What is Measurement: Definition and 1000 Discussions

Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measurement are dependent on the context and discipline. In natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the International vocabulary of metrology published by the International Bureau of Weights and Measures. However, in other fields such as statistics as well as the social and behavioural sciences, measurements can have multiple levels, which would include nominal, ordinal, interval and ratio scales.Measurement is a cornerstone of trade, science, technology and quantitative research in many disciplines. Historically, many measurement systems existed for the varied fields of human existence to facilitate comparisons in these fields. Often these were achieved by local agreements between trading partners or collaborators. Since the 18th century, developments progressed towards unifying, widely accepted standards that resulted in the modern International System of Units (SI). This system reduces all physical measurements to a mathematical combination of seven base units. The science of measurement is pursued in the field of metrology.

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  1. shahbaznihal

    FRR Measurement in Digital Oscilloscope

    Hello, This is my first post in this domain and I am fairly novice in this subject, so please bear with me. I have a GDS-20174A Digital Oscilloscope. I am trying to measure the delay between two BNC cables using a Square Pulse of 2V with an offset of 1 V using the oscilloscope. I am using...
  2. A

    I Muon lifetime measurement experiment

    Hello everybody! I have a question regarding my physics laboratory at the university. I am performing the measure of muon lifetime. The setup is quite standard (coincidence measurement with plastic scintillators). My question is about the time resolution. I have tried to see if the time...
  3. P

    I Measurement with respect to the observable Y

    Hello, I would like to start with an assumption. Suppose a system is in the state: $$|\psi\rangle=\frac{1}{\sqrt{6}}|0\rangle+\sqrt{\frac{5}{6}}|1\rangle$$ The question is now: A measurement is made with respect to the observable Y. The expectation or average value is to calculate. My first...
  4. N

    I Confusion about the thermal interpretation's account of measurement

    I'm a mathematician with a longstanding interest in physics, and I've recently been enjoying reading and thinking about Arnold Neumaier's thermal interpretation, including some threads on this forum. There's something that's still confusing me, though, and I'm hoping someone here can clear it...
  5. MichPod

    A How momentum measurement is defined in Pilot Wave interpretation?

    Considering pilot wave interpretation, a singular particle measurements are fully defined (?) by knowing its wave function (a pilot wave) and the position of the "particle" (some hypotetical point particle riding on the wave). This should provide some sort of "realistic" explanation of how a...
  6. Benjamin_harsh

    Where does the ##Y_{C}## measurement go in this I section?

    calculate the moment of inertia of this I section about centriodal axis (##Y_{c}## = 108.4) Where does ##Y_{C}## measurement goes in this I section?
  7. QuasarBoy543298

    I Particle in free space - what happens to the wave function after measurement?

    If I'm trying to solve the problem of a particle in free space (H = P2/2m ). the eigenfunctions of the Hamiltonian cannot be normalized. now assume I have a legitimate wave function expressed in terms of the eigenfunction of H and I want to measure its energy. what will happen to the...
  8. mPlummers

    Relative error and measurement precision

    NOTE: this is a programming exercise (Python). I started adding to ##x_{true}## an error related to a (for example) 10% relative error, obtaining ##x_{measurement}##. Then i computed ##y_{measurement}##. To find the precision, i calculated ##(y_{true}-y_{measurement})/y_{measurement}##. If it is...
  9. J

    Understanding a simple statement regarding the measurement of temperature

    Summary: 1.In the context of calibrating a scale to correlate volume change with temperature, my book states: "Since all substances change dimensions with temperature, an absolute reference for expansion is not available." What do they mean by an absolute reference in this instance? My...
  10. A. Neumaier

    I Measurement results and two conflicting interpretations

    The following two examples illustrate the differences between the thermal interpretation and Born's statistical interpretation for the interpretation of measurement results. 1. Consider some piece of digital equipment with 3 digit display measuring some physical quantity ##X## using ##N##...
  11. L

    MHB Levels of Measurement, Basic OLS Regression Questions

    Hello soon to be saviors, 😊I have two really simple questions that I have already answered but the teacher wants more info. I am really stumped and I am not looking for the answers so much as an explanation on how to better answer the questions. I will copy and paste the problems and my answers...
  12. A

    A Does Antony Valentini's "sub-quantum measurement" really work?

