What is Theory of relativity: Definition and 146 Discussions

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. P

    I Are there any accepted relativistic interpretations of quantum mechanics?

    From the few interpretations of quantum mechanics that I know, let's say: Copenhagen Many Worlds (MWI) Bohmian mechanics Superdeterminism Retrocausality/transactional Objective-collapse Qbism* Consistent histories* I believe the only one that accepts a relativistic version in Copenhagen...
  2. 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...
  3. 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...
  4. S

    I Special Theory of Relativity & Conservation of Mass

    Does the law of conservation of mass fail to meet the first postulate of the special theory of relativity(the laws of physics are the same in all inertial frames of reference)?
  5. L

    I Acceleration in special theory of relativity

    In a inertial frame of reference ##S## body accelerate with constant acceleration ##a##. Can then exist inertial frame of reference ##S'## which moves with speed ##u## relative to ##S## in which body does not accelerate? And why?
  6. PainterGuy

    Stats on Students Understanding Theory of Relativity

    Hi, I'm not sure if it's a good idea to start a thread about the following problem but I didn't want to PM anyone. Some time ago I came across a thread which had stats related to the problems faced by students learning the theory of relativity. It showed like how many undergraduates really...
  7. Saptarshi Sarkar

    I Why does Special Theory of Relativity leave out Potential Energy?

    While studying Special Theory of Relativity I came across the formula for the energy of a particle. The total energy of a relativistic particle in STR contains the Rest Mass energy and the Kinetic energy. But, in Classical and Quantum Mechanics, we consider the total energy of the particle to be...
  8. A

    I Architecture & Assumptions of General Relativity Theory

    Every theory, whether it is a physical, a psychological or a sociological theory, is defined in terms of an assumed architecture and in terms of a number of assumptions that apply within that architecture. An example from physics is the previously widely accepted dome theory to explain the...
  9. M

    I Connection between General Relativity & Chaos Theory?

    I am very new to such ideas but was wondering if there is any connection to what I am asking. Taking two events, let's say at opposite ends of the globe. Would even A, only have a potential on event B, if light could travel between these event in the given time frame of these event occurring...
  10. V

    B Special Theory of Relativity: Ques on Thought Experiment

    I have a doubt ,the thought experiment performed by einstein he thought that the clock was behind him and he is moving away from clock with speed of light what if he is approaching a clock with speed of light won't time run at very high speed
  11. Orest

    B Solve FTL Problem with Faraday Cage and Relativity Theory

    Is it possible to solve a problem of overcoming of speed of light with solid objects using faraday cage Theory with equivalent charge?
  12. Sandip Patel

    B Which Watch Will Have Slower Time: Object 1 or Object 2?

    Assumption: Object 1 is moving and object 2 is static. It is impossible to say which object is moving without any reference object 3. There are three scenarios possible. 1. Reference object 3 is at same position in space time with object 2, then object 1 is moving and object 2 is static. 2...
  13. R

    B What is the theory of relativity?

    Is the Theorey of relativity that there is no absolute movement, only movement of one frame relative to another or that there is absolute movement but we cannot measure it ?
  14. stickman76

    I Graphic Anim of Special Theory of Relativity: Exploring Interrelationships

    There is a relationship between each of the mathematical values in each of the paradoxes with regard to each observers. There is obviously also a relationship between every situation we study in the Special Theory of Relativity. The Lorentz Transformations obviously prove this. So, I began to...
  15. K

    Special theory of relativity, theoretical problem

    Homework Statement Spaceship A, traveling past us at 0.7c, sends a message capsule to spaceship B, which is in front of A and is traveling in the same direction as A at 0.8c relative to us. The capsule travels at 0.9c relative to us. A clock that measures the proper time between the sending and...
  16. mr1batman

    B Why is the general theory of relativity is so complicated

    why is the general theory of relativity is so complicated i feel that it's very simple no thing hard in it there is a whole website to make people understand it i read the articles and i didn't found any thing complicated knowing the i am 13 so it should be very hard to understand
  17. D

    B What is dark energy in the fabric of space-time?

