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. W

    Relativity: Time dilation and distance calculations

    Homework Statement Could someone help point out certain conceptual errors in my interpretation of the mirror clocks time dilation thought experiment? Say S' is the frame of reference traveling at speed V w.r.t to frame S, which means that events happen at the same coordinate in S'. We know...
  2. B

    B Why Special Relativity have overcome Ether Theory?

    My question is very simple. As far as I know, once upon a time there was the Lorentz Ether Theory. This theory admitted existence of so-called Ether as a certain preferred frame, which was undetectable because of physical contraction of moving material bodies in direction of their motion. In...
  3. L

    Other Graduate Research topic involving QFT and General Relativity

    Last year I finished the undergraduate course in Mathematical Physics. This year, more precisely in March, I'm going to start the graduate course to acquire a master's degree in Physics. Now, for this course I must choose a research topic and find an advisor. This is being a little bit...
  4. B

    Thoughts on Newton's Bucket and the relativity of rotation

    Isaac Newton imagined a bucket of water suspended on a fine (ideally torsionless) rope, set spinning. Friction eventually causes the water to rotate along with the bucket. The surface develops a dip in the middle and rises at the edges owing to the water's inertia. (You see this effect every...
  5. W

    Relativity of Simultaneity and lightening

    Homework Statement You are standing at x = 9.0 km and your assistant is standing at x = 3.0 km. Lightning bolt 1 strikes at x = 0 and lighting Bolt #2 strikes at x = 12.0 km. You see the flash from Bolt #2 at t = 10 μs and the flash from Bolt #1 at t = 50 μs. According to your assistant, were...
  6. R

    Special Relativity: Rotated Michelson Interferometer

    Homework Statement The aether-wind theory of the Michelson-Morley experiment was discussed in class for the special case where the arms of the interferometer (each of equal length L) are parallel and perpendicular to the wind. In this problem we consider the general case for an angular setting...
  7. O

    Special relativity simultaneity

    Homework Statement [/B] Homework Equations The rear clock ahead example gives vL/c^2: The Attempt at a Solution I think the solution is the same, because even if there is a time dilation due to u (downward velocity) both clocks would slow down at the same rate and so the time difference...
  8. Conservation

    I Relativity of Simultaneity and frames

    Hello everyone, sorry if this is a noob question; I'm just starting out with special relativity. I was wondering whether relativity of simultaneity is a direct consequence of our ability to "know" being dependent on sight (light reaching a point). If, for example, we could only judge an event...
  9. binbagsss

    General Relativity asymmetry identity

    Homework Statement I have ##R^{u}_{o b u } F^{o}_a - R^{u}_{oau}F^{o}_{b}## and I want to show that this equal to ##2R_{o[aF^{o}_b]}## where ## [ ] ## denotes antisymmetrization , and ##F_{uv} ## is a anitymstric tensor Homework Equations Since ##F_{uv} ##is antisymetric the...
  10. Crowxe

    I Relativity's "time dilation" or clock accuracy alteration

    i've seen the double slit experiment and the delayed choice . my mind rejected the conclusion, but the experiment setting and configuration of delayed choice is rational and holds water so i accepted the experiment outcome even if it means the world isn't real. i had to give that intro that...
  11. W

    I Explaining Different Types of Time in Relativity

    What different types of time are there is relativity. I have heard phrases like "proper time" "co-oridnate time" and "conformal time". but what would be great to get a layman friendly definition. Thanks.
  12. P

    General Relativity and the Circumference of a Circle

    Homework Statement Calculate the circumference of the circle θ = θ0 (a constant) in the spatial geometry \begin{eqnarray*} dS^2 = a^2(d\theta^2 + sin^2\theta cos^2\theta d\phi^2) \end{eqnarray*} Hence, (by finding R(z)) sketch the cross section of the surface embedded in three dimensions via...
  13. phosgene

    Time taken for two relativistic particles to meet

    Homework Statement A particle P undergoes the hyperbolic motion x_{P}(t) = \frac{c}{a}(c^2 + a^2 t^2)^\frac{1}{2} along the x-axis of frame S, where c is the speed of light and a is a constant. A second particle, Q, undergoes the motion x_{Q}(t) = \frac{1}{2}ct + \frac{c^2}{a} and so...
  14. S

    On the relativity of time and speed

    Speed can only be measured relative to some other object, like the speed of a tennis ball during a match at Wimbledon can only be measured relative to the ground, or a cloud, or the planet Mars. On the other hand, time is relative. An object traveling at speeds approaching the speed of light in...
  15. J

    Relativity Books about Special Relativity for preparation for QFT

    Hello, I want to learn QFT but I feel that my understanding of Special Relativity is not good enough. Could you please recommend to me any good relativity books to fill my gaps? My gaps are mostly conceptual. Thanks in advance!
  16. J

    Quantum Theoretical Physics course textbooks

    Hello, I will be attending an undergraduate course called "Theoretical Physics" and I want to borrow some books from the library that cover the material of this course. I would appreciate any suggestions. The syllabus of the course is the following(I will be translating so I am sorry If...
  17. rharrex

