The relativity of simultaneity and presentism philsciarchive. Einstein, relativity and absolute simultaneity 2005 marked the centenary of one of the most remarkable publications in the history of science, albert einsteins on the electrodynamics of moving bodies, in which he presented a theory that later came to be known as the special theory of relativity. It is routinely assumed that einstein discovered the relativity of simultaneity by thinking about how clocks can be synchronized by light signals, much in accord. We are going to do a number of thought experiments here, and although normally i encourage you to take notes. If simultaneity is relative to a frame of reference, so is duration. The relativity of simultaneity and presentism philsci. Simultaneity in newtonian mechanics and special relativity 1. The determination of whether two distant events are simultaneous depends on the velocity of the observer. They throw the two balls forward at 20 kmh at two other people. This will enable to see that the relativity of simultaneity is simply a relativity i. We suppose a very long train travelling along the rails with the constant velocity v and in the direction indicated in fig.
Kim 1 department of physics, university of maryland, college park, maryland 20742, u. Both views are correct, even though the two observers dont agree on simultaneity. The relativity of simultaneity and presentism arxiv. Einstein begins this book by questioning the traditional concepts of time and space, and asserting that these traditional ideas are in conflict with the idea that light propagates at a constant continue reading simultaneity and. Relativity of simultaneity now suppose a, and at rest in s which is moving at speed v along xaxis. The reanalysis of the concepts of time and simultaneity formed one of the crucial and distinguishing elements of einsteins special theory of relativity of 1905 22. Hey guys, this might seem like yet another basic question, but i was wondering about ros.
According to einsteins special theory of relativity, it is impossible to say in an absolute sense that two distinct events. What we actually mean here is that the concept of simultaneity will depend on which frame you are in. The relativity of simultaneity labs department of plant biology. This overview has been approved by john field, who has kindly allowed his unpublished papers to be hosted on this site. As you can guess from the equations for the lorentz transformation, the concept of time becomes a relative concept since we no longer have the simple relation tt. Relativity of simultaneity university physics volume 3. On the conventionality of simultaneity in special relativity. Oct 27, 2017 both views are correct, even though the two observers dont agree on simultaneity. However, and most controversially, this suggests that the reciprocity principle does not apply to special relativity. According to conventional wisdom, presentism is at odds with the theory of relativity.
The impression that i got from reading about relativity was that relativity of simultaneity was a consequence of lorentz contractions, primarily time dilation. Okay, first thing we want to look at in terms of this whole idea of time being suspect which really has to do with the relativity of simultaneity. The first part of the thought experiment is to establish two simultaneous events in a moving reference frame. But careful analysis shows this not to be the case. Relativity of simultaneity and special relativity incl. Thats probably a good thing, because there is no absolute fact of the matter which of the two events occurred first. He remained in his initial frame of reference and john returned at the same velocity he left with. Instead of an absolute time associated with the rest frame of the aether, actual.
We might have guessed incorrectly that if light is emitted simultaneously, then two observers halfway between the sources would see the flashes simultaneously. Einstein missed the fact that the conven tionality of simultaneity leads to a conventional element in the chronogeometry, since it corresponds to the possibility of. Planes of simultaneity as discussed on the previous page, events that are outside each others light conesi. This is supposed to be shown quite simply just by considering the relativity of simultaneity. Lecture 3 and 4 relativity of simultaneity lorentzeinstein. Therefore, hunter measured the return trip to take 15 hours for his frame same as the outgoing trip. Continuing to examine the figure we see 4 points with their marks. Simultaneity in newtonian mechanics and special relativity. Student understanding of time in special relativity. Wayne laboratory of natural philosophy, department of plant biology, cornell university, ithaca, ny, usa the determination of whether two distant events are simultaneous depends. Utilizing an argument based on the relativity of simultaneity in the tradition of putnam and rietdijk and explicit novel but reasonable assumptions as to the nature of reality, we argue that the.
