macullogh-pitts (sp?) crossover circuit allows you to cross two wires in 2 dimensions and have them act as if they are separate. It makes me wonder how well researched the other claims about the uniqueness of 3+1 space are. Swestrup 05:55, 12 September 2006 (UTC)
The article states that extra dimensions would only appear to make a difference at the subatomic level. But isn't it right that some version of string theory predicts effects on gravity already at the mm- to micrometer-scale? Depending on the size of the compactification, of course. - 80.143.117.226 23:06, 19 January 2007 (UTC)
In the last section, "intelligent life manipulating technology" can be interpreted two ways which ironically both may be correct...
May be it my browser problem. Is this image linked properly?
I'm removing the paragraph on this theory because I've never heard of a theory like this and I couldn't find any references when I googled it. I'm no specialist, though, so if someone can find a good reference please feel free to revert my edit and add the reference. —Preceding unsigned comment added by 201.222.138.228 ( talk) 23:10, 17 May 2008 (UTC) Wow! Faster-than-light revert! I suppose I was wrong, then... Well, at least I tried. 201.222.138.228 ( talk) 23:38, 17 May 2008 (UTC)
I'm also removing this paragraph because don't find it serious. Googled it, and I found ANY, and that is, ANY REFERENCE ABOUT IT. So I'm sorry but I'm removing it, unless someone here could indicate a clear reference to this or the individuals who proposed this theory.
The original text appearing on the article, has been removed and placed here, where people can indicate sources talking about it, to do this "reliable". The text don't indicate who are the people behind the theory, also there are no references about "Jack-in-the-box" (name which sounds suspicious or almost peculiar).
The text says a group of scientists in Portland, Oregon... who? who exaclty? where are thouse scientist? (no source). And then "Jack-in-the-box"... I find this suspicious...
Spiralization and Compression Theory ---- A recent development in physics is the theory of the spiralization and compression of space time, also known as the "Jack-in-the-box" theory. This theory was first put forth in 2006 by a group of scientists working in Portland, Oregon. The theory speculates that over time, all the dimensions of space spiral inward until reaching a state of absolute compression. When complete compression is reached, space springs outward and expands rapidly, as with the big bang, before the cycle is begun again. The highlight of this theory is the independence of time from the spiralization and compression of space. The impact of this theory on relativity and attempts at a unified field theory are yet unknown. However, it has been predicted, using the spiralization and compression theory, that the Large Hadron Collider will produce micro-universes.
Anyway... I will copy the subject of the spiralization and compression theory here... to allow people research on this:
I found the following arXiv documents talking about spiralization theory:
astro-ph/0501170 - West-Side Story (On the History of Density-Wave Spiral Theories in the 1960s) astro-ph/0406143 - Title: Density-Wave Spiral Theories in the 1960s. II astro-ph/0406142 - Title: Density-Wave Spiral Theories in the 1960s. I cond-mat/9502097 - Title: The motion of holes on the triangular lattice: t-J model
—Preceding unsigned comment added by 88.12.170.8 ( talk) 23:55, 11 June 2008 (UTC)
This "spiralization theory" is not in the mainstream of physics and does not deserve front page treatment. 99.161.108.144 ( talk) 22:32, 16 June 2008 (UTC)
could someone please put this in english —Preceding unsigned comment added by 66.0.47.5 ( talk) 16:25, 14 July 2008 (UTC)
Everything is connected; by moving through dark matter time doesn't exist; dark matter is the space between atoms. —Preceding unsigned comment added by 135.196.87.114 ( talk • contribs)
anyone knows? —Preceding unsigned comment added by 70.236.117.86 ( talk) 08:49, 1 October 2008 (UTC)
I call BS. —Preceding unsigned comment added by 66.69.194.16 ( talk) 04:08, 9 October 2008 (UTC)
Could someone take a look at the second paragraph of the section "Privileged character of 3+1 spacetime" and either rephrase it to be more understandable, or remove it. I'll do it in a few days if noone else beats me to it. Cuardin ( talk) 15:01, 27 October 2008 (UTC)
This article reads fairly well and is not too stupid throughout most of its progression. Then we get to the last bit about the necessity of 3+1 in our universe (as circular as it sounds) with the bloated references to Tipler's Godly shenanigans. Somebody needs to do something about this abrupt drop in quality, coherence, and logic.
