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

    Special Relativity, French, solutions manual

    I'm currently reading Special Relativity, the famous book on this subject by French. The book does contain a nice set of problems for each chapter and corresponding answers at the end of the book. The issue I have with the answers though is that they are mostly just the correct answers, there...
  2. adoion

    Was Einstein lucky when not considering twin paradox as paradox?

    hi, Einstein did not even consider the twin paradox as problematic at all, he argued that it is a simple consequence of his special relativity? obviously he never gave a explanation of why the two twins don't age the same he instead left it to others to do so. was Einstein just having a hunch...
  3. M

    Around the Earth Clock: Does Special Relativity Hold True?

    Hi all I just started doing some research on special relativity and I figured something. If two people both reset their watches. One person goes around the Earth once, doesn't matter at what speed, and the other person stays there. The watch of the person that went around the Earth will run...
  4. K

    Velma and Mort's ice cream is melting special relativity problem. Help please.

    Homework Statement Velma and Mort have identical 10-minute melting ice-cream cones. How fast must Velma move in order for her 10-minute cone to last 3 times longer than Mort’s, as measured by Mort?Homework EquationsThe Attempt at a Solution [/B] We have not gotten too in depth into...
  5. K

    Special relativity question: space travel and relativity of time

    Homework Statement You are 20 years old and embark on a mission to a star system that is 200 light-years away. Your ship leaves Earth in 2013 and travels at 0.999c. You do not spend much time at the destination, just head back to Earth. What year is it when you arrive back on Earth? How old...
  6. X

    Do entangled particles decay simultaneously?

    I apologise in advance for my rather minimal knowledge of physics. Please assume that anything I write below is just my current understanding, and may very well be incorrect... Elementary particles decay into other elementary particles. When a a subatomic particle decays into a pair of other...
  7. J

    Velocity of Accelerated Observer in SR: Understanding the Paradox

    Hey, I have a question regarding accelerated motion in special relativity. Suppose an observer has a constant proper acceleration α, his velocity in an inertial frame of a distant observer will then be given v = c tanh(ατ/c), where τ is the proper time of the accelerated observer. Since every...
  8. R

    Precession of relativistic orbit in pure inverse-square force

    PROBLEM: Show that Special Relativity predicts a precession of π(GMm/cl)2 radians per orbit for any elliptic orbit under a pure inverse-square force. where G is gravitational constant, M is mass of larger body, m is mass of smaller orbiting body, c is speed of light and l is angular momentum...
  9. V

    Minimal Special Relativity - Reciprocity of Time Dilation

    Hello, I hope somebody can help me with this question. Homework Statement I have to prove that time dilation is a reciprocal effect by only using the Postulates of Minimal Relativity Theory: 1. Let I be an inertial frame, then I' moving with a constant velocity in a rectilinear motion with...
  10. K

    Special relativity and relative motion question

    Homework Statement Hello all, I have a couple of questions that I am a little unsure of. Could you please let me know if my answers are correct? But more importantly could you let me know if my reasoning is correct? Thanks in advance! 1. Mort stands on Earth. Velma moves away from him in a...
  11. S

    Maximum rest mass in particle collision

    Homework Statement Suppose that a certain accelerator can give protons a kinetic energy of 200 GeV. The rest mass of a proton is 0.938 Gev/c^2. Calculate the largest possible rest mass M0 of a particle that could be produced by the impact of one of the high-energy protons on a stationary...
  12. A

    Special relativity - time dilation

    Consider two events that take place at the origin of the frame of an inertial observer O' . At times t_1 ' = 0 and t_2 ' = T . O' moves with a constant speed v w.r.t. another inertial observer O . 1. Use the Lorentz-transformations to show that these events occur at x=vt in the frame...
  13. R

    Special Relativity Equation: Is This Accurate?

    While surfing the internet, I came across a statement that this is the equation for special relativity: Line 1: x = a + b Line 2: x = a + b (c2/c2) with c = speed of light Line 3: x = a + (y/c2) if y = b(c2) Is this really the one? If not, is it relevant at all?
  14. C

    Special Relativity as a source of Power?

    Hey guys, I've recently learned that magnetism is an electric field viewed from a different frame of reference and that the mathematics of electrodynamics describes this. However something raised my eyebrow which I wasn't quite clear on. If energy is put into a net flow of electrons, the...
  15. P

    General and special theory of relativity in few words

    How can I explain to someone who has only high school level of education in physics, what is general and special theory of relativity about? Each of them separetelly in one or two sentences please. General theory of relativity … Special theory of relativity ... Thank you.
  16. F

    Special Relativity with 2 light beams moving towards each other

    Homework Statement If one light beam is heading toward you from the right, and another is heading toward you from the left, how quickly from the perspective of the right-moving beam is the left-moving beam approaching it? 1) 0 2) c 3) 1.5c 4) 2c Homework Equations (v+w) / (1 + cw/c2) The...
  17. I