    I know that according to Einstein's theory of relativity, space-time is like a fabric which can be pliable. Gravity is the shape, or the warping of that fabric. In this analogy, what would dark energy (the unknown form of energy that is causing the universe to expand) be?
  18. K

    I Force on an Object according to the General theory of relativity

    What is the force acting on an object according to general theory of relativity? If there is a such a force, can we predict the motion of an object in general relativity just using the modified Newtons laws of mechanics i.e using relativistic mass of an object instead of rest mass ?
  19. A

    B Einstein's theory of relativity and time travel

    Hey so from my understanding of Einsteins theory of relativity the closer you travel to the speed of light the slower time is for you, is that right? if it is right does that give to reason that there could be a critical speed past the speed of light for which time for the object traveling at...
  20. ISamson

    B Unify General Relativity & Quantum Theory | Stephen Hawking

    Hello, I have read somewhere that the next major step in physics will be unifying general relativity with the quantum theory. Does anyone know about such? I wanted to know a bit more. I have read about such in the book by Stephen Hawking "A Brief History of Time". Thanks, I. P.S. My apologies...
  21. Divy Jain

    I Interactive Minkowski Diagram Tool

    I've made a Interative Minkowski Diagram Tool, http://divykjain.github.io/IMD You can add events, connect events and add world lines. Lorentz transformation for moving frames also present. I've added support for frame velocities equal or greater than light speeds(but the animations are a mess...
  22. P

    I Query on basic mechanics of Special Theory of Relativity

    The Special Theory of Relativity is based on the observations of an outside observer on a system traveling at the speed of light. There is no single point of reference to determine speed. So speed is determined relative to another object. This being the case an Apple traveling at the speed of...
  23. nomadreid

    I Bauer's Paradox in General Theory of Relativity?

    Has anyone heard of "Bauer's Paradox" in Einstein's working out his equations for General Relativity? The description I came across was extremely fuzzy (something about an expression for a certain tensor adding up to be zero when it shouldn't, or vice-versa), so I am looking for a better...
  24. R

    I Theory of Relativity: Light, Mass & Gravitational Lensing

    If light is pure energy, then how can gravitational lensing work? And if light has some mass, how can it change directions instantly when it is traveling through a prism? My high school science teacher had no answer 45 years ago.
  25. Axidecimal

    Explain how postulates are synthesized into Special Relativity?

    Homework Statement [/B] List two postulates of special relativity and then in your own words explain how these two statements are synthesized in Einstein's theory. Homework Equations 1. The laws of physics are the same in all inertial reference frames. 2. Light propagates through a vacuum...
  26. K

    I Galilean transformation paradox help

    I'm getting quite stuck on this problem here. Galileo said that Xb = Xa - V*Ta. (This follows from dv = dx/t --> Xa - Xb = t*dv --> the above formula) Thus, it is concluded Xa = Xb + V*Ta, but why? In my thought experiment the objects are moving relative to each other, thus if A is moving away...
  27. Basicsofphysics

    A A Unified Theory of Relativity and Particle Physics

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  28. Anjum S Khan

    Einstein's theory of relativity

    A falling apple made Newton to think about gravity. What made Einstien to think and develop his theory of relativity ? What devices/apparatus/equipment did he use for his theory of relativity ?
  29. E

    I Special theory of relativity argument

    Some layman people are against special relativity and stubbornly persist on their theories. One man put the model that the speed of photon is c + v, where v is speed of source. In such case Michelson interferometer is not a good anti-argument. What is, in your opinion about the most simple and...
  30. B

    Frames of Reference: Inertial vs Non-Inertial

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  31. L

    B Theory of Relativity: Time Dilation & Age Difference

    What is theory of relativity and how is it related to gravitational time dilation? If a person travels to somewhere in space where 1 hour there is 10 years on Earth and Comes back, will he be of the same age? Or it will just be an hour?
  32. B

    Relativity of Simultaneity and Time

    Hey guys, i am not a science guy by any means so any answer written for the layman would be much appreciated. i may not be understanding this right but here it goes: In einstein's relativity of simultaneity we talk about how events A,B, and C are simultaneous for one observer (lets call him...
  33. Julian102

    What is the relative area of a rectangular field?

    Homework Statement If the area of a rectangular field has length of 110 m and 80 m.If a spaceship is traveling with 0.9c velocity along the diagonal of the field.Then what is the area of the field seen by the astronaut in the spaceship? Homework Equations L=L(initial) Root over (1- (v/c)^2)...
  34. J

    Roadmap to Understanding the Theory of Relativity

    I just started reading the book The Perfect Theory by Ferreira and it has rekindled an old desire of mine to pursue a study of physics ultimately culminating in being able to fully comprehend (and play with) Einstein's field equations. My problem is I don't exactly know where to begin. I'm...
  35. S

    Solve the Special Theory of Relativity Confusion

    My Question is very interesting. I want an exact answer after correct assessments. Let there is a box or rocket or something in which light starts from point A to point B. When Light is generated from point A, at the exact point that thing box or rocket or frame moves from point X and it moves...
  36. CollinsArg

    Theory of Relativity & Gravity: Is Space Pushing Us to Earth?

