Relativity Definition and 998 Threads

The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively. Special relativity applies to all physical phenomena in the absence of gravity. General relativity explains the law of gravitation and its relation to other forces of nature. It applies to the cosmological and astrophysical realm, including astronomy.The theory transformed theoretical physics and astronomy during the 20th century, superseding a 200-year-old theory of mechanics created primarily by Isaac Newton. It introduced concepts including spacetime as a unified entity of space and time, relativity of simultaneity, kinematic and gravitational time dilation, and length contraction. In the field of physics, relativity improved the science of elementary particles and their fundamental interactions, along with ushering in the nuclear age. With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves.

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  1. jaketodd

    I Event Horizon movie, with some interesting concepts (papers cited)

    Please hear me out; I've referenced some good papers below, and I think you'll find the movie clip intriguing. Is there anything solid to this movie? The faster than light travel. The dimensional gateway. The folding of spacetime, passing through the hole, and then the return of spacetime to...
  2. jaketodd

    I The speed of forces, and applying relativity to force carriers

    Are there any limits to how fast forces can exert influence... or are they all instantaneous? How fast are the forces of a collision? I think frame dragging, with gravity, shows that at least gravity is not instantaneous, because if it is instantaneous, then how would it produce drag - it...
  3. Dennis Plews

    I Higgs Field & GR: Are They Related or Not?

    Since these two pillars of science have mass as a common core, are they related, essentially the same or not?
  4. D

    I Relevant/irrelevant clocks for experimental tests of relativity

    Recently, in this forum, highly respected members referred to clocks like pendulum and hourglass as if they are relevant for relativity. Are they really? Besides the lack of accuracy, they depend on acceleration/gravity, so they would not work at all in inertial frames and they could not...
  5. J

    IB Extended Essay research project on relativity

    Hi guys, I am a first year IB student who has to pick his EE topic. The Extended Essay is an independent, in-depth study of a chosen topic within one of the IB subject areas. I chose to do mine on physics. I have to write 3500 - 4000 words for my EE. I've chosen a set up for an investigation /...
  6. Aerodyn

    B Can Relativistic Mass Create a Black Hole?

    Hello dear colleagues from the physics forum, Following question came to my mind, can you tell me which statement (s) is/are wrong?. Since relativistic mass is weighed with the Lorentz factor for an external observer, it is expected an increase with speed. Such mass (m1) would tend to...
  7. George Wu

    A Relativistically invariant 2-body phase space integral

    I encounter a function that I don‘t know in the calculation of Relativistically invariant 2-body phase space integral: in this equation, ##s##is the square of total energy of the system in the center-of-mass frame(I think) I don't know what the function ##\lambda^{\frac{1}{2}}## is. There are...
  8. V

    B Triplets Paradox: Is There a Solution?

    One person (A) stays on Earth, while another (B) goes on a long journey and returns later. We can calculate the time interval for A and the proper time interval for B. Let's say we get Δt=100y and Δτ'=50y. We then consider a second traveler (C) going on a different journey, departing and...
  9. M

    I Adler's New Book on Relativity: Misprint on Page 16?

    I bought a copy of Adler's new book on relativity. Is there a misprint on page 16 regarding the Lorentz metric = diag (-1,-1,-1,-1) or am I missing something? The text itself after the equation suggests it is the same metric as on the earlier page so that index placement, two lower indices vs...
  10. BadgerBadger92

    B Perception of Velocity in Special Relativity

    If an object is going close to the speed of light, will outside frames of references perceive the moving object as going slow or fast?
  11. E

    General relativity - Using Ricc and Weyl tensor to find the area

    I have the following question to solve:Use the metric:$$ds^2 = -dt^2 +dx^2 +2a^2(t)dxdy + dy^2 +dz^2$$ Test bodies are arranged in a circle on the metric at rest at ##t=0##. The circle define as $$x^2 +y^2 \leq R^2$$ The bodies start to move on geodesic when we have $$a(0)=0$$ a. we have to...
  12. Atabold

