explain the consequences of the postulates of special relativity

Sometimes students have fun sketching a cartoon that explains or demonstrates difficult concepts. This page titled 4.3: Postulates of Special Relativity is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by David J. Raymond (The New Mexico Tech Press) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. Not only do observers in different inertial frames not agree on the duration on time intervals, they do not agree on the length of objects (i.e., the size of space intervals) either. [OL] Explain the postulates carefully. In this chapter, you will learn about the theory of special relativity, but, as mentioned in the introduction, Einstein developed two relativity theories: special and general. [BL] Ask students to round off the value given for c to 3 significant figures and express in scientific notation. Explain how the twin paradox comes about, and also explain why it does not break the symmetry of special relativity. However, if the space shuttle is moving from west to east, i. e., from Los Angeles toward New York, careful measurements will show that the clock in New York strikes the hour before the clock in Los Angeles! Explain the postulates of the special theory of relativity. are licensed under a, The Language of Physics: Physical Quantities and Units, Relative Motion, Distance, and Displacement, Representing Acceleration with Equations and Graphs, Vector Addition and Subtraction: Graphical Methods, Vector Addition and Subtraction: Analytical Methods, Newton's Law of Universal Gravitation and Einstein's Theory of General Relativity, Work, Power, and the WorkEnergy Theorem, Mechanical Energy and Conservation of Energy, Zeroth Law of Thermodynamics: Thermal Equilibrium, First law of Thermodynamics: Thermal Energy and Work, Applications of Thermodynamics: Heat Engines, Heat Pumps, and Refrigerators, Wave Properties: Speed, Amplitude, Frequency, and Period, Wave Interaction: Superposition and Interference, Speed of Sound, Frequency, and Wavelength, The Behavior of Electromagnetic Radiation, Understanding Diffraction and Interference, Applications of Diffraction, Interference, and Coherence, Electrical Charges, Conservation of Charge, and Transfer of Charge, Medical Applications of Radioactivity: Diagnostic Imaging and Radiation. It is important that the dish does not turn. Explain why failure in this case was actually a success. Describe the significance of mass-energy equivalence and apply it in explanations of phenomena such as nuclear stability, fission, and fusion. The second postulate of special relativity states that the speed of light in a vacuum is constant at c = 3 x 10 8 m/s in all inertial frames of reference. It is just something you decide is a fixed point or group of connected points. It was well motivated by Maxwell's equations and by prior experiments. If Michelson and Morley had observed the interference pattern shift in their interferometer, what would that have indicated? Use the Check Your Understanding questions to assess students achievement of the sections learning objectives. But no one is likely to think in earnest that this objection is justified in the present case"). The MichelsonMorley experiment proved it was not. It was well known in the 19th century that the Earths atmosphere only extends to about 100 km up, and since sunlight can reach the Earth, it was postulated that there must be another substance that acted as the medium for the propagation of light (much like sound propagates through air, water, or even solids, but not through vacuum). A velocity vector arrow for the rail car is shown towards the right. ( Most properties, such as mass and volume, have no fixed upper limit. {\displaystyle (x_{1},x_{2},x_{3},t)} Explain what is meant by a frame of reference. B If students watch it just after the text above, they will be adequately prepared. It may work best to just introduce the MichelsonMorley experiment briefly and then watch the animation. (Corey Leopold, Flickr). As he drives by Baltimore, he sneezes again (event D). It was known to travel as waves, and all other types of energy that propagated as waves needed to travel though a material medium. A frame of reference is not a complicated concept. Briefly answer the following question about special and general The person on the train holds two laser pointers, which she presses at the same time (or perhaps a device with a single button that sends out two beams, to avoid experimenter bias). The student is expected to: (3) Scientific processes. 11. Since we agree on at least the order of events at the same point in space, lets take as our time interval the time it takes for the light to travel back and forth between the mirrors once (i.e., one round trip). This link takes you to a video demonstrating how to measure the speed of light using a microwave, a ruler, and a bar of chocolate. , The muons are created in the upper atmosphere (about 20 km up), when cosmic rays collide with atmospheric atoms. 10 The observer would see it moving at a speed that is still less than c. This result conforms to both of Einsteins postulates: The speed of light has a fixed maximum and neither reference frame is privileged. The second postulate is then an assertion that the four-dimensional spacetime M is a pseudo-Riemannian manifold equipped with a metric g of signature (1,3), which is given by the Minkowski metric when measured in each inertial reference frame. Relativity is not new. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. The speed of the reference frame is given by equation (4.2.1), where the slope is simply the slope of the world line connecting the two events. 