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.

View More On Wikipedia.org
Recent contents Top users
  1. S

    Relativity Introduction to general relativity

    Hello! What book should I use as an introduction to General Relativity? Something that includes an introduction of the math behind GR (tensors for example) would be much appreciated. Thank you!
  2. A

    B Question concerning mass effect

    We know that the OBSERVED mass increases as the objects approach near to the speed of light. I was wondering that how does a stationary observer observe an increase in mass of an object which is traveling far away from it. I mean mass is a sensation, how it is observed by a stationary observer?
  3. victorhugo

    I Why don't general relativity and quantum physics agree?

    I always hear that the two 'don't match' and disagree, but never in what... Someone mind explaining?
  4. T

    Special Relativity spaceship problem

    Homework Statement You are on Earth as a spaceship flies past at a speed of 0.99c relative to the earth. A high-intensity signal light on the ship blinks on and off, each pulse lasting 2.2 × 10^(−6) s, as measured on the spacecraft . Your laboratory on Earth has a length of 56.4m. How long...
  5. Matternot

    I Special relativity timebomb on distant planet 'paradox'?

    I thought of this 'paradox' which is somewhat similar to the twin paradox but can't be explained by a lack of symmetry etc. It is very similar to many paradoxes I have heard before of which the resolution is known (which is why I am mostly sure this can be resolved) Bob is looking through his...
  6. S

    Recommended Books for Studying Relativistic Electrodynamics

    Hey guys, Can you please refer some good books to refer to in studying relativistic Electrodynamics (introductory parts), covering the Maxwell's equations in tensor form the L-W potentials and other aspects. FYI am just a beginner in relativistic Electrodynamics. Thanks for the help.
  7. KetilT

    I What is the Simpler Name for Conserved Property of Spacetime?

    If we have come to realize that energy conservation is not the most general conservation law in our spacetime, isn't it odd that we don't have a simple name for the "real deal"? I bumped into this thought through Noether's theorem, which relates symmetries in fields to conservation of all kinds...
  8. J

    Special Relativity Forces and Energy

    Homework Statement Hi, I have this problem: For motion under a pure (rest mass preserving) inverse square law force f = −αr/r3 , where α is a constant, derive the energy equation γmc2 − α/r = constant. Homework Equations E = γmc2 dE/dt = f.u for a pure force The Attempt at a Solution I...
  9. F

    I Formation of Bound Systems, Stars & Galaxies in General Relativity

    In particular how does matter "clump" together to form stars and planets, and how do Galaxy/star systems form? For the latter question is the answer simply that near massive enough bodies, the spacetime curvature is significant enough that the geodesics within its vicinity are closed curves...
  10. K

    Acceleration in a new Coordinate System - General Relativity

    Homework Statement Below: Jac = Jacobian matrix; ξ = d/dφ for some continuous parameter φ which labels different points on the worldline. (I'm sorry for my poor English.) Consider a new coordinate system xµ' which differs from the original Cartesian coordinate system xµ; the Cartesian...
  11. A

    I Superluminal Messaging and Causality Paradox: Myth or Reality?

    If I could route a signal from here-and-now to an event in my past light cone, then clearly I could make an irresolvable causal paradox by having the arriving signal disable the button that sends it, so I'll choose to believe that I can't send messages back in time TO HERE. Now I've heard it...
  12. P

    A Did Einstein Disbelieve in General Relativity Geometry?

    I have read this paper http://www.sciencedirect.com/science/article/pii/S1355219813000695 that the author try to said that einstein not believe that gravity is not cause the space time curvature. I want to know that this is true or not. Because when I have read about general relativity I always...
  13. haushofer

    Insights General Relativity as a Gauge Theory - Comments

    haushofer submitted a new PF Insights post General Relativity as a Gauge Theory Continue reading the Original PF Insights Post.
  14. oa8

    How Fast Must You Travel to See Light Pulses Simultaneously?

