The conflict originates with the radar definition of. The behaviour of measuringrods and clocks in motion. In the present work we have discussed the well known topic of simultaneous passing of photon through both the slit of young double slit experiment. Pdf einsteins relativity, simultaneity and youngs double.
Special relativity is mathematically selfconsistent, and it is an organic part of all modern physical theories, most notably quantum field theory, string theory, and general relativity in the limiting case of negligible gravitational fields. 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. Special relativity read p98 to 105 the principle of special relativity. Describe how simultaneity is a relative concept for observers in different inertial frames in relative motion. We will imagine a series of thoughtexperiments to guide our. A configuration is provided where the results of relativity of simultaneity and absolute simultaneity are calculated which can discriminate if relativity of simultaneity ros is an actual. 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. People travelling in this train will with advantage use. It is commonplace among ordinary folk to associate tense with language. When the observer in the middle sees the two lamps come on. The tutorial concludes by helping students apply the relativity of simultaneity to other contexts. Is the relativity of simultaneity a temporal illusion.
Einsteins rethinking resulted in the special theory of relativity that states that the velocity dependence of simultaneity is a consequence of the relativity of space and time. In this paper i will show that conventional wisdom is wrong. Jul 25, 2019 duration and simultaneity bergson pdf henri bergson introduced new life to french philosophy, examining the nonmathematical sciences from a philosophical stance. The relativity of simultaneity part 1 the weirdness. Simultaneity albert einstein and the theory of relativity. How to do calculation in relativity of simultaneity physics.
Time dilation, length contraction and the relativity of simultaneity are among the strange conclusions of special relativity. Presentism, relativity, and simultaneity william demsar silpakorn university, thailand abstract the atheory of time insists that there is some real ontological fact about what is present. The libretexts libraries are powered by mindtouch and are supported by the department of education open textbook pilot project, the uc davis office of the provost, the uc davis library, the california state university affordable learning solutions program, and merlot. Special relativitysimultaneity, time dilation and length. An animated introduction to galilean relativity, electromagnetism and their incompatibility. Preamble although at first glance it might seem that where the lightnings stroke makes no difference, it is actually of utmost importance.
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. Discovering the relativity of simultaneity how did einstein take the. Duration and simultaneity bergson pdf henri bergson introduced new life to french philosophy, examining the nonmathematical sciences from a. 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. Einsteins idea is to consider two lightnings, simultaneously falling at the trains extremities.
The purpose of this paper is to analyze the doctrine of the. Apr 26, 2018 8 videos play all intro to special relativity course minutephysics bells theorem. The account above uses light signals merely as a means to enable the two observers to determine the time order of the events. Utilizing an argument based on the relativity of simultaneity in the tradition of putnam and rietdijk and novel but reasonable assumptions as to the nature of reality, we will show that the past, present, and future are equally real, thus ruling out presentism and other theories of time that bestow special ontological status to the past. Conventionality of simultaneity stanford encyclopedia of. Signal sent out from b at t 0 is described in s by arrival at a and c given by intersections 1, 1. Time dilation, length contraction and simultaneity. The relativity of simultaneity for observers events lamps turning on in the same inertial fr. Special relativity time dilation length contraction along the direction of motion space and time are relative relativity of simultaneity velocities are relative, except for that of light, and add up in such a way that they never exceed the velocity of light. This is a simple consequence of the fact that the speed of light is the same no matter which.
This type of thought experiment in german, gedankenexperiment shows that seemingly obvious conclusions must be changed to agree with the postulates of relativity. This video is chapter 4 in my series on special relativity, and it covers how things that appear simultaneous from one perspective in our universe arent simultaneous from other moving. The relativity of simultaneity summary the weirdness. The tutorials described in this paper use a variety of instructional strategies. In accordance with the timedilation effect, the elapsed time on the clock of the twin on.
Continuing to examine the figure we see 4 points with their marks. Lecture notes on special relativity macquarie university. Relativity of simultaneity wolfram demonstrations project. Relativity is also the limiting case of another theory quantum. Time dilation, length contraction and simultaneity from. With the help of the example of newtons sailor in the special theory of relativity we have. The relativity of simultaneity for observers and events lamps turning on in the same inertial frame. Lecture 3 and 4 relativity of simultaneity lorentzeinstein.
Even prior to the advent of that theory, however, questions had been raised see, e. The pdfs posted here are updated daily, so we recommend bookmarking. Simultaneity is not wellde ned in special relativity, and so newtons laws of gravity become illde ned. Both views are correct, even though the two observers dont agree on simultaneity. Pdf testing relativity of simultaneity using gps satellites. Relativity of simultaneity can be measured with clocks of gps satellites. Therefore, and since graviton asked this question to better understand the simultaneity of relativity, i will give the answer for both options. However, be warned, the reason that the twin paradox has attracted so much puzzlement is that, although superficially a simple problem, the analysis of the. An analysis based on the properties of electromagnetic waves r. Amongst other things, this latter theory is essentially a theory of gravitation. 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.
In fact by clarifying the physical meaning of the relativity of simultaneity one can inform the philosophical debate and endorse a presentist view. The laws of nature look exactly the same for all observers in inertial reference frames, regardless of their state of relative velocity. It also forces us to make sure that we carefully define many concepts that we dont ordinarily think too. Einstein june 30, 1905 it is known that maxwells electrodynamicsas usually understood at the present timewhen applied to moving bodies, leads to asymmetries which do. How to do calculation in relativity of simultaneity. Oct 27, 2017 both views are correct, even though the two observers dont agree on simultaneity. Max jammers concepts of simultaneity presents a comprehensive, accessible account of the historical development of an important and controversial conceptwhich played a critical role in initiating modern theoretical physicsfrom the days of egyptian hieroglyphs through to einsteins work in. The relativity of simultaneity and presentism philsciarchive. The pdfs posted here are updated daily, so we recommend bookmarking the pdfs instead of saving them locally or printing. Using only special relativity and the fact that newtons theory of gravity works. He realized that the reckoning of simultaneity depended on the velocity of the observer.
