What is Special relativity: Definition and 1000 Discussions

In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates:
The laws of physics are invariant (that is, identical) in all inertial frames of reference (that is, frames of reference with no acceleration).
The speed of light in vacuum is the same for all observers, regardless of the motion of the light source or observer.

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  1. A

    I How does a photon view the universe?

    This question has been bugging me quite some time now. I'll start presenting my background for the problem: Fact: Photons are time-dependent oscillations of electric and magnetic fields as described by Maxwell's equations. Now, I've heard a lot of people, including professors saying that a...
  2. Jefffff

    Pendulum on a Relativistic Train

    Homework Statement In a thought experiment, a train is moving at a speed of 0.95c relative to the ground. A pendulum attached to the ceiling of the train is set into oscillation. An observer T on the train and an observer G on the ground measure the period of oscillation of the pendulum. State...
  3. R

    Special Relativity problem -- An electron travels at 0.422c....

    Homework Statement An electron travels at 0.422c. Calculate the following. (a) the relativistic momentum kg · m/s (b) the relativistic kinetic energy J (c) the rest mass energy...
  4. T

    I A special relativity explanation for the Lorentz Force?

    I am still a bit puzzled by this video: Does this mean that force exerted on an electrically charged particle facilitated by moving through magnetic field B is due to special relativity, and not virtual photons acting as magnetic force carriers? Thanks
  5. Jefffff

    Special Relativity and Space-Time Diagrams

    Homework Statement [/B] S' is moving at 0.5c relative to S. Two events, stationary with respect to S, occur at a distance of 4 light years from the origin at time 3 years and 6.5 years. Estimate the time between the events as measured by an observer in S'. Check your solution with the time...
  6. W

    Deriving Lorentz transformation by light cone coordinates

    Homework Statement Derive the Lorentz Transformation using light cone coordinates defined by ##x^±=t±x## ##x^+ x^-~## is left invariant if we multiply ##~e^φ~## to ##~x^+~## and ##~e^{-φ}~## to ##~x^-~##, that is ##~x'^+ x'^-=x^+ x^-## Homework Equations ##t'^2 - x'^2 = t^2 - x^2...
  7. PhotonSSBM

    Relativity Modern books on Special Relativity

    I'm looking for a rigorous book on SR for some summer reading. Preferably something that covers a lot of the stuff in this document really well, http://ocw.mit.edu/courses/physics/8-033-relativity-fall-2006/readings/guide.pdf The website recommends older books by French and Resnick, but I've...
  8. R

    B Cosmic Ray Muons: Finding Experimental Data for Special Relativity

    Hi everyone, I'm current working on a project about special relativity, and i was thinking writing about the cosmic ray muons. But where do i, as a high school student get raw data of cosmic ray muons? I have searched quite a bit, but it doesn't seems like data like that is public and easy...
  9. tkmanutk

    I Special relativity thought experiment

    The subject of relativity has been haunting me for while now. Everytime i feel i understand a concept, there comes questions withtin that contradict the undestanding. Have been trying to digest the time dilation & symmetry of how it is felt mutually by observers in two different frame of...
  10. F

    B Is special relativity incomplete?

    I feel a difficulty in understanding SP at fundamental level which is somewhat related with twin paradox. Let me take a thought scenario: in empty space or vacuum two boxes(A and B) with their own light sources attached are separated from each other at a far distance r initially. If they are...
  11. almarpa

    Relativity Alternative to Kleppner - Kolenkow chapter on relativity

    Hello all. I am currently using Kleppner - Kolenkow textbook on classical mechanics, and I am really liking it. Now I have finally reached the chapter on spatial relativity, but I have read in several foums that, despite the quaity of the book, this chapter is not as fine as the others (I have...
  12. T

    Moving charge magnetism explanation

    I'm from a country in Africa where I didn't have the privilege of learning the Standard Model, so I'll try and rephrase my question here: https://www.physicsforums.com/threads/why-is-the-electromagnetic-field-not-a-charge-field.857927/#post-5384284 In a way where my ignorance doesn't outrage...
  13. J

    I What is the resolution to the problem with E cross B field and E>B?