    Homework Statement In a certain inertial frame two light pulses are emitted a distance 5 km apart and separated by 5 µs. As observed from another frame, which is traveling parallel to the line joining the points where the pulses are emitted at a velocity v with respect to this frame, the pulses...
  15. K

    (SP. RELATIVITY) Annihiliation of Electrons into Photons

    Homework Statement [/B] An electron e- and positron e+ annihilate to produce two photons. a_ Why are two photons produced rather than one? b_ Assume that the e- and e+ are at rest just before they annihilate. In their rest frame, what are the energies and momenta of the photons? Define the +x...
  16. K

    (Sp. Relativity) Krel / Kcl in powers of (v/c)^2

    Homework Statement [/B] By expanding Krel / Kcl in powers of (v/c)^2, estimate the value of v/c for which Krel differs from Kcl by 10%. Homework Equations Kcl = classical Kinetic Energy = 1/2 m0 v^2 Krel = relative Kinetic Energy = (y-1) (m0 c)^2 The Attempt at a Solution I did a binomial...
  17. G

    B The rubber sheet analogy in Relativity

    Can anyone here settle(or contribute to ) a question that is ongoing at another forum? Who came up with the idea of the rubber sheet analogy in Relativity? Some there have wondered if it was the "rubber sheet geometry" as topology was described as ,apparently that may have ,perhaps...
  18. B

    Studying How to Learn both Differential Geometry and Relativity?

    Dear Physics Forum personnel, Is it possible to learn differential geometry simultaneously while learning the relativity and gravitation? I have been reading Weinberg's book (currently in Chapter 02), but I believe that modern research in relativity is heavily based on the differential...
  19. T

    I How does parallel transportation relates to Rieman Manifold?

    Source: Basically the video talk about how moving from A to A'(which is basically A) in an anticlockwise manner will give a vector that is different from when the vector is originally in A in curved space. $$[(v_C-v_D)-(v_B-v_A)]$$ will equal zero in flat space...
  20. E

    Fermilab relativity energy problem

    Homework Statement This is why we build them as colliders now: Some years ago Fermilab used to extract its high energy proton beam for use by "fixed target" experiments situated at the ends of external beamlines a mile north of the Tevatron ring. The energy available for the production of...
  21. E

    Relativity-Energy Homework: GZK Effect

    Homework Statement <Most of this is irrelevant, the relevant parts are in italics> The Greisen-Zatsepin-Kuzmin (GZK) upper limit on cosmic ray energies The contemporary universe is filled with low energy photons left over from the time when the early universe cooled sufficiently for the...
  22. K

    I Does Special Relativity Apply to a Moving Clock?

    A Moving Clock runs slow. But, If time t has elapsed in the S frame, does SR apply to a clock moving with speed u in the x-direction in the S frame, relative to the S frame? Or does SR apply only when the clock is in another reference frame S' moving in the x'-prime direction, given that...
  23. A

    I Why isn't spacetime considered as true 4D?

    ...and what is the difference between true 4D and the minkowski space? To me, it would be much easier to see universe as a 4D and us humans just experiencing the dimension of time differently. In my mind i pictured the universe as a complete 4D structure which we humans experience in one...
  24. K

    Relativity A First Course in General Relativity

    For those who have read Schutz' book A First Course in General Relativity. Can this book be considered as a deep approach on the subject? Edit --- Do you think I will become a "expert" in general relativity just by reading books like this one I mentioned above? What time it take for learning...
  25. J

    I Time dilation (something seemingly paradoxical)

    Hello. Consider the following case: Two observers, A and B, moving relative to each other with velocity v. For B, it's A that moves (with v) and so DTb=g*DTa (where DT denotes finite time difference and g is/the Lorentz factor gamma). So, (following the same logic as in Morin's Classical...
  26. E

