Observer Definition and 324 Threads

For the observation of the gravitational redshift one needs an adaptation of the GTR of the object (related to the Sun´s gravity) and the observer (related to the Earth’s gravity). I assume that the situation is similar for the observation of the precession of Mercury, another experiment...

Does unitarity of the evolution of wavefunction get rid of the need for a "conscious observer", and does collapse in contrast demand a "conscious observer"? For with unitarity there are is no requirement for such an observer, and collapse can't be explained without such an observer. The...

I am a little confused with the text above. Actually, all is ok until 2.51, i think i am missing something. What is this? Another way to define gamma? (The doubt is not about the raising indices, neither about "n00 = -1", is just where does the equation came from. That is, the equation is easy...

Hello all, let's suppose we have, in a flat spacetime, two observers O and O', the latter speeding away from O, with an uniform acceleration ##a##. In the Minkowski spacetime chart of O, the world-line of O' can be drawn as a parable. We know that the Lorentz boost at every point of the...

for example the car headlight would look faster then c speed. (it speed would be the speed of light +the speed of the car) to observer in front the car. because the light come from the car so the speed of the car would connect with light speed (like when you walk on a train) . so does the light...

I've read that speed of light for a Rindler observer is not constant. I wasn't sure why and I tried to do this as an exercise for myself, I think I came with the correct answer, but I'm not sure, is the following argument correct? Let's describe the (flat) space-time using Rindler coordinates...

My thought process was this, They are asking us to find the frequency of sound received by observer when the source reaches at origin. According to me when the source reaches origin there would be no component of source's velocity in the direction of observer, hence vs=0 vo=0 since the observer...

I think this should be t'= Lorentz factor* (1+v/c)t, but that doesn't make sense to me.

I'm reading a book on principles of relativity, and am going through the definitions of reference frames and free particles. From what I've understood from there and other answers on SE, a non-inertial reference frame is one in which a free particle is measured to be undergoing acceleration...

What counts as an observer, and what does it mean to "observe"? I've read a detector (machine) is an "observer." But how do we know it performed an observation without observing it? Is it possible our observation of the detector retroactively caused the wave function to collapse?

You often hear this debate about the role of the observer in Quantum Mechanics. How you view this role is usually dictates the interpretation you prefer. If it's Copenhagen, then the observer is more robust and plays a crucial role in wave function collapse. If it's Many Worlds, then the...

In MWI, would you say that a measurement puts the observer in superposition of being in the various worldlines? If I said "yes" to that, would I be correct?

Hi all, this is a new scenario I got thinking about after having received great feedback and corrections from other PF'ers in this thread. Thanks again for the great help! This new scenario is similar to the previous one, but with a twist including a mirror. And as I said in that thread, I am...

Hi all, I've just read this entire thread and watched the videos about black holes posted by @PeroK, which I liked very much (thanks @PeroK! :smile:). I am not particularly well aquainted with GR and my questions are concerning the often mentioned statement that an observer that passes the...

I get so many different answers to this question so maybe here someone can pin this down. When I get up in the morning and I turn on my TV, I have over 3,000 channels so is there a universe with a version of me going to each channel? If not, how do I go to one channel over the other? Can my...

According to Everett-interpretation or many world interpretation of quantum mechanics, each decision an observer makes, the world splits into two parallel universes, let’s say an observer in some point in Spacetime is tests the Schrödinger’s cat experiment, in one branch of the universe the cat...

Is it possible that some light signals will never reach the Rindler observer? Just to be clear, by Rindler observer I mean an observer undergoing constant acceleration (as measured in his own rest frame).

Let us suppose a spaceship moving from Earth to another star that is 10ly away with a speed of 0.99c. Calculate the of years spaceship takes to reach its destination (a) in the rest frame of an observer on Earth and (b) as perceived by a passenger on board the ship For (a) I find that ##t_0 =...

If I and the light source are both moving toward one another, I see light blueshifted. What if I'm at rest and the source moving towards me?

Homework Statement Two identical loudspeakers are driven in phase by the same amplifier at a frequency of 680 Hz. The speakers are 4.6 m apart. An observer stands 9 m away from one of the speakers as shown. The observer then starts moving directly towards the closest speaker. How far does the...

This is based on the Hugh Everetts interpretation of quantum mechanics, where the waveform never collapses but the observer becomes a part of it, thus experiencing decoherence of the wave form from their point of view. So, let's say someone is doing the two-slit experiment. The particles going...

I have seen thought problems with an observer on a train or in a station, etc., but I have not seen ones with the observer traveling at relativistic speeds. It seems to me that at sufficient speed he would observe himself exceeding the speed of light due to the slowing of time. This seems like...

The idea of the outcome of an experiment depending on whether or not it is being observed is strange. I have never seen this happening in real live. Still in physics it is held that it does exist: the double slit experiment using very low-energy laser light (assuming that one photon passes the...

I was thinking about the signals Mankind has sent out from Earth greeting other races out there. Is it reasonable to think that even if some being received the signals (data) they would have no idea about locating Earth because it would be in somewhere else in the Galaxy/Universe by then? So...

How fast would the light travel for a SuperBig observer... immagine his head is the size of the Sun, and he is sitting in a room, then he decides to turn on the light in the room... if he is so big, would he have to wait some seconds until the light reaches his eyes? Would it mean that for this...