    B Boundary between Quantum and Relativity

    At what point does quantum physics cease and general relativity take over. Where is the boundary? Is it a quantum of mass?
  18. O

    I Relativity of simultaneity -- an example in D.Morin's book

    Ok, so here's an example from David Morin's book that I seriously don't understand: Two clocks are positioned at the ends of a train of length L (as measured in its own frame). They are synchronized in the train frame. The train travels past you at speed v. It turns out that if you observe the...
  19. E

    I Collision in special relativity

    Let us assume that we have inelastic collision of masses ##m_1=1## and ##m_2=k## This means ##m_2=k m_1##. (##k>>1##) ##v_1=v##, ##v_2=0##, Velocity after collision is ##v'##. Units are such that ##c=1##. Let us assume that ##v_1## is close to one. At inelastic collision we respect conservation...
  20. G

    B Special relativity and sequence of events

    Sorry for my ignorance... still trying to get to grips... If a lady in the middle of a moving train sends out beams to the front and back of the train. They reflect off mirrors back to her and arrive simultaneously because she can't do an experiment to give away that she is moving forward...
  21. H

    I Mass in Special Relativity: Misconception or Reality?

    Hi PhysicsForum, I'm currently reading Spacetime Physics by Taylor and Wheeler and I can't wrap my head around the concept of mass in SR. In the textbook, mass is described as the magnitude of the momenergy 4-vector and is invariant no matter which inertial reference frame you choose. So does...
  22. G

    I A good reference sheet/manual about Einstein index notation?

    I'm not used to Einstein notation and I'm struggling a bit with the more complex examples of it. I got the general gist of it and can follow the basic cases but get sometimes a bit lost when there are a lot of indexes and calculus is involved. All primers I've found online for now only give the...
  23. redtree

    I Special relativity and inertial frames

    What in the mathematics of the derivation of special relativity limits the model to inertial frames? How is an inertial frame defined in the context of the derivation?
  24. Z

    I Is mass conserved in relativistic collision?

    For a particle , E2 = (pc)2 + (moc2)2 and for a system of particle , (ΣE)2 = (Σpc)2 + (Σmoc2)2 so in that way before a collision, (ΣEi)2 = (Σpic)2 + (Σmoic2)2 and after , (ΣEf)2 = (Σpfc)2 + (Σmofc2)2 and as far as i know energy and momentum is conserved . so that means ΣEi=ΣEf and also Σpi=Σpf...
  25. K

    I Coordinate vs. Non-Coordinate Basis in General Relativity

    Is it correct, at least in the context of general relativity, to say that in a coordinate basis, the inner product between space-like basis vectors will be 1, and in a non-coordinate basis the inner product will be defined by the corresponding component of the metric? Can I take this conditions...
  26. Const@ntine

    Relativity in X & Y Axis'-a, V, r

    Homework Statement Liza is driving her Lamborghini with an acceleration of a=(3.00i - 2.00j) m/s^2, while Jill is driving her Jaguar with an acceleration of (1.00i + 3.00j) m/s^2. Both begin from a state of rest, beginning at the start of the XY axis'. After 5.00s: a) What's the magnitude of...
  27. GW150914

    I What would the world be like if c→∞ and h=0?

    What would the world be like if the speed of light is infinity and the Planck constant is zero (therefore the world is totally Newtonian)?
  28. V

    A Relativity in Complex Analysis: Is There a Formulation?

    Is there a formulation of any of the relativity theories in terms of complex analysis? As in - I imagine - every event would be a complex number in a complex field.. or something as such..
  29. C

    B General relativity vs. Newtonian gravity

    I understand that General Relativity can make a difference between a spinning and non spinning mass thus can make better prediction for planetary orbits for example. The effect is frame dragging. However if we simulate a Newtonian gravitation and instead of representing a planet as a sphere...
  30. K

    A Mastering General Relativity: Student Experiences

    In my Google searchs and by reading threads on this forum I've seen that the books people most recommend on general relativity are Graviation, by Thorne, Wheeler and Misner, Wald's book and Weinberg's book. I'm in the first year to get a bachelor degree on physics and I could read any of these...
  31. A

    I General Relativity: Is There No Universal Frame or No Way to Tell?

