Measurement Definition and 1000 Threads

There is one question that I would like to get an answer to in regards to the discussion between @DrChinese and @iste in the thread: https://www.physicsforums.com/threads/a-new-realistic-stochastic-interpretation-of-quantum-mechanics.1060576/post-7138288 In the case where the Bell state test...

when the distance between the two piece of aluminum variate, the capacitance of this self-made capacitor also variate, and I would like the measure the variation of the capacitance caused by a sound wave. If I thought about a De Sauty Bridge but it doesn't fit my requirements. The is this...

Suppose we have a quantum system ##S##, an apparatus ##A##, and an observer, say Alice, ##O##. WLOG let ##S## be a spin-##1/2##particle in a state ##0.6|\uparrow\rangle+0.8|\downarrow\rangle##. The apparatus measure it in the ##\sigma_z## basis. Then the observer sees the result. According to...

Hello , I read the earth and the sun has a mass and google etc gives a measure . When I go the supermarket and buy 1 kg of bananas , they are weighed on scales . Is science lying about the mass of the earth and the sun ?

Hello everyone, In the MCBEND simulation I've conducted, I have found the dose rate of a gamma source in microSieverts per hour (µSv/h). I also know the distance between the detector and the source. How can I calculate the source activity or strength from this information? Thank you, Best wishes

True luminosity of object X = ##T_X## Apparent luminosity object X = ##A_X## Distance of object X from observer = ##D_X## True luminosity of object Y = ##T_Y## Apparent luminosity of object Y = ##A_Y## Distance of object Y from observer = ##D_Y## Apparent luminosity is something measurable I...

Say you had 3 particles all of which were entangled in the GHZ format. What methods could you use to measure the entanglement between two of the particles? Say particle A was far away and particles B and C were close together. If you used magnetic fields at point A to break the entanglement...

We are trying to control a container with water inside. The container has two phases of operation. In one phase, the container is tilted. In this tilted state, the distance from the observation point (red dot) to the surface of the water (distance B) is known from a measurement device. However...

I'm having a hard time since the angle is being measured in frame ##S##. What I have put together so far is ## l_y = l_{y0} = 1m(sin(\theta_\circ)) ## And ## l_x = l_{x0}/\gamma ## Where ## l_{y0} ## and ## l_{x0} ## are the respective x and y values of the meter stick in the proper lengths...

Alan Macdonald claims in "4 Appendix: The Equivalence Principle" of his text "Special and General Relativity based on the Physical Meaning of the Spacetime Interval", that his calculation regarding a 2D-surface of a sphere proves, that the equivalence principle is violated. He defines the...

Greetings, I would like to ask something about the von Neumann measurement scheme in the context of Time~symmetric QM and weak measurements in the popular Aharonov, Bergmann, and Lebowitz (1955, ABL) paper and the Aharonov, Albert, and Vaidman (1988, AAV) paper. Particularly in the latter...

Hi All, We often read that the gravitational field acts by slowing down clocks. Is there any statement that, with the same simplicity, reports on the action of the gravitational field on lengths measured by observers which are close or far from Earth, for example? Best wishes, DaTario

Hi Pfs, I read that pairs of entangled particles were measured on earth along a same direction and that the distance between them was greater than 1000 kilometers. What is the définition of a "same direction" on earth? is Is it related to the direction of a very distant galaxy or somethig like...

I have watched videos on Bell's Theorem and quantum entanglement. What I don't quite get is: if a pair of particles are created and separated and then we measure one we already know the other particle has the opposite orientation. How do we know for sure that the first particle we measure does...

The pure energy coming from a collision and how is it measured or is it just "A Formula" and is any of that energy Dark Energy or even Dark Matter, the reason for the question is because the Dark Energy/Matter vs normal Energy/Matter seems to align with what is seen now after the Big Bang...

How is it possible to measure the second-order correlation function with a device that can only perform start and stop measurements, and for each measurement, it can only record 5 stops? I understand that experimentally it is necessary to measure the coincidences, the independent events in each...

I teach high school and am trying to put together a resource that teaches students how to measure lengths properly with a ruler or meter stick. They don't understand how many decimal places to include in their answer (i.e. they will often write 1.7 cm when it should be 1.70 cm), and they...

I have an encoder that measures the rotational angle of a shaft. The problem is that the other end of the shaft can move in X and Y (forward/backward and left/right) as well as rotate. Assuming I can get couplings to link the shaft to the encoder and the moving item, will the encoder always...

A.E. Allahverdyan, R. Balian, and T.M. Nieuwenhuizen, Teaching ideal quantum measurement, from dynamics to interpretation, Comptes Rendus Physique 25 (2024), 251--287. https://www.researchgate.net/publication/380862732

When you shake back and forth AC gaussmeter ,he significantly increase reading(magnetic field), because device is moved in Earth static magnetic field. Does his acceleration or velocity cause increase in reading and why he even increase reading if magnetic field from Earth is static and...

The Cavendish balance measures the gravitational constant G. To do so requires us to know the magnitude of the smaller and larger masses in the apparatus. However, mass is derived from the weight of an object, which is the gravitational force upon an object, which in turn requires the value of...

What are the independent and accurate ways of determining stellar mass apart from its gravitational effect?

Hi. I can calculate the expectation values in the Bell (or in this case, CHSH) inequality and show that they violate it for entangled particles. But I'm confused about how to calculate them for an actual sequence of measurements, which could look like this ("Paar" is for photon pair): How do...

