Observer Definition and 324 Threads

I have re-written this as as I accidently deleted my original post. I was wondering if the relativistic Doppler shift of a reflection from a mirror moving away from the observer was the same as the Newtonian equation in the special case that the mirror is orthogonal to the direction of motion...

Say I am at point X. My friend, Gary, is 20m from X, and my friend Liam is 40m from X. Gary is traveling at 5 metres per second in a circle around me, remaining 20m from X. What speed must Liam travel at to appear, to me, to be traveling at the same speed as Gary? Is it 10 metres per second or...

My question is about the Quantum Observer Effect. I know in the double-slit experiment originally my mind was set that somehow the measuring device altered the experimental variables but in light of a recent experiment where all possibility of that was null I am again at point zero with this...

wrt means with respect to Homework Statement see attachment that contains full question. firstly read paragraph then see on question. The Attempt at a Solution velocity of sound will be 340ms-1 wrt air or ground(since air i snot blowng). Now speed of soud wrt train A= speed of sound...

My first question is pertaining to Schrodinger's Cat (i know... I am still trying to grasp these concepts). So, wouldn't it make sense that the cat would be a conscious observer therefore causing wave function collapse in the first place? My other question is just a general question about...

These damn shows on the Science Channel seem to raise more questions for me than they answer, and maybe I'm understanding this wrong but here we go... If I were an unfortunate soul who fell into a black hole, the show claims that I will not feel a thing as I pass through the event horizon...

Edit. I think the topic is misinformative and I don't know how to change it. Hey I have to translate this into english so bear with me. Two spaceships are approaching Earth from two directions along the x-axis. Earth observer(EO) calculates their speeds to be 0,8c each. Calculate at what...

Hello all, I was just wondering what 'an observer' might be in quantum physics, and any definition I can come up with just doesn't make sense. I strongly oppose the idea that an observer has to have a conscious. Because in that case, one would have to wonder: what is consciousness? Let's say...

let me first donate a(A,B) is the acceleration of A relative to B Observer 2 and a subject A with mass m are falling down from a building Observer 1 is standing on the ground to observe the motion of these two objects Ignore the air resistance In observer 1,he sees the force acting on A...

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...

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...

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...

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?

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...

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

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...

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...

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)...

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...

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...

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...

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))...

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...

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

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...

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...

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?

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...

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...

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...

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...

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...

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.

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

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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?

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?

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...

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...

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...