    It may be a silly question because I'm not sure if I really understand the result of this theory, but does it say that gravity is the force of the space pushing us to earth? If it is so I have a question that I'll edit here! thank you
  37. K

    General Theory of Relativity: What & Why

    what general theory of relativity deals with. why special theory of relativity fails at one stage
  38. Pejeu

    Spaghettification and gravity in theory of relativity?

    Per my layman's understanding, the apparent force of gravity, as explained by the general theory of relativity, is actually the result of rectilinear motion at uniform speed through warped spacetime. 1. If that's the case, what actually causes gravity for objects at rest with respect to the...
  39. T

    A thought experiment paradox

    I am pretty familiar with the theories of special and general relativity. I know how to add velocities, I know the main postulates and the experimental confirmation. However, I thought of the following thought experiment: There are 3 experimenters (at the same point in space), who adjust their...
  40. Auliter

    Time Travel Possibility: Scottish Scientists Slow Light Speed?

    I've recently read a report about a group of Scottish scientists have managed to slow down the speed of light, not in a certain condition but through a special mask and the particles of light can be forever slowed down. Does that means the speed we need to achieve to make time travel is slower...
  41. A

    Special theory of relativity, a collision between two partic

    A particle of mass m comes with the speed 0.6c and collides with another particle of mass m which is at rest. In the collision melts the particles together and form a particle. What is the mass and velocity of the particle is formed? solution: The momentum and the total energy is conserved...
  42. blue_leaf77

    Were there objections to Einstein's theory of relativity?

    Dear friends, There is something related to the history of theory relativity that has been bothering me this whole time. This is about the two postulates of special relativity. At the time of its invention, probably even up to now (I'm not sure since I'm not theoretical physicist), there had...
  43. 2

    Deriving Gravitational Red Shift: Questions & Answers

    I am trying to derive the gravitational red shift effect but I think I am going about it all wrong. Specifically, I want to derive the change in frequency/ wavelength when a photon moves away from the surface of a star mass M and radius R. So I tried to use relativistic mass of the photon and I...
  44. S

    Time Travel & Theory of Relativity for HS Students

    Hey guys I have an issue I was wondering if you could help me with. There was a book in my high school library about the theory of relativity and time travel. I'm trying to find it again but the fact that I don't have a title for it is making things difficult. (For the record I'm long graduated...
  45. DREAMWALKER

    General Theory of Relativity Question

    Ok, I went through a video to understand it more simply. But there is one point I just don't understand. Which is this: How does Adam think others' clock is SLOW? Shouldn't it be FAST? Here's my breakdown of the video: Adam is in- Space Sarah is on - Ground Beam of light shone from the...
  46. G

    Quantum entanglement and Einstein's theory of relativity

    I have been thinking about this recently. Say two quantum particles, or two clusters of quantum particles, exist in the same universe. 1 is on, for lack of a better term, one side of the universe, one on the other. They are entangled. Because of the distance between them, one is in the...
  47. A

    Einstein's Theory of Relativity

    I've just recently researched a bit of his work with this and just wanted some clarifications: 1. Is Einstein redefining gravity or is he saying it doesn't exist 2. Is it right to say that he is saying gravity is the distortion of the fabric of time and space 3. If gravity is just the...
  48. W

    Is theory of relativity really relative ?

    Einstein made the theory based on Maxwell saying that electromagnetic waves travel with same speed from the view of all inertial & non - inertial frame. Then with what speed relative to a person sitting on light does light travel ?
  49. T

    Theory of Relativity, "you can't tell which mass is moving"

    Hello, I thought of something after watching this video on the theory of relativity. It says "it is impossible to tell which object is moving" Well I have now thought of a scenario where it would be possible. We can observe and measure the delta in speeds of the two masses as they...
  50. sujoykroy

    Does Einstein's General Theory of Relativity imply graviton?

    I was reading Einstein's paper "The Foundation of the General Theory of Relativity" and as i understood, he tried to establish that gravitation arises due to different kind of motions of objects. As per his opinion, in infinitesimally small space-time region special theory of relativity is still...
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