I have done this problem three times now, and keep coming up with an answer that is a factor of 10 off from the answer in the solutions manual. The way I'm doing it is MUCH different than how they did it, so I can't use their method to see where I'm going wrong. I want to find out what I'm...

Feynman, in the third volume of his Lectures on Physics, chapter 1, presents bullets and waves in two different diagrams, Fig 1-1 and 1-2 respectively. https://www.feynmanlectures.caltech.edu/III_01.html It is obvious that bullets are counted individually, the detector registering each hit...

hi , I want to measure the transmission curve and wavelengths of colored mineral glass , which is the simplest way or which instrument can I use ? thanks

Distance and weight are two separate things so....the question cannot be answered?

I stumbled over a datasheet of an old pentode where it says, in the english translation: I thought, wow, I am not sure if I wouldn't have written Ug3=0V instead. I am a theoretician in physics but work more as an engineer and teacher. What happens inside of me seems to be the following: The...

Hello, I'm interested in how measurement, entanglement, bell test etc are handled in QFT. It seems most QFT texts are being quite light on details on the subject. There would be is a preparation step as the start followed by some interaction and a measurement at the end. Interaction is usually...

Hello! If I have a measurement of a (dimensionless) parameter, ##a##, say 998 +/- 3 and the theoretical prediction of that parameter (assuming known physics) is 1000 +/- 4. Let's say that I want to set limits on a new parameter (not included in the theoretical calculations), call it ##\alpha##...

I'm trying to understand how exactly we calculate the detection rate in this specific multiple Stern-Gerlach setup. As written on the image, an (unpolarized) atomic beam is sent through a three Stern-Gerlach apparatuses, and the detector supposedly clicks 25% of the time. When I try to...

My steps would be that I would first calculated ##a_1## and ##a_2##, determined by using that formula with partial derivatives its errors, and then I would made an arithmetic mean of ##a_1## and ##a_2##. I am not sure how to determine the final error, but I think I can use this formula ##\Delta...

using the Earths orbit, what is the maximum distance that can be measured using parallax error?

Bob lives on floor 500 in a 1000 meter high skyscraper. Bob has measured the time it has taken a star to orbit 1 round in the Milky Way relative to Earth. He started by measuring at the time when a single photon from the star was received exactly at the center of his telescope, and ended the...

I read an article about the earth's rotation slowing due to redistribution of mass (probably mostly water). The headline indicated that Earth's rotation could slow to a rate of 25 hours per day, which seems rather large. This follows a publication announcing, Researchers improve measurement of...

Hi Pfs Take a two level system up-down in its up level, There are other observables that commute with that. is it true that applying the Zeno's effect by fast repeated measure of that observable will also freeze the system on up? thanks.

Hello. I am seeking some advice or information regarding a measurement I made using a magnetic sensor. Essentially, to summarize, I measured the socket for a ceiling light using a magnetic sensor, taking the necessary safety precautions. In so doing, in the immediate proximity of the socket, I...

In the 2001 paper Attosecond Metrology, the authors presented the first attosecond pulse setup and explained the measurements. This paper cites another paper quite often to mention similarities in the setup, but emphasized that they chose different observables: and only the choice made by...

I am trying to compare the surface roughness of 3D printed specimens for a school project, but I am realizing I don't have access to any of the standard equipment that would be used to measure it. Are there alternative measurements I would be able to use that would yield similar results, using...

A couple of weeks ago we had an interesting thread where a tangent developed discussing whether real-valued measurements were possible. I would like to generalize that discussion a bit in this one and discuss all scientific purposes, not just measurements. 1) What is a measurement anyway? Is it...

I would like to consult with you about something. Mobile phone towers transmit at relatively high frequencies. From a health perspective, on the internet :) all measurement values are interpreted in microteslas. However, with the Wavecontrol probe (WPF8) I have, only the electric field (E) can...

Hi, I know in todays world we have more sophisticated equipment to measure the propagation delay of electronics equipment, but for my own curiosity i want to know how historically the propagation delay was measured for electronics device such as transistor.

Let's assume Dark Flow is real. If so can't we measure it based on 2 atomic clocks. Dark Flow occurs presumely in a southerly direction. One atomic clock must start at the time the earth's rotation begins to bring the first atomic clock in a slightly southerly direction, (due to the earth's 23.4...

A weak (one photon at a time) beam of laser light strikes a double slit. In case 1 the barrier forming the double slit is a mirror. In case 2 the barrier is flat black. An array of detectors surround the experiment and can detect the photon whether it goes through the slit or is reflected. In...

I've given the question as an image as some of the formatting was difficult for me in the small window given: My work is below. I got (a), but cannot get (b): (a) It was a theorem proved in the text that any measurement on one subsystem will always be fully determined by the reduced state...

For instance this Power Cube device. Is it capable of reporting EXACTLY how hard Francis Ngannou punched, or will it be biased towards mass or speed and overestimate one of the components? How "off" from the actual physics of reality do you expect such a tool to be? 5%? 10%? 20%?

Is it ok to gently squeeze the bulb just after crossing the systolic or diastolic threshold, just to make sure of the exact value?

In the lab, how accurately can we measure momentum? What is the max value of the uncertainty in position as the uncertainty in momentum approaches zero? Or vice versa. What experiments do these types of measurements?

[Mentor Note: Two similar thread starts merged] The questions are from MIT OCW. First of all, I cannot understand what is the meaning of the measurement outcome being 0. How can an eigenvalue be 0? I tried doing the problems guessing that by 0 they mean the posterior state will be |0>. The only...

What are the non-gravitational ways of determining mass of galaxies, and how accurate are they?