    In https://arxiv.org/pdf/quant-ph/0203049.pdf, which is in the realm of Bohmian mechanics, Antony Valentini claims that by having a "non-equilibrium" particle with arbitrarily accurate "known" position, we can measure another particle's position with arbitrary precision, violating Heisenberg's...
  13. D

    MHB Appropriate graph to illustrate multiple differences in measurement?

    I have two groups (expert & novice) that were tested on walking with stilts and without. The results were: walking velocity (cm/s) cadence (steps/min) stride length (cm) What would be the appropriate graph to run with RStudio to account for the three different measurements? Thanks, Dants
  14. J

    B Trivial questions regarding parallax and measurement of distances.

    While trying to understand parallax and its use in measuring distances here, I had a few questions. (1) Parallax is defined as the apparent movement of an object with reference to another object in the background when one views it from different angles. As in the movement of a finger relative...
  15. shehanshashika

    Figuring Out the Reactive Energy Measurement Method with Field & Lab Tests

    The digital CT (current transformer) operated energy meters are tested in field using consumer's load conditions by means of a parallel test equipment. It was observed that the reactive energy measurement has high accuracy mismatches on harmonic polluted loads. Some literature indicates that...
  16. P

    Voltage measurement of a point charge

    If we have a point charge of significant value, would osciloscope measure voltage if we just point the electrodes in two diffrent point in space?
  17. entropy1

    I Does Quantum Mechanics Suggest a Conservation of Possibilities?

    Suppose we have a quantum object in superposition to some measurement basis, given by: ##\frac{\sqrt{2}}{\sqrt{3}}|a \rangle + \frac{1}{\sqrt{3}}|b \rangle##. (1) Suppose the measurement is made, and the system evolves, according to MWI, into ##\frac{\sqrt{2}}{\sqrt{3}}|a \rangle|W_a \rangle +...
  18. Abimbola1987

    Measurement of vacuum diode electron flow

    Dear Sirs, After my theoretical post on vacuum diode electron flow, I decided to try and measure it physically. I didn't have a vacuum tube, so I improvised with some tungsten wire, aluminum sheets and some screws and the result was usable. Obviously the tungsten wire fails after some time due...
  19. Peter Morgan

    A Schrödinger's cat: what's the state?

    A physicist prepares a box and tells us that in the box there is a cat that is in a superposition of being alive and being dead. How can we be sure whether they're telling the truth? Is the state a superposition or a mixture? If we open the box and measure only whether the cat is alive, using...
  20. S

    A Definition of bi-local measurement by Masanes et al.

    Dear experts, I'm currently working my way through the paper Masanes, Galley, Müller, https://arxiv.org/abs/1811.11060. On page 3, they define what they call a bi-local measurement: If we have two systems a and b and we define an outcome probability function for some measurement f on system a...
  21. J

    I Can anything be measured with a single measurement?

    If I want to measure my height, I need to find not only the location of the top of my head, but also the location of the bottom of my feet. The difference is my height. I make those measurements by placing the end of a tape measure against the floor, and then find where the top of my head is...
  22. Auto-Didact

    A Ballentine: Decoherence doesn't resolve the measurement problem

    This thread is a direct shoot-off from this post in the Insights thread Against "interpretation" - Comments. I am usually not a big fan of Ballentine, but I tend to fully agree with him on the following issue (taken from this paper, credits to @bhobba) Decoherence theory is a pragmatic...
  23. entropy2information

    B Doesn't the choice of measurement prove free will

    I was reading the free will theorem and it basically says that subatomic particles and observers have to have free will because there's nothing prior to measurement that predetermines the outcome. Here's more: The free will theorem states: Given the axioms, if the two experimenters in question...
  24. B