    I Vacuum solutions in general relativity

    If we look Einstein equation ##G_{\mu\nu}=0##, which nontrivial aspects it can gives? One phenomenon is gravitational wave. I suppose that we are also free at initial conditions for this equation, thus we can begin with curved space time? What else?
  27. E

    How can I submit for comments to STR and GTR experts my work

    I have a third circle degree in Physics and I used to be in Theoretical Physics research. Since long, I work in a different field. Therefore, I have no contacts with the international scientific community. I prepared a paper with title “A Heraclitean approach to the Relativity Theories” and...
  28. adamaero

    Light hours special relativity time dilation

    Homework Statement http://phy240.ahepl.org/Chp1-Relativity-Serway.pdf#page=39 #32 Planet R is 25 lighthours away from Earth. It takes 25 h (according to an Earth observer) for a spacecraft to reach this planet. The clocks are synchronized at the beginning. What is the spacecraft 's time...
  29. adamaero

    Special relativity ~ show that....given this

    Homework Statement A rod of length L0 moves with a speed v along the horizontal direction. The rod makes an angle of θ0 with respect to the x'-axis. (a) Show that the length of the rod as measured by a stationary observer is given by L = L0*√[1-(v2/c2)cos2θ0] (b) Show that the angle that the...
  30. A

    B General Relativity and Newtonian Mechanics

    Hello, I wanted to know how Einstein's General Relativity and its equations simplify to Newton's Universal Law. Einstein's equation is obviously a much more generalized version of Newton's law and gives much more accurate predictions that Newton's laws even if we don't think of Newton's gravity...
  31. A

    How do we measure that two objects can have different time?

    How is this done in practice? I know that in GR the gravity is believed to curve not only space, but also time, and this prediction has been confirmed somehow in practice. How can we measure that? Because as far as i know, there is no device that actually measures time, but instead measures a...
  32. Elvis 123456789

    Determining beta as a function of relativistic momentum

    Homework Statement For a fast moving particle, its momentum and energy are frequently easier to measure than its velocity. a) Show that the factor of beta (as defined by β=v/c), can also be determined by measuring the ratio of relativistic momentum (p) and total energy (E). b) Sketch...
  33. P

    Special Relativity simultaniety

    Homework Statement Two events occur in an inertial system K as follows. Event 1: x1 = a, t1 = 2a/c, y1 = 0, z1 = 0 Event 2: x2 = 2.6a, t2 = 1.9a/c, y2 = 0, z2 = 0 What is the velocity of the frame K' in which these events appear to occur at the same time? Express the velocity vector using...
  34. RJLiberator

    Special Relativity Question (Lorentz)

    Homework Statement Synchronized clocks A and B are at rest in our frame of reference a distance 2 light minutes apart. Clock C passes A at a speed of c*4/5 bound for B, when both A and C read t =0 in our frame. a) What time does C read when it reaches B? b) How far apart are A and B in C's...
  35. E

    Field transformation laws - Relativity

    Homework Statement The electric and magnetic fields of a 1 Coulomb charge Q are measured by a pair of field measuring instruments. From the perspective of observers in frame O, the charge is at rest at the origin and one of the field-measuring devices is also at rest, with position (x,y,z) =...
  36. E

    Relativity -- Momentum and energy

    Homework Statement (a) A proton at rest has energy Eproton = mprotonc2 ≈ 938 MeV. (Its momentum is zero). The protons which circulated inside the Fermilab Bevatron had energies close to 1000 GeV (1GeV = 1000 MeV). What value of γ did a Tevatron proton have? (b) Somehow a Bevatron proton...
  37. tomdodd4598

    I Special Relativity Approximation of Gravitation

    Hey there, I have two questions - the first is about an approximation of a central gravitational force on a particle (of small mass) based on special relativity, and the second is about the legitimacy of a Lagrangian I'm using to calculate the motion of a particle in the Schwarzschild metric...
  38. RJLiberator

    Relativity Questions and Frames (How fast....)

