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. J

    Calculating the Speed of Airplane Above an Observer

    Homework Statement An airplane flying horizontally at an altitude of 3 miles and at a speed of 480 miles per hour passes directly above an observer on the ground. How fast is the distance from the observer to the airplane increasing 30 seconds later? Homework Equations The...
  2. J

    Does pressure depend upon the observer?

    Suppose you have a tube of moving water where bernoulli´s equation can be apllied and the water is at the same elevation all over the tube. Consider two points, 1 and 2. We have : p_1 + \frac{1}{2}\rho (v_1)^2=p_2 + \frac{1}{2}\rho (v_2)^2 On different inertial referentials the velocities...
  3. D

    Wave function of an observer, 'always collapsed'?

    Would it be correct to say, that the observer's wave function is 'always collapsed'? I.e. that the observer can always be completely described by a bit string, while everything else only by a 'qbit string'.
  4. C

    Can a moving observer detect a magnetic field from a stationary electric charge?

    Can anybody provide me with a link to a REAL life experiment (a credible source, and not a thought experiment. ) when a moving observer relative to an electric charge can see a magnetic field? I'm thinking to a sensor that is spinning around an electrically charged sphere or disc...if in REAL...
  5. M

    Parallax, angle to observer etc.

    Hi, I'm a mathematics analphabet, but still, sometimes I come across a problem, that I just can't keep away from. I hope someone finds this one worth a thought. Here it is: An observer is looking at a long object with marks spaced equally along its length (like a measuring rod or a...
  6. D

    Schwarzschild solution and velocity of stationary observer

    Hey all, I suddenly find myself very confused about velocity and coordinate systems. I have a feeling this is very simple, but sometimes the mind just curls up, you know? ;) When you ask what an observer observe, you need to see things from his point of view - his reference frame. And his...
  7. marcus

    Entropy depends on observer (Dialogue on the Nature of Gravity)

    In the past several major advances in physics have been associated with the discovery that something wasn't absolute, but depended on the observer. Padmanabhan just posted A Dialogue on the Nature of Gravity, which is remarkably readable, and which argues among other things that entropy is...
  8. G

    Quantum Observer: Can We Perceive Atomic Reality?

    Let us say that we had a higher degree of sensory ability and were able to perceive smaller wavelengths of electromagnetic radiation ('directly' or 'naturally' perceive - not through equipment that traces them out for us to see as visible light) --- small enough to consider atoms. Would...
  9. V

    Regarding the observer effect.

    I got a question. Is this excerpt from wikipedia correct? http://en.wikipedia.org/wiki/Observer_effect_(physics ) Does that mean there is no observer effect when acts of observation and measurement are defined in quantum terms? Does anyone have sources that augment or dispute this...
  10. J

    Double Slit Experiment - Blind Observer

    Hi, I have a question about the famous double slit experiment. They say that if an observer like a camera or a person is watching the experiment then it collapses the wave function and two marks appear instead of an interference pattern. Does anyone know what what happen if a totally...
  11. R

    Why is the speed of light constant and independent from the observer?

    Why is the speed of light constant and independent from the observer?
  12. R

    Dual of the inertial observer

    If an inertial "observer" or state has mass and no rotation, then a massless state with rotation (i.e. having maybe a generalized rotation such as "spin," e.g. a photon) seems to be dual to that state. Would this viewpoint then take the photon as a "matching" channel or "process" for...
  13. E

    Energy time relationship from an observer in space

    So here we have the simple equation: E\uparrow T\downarrow This can also be stated by saying that the more massive (energetic) an object in space is, the less time it will exist for. But if time passes slower in areas of space near more massive bodies, wouldn't an observer near...
  14. P

    Human observer & cosmological interpretations

    Hi! This is my first time on here and my first post. I don't do professional work in this field but it has been a keen interest of mine over the years. Anyway, if someone can share some insights, I would really appreciate it greatly! Given the divide between classical physics and quantum...
  15. J

    Question about 'uniform' pseudo-field felt by accelerating observer

    From some previous discussions in this forum I had gotten the idea that under the equivalence principle, observations inside a small room sitting on the surface of a planet should be seen as equivalent, not just to any ol' accelerating room in flat spacetime, but to a room undergoing Born rigid...
  16. H

    Does an observer on a carousel see a horizon?