    A Measurement and the Conservation of Momentum

    If you prepare a particle with a “relatively precise” momentum by the act of filtering or measuring its momentum. It’s state will collapse into a momentum eigenstate and the measured momentum will be the corresponding eigenvalue. The position state will now be nearly uniformly spread out and...
  25. PGaccount

    I Understanding Bohr's Theory: Spacetime & Energy Momentum Relations Explained

    The spacetime and energy momentum relations can be written as t2 - x2 = s2 P+P- = m2 Niels Bohr says that "the spacetime or energy momentum relations must be applied at least twice, otherwise they are not defined". Does anyone know what he means by this?
  26. S

    I Compound double slit with measurement on only one

    This question relates to the double slit experiment where measurement affects whether an interference pattern is generated. If an experiment were performed where electrons were sent through a double slit with another double slit behind the first double slit, and the measurement device measured...
  27. G

    I Send the measurement device through a double slit

    Hi. Double slit experiments are being performed successfully with increasingly large molecules. Some physicists (e.g. Anton Zeilinger) believe it might work with viruses as well. Assuming it works with a system that qualifies as a measurement device (be it a virus or something else complex...
  28. D

    I Can I steer myself into one of the Many Worlds like this?

    Given an ideal "box" as used by Schrodinger; - have a quantum event occur inside it, e.g. sudden cat death with 50% probability. - have a machine in it that sends out a qubit, fully entangled with the box' internal state, at regular intervals. - the qubit is a polarised photon - outside, use a...
  29. A

    Time-varying electric field measurement using dipole

    Hello, I am trying to measure the time-varying electric field of a parallel plate capacitor using short dipole antenna, but my numbers are off by almost 100 times. I have a parallel plate capacitor, A=23cmx11cm, d=10cm. I apply 10sin(2pi*1KHz) and 10sin((2pi*1KHz)+180deg) to each plate. I am...
  30. K

    MHB Sound measurement percentage in tolerance

    I have a graph measuring 1/3 octave sounds checking if they fall into a range so they are within a defined tolerance. If for example, I have 20 specific 1/3 octave frequencies I am looking at, I can figure out a percentage of which of the 20 frequencies fall in tolerance fairly easily...
  31. R

    I If the wave function is complex and the measurement is real

    Would not any real measurement taken on a complex state logically require that the results of the measurement have less information than the state? Although I’m just beginning in QM, it appears to me unsurpring that a real measurement on the complex wave function seems to collapse the wave...
  32. bland

    I Accuracy of time dilation measurement *in principle*

    Sorry that's the best wording for a title I could come up with. Anyhoo my question is one that I have wondered about for a long time, and I am prompted to post now after seeing this article on the new atomic clock. Let's assume that we have clocks that can measure time to an arbitrarily...
  33. T

    A How much does peculiar velocity affect distance measurement?

    I'm a PhD student who's taken GR, so I have studied gravity and cosmology, and we have the underlying assumption of homogeneity and isotropy, but since this assumption comes from how we've calculated the distribution of galaxies in the visible universe I want to make sure I really understand it...
  34. C

    Is there an uncertainty in energy measurement in quantum mechanics?

    Let's say I have a system whose time evolution looks something like this: This equation tells me that if I measure energy on it, I will get either energy reading ## E_0 ## or energy reading ## E_1 ## , when I do that, the system will "collapse" into one of the energy eigenstates, ## \psi_0 ##...
  35. D

    MHB What is the total area of the doors and windows in the room?

    I am having trouble figuring out the answer to the following question, I am not sure how to get to my answer.Calculate the area of each wall, including any doors and windows (The room is rectangular in shape. The floor is 18 ft. 5 in long by 9 ft 6 in wide. All of the walls are 8 ft high. You...
  36. B

    Temperature Measurement: Are All Thermometers Created Equal?

    What is the difference in temperature with different thermometers for the same object? Thanks !
  37. A

    How do I use full-bridge strain gauge circuit to measure F?

    Hey all, I am using a Wheatstone bridge with 4 strain gauges as resistors. I have a formula for the output voltage (Vout). My questions is how do I make it so instead of voltage I measure force? Do I simply apply a set max. force (let's say 140N), see what voltage I get (Vout,max) and then use...
  38. MichPod

    I Why protective measurement is important to understand psi?