    Special Relativity transformations

    Homework Statement A rod of rest length 1,0m is moving longitudinally on a smooth table with a velocity 0,8c relative to the table. A circular hole of rest diameter 1,0 m lies in its path. The diameter of the hole as seen by the rod is going to be larger?Homework Equations The Attempt at a...
  18. D

    Special Relativity: Velocity Addition

    Homework Statement Two objects fly toward you, one from the east with speed u, and the other from the west with speed v. Is it correct that their relative speed, as measured by you, is v+u? Or should you use the velocity addition formula, V=(u+v)/(1+uv/c2)? Is it possible for their relative...
  19. M

    Independent Study: MIT OCW-Based Relativity/ Special Relativity

    Hi, I am a Junior in high school and if I can, I would like to do Independent Study next year based on either the OCW for http://ocw.mit.edu/courses/physics/8-20-introduction-to-special-relativity-january-iap-2005/ or 8.033 - Relativity. I wanted to know if they most likely would be possible for...
  20. R

    What is the energy of photons in pion decay at rest?

    Apologies, this is going to be a bit disjointed, I don't want to write the full question down as I don't want anyone to give me a solution as its an assignment question. 1. am i correct in assuming when a pion decays at rest its energy will be given by: E^2 = p^2 c^2 + m^2 c^4 which...
  21. D

    Special relativity change in rest mass

    A nucleus of rest mass m initially at rest in the lab absorbs a photon such that its total energy becomes 1.01mc^2. I've calculated the energy of the photon to be greater than the change in rest mass of the nucleus this is on track because the follow up question is why is the required energy...
  22. N

    Incorporation of special relativity into general relativity

    I am writing a paper about SR and GR. I have the following: Special relativity deals with inertial reference frames and flat space. General relativity deals with accelerating reference frames and curved space. Inertial reference frames are only an approximation that applies in a region...
  23. O

    Current through a wire and special relativity

    When I studied special relativity for the first time, I encountered the exemple of a infinite neutral wire in the laboratory frame of reference, R, through which a constant current is running. In this frame of reference, the electrons in the wire are moving with a velocity +v and the ions...
  24. B

    Special relativity, light direction and wave source.

    If the speed at which light waves propagate in vacuum is independent both of the motion of the wave source and of the inertial frame of reference of the observer, why isn't the direction? Shouldn't the light travel directly upward from the point of emission and not diagonally, following the...
  25. D

    What space contracts in Special Relativity?

    Hi. I know that space for an object in motion will contract, relative to an observer. We generally read that space contracts for the object in the direction of motion. But doesn't space around the object also contract? Can someone clarify this? Thanks.
  26. M

    Confusion about special relativity

    So I just started taking Modern Physics and we are currently discussing special relativity. And needless to say, its giving me a headache. Here's my confusion: First, my Professor is Russian, and while his accent isn't so thick that I can't understand him, his grasp of English itself, is such...
  27. bcrowell

    Open-Source Book on Special Relativity - Free Download

    I've written an open-source book on special relativity: http://www.lightandmatter.com/sr/ . It's a work in progress, but at this point it's fairly complete in its coverage of topics, and I would welcome feedback. "Open-source" means that the LaTeX source code is available, and it's under the...
  28. Y

    Special Relativity Time Dilation/Length Contraction Problem

    Homework Statement You are exploring a newly discovered planet when a colleague contracts a deadly alien virus. Left untreated, it will probably kill him in 5 days, but the nearest medical station is 10 light-days away! How can you get him there in time? Homework Equations Δtp=L/v...
  29. D

    Is Special Relativity Testable?

    The basic premise of special relativity is that absolute motion is not detectable. Experimentally, this involves only two general cases, (i) detection via mechanical objects and (ii) detection involving light rays. Case ii readily resolves into two sub-cases, ii-a, detection involving...
  30. L

    Special Relativity Spaceship Question

    Homework Statement bob and anna are in two space ships of proper length 100m; anna's ship passes bob's and is moving in the -x dir at v=0.75c. the front of anna's ship and the tail of bob's ship coincide at x=x'=t=t'=0. bob sits at the window in his ship and sees a clock inside anna's ship a)...
  31. E

    Is My Calculation of Lorentz Transformation Correct for Δx and Δt'?

    Homework Statement Homework Equations The Attempt at a Solution Hey, I would really appreciate some help with this. I have worked out the Lorentz factor to be 5.025. Am I right to assume that Δx = 200000km, and Δt' = 1.2s and I have to work out Δt and Δx'? If these are correct I have...
  32. L

    Special Relativity: Object Motion and Time Dilation

    Homework Statement An object moves at v=0.94c in the frame of a laboratory for 32 us, decaying as it reached the other end. a) how far did it move in the frame of the laboratory? b) how long did the object travel in its rest frame? c) in the rest frame, how long is the laboratory? Homework...
  33. Pezz

    Special Relativity - Events and Frames of Reference

    Hello everyone :). I'm new here and wasn't sure where to post my physics question so here I am in the homework help section as my question is homework related... The problem I'm having is of very basic nature however I might have some trouble wording it. I understand an event is something that...
  34. genxium

