What is Equivalence principle: Definition and 155 Discussions

In the theory of general relativity, the equivalence principle is the equivalence of gravitational and inertial mass, and Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.

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  1. K

    Question about equivalence principle

    Let me restate my problem in a more clear way i think. Situation A: a accelerated rocket in flat spacetime. the observer in the rocket could think he is in a gravitation field equivalently.All experiments he do are like in a gravitation field downward. SituationB: a apple falls down under...
  2. S

    Can Equivalence Principle Be Violated?

    Read about this experiment and the results obtained: http://www.physorg.com/news/2011-07-gyroscope-unexplained-due-inertia.html What's going on here? Why is the laser gyro accelerating? If this effect proves to be reproducible, would it not indicate the violability of the so-called...
  3. J

    Equivalence Principle precision

    I found 2 tables describing raising precision in experiments performed to investigate Equivalence Principle: http://en.wikipedia.org/wiki/Equivalence_principle#Tests_of_the_weak_equivalence_principle http://en.wikipedia.org/wiki/Hughes%E2%80%93Drever_experiment#Modern_experiments I can't...
  4. I

    Do tidal forces mean the Equivalence Principle is BS?

    From another thread this question came up: What about tidal forces? Although they could be incredibly small (and I don't think anyone denies they exist) you could conceive of a test in a closed room that detects tidal forces (if it is gravity) and when it doesn't detect them it is uniform...
  5. G

    Charge and the Equivalence Principle

    A charged particle is held at rest inside a box in gravity-free space. The box is accelerated uniformly. The charge theoretically radiates electromagnetic power. Now picture the same box held at rest in a gravitational field. Does the charge radiate?
  6. J

    Equivalence Principle: Are there any restrictions

    Hello all. I've been thinking a lot about the Equivalence Principle as it has been taught to me: "The effects of the acceleration (vector) a of a referential are indistinguishable of those of a gravitational field (vector) g=-a". The same book has the phrase: "There is no experience that...
  7. R

    Help with equivalence principle please.

    I am just trying to understanding of the equivalence principle and was hoping someone would be kind enough to sense check my thoughts below. 1) If I was in a rocket ship accelerating at a rate of 1g relative to the earth, the clock on my ship would tick at the same rate as a clock on the...
  8. TrickyDicky

    Weak equivalence principle and GR

    In another thread, it's considered a generally accepted fact that the WEP is not valid anymore the way it was initially postulated: I find this surprising, because such a change in the principles of the theory should be more stressed in introductory GR textbooks, and kind of disturbing...
  9. Matterwave

    Equivalence Principle: Questioning Inertia & Gravity

    Hey, so I have a question. The equivalence principle, the way it has always been taught to me, states that the "gravitational mass" is equal to the "inertial mass". Or, in other words, that the amount of inertia an object has really in some way "equal" (or proportional) to the amount of...
  10. C

    Equivalence Principle Explained - What is it?

    The Equivalence principle says or at least this is what i learned , Is that being in free-fall is the same as being out in space , But in free fall if you shined a laser up it would get Doppler shifted and gravitationally red shifted but out in space it would not . Or do i have something wrong.
  11. U

    Consequences of the Equivalence Principle

    I was reading a book on SR and GR and it used the example of a falling elevator with a light beam traveling through it. Considering this setup leads to the conclusion that light bends in a gravitational field. My question is, would light bend as a result of any kind of acceleration given the...
  12. Buckethead

    Equivalence Principle question

    According to Einstein's Equvalence Principle inertial mass and gravitational mass are interchangable. If we lived in a universe where these two masses were not equal, how would this translate into everyday experience? For example, if gravitational mass were twice the value of inertial mass...
  13. H

    Testing the Equivalence Principle with Spectral Anisotropies

    It suddenly occurred to me that I've never heard of a test of the Equivalence Principle itself - such as something like ... An accelerating laboratory [in space] can see very obvious effects in external astronomical observations. Depending on the rate of acceleration, there would be...
  14. H

    Deriving the Schwarzschild metric just by using the equivalence principle

    I've read a few papers about derivation of the Schwarzschild metric by using the equivalence principle ( http://cdsweb.cern.ch/record/1000100/files/0611104.pdf" )... but I couldn't understand them completely they assume , According to Einstein’s equivalence principle, that the influence of...
  15. I

    Why is the Equivalence Principle True?

    The equivalence principle states that an accelerating observer who has no external information (view of fixed stars, etc) can in principle not perform an experiment to determine whether he is either undergoing linear acceleration or at rest in a gravitational field. This leads to the equivalence...
  16. C

    Is the equivalence principle good for anything?