    Why protective measurement is important to understand whether the wave function is the ontic property of a single particle and not of the ensabmle of similarly prepared particles? I need some help with understanding the following topic (which is currently above my level so I may easily miss...
  39. mfb

    I Measurement of Earth's mass - with neutrinos

    At very high energies Earth absorbs a relevant fraction of neutrinos passing through it. Experiments receive more of these neutrinos from above than from below and the difference depends on the mass of Earth. So why not measure it? Neutrino tomography of Earth The uncertainty is very large, of...
  40. O

    I Measurement OF a Beamsplitter - Destroys Quantum Interference?

    In those experiments demonstrating quantum interference which rely on a beam splitter to create a superposition of a photon taking different paths, what would happen if one made a sufficient "measurement" of the momentum of the beamsplitter itself? Would or should it destroy the interference...
  41. T

    Regarding the measurement of horsepower

    I teach aerodynamics. One horsepower is 550 lbs moved one foot in one second. My question is this. Does that assume that the 550 lbs is being lifted vertically against gravity? As opposed to moving, say, a 550 lb chunk of concrete across a floor. And if so, does the gravity value of...
  42. S

    I Historical basis for: measurement <-> linear operator?

    What is the history of the concept that a measurement process is associated with a linear opeartor? Did it come from something in classical physics? Taking the expected value of a random variable is a linear operator - is that part of the story?
  43. DracoMalfoy

    Measurement and Graphing. Dependence of a Pendulum on length

    For the experiment, we were to determine the relationship between two quantities through linearization after collecting measurements. To verify that P~L^1/2. and determine proportionality constant, C. P=C√L/g= (Cg^-1/2)(L^1/2) Materials used were a timer, string(The pendulum on length), and a...
  44. Pushoam

    Momentum measurement of a particle in Quantum Mechanics

    Homework Statement What will momentum measurement of a particle whose wave - function is given by ## \psi = e^{i3x} + 2e^{ix} ## yield? Sketch the probability distribution of finding the particle between x = 0 to x = 2π. Homework Equations The Attempt at a Solution The eigenfunctions of...
  45. Nevada City Bob

    Bob from Nevada City, CA

    Hi. I'm a retired software engineer who has always been fascinated in science. I was a math major in college, before the time that computer science majors were a thing. My key areas of interest these days are particle physics and quantum mechanics. I'll be asking some questions that have...
  46. Alex Torres

    B Measure Quantum States w/o Observation: Is It Possible?

    When talking about measurement in QM it's completely normal to think right away about someone doing "something" to get or "observe" a definite quantum state... ...but how about the screen in a standard DS? ...there we get clumps if we measure a quantum state at the slits or fringes if not...
  47. entropy1

    I World selection in case of entanglement measurement

    Suppose we have a pair of spin entangled electrons, measured by resp. Alice and Bob. The basises of Alice and Bob make an angle of α=10°. If Alice and Bob wind up in a joint world where Alice measures ##|u\rangle##, then the probability that, in that world, Bob measures ##|d\rangle## is...
  48. G

    A Quantum measurement and entropy

    A quantum system goes from an uncertain to a certain state upon measurement.This indicates a decrease of entropy--is there a corresponding increase of entropy elsewhere(environment/observer)?Is there any work done on the system in the act of measurement?
  49. D

    B The Nature of Measurement and Interaction in Quantum Mechanics

    I am still confused about the difference between measurement and interaction. I mean when electrons are traveling from source to the screen through the slits, there are air molecules in their way. And even if the electron double slit experiment is carried out in total vacuum in a completely...
  50. Alex Torres

    I FTL communication via delayed choice measurement

    <Moderator's note: 2 threads merged as it is an identical topic.> Given Kim's version of DCQE, let's say Bob in on Earth looking at d0, Alice is on Mars holding the prism that deflects the idler coming from (a) to d3 or (b) to d4. After the experiment run ends Bob should get clump at d0 without...
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