In particular, the role of oneway assumptions in the foundations of special relativity is emphasized. Then, were going to make further observation as well with this whole idea, the relativity of simultaneity and especially, what bob is observing here. So in overall, loss of simultaneity arises due to finite speed of communication and in addition is dependent upon the relative speed and relative location of the event wrt to two observers. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext.
The most familiar example is the length of a moving body, since that length is given by the distance between the objects endpoint at the same moment in time. We present a relativistic spacetime diagram that displays in true magnitudes the readings daytimes of two inertial reference frames clocks. Relativity of simultaneity without light signals the effect just described is the relativity of simultaneity. The relativity of simultaneity summary the weirdness. In this demonstration, light pulses are emitted at the center of a moving train and strike both ends. To derive the formula for the relativity of simultaneity, lets use a thought experiment based on the example given in the previous section. An analysis based on the properties of electromagnetic waves r. Relativity of simultaneity we tend to think of the word simultaneous as being fairly easy to define. Time dilation impacts the rate of change of time in different frames of reference but simultaneity is checking now, which is due to finite speed of light. The relativity of simultaneity permeates special relativity. Ifs is real timelike interval, the strict order of events is determined. The question of simultaneity in relativity and quantum mechanics. So lets remind ourselves, this is really a combination of this last three video clips, or video clip one and then this previous one, where we were.
The relativity of simultaneity u p to now our considerations have been referred to a particular body of reference, which we have styled a railway embankment. In the flat minkovskian spacetime the pseudo euclidian metric is defined by notion of the spacetime interval s between two points, i. There is one more than would suffice for einsteins description of relativity of simultaneity, but this will help our analysis. Wayne laboratory of natural philosophy, department of plant biology, cornell university, ithaca, ny, usa the determination of whether two distant events are simultaneous depends on the velocity of the observer. How to do calculation in relativity of simultaneity physics. The restriction by the roundtrip isotropy condition on the admissible distance.
In this paper i will show that conventional wisdom is wrong. This velocity dependence is typically explained in. Write out the structural models equation derived from economic theorymodel in terms of causal effects. But careful analysis shows this cannot be the case if the speed of light is the same in all inertial frames. Lecture 3 and 4 relativity of simultaneity lorentz. If the units matter, then one has to find and insert the missing cs. May 05, 2007 imagine two observers, one seated in the center of a speeding train car, and another standing on the platform as the train races by. Signal sent out from b at t 0 is described in s by arrival at a and c given by intersections 1, 1. This is a simple consequence of the fact that the speed of light is the same no matter which. Relativity of simultaneity and quantum mechanics with mention of a recent experiment in geneva the above structure is at the same time topical as well as, roughly, chronological.
Initial concepts 1 a spacetime is a 4dim collection of points with additional structure. The relativity of simultaneity for observers and events lamps turning on in the same inertial frame. Einsteins idea is to consider two lightnings, simultaneously falling at the trains extremities. The moment you understand the real significance of relativity of simultaneity, you will never forget that the future also your future already exists. That special relativity is compatible with absolute simultaneity. If y1 and y2 are measured in units of mk14, the groundstate wave function of this oscillator system is.
Illustrating the relativity of simultaneity and the thought experiments associated with it equations 12, and 14 leads to a relativistic spacetime diagram that enables us to find out the location of an event in k and the location of its einsteinlorentz transformed correspondent in k. We show that two principal methods of synchronization can be considered. One of the most fundamental deductions albert einstein made from the finite speed of light in his theory of special relativity is the relativity of simultaneitybecause light takes a finite time to traverse a distance in space, it is not possible to define simultaneity with respect to a universal clock shared by all observers. It can lead to unexpected behavior in any quantity that requires synchronized clocks for its measurement. How to do calculation in relativity of simultaneity. One of the most fundamental deductions albert einstein made from the finite speed of light in his theory of special relativity is the relativity of simultaneity because light takes a finite time to traverse a distance in space, it is not possible to define simultaneity with respect to a universal clock shared by all observers. Simultaneity and synchronization a question of time. Synchronization by the einstein procedure and by slow clock transport turn out to be equivalent if and only if the time dilatation factor is given by the einstein. Abstract in relativity, two simultaneous events at two di. The question of simultaneity in relativity and quantum.