    I have been unable to find a satisfactory explanation of this problem, elsewhere. Consider an uniform electric field, E, along the y axis. Consider also a uniform magnetic field, B, along the z axis. If we release a particle (charge=q, mass=m) at rest on the origin at time t=0, what will be...
  14. P

    How Long Does a Relativistic Journey to a Star 65 Light-Years Away Take?

    Homework Statement Suppose you decide to travel to a star 65 light-years away at a speed that tells you the distance is only 25 light-years. How many years would it take you to make the trip? Homework Equations ∆t=∆t0/(√ (1−v2/c2 )) / ∆t0 = ∆t √(1−v2/c2) L=L0√ (1−v2/c2) The Attempt at a...
  15. T

    Why is the electromagnetic field not a 'charge field'

    This question is a continuation/topic-extrapolation of: https://www.physicsforums.com/threads/flux-in-magnetic-core-according-to-special-relativity.856482/#post-5374651 My question is 'how is the electromagnetic field different from some sort of mere electric-charge field?' The issue I have...
  16. T

    Proper movement, reference frames and gravitational waves

    Hi, So apparently electrons don't orbit the nucleus of atoms so I'm assuming the lack of movement means that no energy from the atom is radiated away from an atom due to minuscule gravitational waves, over the life of the universe. But gravitational waves have got me thinking about reference...
  17. S

    I Length Contraction: Lorentz vs Einstein Explained

    I read that: "Length contraction is caused because moving objects bend space. And that is the difference between Lorentz's and Einstein's length contraction concepts. Lorentz thought length contraction really occurs but Einstein thought that length contraction is a consequence of bending space...
  18. Mark Harder

    Speed of Gravity Waves: An Unmeasured Assumption?

    Many popular accounts claim that gravity waves move at the speed of light. Now, I know 2 things: Special relativity says their speed cannot be greater than the speed of light in a vacuum. Gravity is a different fundamental force than the electromagnetic force. The same goes for their fields...
  19. MathematicalPhysicist

    Exercise 26 in Schutz's First course in GR

    Homework Statement The question as follows: Calculate the energy that is required to accelerate a particle of rest mass ##m\ne 0## from speed ##v## to speed ##v+\delta v## (##\delta v \ll v##). Show that it would take an infinite amount of energy to accelerate the particle to the speed of...
  20. C

    Does the bullet reach its target?

    Homework Statement As outlaws escape in their getaway car, which goes 3/4c, the police officer fires a bullet from a pursuit car, which only goes 1/2c. The muzzle velocity of the bullet (relative to the gun) is 1/3c. Does the bullet reach its target according to Galileo? According to Einstein...
  21. JonnyMaddox

    Explicitly Deriving Spinor Representations from Lorentz Group

    I'm currently reading a book on relativistic field theory and I'm trying to understand spinors. After the author introduces the four parts of the Lorentz group he talks about spinors and group representations: "...With this concept we see that the 2x2 unimodular matrices A discussed in the...
  22. A

    Writing an Abstract for Special Relativity: Tips & Tricks

    I will be giving a speech for my class and my teacher wants an abstract. I will be talking for about 45 minutes and i want to explain time dilation, length contraction, Einstein postulates, twin paradox, and the Muon experiment. But I am not sure how to put it all into an abstract.
  23. T

    Flux in magnetic core according to special relativity

    Hi, So say you have a magnetic flux in a closed magnetic path circuit (like a TX core). Well I mean we draw arrows and stuff to indicate how the magnetic flux travels, but after watching this: I'm having trouble understanding why there is any flux moving through at all. Can someone please help...
  24. D

    Proving Time Dilation: Troubleshooting Tips

  25. Z

    Special Relativity Books: An Illustrated Guide & Beyond

    Hi there, I am wondering what would be a good book to study the math of special relativity for a non physicist. I started with the " An Illustrated Guide for Special Relativity" by Tatsu Takeuchi which I found nice and easy book to start with. To put it in another way, where should I go after...
  26. J