    Einstein relativity between 2 coordinates systems

    I calculated the speed using the information provided through the above equation and finding V' = 1.2 m/s. However, the first solution must be -1,2 m/s. I don't know how to reach it, any suggestion?
  13. YRC

    A Special & General Relativity: CTC Metrics in Cylindrical Coordinates

    I am studying metrics that exhibit CTCs. I was looking at a few different metrics... Tipler's solution Godel metric Kerr metric For starters to compare them, I am trying to convert said metrics into cylindrical coordinates. Thanks in advance for any help😃
  14. J

    Relativity Recommended general relativity textbook

    Hi, I am looking to study general relativity at my own steam (currently finishing 1st year physics at Warwick) during the summer. What textbook(s) would you recommend? I've heard good things about A. Zee's 'Einstein Gravity in a Nutshell'- is that worth it, and would it be suitable for someone...
  15. A

    B The synchronization of clocks and the relativity of motion

    In his thought experiment on the relativity of simultaneity, Einstein synchronizes two clocks A and B (at either end of a rod) to the clock C in a stationary frame, while A and B (the rod) is moving relative to C. The equations Einstein finishes with demonstrate how observers moving with A and...
  16. AronYstad

    Special Relativity - Which reference frame experiences which time?

    This was a practice question, so it had the answer with it, which is 31 minutes. However, I'm confused as to why Lisa experiences T0. It isn't exactly an event happening in Lisa's rocket, but rather her just moving through space. From her perspective, it should look like Earth is moving at the...
  17. E

    ChatGPT Results: Testing Special Relativity

    Hi guys, I have heard a lot of claims about ChatGPT and how it is going to put a lot of people out of work. I have a friend who is a teacher of humanities and he is fearful of losing his job in the long term. People seem to be in awe at the thing and think it understand what is saying. So I...
  18. I

    I Determinism & General Relativity: A Physics Primer

    I know nothing about physics, to be clear. My friend was saying due to general relativity, the faster you move through space, the slower you move through time. Objects with a heavy mass (like a blackhole) can distort the fabric of space time and being near its gravitational pull means that you...
  19. S

    Opening a portal to the center of the Sun

    Whilst perusing a D&D forum, I stopped to answer a question someone put out which was "what would happen if we used the gate spell to open a portal to the middle of the sun?" I replied (this was a while ago) and whilst I'm reviewing it, I am troubled by the fact that this uses such high forces...
  20. Omega0

    B Is a Spin 2 Particle the Key to Understanding Gravitation in Quantum Mechanics?

    I have some questions regarding the expected exchange particles for gravitation. From my understanding the following was valid: We can linearize the equations of GTR for weak fields "Quantum mechanics" (Schrödinger, Dirac equations) are linear Those linear equations allow eigenstates and...
  21. S

    I Explore Spacetimes, Metrics & Symmetries in Relativity Theory

    I was discussing this paper with a couple of physicists colleagues of mine (https://arxiv.org/abs/2011.12970) In the paper, the authors describe "spacetimes without symmetries". When I mentioned that, one of my friends said that no spacetime predicted or included in the theory of relativity...
  22. Erland

    I Understanding Einstein's second postulate of special relativity

    Einstein's two postulates of special relativity reads, according to Wikipedia: The postulates are most often formulated similarly to this. But in my opnion, the second postulate shouldn't be formulated as above, because then one misses the point. This is particular true for the second...
  23. A

    B Relativity of Measures: A vs B Frame & Light Source S

    A frame “A” of three perpendicular axis (x, y, z) and an identical frame “B”, with an observer at rest in each, are moving toward each other at 1/2c on their common x axis. Centered between A and B on x is a light source S. At the time t1 when A, B and S coincide on x, S emits a light flash...
  24. ka_reem13

