Slashdot Mirror
Physicist Claims Time Has a Geometry
sciencenews writes to tell us that a physicist at Stanford has just recently published a peer review website for several physics lectures focusing on a single underlying idea that "time is not a single dimension of spacetime but rather a local geometric distinction in spacetime." The science is presented quite clearly and originally uses GPS systems as a point of focus. From the article: "Not too long ago, people thought the Earth was flat, which meant they thought that gravity pointed in the same direction everywhere. Today, we think of that as a silly idea, but at the same time, most people today (including most scientists) still think of spacetime as if it were a big box with 3 space dimensions and 1 time dimension. So, like gravity for a flat Earth, the single time dimension for the 'big box universe' points in one direction, from the Big-Bang into the future. A lot of lip service is given to the idea of "curved spacetime", but the simplistic 3+1 'box' remains the dominant concept of what cosmic spacetime is like."
Robert Heinlein used this as the central idea of his book "Then Number of the Beast" in 1986 The Number of the Beats
You are in a maze of twisted little posts, all alike.
Wasn't this the point he was trying to make? People are very familair with the concept of multiple spatial axes which can lead to spatial geometry (and hence spacetime geometry) but that time is taken as a single, fixed axis, which he thinks isn't the case, which would lead to differences in how many aspects of relativity would have to be interpreted?
Once again, as I mentioned in a post I made above: It's late, and I haven't read his presentations, so I may have completely missed his point. If it is as mundane as you suggest, then this post can be ignored and written off as a sleepy error, and I apologise for the inconvenience.
Multidimensional representations of time do not get you to Oz. "Pantheistic solipsism" does, according to the book. The central idea of that book was that the world was all myth, and as such there's no reason you can't hop from myth to myth, as long as your particular myth was written by someone who will script you to do it. The parallel universes were only parallel in that they were all represented in works of fiction.
REM Old programmers don't die. They just GOSUB without RETURN.
http://www.bede.org.uk/flatearth.htm -- This is one myth that really needs to die! Even more so than that Betsy Ross was involved with the American Flag.
There is definitely a good case to be made that the past-versus-future arrow of time is not fundamental. Basically our psychological sense that the past is different from the future comes from the direction of the thermodynamic arrow of time, but the second law of thermodynamics doesn't come from the basic laws of physics (which are essentially time-reversal symmetric) but from the boundary conditions of the universe: for some reason unknown to us, we had a low-entropy big bang. The meaning of "past" is really "that way to the big bang."
It's also probably true that in a complete theory of quantum gravity, the picture of three space dimensions plus one time dimension (3+1) would break down completely at small scales. The whole idea of distance and dimensionality is probably a large-scale approximation that loses its validity at small scales. There is a strong argument to be made that for fundamental reasons, spacetime must be discrete, not continuous, at the Planck scale. The only people seriously trying to construct discrete theories of quantum gravity right now seem to be the people doing loop quantum gravity (not string theory, which uses a flat 3+1 background of spacetime). For a good popular-level account of this kind of stuff, see Smolen's Three Roads to Quantum Gravity. In loop quantum gravity, they are able to construct an infinite set of possible universes (each one is a type of knot), but the problem is that none of them can be proved to resemble flat 3+1 spacetime, even asymptotically. In other words, there's no way you can even take this tangle of events and figure out whether it has anything like time and space that you can define on it. It's like being a flea living in a world that consists of threads woven together. On your scale, can't be sure whether it's a one-dimensional piece of yarn, a two-dimensional piece of fabric, or a three-dimensional wad of wool.
Find free books.
This leads to the "obvious" conclusion that you should be able to significantly accelerate nuclear decay by emitting neutrinos of just the right spin. (Now all we have to do is figure out how to generate neutrinos!) It should also be possible to reduce (but not totally suppress radioactive decay) by shieling out all incoming neutrinos, as that would eliminate one possible decay path.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
...that's like saying ther's no "up" separate from "east". The real question is if they are orthogonal.
I have discovered a truly remarkable sig which this 120 chars is too small to contain.
Jump to page 25 of the second set of slides, where the author shows two time vectors at an angle to each other. If you have two observers, one with each time vector, then each observer thinks that the other is slowed down. Each sees redshifted light from the other.
This angle between time vectors can be caused by gravity or by the curvature of the universe.