    Special relativity shows that any accelerated observer sees an event horizon. In fact, if an observer is accelerated by a, the horizon is at distance l=c^2/a in the direction opposite to a. If an observer is on a carousel or merry-go-round, he is accelerated inwards. Does he then see a horizon...
  17. E

    Understanding SR: A Travelling Observer & Photons

    I am currently trying to understand SR and am confused on this postulate. Lets say somone is traveling on a some kind of machine that emits photons. When that photon is emited will the person traveling on the machine measure the photon going c or will they measure it going c-v? My next...
  18. J

    Modern Physics, The Observer, and free-will

    Hello, First off, I would like to say thank you for being of much help as I browsed these forums a little and gained some information. Second, I would like to say that at this in point of time my understanding of Physics is limited, so I do not intend to put myself across as...
  19. F

    2 observer diagram, relativity

    Homework Statement A futuristic flying car, 100m long in the horizontal x direction, lifts off vertically from the ground at 0.1c. A plane flies past at 0.65c in the positive x direction. According to the ground observer the car remains parallel with the horizontal x axis. a. draw a 2...
  20. A

    Quantum Experiment: Results & Observer Impact?

    During a quantum experiment there is an observer and you get a result. You perform the same experiment without an observer and get another result. Is this true? The link below is very good at explaining, it's animated too but that's good, it is fun to watch...
  21. H

    Does Bernoulli’s principle depend on the observer?

    Hello. I’ve found in the forum this thread that had the same question I’d thought. https://www.physicsforums.com/showthread.php?t=143593 But there were too much things involved in it. I would like to know if Bernoulli’s principle effects change if the Observer velocity changes. For instance...
  22. B

    Best name for the length of a moving rod measured by a stationary observer

    I find in the literature of the subject different names for the length of a moving rod measured by an observer relative to whom it moves. Please let me know if ther is a standard name. Thanks
  23. S

    Stationary charge and accelerated observer

    Accelerated charge radiates as observed by a stationary observer..is the converse also true?..i.e. Does a stationary charge observed by an accelerated observer radiates?
  24. Holocene

    Is Consciousness Found in Everything in the Universe?

    Sorry if this is more of a philosohpical question, but With both the strange perplexity and proven aspects of quantum mechanics in mind, do you think we will ultimetly need to devote a science beyond even neurophysiology to understanding what consciousness really is?
  25. rcgldr

    Speed of light - with observer experiencing gravity

    This is related to time dilation effect due to strength of gravity, basically GR effect on calculated speed of light. Two observers, observer#1 on a very large non-rotating sphere, experiencing 1.0g of gravity, observer#2 is a large distance from the sphere, experiencing 0.1g of gravity. Both...
  26. M

    Consciousness of Double Slit Observer

    Have any experiments been conducted that explore the state of consciousness of the observer in the double slit experiment? My understanding of the double slit experiment is this. Shoot one photon at a time through a slit and you get a line of light (particle model). Shoot single photons...
  27. U

    When is the next 13.00 Local Sidereal Time for a UK observer?

    When is the next "13.00 Local Sidereal Time" for a UK observer? Anyone with software or equations to work that out?
  28. P

    Time-A factor of the observer?

    Just imagine, a man who has been frozen completely, cannot move, does not sense, but he is alive and his internal organs are working perfectly. What is time for him? I mean, he is not sensing anything he is not sensing his living nor anything that is going around him? So, time doesn't exist for...
  29. S

    Why is the speed of light the same to any observer?

    And the 2nd question: Do we know why is the speed of light 3*10^8 m/s? What determines this value? (I'm not asking about system of units) S.
  30. R

    Exploring the Observer Effect in the Double-Slit Experiment

    Hello, I am new in this forum and I am not a scientist Can someone help me to understand the following question: does this String theory confute and negate the Observer Effect and that there is a subjective reality? Or it confirms it Thank you so much Rossella
  31. M

    What beat frequency will the observer detect?

    Homework Statement Two trains emit whistles of the same frequency, 282 Hz. If one train is at rest and the other is traveling at 45 km/h away from an observer at rest, what beat frequency will the observer detect? Homework Equations The Attempt at a Solution I used listener...
  32. B

    Physics: doppler effect (observer & source in motion)

    Homework Statement A train is moving parallel and adjacent to a highway with a constant speed of 25 m/s. A car, at time t0, is 42 m behind the train, traveling in the same direction as the train at 49 m/s, and accelerating at 4 m/s^2. The train's whistle blows at a frequency of 460Hz. The...
  33. G

    Local acceleration experienced by observer

    I have read a number of threads on acceleration and special relativity, but can't find what I'm looking for. I would like to know, in the context of special relativity, how to compute the acceleration "felt" by an observer, and how to transform this acceleration into different inertial frames...
  34. C

    Einstein's Thought-Experiment: Disgruntled Observer's Perspective

    Let’s put an observer in a 3-D frame of reference at x=0, y=0, z=0 to observe one of Einstein’s thought-experiments. You know the one - where a spaceship is equipped with a photon emitter, a mirror and another observer whose frame of reference is at rest with the spaceship. Let’s have the...
  35. N

    Frequency involving moving observer and source

    Homework Statement You are driving along a highway at 27.5 m/s when you hear the siren of a police car approaching you from behind and you perceive the frequency as 1250 Hz. You are relieved that he is in pursuit of a different speeder when he continues past you, but now you perceive the...
  36. D

    The Observer Effect: Testing Double-Slit Experiment?