    AP French Relativity chapter 3 problem

  25. C

    B A thought experiment of the relativity of light

    A light source in uniform motion emits a flash of light. A spherically symmetric wavefront propagates from a central point, the source, or the “origin” of emission. The wave front remains at c relative to the origin as measured by all observers. How fast do these origins move? Am I missing...
  26. bhobba

    Relativity Lenny Susskind Has Done It Again - General Relativity

    This time with General Relativity: https://www.amazon.com/dp/1541601777/?tag=pfamazon01-20 I got a copy as soon as I noticed it. And it is good - as all his books are. Notice - number one best seller. Lenny deserves a medal. There is a genuine thirst for science beyond banal...
  27. Arman777

    Python GTRPy - A python package for General Relativity Related Calculations

    Hello, everyone I am now working on this project quite a while now and I just wanted to share it with this forum, which I was a member for a long time. I am working on a python application about GR and I believe I managed to create a very user-friendly layout. It's called GTRPy, and it allows...
  28. P

    A Popular Pseudoscience Video on General Relativity: Analysis & Criticism

    Here is the video: [link deleted by moderators] His basic idea is to take the spacetime interval and add a 5th term for the 5th dimension he is describing so it looks like: $$\Delta S^2 = c^2\Delta t^2 + c^2\Delta w^2 - \Delta x^2 - \Delta y^2 - \Delta z^2 $$ where w is the difference in time...
  29. James1238765

    I Modeling the Earth and Sun (2 body orbits) using general relativity?

    Modeling the time evolution of the sun and earth orbiting each other using ##F = \frac{GMm}{r^2}## is straightforward. However, it appears that modeling the time evolution of the same 2 body system using general relativity seems to be a hard/intractable problem? There was in depth discussion by...
  30. S

    I Can time be another basis vector under Galilean relativity?

    I refer to the video of this page, where there is a description of Galilean relativity that is meant to be an introduction to SR, making the comprehension of the latter easier as a smooth evolution from the former. All the series is in my opinion excellent, but I think that this aspect is...
  31. EclogiteFacies

    I Special Relativity philosophy and anxiety

    Hello all you clever people, I was wondering if you guys could answer a question for me regarding special relativity and the none existence of time. At least in the sense that the block universe people believe. So I'm writing as if the block universe is the correct interpretation What does...
  32. H

    B Relativity & Gravity: Resolving the Discrepancy

    I listened to and quite liked Sabine Hossenfelder's recent vid on relativity. Though one thing struck me as wrong. "Gravity is not a force," so it's effects does not cause true acceleration, so it has no effect on time. OK, but I'm pretty sure that satellites in different orbits have...
  33. L

    I Exploring Special Relativity: Patterns, Conjectures and Questions

    I have previously studied special relativity, but only at an introductory level. So I decided to explore the subject more in detail later by thinking and working things out on my own, in addition to doing research online. In particular, I seem to have noticed some intriguing patterns between...
  34. Ahmed1029

    I Charge conservation and special relativity

    If conservation of charge gets violated in future experiments, what would be the implications on relativity? I have some faint idea that this will cause photons to have non-zero rest mass, but does this affect special relativity at all? Also, does special relativity make conservation of charge...
  35. Ahmed1029

    I Is this just a typo in Schutz' book on General Relativity?

    I'm wondering is I'm missing something, or this should be " a non-zero component"?
  36. J

    Is Doubly Special Relativity Connected to Variable Light Speed?

    Hello. This is my first post on this site. anyone here familiar with "Doubly Special Relativity"? an ARXIV paper was linked in the OP. Some follow up links or other advice would be appreciated. Kowalski-Glikman, J., "Introduction to Doubly Special Relativity", (2004). arXiv:hep-th/0405273...
  37. D

    I Metrics of GR Solutions: Comp List, Hist & Viability

    Does anyone know of a comprehensive list of solutions to GR, their developmental history, and the viability for serving as a practical model for the observable universe?
  38. Ahmed1029

    I How is photon momentum compatible with special relativity?