In the gravity case, it is used to explain discrepancies in all sorts of measurements, from the Pioneer spacecraft, to the changes in the orbits of various celestial bodies, to discrepancies in the GPS, to the apparency that a U.S. atomic clock and a French one will each think the other is ticking slower. This is what most of the first slide show is about.
In the cosmological case, the idea is that the universe is round (see page 28 of the second presentation) and that the redshift that we think is due to the expansion of the unverse is actually due to the curvature of the universe, i.e., a galaxy around the universe from us will appear to have slower time, because its time vector is going in a different direction than ours. A galaxy ninety degrees around would appear to have time completely stopped, so it would be invisible to us (frequency of zero). Galaxies further away than that would be going backwards in time from our perspective, but we can't see them.
This is an idea I have not seen before. It seems really neat to me. It seems plausible but then (a) I can't personally verify the observations that he claims validate his theory; he could have produced fake graphs and they would fool me, but I would think it would be easy for him to get caught at that, and (b) even though I've had calculus up to differential equations, I never had non-Euclidean geometry or higher-dimensional stuff, so I can't actually follow his calculations very well. Then again, I didn't try very hard.
We shall soon see if he has made a significant error. The numbers and the observations will tell the story; either they work out, or they don't.
Sunlit World Scheme. Weird and different.
What are you talking about? The Lorentz transformation has only one degree of freedom in the time dimension. We call it the future or the past. This guy is suggesting that time has more than one degree of freedom. Which is nothing new...
The best education consists in immunizing people against systematic attempts at education. - Paul Feyerabend
I found this reference :
.etc.
Multidimensional Time Simplifies General Relativity
Authors: Mayer, Alexander
Affiliation: MIT
Journal: American Physical Society, Second Meeting of the Northwest Section 2000 May 19-20, 2000 University of Oregon Eugene, Oregon, abstract #CP1.013
Publication Date: 05/2000
Abstract
The Minkowski metric is interpreted to imply that time is multidimensional. Multidimensional time simplifies the derivation of equations describing gravitational relativistic phenomena and challenges interpretations of the theory in the strong field limit.
and this one
Title: On the Cause of Geodetic Satellite Accelerations and Other Correlated Unmodeled Phenomena
Authors: Mayer, A. F.
Affiliation: AA(Affymetrix, Inc., 3380 Central Expressway, Santa Clara, CA 95051 United States ; amayer@alum.mit.edu)
Journal: American Geophysical Union, Fall Meeting 2005, abstract #G41B-0363
Publication Date: 12/2005
Origin: AGU
AGU Keywords: 1229 Reference systems, 1243 Space geodetic surveys, 6964 Radio wave propagation, 7504 Celestial mechanics, 7969 Satellite drag (1241)
Abstract Copyright: (c) 2005: American Geophysical Union
Bibliographic Code: 2005AGUFM.G41B0363M
Abstract
An oversight in the development of the Einstein field equations requires a well-defined amendment to general relativity that very slightly modifies the weak-field Schwarzschild geometry yielding unambiguous new predictions of gravitational relativistic phenomena. .
"Since there are no reasonably permanent irregularities such as hills and valleys on the oceans"
:)
:) *hangs head in shame*
Sorry, I apologize in advance because I do agree with you but that statement triggered the nitpick in me *can't resist*
You (and other Slashdotters) might very well be aware of the following and it is not in any way intended as any form of criticism. I sincerely apologize for any wrongful or lacking details (should be plenty of those), I am not an oceanographer and do feel free to correct me if wrong.
It's funny since there actually are hills and if not exactly valleys then at least depressions on the oceans due to both varying gravitational influences both internal (reasonably permanent) and external (cyclic) as well as differing precipitation and evaporation rates (fairly permanent though sometimes irregular and/or cyclic).
So the ancients would actually be right in thinking like you say although at least somewhat wrong as well (but as you mention they had other methods anyway http://en.wikipedia.org/wiki/Spherical_Earth).
But you are completely correct. Once again sorry I just had to get it out of my system lol
--
this additional sig includes a portrait of Mohammed in support of freedom of expression, feel free to reproduce it
this comment is provided "as is" and without any express or implied legibility or congruity [...]
If you look at his colleagues,
i ng.html
http://www.scu.edu/spo/spring_03_2.htmhttp://www.stanford.edu/dept/physics/people/visit
then cross-reference a few of them:
http://www.gf.org/lfellow.html
Douglas N. C. Lin, Professor of Astronomy and Astrophysics, University of California, Santa Cruz: 1991
If you look him up he is all over about Astrophysics and applied mathematics.