1999-2023, Rice University. = [citation needed]. When the speed of one frame of reference past another reaches the speed of light, a time interval between two events at the same location in one frame appears longer when measured from the second frame. It shows what Michelson and Morley expected to observe. For the moving observers the light has to travel farther in the rest frame to reach the observer receding from the light source, and it therefore takes longer in this frame. Just as he passes New York he sneezes (event A in figure 4.5). This experiment could be demonstrated to the class if a microwave is available in the classroom. In Albert Einstein 's original treatment, the theory is based on two postulates: [p 1] [1] [2] The laws of physics are invariant (identical) in all inertial frames of reference (that is, frames of . The laws of physics are the same in all inertial frames of reference. Without a "bridging hypothesis" as a third postulate, the 1905 derivation is open to the criticism that its derived relationships may only apply in vacuo, that is, in the absence of matter. Because the pulse from the right reaches her first, in her frame of reference she sees the bulbs as not having flashed simultaneously. Two events (such as A and E in figure 4.5) are collocated if they have the same x value. It might be better to let the students do the experiment at home so they can get more of a hands-on experience. The wave in a microwave is a standing wave with areas of high and low intensity. ) (In practice, these conversion laws can be efficiently handled using the mathematics of tensors.). t Discuss how accepting unexpected results is an important ability for scientists. Nonetheless, they do exist, and can be measured - and matter a lot in situations where speeds are high, such as in particle accelerators and cosmic radiation. p , Table 10.1 summarizes the differences between the two theories. Einstein began with two simple postulates based on the two things we have discussed so far in this chapter. The LibreTexts libraries arePowered by NICE CXone Expertand 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. 1 If this bridging hypothesis had been stated as a third postulate, it could have been claimed that the third postulate (and therefore the theory) were falsified by the experimental evidence. , When the speed of an object approaches the speed of light, its length appears to increase when viewed by a stationary observer. Remember that velocity equals distance divided by time, so t = d/v. High temperature: Very hot temperatures are encountered in this lab. However, for the stationary observer it seems that the light has moved in the direction parallel to the mirrors as well (see figure \(\PageIndex(1)\)b). To that end, we can construct a light clock: we place two mirrors in parallel, and let a beam of light bounce back and forth between them (Figure \(\PageIndex{1}\)). Which of Einstein's postulates of special relativity includes a concept that does not fit with the ideas of classical physics? If light speed is a constant and the two frames of reference are both valid, then simultaneity is not the same for all observers. e., the distance between two well-separated events can be zero. ) The two lengths are thus related by the inverse of the \(\gamma\) factor that relates two time intervals. Since the time interval for the roundtrip of the light in the comoving (or in this case, co-stationary) light clock is measured to be less than that of the moving clock, the stationary observer concludes that the moving clock is running slow. , Light is involved in the discussion of relativity because theories related to electromagnetism are inconsistent with Galileos and Newtons explanation of relativity. 2 One advantage of this formulation is that it is now easy to compare special relativity with general relativity, in which the same two postulates hold but the assumption that the metric is required to be Minkowski is dropped. They imply that there are no such things as universal measures of time and length, nor even agreement on whether events are simultaneous or not. However, he sees observer A receive the flash from the right first. Various English translations on Wikisource: This page was last edited on 9 March 2023, at 08:04. The principle of relativity applies to Einsteinian relativity just as it applies to Galilean relativity. Special relativity applies to Minkowski space, or "flat spacetime" (phenomena which are not influenced by gravitation).. Einstein knew that some weaknesses had been . The theory of Special Relativity and its implications spurred a paradigm shift in our understanding of the nature of the universe, the fundamental fabric of which being space and time. Want to cite, share, or modify this book? At the time, it was not generally believed that light could travel across empty space. This is a diagram of the instrument used in the MichelsonMorley experiment. and you must attribute Texas Education Agency (TEA). For example, when you look up at celestial objects in the sky, you choose the earth as your frame of reference, and the sun, moon, etc., seem to move across the sky. It is all relative. m/s By the end of this section, you will be able to do the following: The learning objectives in this section will help your students master the following student standards: [AL] Discuss the history of the concept of the ether. However, Maxwell's equations rely on several other postulates, some of which are now known to be false (e.g., Maxwell's equations cannot account for the quantum attributes of electromagnetic radiation). They can then show the cartoon to the class and explain their reasoning. B Comparing Special Relativity and General Relativity, Calculating the Time it Takes Light to Travel a Given Distance, https://www.texasgateway.org/book/tea-physics, https://openstax.org/books/physics/pages/1-introduction, https://openstax.org/books/physics/pages/10-1-postulates-of-special-relativity, Creative Commons Attribution 4.0 International License, Applies to observers moving at constant speed, Applies to observers that are accelerating, Most useful in the field of nuclear physics, Accepted quickly and put to practical use by nuclear physicists and quantum chemists, Largely ignored until 1960 when new mathematical techniques made the theory more accessible and astronomers found some important applications.

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