    Homework Statement The International Space Agency is designing a spaceship to reach the star Proxima Centauri, 4 cyrs (light years) away so that the on-board crew will age 4 years from departure to arrival. How fast must the ship travel? Homework Equations t(moving clock) = t(stationary...
  39. CactusLand

    B Free Will & Relativity: A Thought Experiment

    I watched a documentary by Brian Greene, "The Illusion of Time" a few weeks ago, and a question has been bothering me ever since. In the documentary he explains that an alien, traveling toward the earth, would see into our future. So here is my question. The second half of a college football...
  40. RJLiberator

    General Relativity Problem (frames of reference)

    Homework Statement A clock moving at v = (3/5)c reads 12:00 as it passes us in our frame of reference, how far away will it be (in light hours) when it reads 1:00. Homework Equations I denote a prime to mean the reference frame of the clock at rest. I use regular lettering to denote 'our'...
  41. Bristlethorn

    I Exploring the Hierarchy of Time: Δt, Δs, and Δτ

    Hi, all. My textbook presents an hierarchy of the three types of time, but doesn't back it up or explain where it came from. According to it, Δt ≥ Δs ≥ Δτ Where - Δt is the coordinate time between two events as observed in an inertial frame, - Δs is the spacetime interval between two...
  42. john baez

    Insights Struggles with the Continuum - Conclusion - Comments

    john baez submitted a new PF Insights post Struggles with the Continuum - Conclusion Continue reading the Original PF Insights Post.
  43. john baez

    Insights Struggles with the Continuum - Part 7 - Comments

    john baez submitted a new PF Insights post Struggles with the Continuum - Part 7 Continue reading the Original PF Insights Post.
  44. Elvis 123456789

    Another relativistic particle decay question

    Homework Statement Unstable particles cannot live very long. Their mean life time t is defined by N(t) = N0e−t/τ , i.e., after a time of t, the number of particles left is N0/e. (For muons, τ=2.2µs.) Due to time dilation and length contraction, unstable particles can still travel far if their...
  45. J

    B Relativity & Physics Concepts: A Book Explained Simply

    Hi Everyone! I used to have a book that explained physics concepts quite simply. I used to read it when I was about 8 or 9 years old and one chapter really stuck with me (I'm 25 now). I'm not sure where the book went, and have been looking for it for some time and think this might be the best...
  46. T

    Special Relativity: time for light to traverse a rocket

    Homework Statement A 35 m long rocket is receding at 0.6c. From the point of view of a stationary observer, how long does it take for light to travel (a) from the bottom of the rocket to the top and (b) from the top to the bottom? Homework Equations t = d/v L = L0 / gamma The Attempt at a...
  47. T

    Special Relativity -- elapsed time while traveling at 0.95c

    Homework Statement A particle moving at 0.95c travels 10 m, as measured by a stationary observer, and then disappears. How long did the particle live (a) from the point of view of the observer and (b) from the point of view of the particle? Homework Equations t = d/v d = d0/gamma The Attempt...
  48. Destroxia

    Special Relativity: Super-Novae light on earth

    Homework Statement A nova is the sudden, brief brightening of a star. Suppose Earth astronomers see two novas occur simultaneously, one in the constellation Lyra. Both nova are the same distance from Earth, ## 2.5 \times 10^3 [cy]##, and are in exactly opposite direction from Earth. Observers...
  49. e2m2a

    I General Relativity vs Newtonian Weak Field: G Force?

    When does GR apply in gravitational fields as opposed to Newtonian gravitation? Another words, what would be the strength of the graviatational field before we abandon Newtonian gravity and start implementing GR? 10 g's, 20 g's?
  50. Elvis 123456789

    Spaceship voyage at close to light speeds

    Homework Statement The last of the human race are leaving the earth, after a total nuclear destruction, to reach the only known planet suitable for lives, 2 million light years away from earth. They are traveling on the spaceship ARK, capable of close to speed of light. There is only enough...
Back
Top