    In relativity, momentum of a body is given by ##p=mv/\sqrt{1-v^2/c^2}##, but if mass is exactly zero and velocity is exactly ##c##, how is the photon momentum even defined? I don't think this problem can be resolved by simply stating the other formula relating energy to momentum, since it was...
  39. K

    Relativity Calculation: Two bodies traveling at relativistic speeds

    Body 1 travels 48 light years from point A to point B at 82% of light speed. Body 2 leaves point A 33 years after Body 1 and travels the 48 light years to point B at 99.99995% of light speed. What I think I know: Body 1 takes 58 years to reach point B according to an earth observer. Body 1...
  40. P

    A Time Travel, General Relativity & Information Paradoxes

    General relativity permits some exact solutions that allow for time travel. Some of these exact solutions describe universes that contain closed timlike curves, or world lines that lead back to the same point in spacetime. I wondered if these solutions also permits Causal loops? Such as the one...
  41. N

    I Do AEST (Absolute Euclidean Spacetime) models work?

    I was reading a paper by J.M.C Montanus which was published in <low quality journal reference removed> in which he claims under AEST the new gravitational dynamics and electrodynamics are reformulated in close correspondence with classical physics, and subsequently leads to the correct...
  42. AndrzejB

    Can Special Relativity Explain the Alice and Bob Spin Measurement Paradox?

    Alice measures the spin, also Bob measures. If we assume that the signals (from Alice to Bob) were sent, they had to be with the speed e.g. 10 c But in another frame of reference Bob first measures, next Alice. Measurement of Alice was cause and was sent back in time, or measurement of Bob was...
  43. A

    B Principle of Relativity: Classical Physics Example

    hi everyone "The principle of relativity: The laws of physics are the same in all inertial reference frames." Is in classical physics The laws of physics aren't the same in all inertial reference frames!? Give an example in classical physics Thanks
  44. racerunner

    B Muon Tomography Evidence for Special Relativity?

    Muons are a popular way to provide evidence for Special Relativity. But, does Muon Tomography provide evidence for SR? Can you calibrate your muon detectors without reference to SR? Is there any need to refer to SR when interpreting the data? I tutored a high school student who argued the...
  45. anm_ol

    Relativity Free Books & Lectures on Special Theory of Relativity

    I recently viewed some online free lecture series on Special theory of Relativity. I think I have an understanding of the basics so far, but would like some books for problems on special relativity. (Preferably solutions or at least answer keys included). It would be a great help if they...
  46. Ahmed1029

    I Instantaneous coordinates of an event in space (special relativity)

    In relativity, no signal travels faster than light, and hence if something happened away from me, I will only know about it after some time. This means I cannot measure instantly the position and time of something as it happens; this would violate special relativity. I however imagine that I...
  47. DmitryS

    B A question about relativity of simultaneity

    Hello. I'm new here and very much afraid of breaking rules. I would gladly post this question in the Homework section, because it's homework, but my question doesn't fit the template, it's a theory question. I hoped to find it in Relativity FAQ's, but it's not there. I can tell you I grasped...
  48. BadgerBadger92

    I Difference Between Lorentz Transformation & Special Relativity

    Sorry for the extra question. Just have a lot of questions lately and I know some people around here are annoyed with that.
  49. M

    Relativity Resources to start understanding relativity

    Hi everyone, I want to learn relativity but right now I don't know where to start. I have been doing Newtonian mechanics for quite some time from resnik and Irodov and want to go further. Which book should I now read?
  50. H

    I Def Proper Time GR: Half or Integral Along Path?

    In texts on General Relativity, the proper time ##d\tau^2 = -ds^2## (with an appropriate choice of metric signature) is commonly said that the time measured by a timelike observer traveling along a path is given by the integral of ##d\tau## along this path. Of course it's possible to construct a...
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