Betty Young, Santa Clara:
Now if you research Betty you find this:
u ng.cfm
http://www.scu.edu/cas/physics/facultyandstaff/yo
Now whatever becomes of this Alex Mayer and his credentials are yet to be determined. However, I doubt Stanford would even allow him web space under the Physics department if he didn't have the credentials to back it up.
How exactly would you perceive time as moving forwards or backwards? Time could very easily move forward and backwards, you just wouldn't be able to detect it. If you could reverse time while a person was drawing a picture, you'd see that with each reversed second that data is erased from the finished product. The perception that time moves forward for us, may simply be a side effect of the fact that we retain data about previous interactions, but have this lack of data about the future that slowly gets sketched in during the present. So time could very well move forwards and backwards, indefinately, but you would only perceive its forward motion because as a function of time, the data does not exist yet.
Math theorems don't necessarily have to apply to the physical universe. The axioms on which the theorems are built are explicitly part of the theorems, leading to a logically self-consistent system. That is, you define the particular 'universe' you want to study by setting down axioms, then you prove things which you know are true about that universe because you've derived them in a logical fashion from those axioms you've set down.
Alexander Mayer is a visiting scholar at the Physics department at Stanford, which means that he is likely either an adjunct professor or a post-doctoral student, though he may be a PhD candidate. If you simply looked at the pages for the Physics department at Stanford, you'd have found that easily, rather than confining your search to the university's directory.
What is this 'reality' you speak of?
Mathematics isn't constrained by our perceptions of what it 'should' be or what feels right. It's constrained by the axioms and principles we build it from. And in this case, 0.9 recurring is exactly equal to one. As you demonstrated, there are countless proofs of it (the one you selected being one of the less rigorous ones), and since the proofs are not incorrect, it means that their conclusion is wholly true, from a mathematical point of view.
Strictly speaking, math is every bit as empirical as physics. People have less confidence in physical theorems than math theorems because physics relies on math, and because physics has a heavy dependence on observations. But the basic validity of math also depends on observations. In particular, where mathematical systems can be interpreted as describing themselves, it is no longer safe to think of "math reality" versus "physical reality" as being complety distinct. One example that comes to mind is the Axiom of Choice; you can take it to be true or false, and in both cases you get a logically consistent mathematics (like euclidean vs noneuclidean geometry). But despite this empirical status, the Axiom of Choice has major consequences for abstract mathematical "truth".
Also, from philosophy standpoint, math relies on lots of nontrivial physical observations that humans take for granted (e.g. of paper, of mental states, etc). This concern goes beyond mere speculations about pathological situations (what if I'm insane? what if my life is a conspiracy like in the Matrix?). A key result of the 20th Century is that it's entirely possible that study of arithmetic will one day lead us to conclude that our basic model of arithmetic is logically inconsistent. In fact, Kurt Godel showed that proving the consistency of arithmetic is actually impossible in any conventional mathematical/metamathematical system.
-Gonz
hi,
...
[disclaimer: i am an experimental high-energy physicist -- i am not an "expert" on GR but it's a sucker bet that i know more about GR than most of y'all do]
i've gone through the lengthy lecture presentations and mayer meets the (or at least my) criteria for good science from a theorist -- he makes specific predictions which can be tested against empirically obtained datasets -- however, i didn't do the nasty integrals required to be done to see if he was simply lying and i will have to take him at his word that he has done them
essentially, the kernel of his hypothesis is contained at page 32 of his "lecture 1" pdf -- it is a small correction (in the weak-field approximation if i grok correctly) of the underlying metric which is the differential element which is used in standard GR calculations
*everything* in GR depends on the metric -- if mayer's metric can be empirically (or theoretically) motivated and, while using the differential geometry/GR mathematical machinery accrued over the last century or so, it can provide a more close approximation to empirical results than standard GR, then it is valid and more than worthy of further consideration
mayer provides a *very* long list of predictions about phenomena where standard GR predictions have failed to match the data and each of his predictions seems more or less rigorously derived from his singular assumption -- whether he has published or not (and a spires search did not yield any publications), and whether he is a post-doc, professor, grad student or invertebrate, he makes no appeal to authority (as i somewhat do in this posting) -- he only asks that his predictions be tested against unbiasedly observed reality
yo, gotta go --- i see it's super bowl time, chips and beer are waiting
cheers,
kevin