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Subatomic particles can take the form of a wave or a particle. While in wave form, it is not like a physical wave, but rather a probability wave, (i.e. a wave of information about where the particle is probably located etc.) And while in particle form, a photon, for example, can knock electrons...

I have read that when an electron is observed, it behaves differently to when it is not being observed. Could someone please expand on this, or indeed correct me. In what way does an observed particle behave differently to a particle that isn't being observed by somebody's consciousness?

How exactly does the mere act of observing collapse the wave function of, say, photons? I don't quite understand that one. And Richard Feynman's question related to Young's double slit experiment and the fact the electron went through both slits, as well as neither, and just one slit, and just...

I'm just a layman here, who enjoys science and astronomy. I was reading about the temperatures of the cores of black holes being extremely cold, and how time at the singularity...progresses super, super slowly. But this is only as measured from an outside observer's perspective (such as from a...

Why the speed of light is constant for every observer ? Is it a special thing for photons cause I guess there's no other elementry particle that can move with c ? Also I want to investigate the constant of c for every observer, in the perspective of particle relationship. For example, can I...

I would like to know whether my thought is right or wrong about time dilation example. Let's say, A person is standing at a starting point so his velocity is 0 ms'1. A car runs from that point in the velocity of 3 ms'1. A photon from a light source at that point is also emitted at the same...

We were shown the answer to this question as a worked example: A photon is emitted from a radius ##r_2## and travels radially inward to ##r_1## until it's reflected by a fixed mirror and travels back to ##r_2##. Calculate the time taken for the photon to travel in and back, according to a...

In almost general case, the space-time metrics looks like: \begin{equation} ds^2 = g_{00}(dx^0)^2 + 2g_{0i}dx^0dx^i + g_{ik}dx^idx^k, \end{equation} where ##i,k = 1 \ldots 3## - are spatial indeces. The spatial distance between points (as determined, for example, by the stationary observer)...

Hi, I have a 2nd order of sliding mode observer of the form: \dot{\hat{x}} = \hat{f}(x,t) + \delta f + \Psi(u,y) +[ \frac{d \Omega}{dx}]^{-1} \upsilon where ##\upsilon##: \upsilon_1= \alpha_1 \lambda_1^{1/2} | y_1 -\hat{x}_1|^{1/2}*sign(y_1 -\hat{x}_1) \upsilon_2= \alpha_2...

Hello there, My question is: Is there a double slit-experiment done with all of the measuring equipment in place and all of the equipment activated but without a conscious observer? Proving there is no differentation pattern regardless of a conscious observer. Thanks in advance

Hi all, Suppose we have some particle in state $$|\Psi\rangle=\frac{1}{\sqrt{2}} (|U\rangle + |D\rangle)$$ It starts interacting with its environment, including Experimenter 1 (E1). From Experimenter 2's viewpoint, this can be represented as: $$|\Psi\rangle=\frac{1}{\sqrt{2}} (|U\rangle...

I studied only half a semester of quantum physics in high school (which i only finished 8 months ago and came first in physics luckily) but i remember Heisenberg's uncertainty principle. All over youtube people were saying things like "this is God's way of keeping us from getting into perfection...

Homework Statement A.P. French q.no. 4.3 Homework Equations t = L\c, (1) L0 = ϒ L The Attempt at a Solution The observer's frame is that frame w.r.t. which the meter stick is moving with speed 0.8c. The observer sees the mid-point at (x,y) at a time to(measured from the clock situated at...

If I've understood correct, every particle in the universe exists in a waveform, which I've understood to mean propability where the particle does exist? Then which I've understood is, that the wave transforms into a particle only when observed, is this correct? Then if it is correct, how...

SI defines one meter as the distance traveled by light in one upon 299792458(=k) seconds, from which we get that, D=c*k, where k is marked above. So, let's consider two frames on at rest wrt the earth(f1) and another moving at, say 0.99*c(f2). SR says that the time dilates for f2 wrt f1. And...

I want to prove that ##E = -g_{\mu \nu}u^\mu p^\nu## is the energy measured by an observer with velocity ##u^\mu## of an object with momentum ##p^\mu##. My reasoning is that in special relativity we know that ##\gamma m = E##. We can transform to coordinates where ##u'^\mu = (1,\vec{0})##. Since...

Lets suppose that two points A and B are very close together compared to their distance from an observer who is very far. Suppose the distance from observer to point A is DA and to point B is DB. How precisely we can find the distances separately.

How much importance does light (electromagnetism) have to do with the "Observer Effect" in the Double-slit experiment? From my research, it seems that the only successful "Observer Effects" in the Double-slit experiments, wherein, the interference pattern transitions to a clump pattern, is...

Basic double slit experiment one observer knows the path of the particle. The back screen is a locked room and has never been seen. The observer dies and I decide to look at the screen. What will I see? I'm assuming the wave will still be collapsed.

No. This is a noncovariant, observer-specific view.In the covariant, observer-independent view of fields, states are labeled instead by the causal classical solutions of hyperbolic field equations. On the collection of these the Peierls bracket is defined, which is the covariant version of the...

I was just reading the thread about the dead cat/live cat. Is the state of the cat dependent on the knowledge of the observer?

What happens if a source and the observer move at the same direction? Always hear how only one of them doesnot move, or when they move towards each other. For example. An ambulance moves towards direction A with Va. A biker moves towards direction A as well, with Vb. What happens to the...

If reality requires an observer, and life on Earth is only 3.8 billion years old- yet the universe is 13.8 billion years old, who was the observer for the first 10 billion years?