Maybe forget relativity of simultaneity for a moment, as youre stuck on thinking its absolute. Notes for mechanics and relativity there is, in nature, perhaps nothing older than motion, concerning which books written by philosophers are neither few nor small. Special relativity may be divided into 1you shouldnt feel too bad about having spent so much time learning about a theory thats just the limiting case of another theory, because youre now going to do it again. Pdf relativity claims that the simultaneity between two or more observers, each traveling in different inertial reference frames irfs is. This page uses animations to explain them in more detail. Initial concepts 1 a spacetime is a 4dim collection of points with additional structure.
So every point in spacetime is assigned 4 quantities. There is no reference frame in which light can appear to be at rest. Pdf the problem with the relativity of simultaneity researchgate. The debate about the conventionality of simultaneity is usually carried on within the framework of the special theory of relativity. 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. The approach taken, however, is to help students go through the reasoning required to develop a functional understanding of the relativity of simultaneity. There is one more than would suffice for einsteins description of relativity of simultaneity, but this will help our analysis. 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.
Ever since the now infamous comments made by hermann minkowski in 1908 concerning the proper way to view spacetime, the debate has raged as to whether or not the universe should be viewed as a fourdimensional, unified whole wherein the past, present, and future are equally real or whether the views espoused by the possibilists, historicists, and presentists regarding the unreality of the. The validity of thought experiments can only be determined by actual observation, and careful experiments have repeatedly confirmed einsteins theory of relativity. The relativity of simultaneity and presentism philsci. Basically, special relativity can be stated as the invariance of any spacetime interval that is the 4d distance between any two events when viewed from any inertial reference frame. Up to now our considerations have been referred to a particular body of reference, which we have styled a railway embankment. Lorentzs theory of electrodynamic relativity formulated during 18951905 8, 9, and from einsteins own version of relativity in 1905 with di ering interpretation 10, are at the basis of the. However, which kinds of things can be tensed is a substantial question. We are going to do a number of thought experiments here, and although normally i encourage you to take notes. The relativity of simultaneity permeates special relativity. This is supposed to be shown quite simply just by considering the relativity of simultaneity.
But bob thinks alice has messed up, alice thinks that bob has messed up in terms of his clock. Stu dents take about 2 h to work through the pair of tutorials. Relativity of simultaneity now suppose a, and at rest in s which is moving at speed v along xaxis. Wayne laboratory of natural philosophy, department of plant biology, cornell university, ithaca, ny, usa the determination of whether two distant events are simultaneous depends. 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. Relativity of simultaneity without light signals the effect just described is the relativity of simultaneity. 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. The special and the general theory, by albert einstein this ebook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. 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. We suppose a very long train travelling along the rails with the constant velocity v and in the direction indicated in fig. The relativity of simultaneity let me begin with a little homily.
But bob thinks alice has messed up, alice thinks that bob has messed up in terms of his clock synchronization. This is a fundamental result of special relativity. The theories of relativity and bergsons philosophy of. What we actually mean here is that the concept of simultaneity will depend on which frame you are in. The hueristic value of the theory of relativity 15. It is often alleged that this theory is inconsistent with the theory of special relativity. Special relativity rensselaer polytechnic institute. Intuitively, it seems that the time for a process, such as the elapsed time for a foot race figure \\pageindex1\, should be the same for all observers. It also forces us to make sure that we carefully define many concepts that we dont ordinarily think too much about in our small, slowmoving world. According to conventional wisdom, presentism is at odds with the theory of relativity. 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. Later, einstein was able to further develop this theory, leading to what is known as the general theory of relativity.
They throw the two balls forward at 20 kmh at two other people. Lecture 3 and 4 relativity of simultaneity lorentz. We also acknowledge previous national science foundation support under grant numbers 1246120, 1525057, and 14739. Relativity both the special and general theories, quantum mechanics, and thermodynamics are. May 05, 2007 this is a fundamental result of special relativity. The twin paradox is an interesting example of the relativity of simultaneity and time dilation and deserves close study so that these features of special relativity can be understood. One of these can be loosely characterized as a series of steps.
Simultaneity side 1 introduction special relativity forces us to really think about many things we used to take for granted. A closely related phenomenon predicted by special relativity is the socalled twin paradox. On the relativity of the conception of distance 11. From different reference frames, there can never be agreement on the simultaneity of events. Suppose one of two twins carrying a clock departs on a rocket ship from the other twin, an inertial observer, at a certain time, and they rejoin at a later time. We present a relativistic spacetime diagram that displays in true magnitudes the readings daytimes of two inertial reference frames clocks. In the appendices after the main text i also give the physics background and easily veri able proofs for the assertions made in the text, pertaining to relativity, simultaneity and time dilation, clearly distinguishing beliefs and facts. In this demonstration, light pulses are emitted at the center of a moving train and strike both ends. It can lead to unexpected behavior in any quantity that requires synchronized clocks for its measurement. 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 light signals themselves are not an essential part of the effect and they can be distracting. The relativity of simultaneity labs department of plant biology. Our goal will be to go behind the mythmaking and beyond the popularized presentations of relativity in order to gain a deeper understanding of both einstein the person and the concepts, predictions, and strange paradoxes of his theory.1194 980 1077 1644 278 178 1107 844 190 1414 1349 227 1148 1241 240 470 330 533 703 1632 587 1434 1636 225 1658 434 1469 1138 1374 716 1021 1449 223 617 748