Hi in your section about space-time intervals. When defining time-like intervals, you've put when . Please correct me if i'm wrong, but this appears to be incosistent with your formula for the spacetime interval. Either the inequality needs flipping or a minus sign needs changing. Similarly for space-like intervals. —Preceding unsigned comment added by Father lent ( talk • contribs) 03:28, 24 March 2009 (UTC)
Is it just me, or does the space-like and time-like sections contradict themselves? For the space-like interval in big bold letters, , and in smaller letters in the text following. —Preceding unsigned comment added by 129.105.244.231 ( talk) 16:57, 3 August 2009 (UTC)
It seems to me that we still need to nail down the sign convention and ideally get something more set in stone across most other wiki pages. There are too many people trying to impose their own sign conventions on pages that it's starting to get a little ridiculous. Either they don't know that the signs can be interchanged at whim, as long as we are consistent, or they're being stubborn. I think this may be an area worth consolidating on. (Tough area to mod especially with some more crackpot ideas slipping in when it comes to relativity and other fields at the forefront of current research.) Perhaps consider 'stamping' pages as approved by people with the appropriate accredited degrees (i.e. Degree in Physics, Astronomy or Mathematics)? I think it would be good to try to provide some verification to pages (this goes beyond the relativity page). <Don't have an account yet> —Preceding unsigned comment added by 81.106.135.150 ( talk) 21:32, 11 August 2009 (UTC)
How people can so bastardize Einstein's works is beyond me, but I guess it's easy to butcher the man's theory when he's no longer around to defend himself. Thank you Michio Kaku and thank you Discovery Network for turning Einstein's Space-Time into a crock full of magical thinking, you couldn't have missed the point any further if you tried.
Can we PLEASE have Einstein's writings on this topic including amid all this sci-fantasy, so that people can actually read Einstein's thoughts and not simply be left to rely on second hand interpretations for speculatory astrophysicist like Dr. Kaku?-- 67.58.84.106 ( talk) 16:58, 18 June 2009 (UTC)
Isn't normal time just "earth time"? That is One Year is the time it takes for Planet Earth to go around the Sun. One day is the time for Earth to go around it's own axis. 364 "days" is the time the planet takes to go around the sun. 24 "hours" is just the arbitrary way we cut this up from there and from there it's cut into these arbitrary "minutes" and from there "seconds" which is both 60 units... From there we part "time" into new units like milliseconds etc. So for example MARS time would be completely different...
So my question is, how does this relate to the time talked about in "spacetime"? It's not just for me, it might add something to this wikipedia entry... Deathcreepscloser ( talk) 21:44, 19 October 2009 (UTC)
I have added a reference to to the Incas' concept of Pacha to historical section. This is a deep insight having no analogies in the other cultures. I guess, this may be worthy of more detailed explanation. Raoul NK ( talk) 06:57, 23 October 2009 (UTC)
I have removed the reference to "Pacha," since it is not related to the subject of the article. Spacetime, as it is being defined in this article, is a geometric object simplifying the mathematical representation of Einstein's theory of relativity. I would suggest that vague cultural notions of the wholeness of spatial and temporal experience are actually quite common throughout history, and that perhaps a new article or section be formed to treat philosophical or cultural concepts that bear some resemblance to the mathematical concept. I think there will be no argument that the "Inca" concept of "pacha," which has not been studied in a peer-reviewed publication as having any connection to that "ancient" empire (from the 1200s C.E.), has no historical link with western mathematics and the geometric object called Spacetime. —Preceding unsigned comment added by 204.69.190.75 ( talk) 23:23, 8 November 2009 (UTC)
Ok, great. That edit was removed and the "pacha" bullshit re-instated." I'm just going to come out and say that to have the first line of a section called "historical origins" of one of the most celebrated products of western culture be an assertion that an obscure 13th century South-American empire figured it out long ago downright insulting. That's like telling the world that some Englishman invented Kabuki Theater because there is some documented case of a play with white make-up pre-dating the Samurai Era in Japan. Spacetime is a mathematical object; its history has nothing to do with the Inca Empire, and that reference and the prominent picture of some Incan holiday should be immediately removed. —Preceding unsigned comment added by 204.69.190.75 ( talk) 23:38, 8 November 2009 (UTC)
Why is it stated thta "thus, all other cases except N=3 and T=1, from an anthropic and physical perspective are ruled out", when it is obvious this is a fallacy to start with. The arguments provided do not reach this conclusion at all.
It has been said in the article that because of all the instabilities created when taking into account more or less spatial and temporal dimensions that the universe AS WE KNOW IT might not exist. I fail to see how a universe that does not have electrons or atoms would not exist just because it is incomprehensible to us. It's as if you're saying God doesn not exist because we can't see it... 204.17.179.2 ( talk) 20:33, 4 November 2009 (UTC)
The article states that Weyl showed that Maxell's equations "don't work" in anything but 3+1. This is extremely vague and needs some sort of explanation. Even discounting current frivolous extra dimensional theories top physicists have been doing work in other D+1 dimensional theories (Schwinger in 1+1 QED, Wilczek w anyons in 2+1) and I find it hard to believe such a result would have been completely ignored by mainstream physics. —Preceding unsigned comment added by 128.230.52.206 ( talk) 17:29, 5 November 2009 (UTC)
I have removed the weasely phrase:
What we do find in the Time Machine (see for instance [4]) is the phrase
The words Viking or Vikings do not appear in "Time Machine", so I assume that the Viking thing is a mistake and should only be included if a hard source is found for it. DVdm ( talk) 21:12, 29 November 2009 (UTC)
An article about Quantized spacetime was uploaded today. There is also the article about quantum spacetime, a concept that is not mentioned in this article. It appears to me that these two concepts are different. This will have to be explained here. Andreas (T) 15:10, 12 January 2010 (UTC)