    Revolving light source and creation of angular momentum

    Let's say a train powered by electric third rail drives around without friction on a circular track, and light is shining out of the train windows, said light carries angular momentum, like light emitted from rotating or revolving things tend to do. Where does that angular momentum come from...
  27. J

    Electric Field of Moving Charge: Effects on Distance

    First I stand next to a point charge, then I start moving away or towards the charge, which causes the charge to be further away from me according to me (my ruler contracts according to an inertial observer), and as electric field of a point charge decreases with distance, the electric field...
  28. A

    How is the magnetic field related to Special Relativity

    Purcell has a paper in which he derives the magnetic field by assuming a charged particle travels alongside a conducting wire at the same velocity as the conduction electrons in the wire. The conduction electrons and the test charge are moving together but the positive charges are moving...
  29. J

    How Does Relativistic Speed Affect the Force Exerted by a Train on Rails?

    I came up with this problem, which is non-trivial at least for me: Train accelerates with constant proper acceleration. When the speed of the train relative to rails is zero, rails feel the train exerting 1000N force on the rails. What force do rails feel the train exerting on the rails when...
  30. L

    I Are Special Relativity effects valid for angular velocity?

    I like a to ask a very simple question. I have read about time-dilation when it comes to SR. So, like: (1.) A and B are are rest and close to each other. (2.) B starts traveling at .5C relative to A, away from A, in a straight line. (3.) B comes back at .5C towards A. Now, according to SR, A...
  31. Dennydont

    Photon colliding with stationary mass

    Homework Statement A photon with energy E collides with stationary mass m. They form a single particle together, what is this new particle's mass and what is its speed? Homework Equations Energy-momentum 4-vector P=(E, px, py, pz) Possibly P2=m2 The Attempt at a Solution Using 4- momenta, the...
  32. E

    Unraveling the Metric Found in Special Relativity

    In special relativity, we can prove that the metric is -+++ for all observers and that is by making use out of lorentz invariance. Some on this forum say that it comes as a result of constancy of light and others say that Minkowski predated einstein in making that metric, which was confusing...
  33. philton

    Phonon Lorentz Invariance in Superfluids - Papers?

    It is said phonon(not photon) in superfluid experiments could also produce similar upper-limit speed effect which I'm not sure if that's also Lorentz invariant. Another problem is that I can't dig out those paper that demonstrates this kind of effect. Anyone ever seen any of this paper? Thanks..
  34. Dennydont

    How does the doppler effect resolve the twin paradox?

    If you had twin 1 on the earth, and twin 2 fly to a star and back at a speed of v with the Earth and star separated by a distance L, twin 1 sends out flashes at intervals of t seconds (measured in his frame). Taking into consideration the numbers of redshifted and blueshifted flashes that the...
  35. T

    Interstellar travel and Special Relativity

    I always ask myself this question, and I think it is better to ask people that really know about this. Due to the impossibilities that Special Relativity poses, such as any object with mass not being able to travel at the speed of light. If we don't manage to at least scratch that speed, I...
  36. M

    I Questions about time dilation, special relativity, etc.

    I am a newbie to quantum physics but have been actively reading much about it for a couple weeks. However there are a few questions I simply cannot seem to find the answer to in regards to time dialation, the relationship between speed of light and time, etc. It seems like many sources repeat...
  37. G

    I Pseudorandom Entanglement and Special Relativity

    I was thinking about the superluminal speeds observed with quantum entanglement. Perhaps the particles are not really entangled, each of them just changes their spin with an in-built pseudorandom algorithm, allowing them to appear to be "in-sync" and thus entangled. This is just purely...
  38. N

    Special Relativity: Time dilation

    Hello. This is not a concrete problem, rather conceptual question. Homework Statement 2. Homework Equations 3. The Attempt at a Solution [/B] Spaceship with speed v with respect to the Earth is traveling from the Earth to say some distant star, which is distant L apart from the Earth looking...
  39. S

    How Close to Light Speed Do Protons Move in the LHC?

