What is Observer: Definition and 322 Discussions

The Observer is a British newspaper published on Sundays. In the same place on the political spectrum as its sister papers The Guardian and The Guardian Weekly, whose parent company Guardian Media Group Limited acquired it in 1993, it takes a social liberal or social democratic line on most issues. First published in 1791, it is the world's oldest Sunday newspaper.

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  1. L

    Question on observer of double-split experiment

    Question on "observer" of double-split experiment From what I understand when we detect from which of two splits each electron passes we see two lines on the board. But, the moment we don't electrons become self-interfering waves. A puzzling result. My question is, can you explain me how we...
  2. R

    Observer independent collapses?

    Are there any inctances where by examing the trajectory where a subatom went are there experiments where wave functions collapse independently of an observer? Also I was wondering if wave functions collapse naturlley in the universe when they collide into other subatoms or such things. A...
  3. C

    Frequency percieved by observer from emmiter

    http://img511.imageshack.us/img511/1282/problemae.jpg This problem is fairly easy, but I just need a little help when it comes to take into account the direction of the moving cars. (English is not my first language by the way, so bear with me, hehe) Homework Statement There is an ambulance...
  4. D

    Someone moving near c to an observer?

    I think i understand that if my friend, let's call him bob - were to travel to the moon and back at near the speed of light, when he got back, it would seem like only seconds to him but centuries could easily have passed on Earth once he comes back to a stop. my question is - if bob launched...
  5. K

    Black hole falling time for external observer

    It is well know that it takes pi*m time to go from rest at the surface of a Schwarzschild black to the singularity. How much time does an external observer at infinity experience then in that time? How do I show it?
  6. H

    Qualifications of an Observer

    Qualifications of an "Observer" I believe that Quantum Mechanics places an onus on an "Observer" to collapse the wave function of any particle(take an electron for example). My question is what defines an "Observer"?What are the necessary attributes required to be an observer? I have read...
  7. N

    How is observer defined in context to quantum physics?does it have

    how is observer defined in context to quantum physics? does it have to b a conscious observer?
  8. Pythagorean

    Can we really observe the average trajectories of single photons?

    http://www.sciencedaily.com/releases/2011/06/110602143159.htm Sacha Kocsis, Boris Braverman, Sylvain Ravets, Martin J. Stevens, Richard P. Mirin, L. Krister Shalm, Aephraim M. Steinberg. Observing the Average Trajectories of Single Photons in a Two-Slit Interferometer. Science, 2011; 332...
  9. A

    Role of Observer in Double Slit Experiment

    In the double slit experiment, there is interference between the fired particles when both slits are opened. Yet, when an observer checks to see what's actually going on by looking at the slits as the particles pass through them, the interference disappears. In other words, the particles act...
  10. S

    Metric for an observer in free fall two schwarzchild radii from black hole.

    Hi all, I have a GR exam on tuesday and getting a bit confused as to how to find the metric for an observer in free fall a distance two schwarzchild radii from a black hole. I know this is a bit of a basic question but I am just wondering if I am correct to substitute r=2rs and dt=d(tau)...
  11. C

    Does the breakdown of the wave function need a concsious observer?

    Someone told me that in the experiments which display the collapse of the wave function, there is no need for a conscious observer. They said if we left an observing instrument on its own it would manage to do the same thing. Is this true? In fact this person thinks that the instrument...
  12. E

    Reality exists when observed, but who is the observer?

    Hi, Reading about quantum mechanics, the probability wave is so that a particle can be everywhere. But when observed, it's probability wave collapses and the particle has to take a definite state. The example were given for Schrödinger's cat, which is either alive or dead only after we...
  13. M

    Velocity of Light, for an Accelerating Observer

    I have finally been able to derive the velocity of a light pulse, according to an accelerating observer. The reference frame for the accelerating observer is taken to be the CADO reference frame, which is the only choice that I consider to be acceptable. The CADO reference frame is described...
  14. L

    Local Coordinates for Non-Uniformly Accelerated Observer

    Hi, I'm reading a paper about acceleration and the author states the local coordinates of the observer (\tau,x) (for a non-uniformly accelerated observer) are specified (in relation to the inertial coordates (T,X))...
  15. P

    Double Slit and The Observer

    Double Slit and "The Observer" Hi! First of all, I am just getting started in Physics, so I apologize if this is a silly question. I was talking with my boyfriend (who has a degree in physics) about the double slit experiment. Obviously, if you perform the experiment one electron (or...
  16. P

    Is this right? - Rietdijk proof future determined, already past for distant observer

    is this right? - Rietdijk proof future determined, already "past"for distant observer http://www.jstor.org/pss/186637 see details. I totally agree!
  17. Z

    Do you have to travel away from the observer for time to slow down?