    I heard that there is now consensus in literature that a charged particle will take a DIFFERENT path around a neutral object than an uncharged particle. The reason is that the charged particle will radiate. I have even heard physicists try to wave this away as "well a charged particle needs...
  17. E

    Quantum physics and equivalence principle

    I read some articles, where equivalence principle is no more valid in quantum area. One example are neutrinos, changing colours (electron, muon, tauon neutrino). But formulae are not derived from fundaments, so I do not understand, where it is the catch. I read also about COW experiment...
  18. G

    Equivalence Principle: Mass Increase With Time?

    An uncharged, isolated particle of mass m is subjected to a constant force that increases its speed relative to an IRF. Its mass presumably increases as long as the force acts. Does the mass of an identical particle, held at rest in a gravitational field also increase with the passage of time...
  19. G

    Equivalence principle to other forces?

    Why is it that to derive general relativity you use the equivalence principle on gravity and not electromagnetism for example?
  20. TurtleMeister

    Question about equivalence principle

    First, I would like to say that this is my first post in this forum and that my knowledge of GR is weak. So I am hoping that my question can be answered in layman terms. If I hold a 1kg object in my hand, I can easily feel it's inertia if I move it from side to side. I could also measure it's...
  21. V

    What is the difference between the equivalence principle and Newton's third law?

    The equivalence principle is a straightforward application of Newton's third law, isn't it? There's nothing new in it
  22. D

    Weak Equivalence Principle (WEP)

    As most of you probably know, the WEP states that the intertial mass and gravitational mass of any object are equal. This principle has base in Galileo's observations, that all free-falling objects have a constant acceleration. What I would like to get clear is the order of arguments that leads...
  23. S

    Confused about Equivalence Principle

    Suppose I set up two labs, Alice on Earth and Bob in a region of intergalactic space (or maybe in a void) where the Riemann tensor is zero. I accelerate Bob's lab at 32.2 ft/sec/sec. Both measure the Riemann tensor using identical equipment. Alice will get a nonzero value for some components...
  24. JK423

    An idea on explaining the weak equivalence principle

    An idea crossed my mind on how to explain the weak equivalence principle(WEP) without using the gravitational law: F=G m1m2/r2 Part of what WEP sais is that assuming we are in a uniform gravitational field, if we let two objects of different masses, they will fall with exactly the same speed...
  25. N

    Equivalence Principle & Gravitational Time Dilation

    I'm reading in a textbook (Gravity by J. Hartle) that gravitational time dilation is implied by the equivalence principle. The following thought experiment is described. A vertical rocket at rest in a uniform gravitational field (no tidal effects) is compared to a rocket constantly...
  26. L

    Strong Equivalence Principle Question

    My notes say that a photon traveling from a high altitude to an observer at low altitude appears to have a higher frequency i.e. gravitational blue shift. now I am having trouble getting this: the strong equivalence principle says we can substitute this "laboratory" with a laboratory that...
  27. L

    Electrodynamic checks of the equivalence principle

    Hello, I would like to know if there are experimental tests of the Equivalence Principle in the realm of electrodynamics. The book by http://books.google.com/books?id=BhnUITA7sDIC&pg=PP1&dq=Theory+and+Experiment+in+Gravitational+Physics&lr=#PPP1,M1" contains a lot of material about the...
  28. L

    Equivalence principle and gravitational neutron diffraction

    In Modern Quantum Mechanics, Sakurai say that at quantum level the gravity is no more geometrical because the schrodinger equation depend on the fraction \frac{m}{\hbar}. Can someone explain better this claim or link me some detailed paper on this argument?
  29. C

    Equivalence Principle Question

    I was wondering whether or not astronauts who weighed differently on Earth would weigh differently on a spaceship accelerating to simulate gravity. Do the astronauts who have more mass experience a greater force in the ship like the would on Earth or does each astronaut weigh the same on the ship?
  30. P

    Equivalence Principle & Tidal Effects

    It is my understanding that the Equivalence Principle postulates that if I were standing in a closed room, I would not be able to distinguish whether the downward force that I felt was caused by (1) the presence of a massive body such as the Earth exerting a downward gravitational force or (2)...
  31. L

    Explaining the Blue Shift in Terms of the Strong Equivalence Principle

    Ok so I was answering a question about a spacecraft accelerating through deep space with observer A in the front and observer B in the rear. I was asked to explain why a phton sent from A to B would appear blue shifted to B - simple enough I just plugged in a positive velocity to the...
  32. J

    Is the Equivalence Principle Contradictory in General Relativity?

    Hello, I can answer some basic questions about GR, but I don't teach it, and I am not proficient in it. Yesterday a student asked a question that I felt I couldn't do justice to. Can you help? I had the student email the question so I could ask around. So far I haven't gotten any useful...
  33. atyy

    Equivalence principle & accelerated charge

    This thread discusses an interesting point Jonathan Scott brought up at https://www.physicsforums.com/showthread.php?t=264782&page=2. A naive application of the equivalence principle (EP) would suggest that a free falling charge does not radiate, and that a charge on the surface of the Earth...
  34. S

    Equivalence principle and Acceleration

    From equivalence principle, being on Earth is equivalent to being on lift accelerating at 9.8 m/s2...so if we are in a lift and that accelerates at 9.8 m/s2 then at some time we will cross the velocity of light.. my questions are 1) is Earth accelerating ? 2) what happens if the velocity...
  35. K

    Equivalence principle and Helium balloon.