    I've heard that unlike Special Relativity, General Relativity claims that you can' say any reference frame is better than another frame, including frames in which Newton's Laws don't hold. I've seen debates about this specifically in the context of geo/helio-centrism. From what I understand...
  32. 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...
  33. K

    Relativity Book on General Relativity -- especially on Black Holes and Graviational Waves

    Hi. (I'm sorry for my poor English.) I'm looking for a good book on General Relativity, specially on Black Holes and Graviational Waves. I got Schultz book once ago, but it has a fuzzy notation and does not deal with the math as I suppose to. I know the basics of Differential Geometry, Topology...
  34. G

    Different formulations of the covariant EM Lagrangian

    Homework Statement I'm reading through A. Zee's "Quantum Field Theory in a nutshell" for personal learning and am a bit confused about a passage he goes through when discussing field theory for the electromagnetic field. I am well versed in non relativistic quantum mechanics but have no...
  35. Farhad70

    Other Choosing fundamental journals or conferences

    I have done a fundamental research about relativity but i can't find right journal or conference. can anyone help me?
  36. Jeff B L

    B Special case of the twin paradox in special relativity

    There is something about the twin paradox in special relativity that has always bothered me. One twin sets out on a journey at a large fraction of the speed of light, turns around and returns. The fact that the returning twin is the one who is younger is explained by the fact that they are the...
  37. Anypodetos

    I Understanding Electromagnetism & General Relativity

    I'm trying to understand how the various EM tensors work in General Relativity. The only source I've found is https://en.wikipedia.org/wiki/Maxwell%27s_equations_in_curved_spacetime, but there are two things I don't get. Why do they use ordinary partial derivatives instead of covariant ones...
  38. T

    A Why General Relativity is non-renormalizable quantum theory?

    Hello I have not understand this.
  39. M

    B Learn Relativity Theory: Math Education Needed?

    What knowledge based are needed in relativity theory, not general public science education level, but true and mathematically. I have calculus and linear algebra education in university, Chinese engineering degree, quite rigorous in math education. Can I actually pick up relativity theory myself...
  40. K

    Special Relativity: Find speed of 3rd object.

    Homework Statement Rest length of Ship B is twice that of Ship A. Ship A travels at 0.5c relative to a "fixed" observer. Ship B travels at such a speed that the same "fixed" observer measures Length B = Length A. How fast is Ship B traveling? 2. Homework Equations [/B] All given in statement...
  41. J

    Relativity: Is "c" Speed in Vacuum Only?

    Hi all. New to PFs. I deal in (exotic) human biology, which happens to have put me at the intersection of fields and, in this instance, conceptually more challenging physics. I'm presently involved in a comparative analysis of biological versus physical time contraction-dilation. I happen to...
  42. nomadreid

    I "relativistic mass" still a no-no?

    The Wiki article https://en.wikipedia.org/wiki/Mass_in_special_relativity seems to advise "don't use the expression 'relativistic mass'; stick to 'relativistic momentum' pγ". So what does one do if Alice were to measure Bob's mass while Bob is traveling at velocity v with respect to Alice, and...
  43. hsdrop

    B Measurements within our solar system with relativity in mind

    ok I know that anybody in the heavens will bend spacetime with the gravity it has. What I was wondering was how do we measure around them like from the Earth to mars. When Mars in now quit on the opposite side of the sun ( so we can see it at sunset). do we measure the parabolic curve in...
  44. MarSuper

    B Why is there a limit to the speed of light in special relativity?

    I have a question about Special Relativity. If a person is in a rocket ship traveling at 99.999999 percent the speed of light and they are standing at the back of the ship. Will they be able to walk to the front of the ship or will inertial resistance prevent them from doing so?
  45. TheSodesa

    A relativistic electron in a potential box

    Homework Statement In a potential box (##L = 1.00pm##) an electron moves at a relativistic speed, meaning it's momentum can't be expressed as ##P = \sqrt{2mE}##. a) Using the uncertainty principle, show that the speed is indeed relativistic b) Derive an expression for the allowed energy states...
  46. lonewolf219

    Help with tensor formulation of special relativity

    Homework Statement Hi, I can't seem to understand the following formula in my professor's lecture notes: F_αβ = g_αγ*g_βδ*F^(γδ) Homework Equations Where g_αβ is the diagonal matrix in 4 dimensions with g_00 = 1 and g_11 = g_22 = g_33 = -1 and F^(γδ) is the electromagnetic tensor with c=1...
  47. Erenjaeger

    Understanding the Relativity Equation to Solving Homework Problems

    Homework Statement not sure fully sure on this equation Homework Equations f=fo√(1±v/c)/(1±v/c)[/B]The Attempt at a Solution is it just the relationship between the observed frequency and the proper frequency or something? [/B]
  48. T

    Special relativity momentum and energy conservation

    Homework Statement Two identical particles of mass m travel towards each other at speed v; they combine and form a single new particle. By employing conservation of momentum and conservation of energy, what is the mass of this new particle in Homework Equations Relativistic momentum and total...
  49. S

    Books and Plan to Study Relativity (SR and GR) in Detail

    Hi, I am a Physics graduate and I am VERY mathematically inclined. (This does NOT mean I know a lot of math. My curriculum focused on experimental physics - which left me with a very keen desire to study all the mathematics involved - so I do need to start from scratch.) I would like to study...
  50. Toby_phys

    Paradox found in my first relativity sheet

    We have got some SR work to do, however we have only had 1 introductory lecture. I have a problem with one of the problems. Question: A rod of 1m parrallel to the x-axis, travels at un-relativistic speeds at 45 degrees. It passes through a slit - also parallel to the x-axis - that is 1.1 meters...
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