    From my intuitive perspective on time dilation. The faster an observer is going relative to another, the slower in time the observer moves with respect to the to the other. However, I always pictured that this only works if the observer is moving away with respect to an observer at rest. Since...
  18. P

    Rindler Observer: Unruh Effect & Spacetime Geometry

    Hi, I read sean carroll book, "spacetime and geometry" and in the last chapter where he tries to derive unruh effect, he introduced the concept of Rindler coordinate. There is this part where he considers an accelerating observer in minkowski metric and introduce the trajectory blah blah...
  19. P

    The speed of light with an accelerating observer.

    You are one light year away from Earth, at rest in Earth's frame of reference. A flash of light is emitted from Earth. You begin to accelerate toward Earth. Does it still take exactly one year for the light to reach you from the time it was emitted?
  20. W

    Time elapsed for observer (from POV of Traveler)

    Hey guys, I have a question about elapsed time of the observer from the POV of the traveler. To make things simple I'll just basically explain what my question is. Person A is the observer (on earth) and person B is the traveler (flying at close to the speed of light) Person A's...
  21. M

    Doppler Effect, Stationary source moving observer

    Homework Statement My books states, considering a stationary source emitting waves at frequency f, such waves having velocity v, and an observer approaching the source along a linear path at velocity vO we have that: The observer registers the velocity of the waves at v+v0. Up until now all...
  22. M

    How to be an Inertial Observer?

    I think this "elephant-in-the-room" issue is important enough to deserve its own thread. I believe it is at the root of many of the disagreements that repeatedly occur on this forum. So I copied my last posting over from the "The case for True Length = Rest Length" thread. Here is that...
  23. A. Neumaier

    Exploring the Limits of Measurement in Quantum Mechanics

    The relation between observer and observed is one of the controversial issues in quantum mechanics. In view of related discussions in other threads, let me summarize some statements by two of the most influential thinkers on the matter: John von Neumann and Eugene Wigner. Von Neumann...
  24. X

    Does a T.V. transfer energy to the observer?

    I know this is silly but I wanted to ask. After reading a bit on energy and not beeing able to create it or destroy it, it made me think imediately about a tv. When I turn the t.v on am I getting anything out of it even if it is all in the mind or memory or whatever? If I spent two hours...
  25. N

    What is SPEED OF LIGHT With Respect to an Observer?

    Can anyone please tell me what does SPEED OF LIGHT WITH RESPECT TO AN OBSERVER mean? Some explain it like this: If there are two poles 10km apart, in front of an observer and he sees a ray of light passing past them, then he would see that the light would cross the poles in time 10/c. Is it...
  26. P

    Could an observer prove he is in a CTC?

    I think an interesting question is: could an observer prove he is in a CTC? Intuitively I would think the answer is no. But I am interested in proofs, conjectures or opinions.
  27. J

    Control Systems: Uncertainties w/ State feedback & Observer controller

    Homework Statement Consider the continuous time state space model governed by: A = [-1 0;1 0] B = [1; 0] C = [1 -1] D = 0 a) suppose we are using the following state feedback and observer gains K = [k1 k2] L = [l1;l2] find the loop gain symbolically using MATLAB (aka find...
  28. S

    How does a quantum mechanical state 'look' to different observer

    Hi all I am a little disturbed by the above thought about transformation of quantum state(or it's discription) between different frames of references. The doubt can be translated for a two state system as follows: Let an observer has decided about her(his) x, y & z directions. He now...
  29. B

    Capacitor and observer, what does he measure?

    An observer is standing right outside of a charged capacitor. Can he feel a negative or positive (or both) charge from the plate?
  30. P

    Calculating Delta-T' for Observer B's Journey

    I was wondering how you would calculate the delta-T'(would it be correct to word delta-T' as change in time change?) for this example: (this is not a HW question) observer A is at earth. observer B fly's 10 light years away at .5c to a non-rotating black hole 1 million times the mass of Earth's...
  31. P

    Fermi Normal coordinates for an infalling observer

    I thought I'd present some plots for the Fermi-normal coordinates (only in the r-t plane) for someone falling into a black hole "from infinity". Fermi-normal coordinates radiate a set of space-like geodesics from some point on the worldine of an object - in this case, the worldline of an...
  32. G

    How does one observer win out over another?

    Ok, I am an absolute beginner. I've just seen the basic experiment of shooting a particle(unobserved) through 2 slits and seeing on the wall behind that it has landed in all of the possible places it could go simultaneously.. and of course when it is observed at slit level it behaves differently...
  33. J

    Delayed Quantum Erasure Double Slit with Observer Choice Available

    In the paper "Double-Slit Quantum Eraser" by Walborn, Cunha, Padua, and Monken (see http://grad.physics.sunysb.edu/~amarch/Walborn.pdf and discussion of the paper at http://grad.physics.sunysb.edu/~amarch/ ), a double-slit quantum erasure experiment is performed with a delayed eraser. When the...
  34. L

    Can an observer be in a superposition?