Paradoxes of special relativity and quantum mechanics. Floyd university of toronto july 22, 20 this document outlines the nature of simultaneity bias in regression analysis and the standard method for dealing with it, twostage least squares. The account above uses light signals merely as a means to enable the two observers to determine the time order of the events. For example, if you are standing near two people and these two people clap their hands once. One of the most dramatic consequences of einsteins theory of special relativity is the relativity of simultaneity, the fact that events perceived as simultaneous by one observer appear separated in time in a different frame of reference. Shaffer, and stamatis vokos department of physics, university of washington, seattle, washington 981951560 received 26 july 2000. Discovering the relativity of simultaneity how did einstein take the. In fact by clarifying the physical meaning of the relativity of simultaneity one can inform the philosophical debate and endorse a presentist view. The light signals themselves are not an essential part of the effect and they can be distracting. Relativity of simultaneity wolfram demonstrations project. John measures his time to be 12 hours, but he measures hunters time to be 9. When the observer in the middle sees the two lamps come on. However, for the variables x1 and x2, the story is quite di. So every point in spacetime is assigned 4 quantities.
In econometrics, something called the simultaneity occurs when a variable on the righthand side of the casual inferential model equation and the variable on the lefthand side of the same model equation influence each other at the same time. From hunters perspective, nothing new has happened. Describe how simultaneity is a relative concept for observers in different inertial frames in relative motion. Maybe forget relativity of simultaneity for a moment, as youre stuck on thinking its absolute. In this paper the classical topic of conventionality in defining the simultaneity or synchrony of distant events is tackled again, and the validity of reichenbachs view is carefully circumscribed. Pdf is the relativity of simultaneity a temporal illusion. In physics, the relativity of simultaneity is the concept that distant simultaneity whether two spatially separated events occur at the same time is not absolute, but depends on the observers reference frame. The relativity of simultaneity let me begin with a little homily. In this example it is considered that to a stationary observer watching 2 towers being demolished simultaneously the resulting pile of rubble would be symetrical but a fast traveller moving from left to right might calculate that the west tower collapses or collapsed before the east tower. The question of simultaneity in relativity and quantum mechanics y. In nontechnical presentations of the theories of relativity even the best of them the austere pictures of worldlines of clocks are sometimes humanized or anthropomorphized by adding a human observer to the world line to go along with the clock. This journey of the beam of light takes longer relative to the train cars frame of reference than relative to the. The relativity of simultaneity and presentism mario bacelar valente abstract according to conventional wisdom, presentism is at odds with the theory of relativity.
Tooley a defense of absolute simultaneity offers two arguments in favor of absolute simultaneity, a metaphysical one and one appealing to quantum mechanics. People travelling in this train will with advantage use. Noz 2 department of radiology, new york university, new york, new york 10016, u. Imagine two observers, one seated in the center of a speeding train car, and another standing on the platform as the train races by. The conventionality of simultaneity in einsteins practical. The latter benightedly runs afoul of callenders coordination problem while the metaphysical argument rests on a dubious inference to the best explanationtype maneuver for the. The role of convention in various definitions of clock synchronization and simultaneity is investigated.
The relativity of simultaneity part 1 the weirdness. In physics, the relativity of simultaneity is the concept that distant simultaneity whether two spatially separated events occur at the same time is not absolute, but depends on the observers reference frame description. The relativity of simultaneity steven savitt 6 2 if one follows this convenient course, one might find oneself from time to time puzzling over an equation in which the units on the two sides do not match. Andersen march 30, 2016 1 einsteins original paper shown below is paragraph 2 of einsteins paper. The two people do not actually observe the lightning strike at the same time. Up to now our considerations have been referred to a particular body of reference, which we have styled a railway embankment. Econometrics is a method of causal inference applied to economics.
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