    Homework Statement a) The LHC was designed to collide protons together at 14 TeV centre-of-mass energy. How many kilometres per hour less than the speed of light are the protons moving? b) How fast is one proton moving relative to the other? Homework Equations The Attempt at a Solution a)...
  40. M

    Light Beam Opposite Motion: Einstein Special Theory

    Hello Everyone. I recently studied the Einstein special theory of relativity. I studied the thought experiment where a beam of light is thrown from a moving spaceship in the direction of its motion and the distance after a certain time interval was different from perspective of a man on...
  41. F

    Special Relativity Effects: Exploring Time Dilation & Mass Dilation

    Hello Forum, I have been studying special relativity and its unique phenomena (time dilation, length contraction, mass dilation, etc.) I would like to make sure that my understanding of these interesting phenomena is correct. For example, the length of an object is not an absolute. What we...
  42. N

    Lorentz Transformations or Dilation/Contraction?

    I'm doing a class on special relativity and when doing some problems, I'm never sure whether I should be using the Lorentz transformations (Eg. x' = γ(x-vt) or t'=γ(t- (v/c^2)x)) or the Time dilation and Length contraction equations to find t or x! Can anyone explain if there's any way of...
  43. A

    Is There More to Special Relativity?

    Is special relativity finished? It seems to me that there is more to special relativity. If we define C as equal to 1. (time = nanoseconds and length = feet) then we do a special relativity experiment an interval is defined. This interval is given by the square root of X squared...
  44. aamirza

    Special Relativity -- Elastic Particle Collision Algebra

    Homework Statement Consider the following head-on elastic collision. Particle 1 has rest mass 2mo, and particle 2 has rest mass mo. Before the collision, particle 1 movies toward particle 2, which is initially at rest, with speed u (= 0.600c ). After the collision each particle moves in the...
  45. B

    Is a Rapidly Rotating Searchlight a Violation of Special Relativity?

    Homework Statement Consider a searchlight on the ground that casts a spot on a cloud 1500 m overhead. If the searchlight is rotated rapidly−say, 40 ∘ in 1 μs−—how fast does the spot move in the Earth reference frame when the searchlight is directed vertically upward? I have solved this part...
  46. B

    Special Relativity - Dynamics -- Traveling in Space

    Homework Statement [/B] Assume that 437 days is a reasonable limit for how long a human can endure constant-velocity space travel. Proxima Centauri, the star closest to our Sun, is 4.24 light years away from Earth. If you wanted to fly to Proxima Centauri within the 437-day limit in a rocket...
  47. B

    Special Relativity -- Kinetic Energy

    Homework Statement An electron e− and positron e+ moving at the same speed in the Earth reference frame collide head-on and produce a proton p and an antiproton p¯. The electron and positron have the same mass. The proton and antiproton also have the same mass. The mass of the proton is 1836.15...
  48. B

    Speed of Ships -- Special Relativity

    Homework Statement Galaxy A moves away from galaxy B at 0.650 c0 relative to B. A spaceship leaves a planet in galaxy A traveling at 0.550 c0 relative to galaxy A. If the direction in which the ship travels is the same as the direction in which A is moving away from B, what do observers in B...
  49. B

    Special Relativity -- Dynamics -- Energy

    Homework Statement Antihydrogen is the only antimatter element that has been produced in the laboratory, albeit just a few atoms at a time. Each antihydrogen atom consists of a positron in orbit around an antiproton and has the same atomic mass as hydrogen. If an antihydrogen atom collides with...
  50. I

    OPERA experiment - Special Relativity

    Homework Statement In 2011, researchers at the OPERA experiment thought they had seen neutrinos with mass m and energy E = 28 GeV moving faster than light. The baseline between the source and the detector was 731 km, and the neutrinos seemed to arrive 60.7 ns early, compared to the maximum...
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