    I keep seeing references to the observer effect in the double -slit experiment where the a of observing the photon or electron going through the slits causes a collapse of the wave function. so, instead of getting a cool interference pattern, you get the pattern expected if the light was...
  37. G

    Is the direction of a pulse from a laser pen dependent on the observer?

    Suppose I am in an inertial non-accelerated reference frame, and I observe a laser pen moving in a direction perpendicular to its length at a uniform constant velocity of one meter per second. If the laser pen were to fire very briefly, say for 1 millisecond, while in this state of uniform...
  38. U

    Electric field becomes electromagnetic waves if observer is moving

    At school (a long time ago that is) we were taught: 1. a stationary charge produces a static electric field. 2. a moving charge produces a magnetic field, plus an electric field that is slightly different from the original electric field of the stationary charge. 3. a periodically...
  39. M

    Does the temperature of a body depend upon the frame of the observer?

    does the temperature of a body depend upon the frame of reference from which it is observed?
  40. D

    Could moving observer be stationary vs moving and still give Albert the same results

    Could the moving observer be at some distance instead of moving and still give Albert the same conclusion? In IX. The Relativity of Simultaneity, Albert describes two simultaneous lightning strikes and two observers. One of the observers is stationary at a mid point between the simultaneous...
  41. F

    News Ahmadinejad offers to be an observer at US presidential election

    http://www.guardian.co.uk/uselections08/story/0,,2217495,00.html After a succession of corrupt elections in the US this doesn't sound like such a bad idea at all, especially with evangelicals subverting the Republican party & American democracy in general.
  42. A

    C independent of observer and emitter

    When we say that the the velocity of light, c, is independent of the velocity of emitter or the observer, does it mean that .. if we are in an spaceship and measure c with Fizeau arrangement we will obtain the same result, no matter the velocity of the spaceship nor the velocity of the...
  43. E

    Doppler Effect II (Both observer and source in motion)

    Homework Statement You're flying in an aircraft at 46 m/s. An eagle flies directly towards you at 11 m/s. Speeds are relative to ground. The eagle emits a cry at 3400 Hz, and the speed of sound is 330 m/s. What frequency do you hear? Homework Equations f_o = f_s\left(...
  44. C

    Another misleading observer example, or not?

    In this example, which I found via Wikipedia on Delayed Choice, http://www.bottomlayer.com/bottom/basic_delayed_choice.htm" it makes the "observer" special, i.e. it's the observer who "chooses" whether the photon goes through one slit or the other, or through both as a wave, or more...
  45. M

    ZExploring the Observer Effect: A Look at Schrödinger's Cat and More

    Alright, I've been doing a lot of reading and talking with my professors at college, and I just can't seem to wrap my head around the observer effect. Basically, Schrödinger's cat. I've heard a lot of analogies to compare it to, but I'm still baffled by it. I've heard "If a tree falls in...
  46. M

    If an observer accelerates he must rotate in space-time?

    It is my understanding that if an observer accelerates he must rotate in space-time. But then why is that factor generally omitted in the calculations related to accelerations?
  47. Q

    Why does an observer affect the electron?

    :smile: Hi all, In quantum physics (i.e. the double slit experiment with electron), why does mere act of observing the electron affect the fact of whether its a wave or particle? Please answer in laymens terms if possible as i am no physicist! Thanks in advance :smile:
  48. Oxymoron

    Doppler & Gravitational Redshift: Non-Inertial Observer in SR?

    In Special Relativity, If an inertial photon emitter, A, emits photons every second and an observer, B (moving away from A at a constant velocity v), intercepts these photons and instantaneously reflects them back to A then we would expect to see the Doppler redshift effect. My question I...
  49. G

    Understanding the E Field Observed by a Stationary Observer

    I have a problem that I can not understand what I am doing wrong. A rocket moves at 1.0*18^6 m/s. Inside is an E Field (coming out of the page of the book) that is 2.0*10^6 V/m. There is also a B Field in the rocket pointing up that is -1.0 T. What is the E Field observed by someone on Earth...
  50. Oxymoron

    Is the Muon's Perception of Distance Correct in Relativity?

    A muon is created 3km above the Earth's surface heading downward at a speed of 0.98c. It is able to survive 2.2\mu s in its own frame before it decays. (1) The muon travels a distance of 647m before it decays in its frame d = vt = (0.98\times 3\times 10^8m/s)(2.2\times 10^{-6}s) = 647m...
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