    Homework Statement Use the equivalence principle to explain the observation that a helium balloon leans forward in a forward-accelerating car. Homework Equations I don't think equations are needed. The Attempt at a Solution I'm completely confused on this question
  36. S

    Does the Black Hole Event Horizon violate the Equivalence Principle?

    My understanding is that, according to the Equivalence Principle, accelerated motion is indistinguishable from that of being in a gravitational field. So then, at the Event Horizon of a black hole, where gravity is too great for light to escape, wouldn't that be equivalent to accelerated motion...
  37. Y

    Problem with equivalence principle.

    Einstien gives the example of an observer riding on the rim of a spinning disc. Using his length contracted rulers he measures the perimeter to be greater by a factor of gamma (y), than the 2\pi R he would have measured when the disc was stationary. When he measures the radius with the same...
  38. O

    Galileo's experiment and Equivalence Principle

    FREE FALL OF BODIES 3-body problem (special case) According to the Newton's Mechanics: Let us consider a mass M of radius Ro. At a distance h from the center of this mass M, we place a spherical shell (e.g a spherical elevator) of mass m1 and radius R. Moreover, at the...
  39. T

    Equivalence principle & nonlinearity

    How does nonlinearity of the gravitational field equations follow from the equivalence principle? I remember hearing a handwaving example of this & I'm interested in more details.
  40. L

    Tests of equivalence principle based on fluid mechanics

    Were there some tests of this kind? Would that have some meaning? Would the fluid world be very strange if the EP was (somewhat) in default? Some brainstorming on fluid mechanics and the Equivalence principle, to take another point of view? Thanks, Michel
  41. N

    Equivalence Principle: Understand Constant Acceleration & Warped Spacetime

    Sorry for so many questions. In Einsteins equivalence principle, it states that an observer in a close room at 1G accel would not know the difference between that or whether he was standing on the Earth. This makes fine sense to me. But it also states as well that it is independent of...
  42. L

    How can I show that G=8pT implies the equivalence principle ?

    If I am asking this question, this is maybe a proof that I need a strong "back-to-the-basics". Could you give the way? Thanks, Michel
  43. K

    Does the Equivalence principle holds in QM.

    Does the "Equivalence principle" holds in QM. If we know that in QM under an "small" height so z<< R_{earth} (radius of the earth) so the QM equation is (SE): -D^{2}\Phi (z) +2m^{2}gz\Phi (z) =2mE_{n} \Phi (n) SO the wave function is just a "Airy function" and | \Phi (z) |^{2} is an...
  44. J

    Gravity / equivalence principle

    This may be stupid question... Equivalence principle - there is no experiment in a closed laboratory to determine if the lab is accelerating or at rest in a uniform gravitational field. It seems, then, that it is a fundamental property of the universe that one can always consider themselves...
  45. H

    Schrödinger equation and equivalence principle

    May be this is a silly question, but if one converts the nonrelativistic Schrödinger equation for a free particle to an uniformly accelerated frame, is the result the same as the Schrödinger equation for a particle within a gravitational potential? I was trying some simple calculations but did...
  46. N

    Question about the equivalence principle

    - Albert Einstein, Relativity: The Special and General Theory, Section 23 I'm confused about how gravity could account for all of the observations of the observer on the rotating disc. If the observer dropped a ball, he would see it fall away from the disc initially, as expected if there was...
  47. H

    The energy-momentum tensor and the equivalence principle

    Is it correct that the only way to have a theory of gravitation that fulfills the equivalence principle is to make use of a tensor as the source of gravity (and not a scalar or a vector, for example)? How can this be proven?
  48. P

    Does the equivalence principle hold for charged particles?

    I'm new here so this may be an old question. The equivalence principle states (roughly) that one can't distinguish between an accelerating frame and a uniform gravitational field. But an accelerated charged particle radiates. Thus the EP seems to imply that a stationary charged particle in a...
  49. W

    Does light bending doubly violate the equivalence principle?

    The equivalence principle (EP) - which is the basis of general relativity – states that you cannot distinguish between an object’s behaviour in a uniform gravitational field from that in a uniformly accelerating frame. If light travels vertically in a gravity field it loses or gains energy, and...
  50. C

    Special Relativity - Transformations and Equivalence Principle

    I am going to try to explain relativity without light or maxwell's equation. Light or Maxwell's equation or electromagnetism has nothing to do with relativity. a) The speed of light (and not light itself - note the difference) has something to do with it. b) The fact that M&M used light...
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