    [Special Relativity]Questions on Maxwell Equations' Derivation

    In Einstein's paper section 6 (I'm reading an English version online: https://www.fourmilab.ch/etexts/einstein/specrel/www/), it's said that one of the Maxwell Equations in frame K \frac{1}{c}\frac{\partial X}{\partial t} = \frac{\partial N}{\partial y} - \frac{\partial M}{\partial z}, where <X...
  35. D

    Lorentz contraction and Time dilation (Special relativity)

    A quick question. It's been a long time since I had anything to do with special relativity, so I really can't remember much. But last night I was thinking about the "proof" of special relativity with the case of muons. So basically: Muons are created when particles hit the atmosphere. They...
  36. R

    Special Relativity - Angle Transformations

    Homework Statement A rod of length L_0 moves with a speed v along the horizontal direction. The rod makes an angle of θ_0 with respect to the x'-axis. (a) Show that the length of the rod as measured by a stationary observer is given by L=L_0\sqrt{1-\frac{v^2}{c^2}cos^2θ_0} (b)...
  37. aditya ver.2.0

    Query regarding Special Relativity

    According to SR, there is no measurement that can determine whether an object is stationary or under motion. So if two metallic balls collide with each other, then aren't there motion between the two balls? Only then they will collide.
  38. C

    Special relativity and accelerated frames

    SR directly addresses only inertial frames. Can SR be applied to analyze accelerated frames? For example, consider a point on the rim of a rotating disc. I have see an analysis which makes claims by assigning an associated, instantaneous inertial frame comoving with the point at each...
  39. W

    Length, time and velocity in relativity (special?)

    10. The average lifetime of a pi meson in its own frame of reference is 2.6 x 10^-8 s. If the meson moves with a speed of 0.95c, what is (a) its mean lifetime as measured by an observer on Earth and (b) the average distance it travels before decaying, as measured by an observer on...
  40. I

    Help in Special Theory: Relative Velocity of Spaceships

    Here's a weird question where I don't quite know if length contraction or time dilation play a role. Say I have 2 spaceships moving towards each other. rest length of spaceship A is La and spaceship B is Lb. The pilot in A determines that time taken for the spaceship B to traverse the length...
  41. A

    (Special relativity) Binomial Approximation

    Use the binomial approximation to derive the following: A) γ=1+.5(β^2) B)1/γ=1-.5(β^2) C)1-(1/γ)=.5(^2) I know the approximation is 1+(.5β^2)+(3/8)β^4+... A) is self explanatory but not sure how to derive B) and C)
  42. M

    Special Relativity Book for Jackson Notation - Does it Exist?

    I haven't specifically studied SR yet. My only exposure to it has been in the classical field theory section of Jackson's Electromagnetism and Landau Lifshitz Classical Theory of Fields. I understood what was going on and how it was related to the electromagnetic field etc but I don't feel as if...
  43. P

    Word Problem about Special Relativity

    hi. i am getting really confused about which should be the primed and unprimed values. id just like to check if what i did was right. thank you. :D Problem: A meterstick is glued to the wall with its 100cm end farther to the right in the positive direction. It has a clock at its center and...
  44. W

    Evidence of Special Relativity

    I know that the example of time dilation and length contraction due to Special Relativity is usually given as the mountain top / sea level decays of muons created by cosmic rays but what is the evidence for mass change?
  45. K

    Challenging problem involving special relativity

    Homework Statement The creation and study of new and very massive elementary particles is an important part of contemporary physics. To create a particle of mass M requires an energy Mc2. With enough energy, an exotic particle can be created by allowing a fast-moving proton to collide with a...
  46. J

    How Does Relativity Affect Observations of Approaching Spaceships?

    Two spaceships approach an observer from an equal distance and from an opposite direction with an equal speed in the observer's intertial reference frame O. The speed of a spaceship in the intertial reference frame of the other spaceship S is 0.8c , what is the speed of one of the spaceships in...
  47. P

    A question on the lorentz transforms and special relativity

    Homework Statement Not sure whether to put this in advanced or intro forum, but ill just put it in here. So here's the context of the question: a linear swarm of 3 meteors are traveling at a speed of 0.9c towards our solar system (in the solar system reference frame). Each adjacent meteor is...
  48. T

    Thought experiment of Special relativity

    I have a little bit confuse on the Simultaneity I know if there are 2 coordinates. One coordinate S' is moving V relative to S. We all in inertial reference frame. like the following graph...
  49. C

    Simple special relativity, length from duration

    I'm thinking about a very basic scenario in special relativity, but I've got something backwards, and I could use help understanding why it's wrong. Suppose a rod R is moving past an observer O at speed v. The observer wants to know how long the rod is, so he starts his stopwatch as soon...
  50. E

    Derivation of Velocity from Acceleration in Special Relativity

    I got stuck in deriving the velocity of the particle from the acceleration equation. Here are the details of the problem. The acceleration of a particle with a relativistic momentum is \vec{a} = \frac{\vec{F}}{\gamma m} - \frac{\vec{v}}{\gamma m c^2}\left(\vec{F} \cdot \vec{v}\right)...
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