    If I had a measuring device which causes decoherence of some quantum experiment: Is it possible to put (somehow) this observer/measuring device into a superposition of two different states? So instead of the wave function collapsing to ______/\______ it would collapse to __/\___/\__ (or...
  35. I

    Age comparison to observer on Earth (time dilation)

    Homework Statement Alpha Centauri is about 4 light years from the Earth. If you were to travel to Alpha Centauri and back at the speed of the electron that you calculated in question A (0.780c), how much would you age compared to an observer on Earth? Homework Equations There equations...
  36. morrobay

    Double slit interference destroyed by observer or by photons

    When the electron double slit interference pattern is destroyed during measurement detection, to determine which slit the electron passed through, the explanation is that the observation is responsible. Given that detection is done with photons that can interact and alter the path of the...
  37. N

    Can an observer know he's in a black hole?

    My question is about an observer inside the event horizon of a black hole, but not yet at the singularity. Let us say the observer is inside a sealed vessel, so he can only measure local properties of space-time, and their derivatives with respect to space and time. Is there any experiment he...
  38. G

    Is the Schrodinger's Cat Experiment Flawed Due to the Cat Being an Observer?

    Please forgive my ignorance, I have no educational qualifications and am finding my self being sucked into the wonderful scientific world but one thing that troubles me is the Shrodingers cat experiment. As I believe it to be the case that in order for the uranium atoms to decay they need an...
  39. E

    Treating the Observer as a Quantum Object: Implications and Considerations

    What happens if we treat the observer as a quantum object in an experimental set-up? I don't have a specific model of an 'observer' - all suggestions are welcome. I'm curious whether the consequences are compatible with the principle of relativity (that observers shouldn't be...
  40. C

    Making sense of observer participation in physics

    It’s now taken for granted among physicists that whatever the fundamental structure of physics may turn out to be, it's nothing at all like what we experience. Both Relativity and Quantum Mechanics are thought to describe a universe that's so radically different from the world we deal with in...
  41. M

    Is Mass Relative to the Observer?

    I know that time and velocity are relative to the observer, but what about mass? For example, if my friend were to go 0.999c, we know that his mass would increase to me. But would he measure the same increase, or would he feel the same?
  42. P

    Speed of light viewed by stationary observer

    Homework Statement Describe what happens to an object traveling close to the speed of light from the point of view of a stationary observer. (Hint--there are three differences). The Attempt at a Solution I just don't understand what it means by there being three differences?
  43. P

    Frame of reference of any observer

    Let's consider flat 4D Minkowski spacetime. Is it possible to define (local) coordinate system for any observer (its natural reference frame) so that these coordinates posses interpretation of time and spatial position measured by this observer? It can be done in two dimensional Minkowski...
  44. K

    Can a computer be an observer?

    Hello all, I am writing an article on the definition of "observer" in a quantum mechanics context. From what I know about QM, most consider that an inanimate apparatus and even individual particles can function as the "observer" in quantum measurements. I also know that the 1991 experiment by...
  45. R

    Speed of a moving observer toward stationary source (sound frequency)

    Homework Statement A stationary whistle emits a sound of 190 Hz. If a car hears the whistle with a frequency of 198 Hz, how fast was it moving (in m/s)? Use 340 m/s for the sound velocity Homework Equations f'=(1+Vo/V)f ======>>>> equation for the observer moving toward stationary...
  46. D

    Is universe really observer dependent?

    Is universe observer dependent? Any thoughts.
  47. H

    Observer types to make the wavefunction collapse.

    Hi there, I'm not extremely adept at understanding what I like to think of as the "Philosophical" side of QM but I find I have a problem with some aspects of an interpretation of the wave function collapse. I also could be misunderstanding what people are saying. When people talk about...
  48. R

    Does different observer affect double slit particle experiment

    if the double slit particle experiment is observed by an animal and not by any human for eg. chimpanzee, through which slit the particle has passed would it collapse the wave function and form particle pattern. The particle are only observed by the chimapanzee, so it can know which slit the...
  49. R

    Doppler Effect: Moving Observer riding on moving source With reflection off wall

    Homework Statement A bus is moving at 37.00m/s towards a wall. The sound from the bus has an original wavelength of 0.1500m. The sound from the bus reflects off the wall. What frequency sound does an observer on the moving bus hear from the reflection?? Homework Equations Moving Observer: fo...
  50. K

    Double slit experiment, observer effect

    It was a good while ago since I heard about this particular experiment, but I remember vaguely reading about how in one instance they recorded the observations, but then deleted the data before anyone could look at it, and in that instance the wave was still produced. Thus showing that it really...
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