The result of sampling the property of a system

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1answer
12 views

Rules of thumb for estimating visual angles

Tonight I've looking at an optical phenomenon presenting as rather large ring around the moon. I'm thinking it's probably a 22 degree halo, but it seems kind of big... maybe 46. Anyway, I realised I ...
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0answers
17 views

Can a Bell state measurement be described in the Von Neumann measurement scheme?

I have been reading and studying this article recently about non-local weak measurements and quantum erasure. Usually the weak measurement formalism is described using the Von Neumann scheme for ...
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1answer
26 views

Relative uncertainty blows up near offset

I'm looking to calculate the relative uncertainty for a magnetic field measurement. My device takes an initial reading but then performs operations on this using its calibration parameters. My ...
-1
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8answers
248 views

How to measure the diameter of a thin wire? [closed]

I'm working on a project and I need to measure the diameter of a thin bare copper wire but I don't know how. Can you please tell me a way to measure the diameter of a wire? Can you give me a way, ...
1
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1answer
37 views

Information and entaglement via determination of the first's system state with interaction

Could we have entangled systems (microscopical or macroscopical) and construct a way of altering the state of one of the two entangled parts (let's say by Alice) via interaction and thus making the ...
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0answers
21 views

Measurement of drag (?) tension between two surfaces

I want to know if there are (reasonably inexpensive) devices to measure the tension between two surfaces. Beware of my terminology: the first help I need is to actually formulate my question ...
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0answers
18 views

How accurate is the Callendar-Van Dusen equation?

... over 0 degC to 100 degC? The equation itself can be found here I can do a very accurate one point calibration of a 1/10 DIN PT100 sensor at 0 degC. If I use the equation to correct for non-linear ...
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0answers
26 views

How do scientists measure miniscule constants like the mass and charge and speed of an electron?

What can measure the extremely tiny mass of an electron? Is it through indirect means? The same goes for charge. The pull of a single electron must be infinitely small. And if one is to attempt to ...
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2answers
32 views

Stern-Gerlach apparatus, measurement problem? [closed]

Consider the diagram below: It is 3 Stern-Gerlach apparatus along with some 'lenses' (illustrated here by lines). Question What would the output at A and B be? Additional information The ...
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1answer
34 views

Vernier Caliper the principle behind it [closed]

I know how to use a caliper but on what principle does devices like caliper and screw gauge works. Can someone derive its formulae. I am more or less interested in its mathematical aspect.
2
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1answer
87 views

Transition from one state to another in Quantum Mechanics

I have seen other questions in this website that ask the same question, but no answer was clear enough for me. So, when we measure an electron's position we know that the wavefunction $\psi$ peaks ...
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1answer
27 views

How does one measure the state probabilities of a 2 level Hydrogen atom qubit?

I have been struggling with trying to understand how one could measure the probabilities of a superimposed Hydrogen atom's two energy states. Say the atom is in a superimposed state: Psi = a|0> + ...
2
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0answers
29 views

Limits on the information obtained through optical measurements

Consider a Gedankenexperiment shown in the figure below. There are two lasers $S1$ and $S2$ with exactly the same specifications on paper. In practice, they are of course somewhat different but ...
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1answer
79 views

How can I measure a length of over 4 feet to an accuracy of 1/100th of an inch?

How can I measure a length of over 4 feet to an accuracy of 1/100th of an inch ? I want to make several metal standard bars of a particular lengths, some of which are over 4 feet and I want the ...
6
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5answers
763 views

Number of significant figures

I am looking for an intuitive answer that will explain me why there are only two significant figures in say the number 1500. Also definition from wikipedia: The significant figures of a number ...
2
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4answers
57 views

Is there a maximum accuracy for positions in the universe?

I was thinking how, since an object in our universe can move from one position to another, it must have passed through all the positions between those two positions. (I am thinking it moved it a ...
0
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0answers
33 views

What is source of Infrared Radiation from some solid object? [duplicate]

I use a Fluke infrared temperature measurement meter for various applications. I have not thought too much about the source of that infrared radiation until recently. Assume some solid with maybe a ...
4
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2answers
53 views

How to measure temperature of a laser cooled sample at picoKelvin temperatures?

I'm reading about laser cooling.. my question is: how can the temperature of the sample be measured? (using laser cooling we can reach $10^{-12}K...)$
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1answer
72 views

Question about the double slit experiment

If we measure a particle before it passes through the slit, would we see the particle or the interference pattern on the screen after the slits?
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1answer
52 views

Compatible Observables and Measurement

Suppose $A$ and $B$ are compatible observables (i.e. $[A,B] = 0$). We take the eigenkets of $A$ to be $|a_1 \rangle \ldots |a_N \rangle$. Further, we suppose that the first $k$ eignekets of $A$ are ...
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3answers
76 views

How do we measure mass?

How do you measure mass? Weight is easy using a scale, but we can't measure mass that way, because then mass would be different on every planet. I know there was a Veritasium video (here) on defining ...
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0answers
26 views

Thermistor calibration - estimation of number of reference temperature points needed

A thermistor changes resistance with the temperature in a non-linear way and follows the exponential Arrhenius equation. Two reference points, ice slush water and boiling water, are used for ...
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0answers
23 views

Measurement of two qubits in a tensor product space

I understand that if we have two qubits, say $\Psi \in \mathcal{H}_1 \bigotimes \mathcal{H}_2$ where Alice has the first qubit, and she makes a measurement and ends up with the state $\phi \in ...
2
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1answer
36 views

How to measure the fineness of a textile fibre by diameter and fibre length?

I measured the diameter (um) and the fibre length (cm) of different (loose) textile fibres and have an average. Now there must be a relation between these two factors that gives an idea of the ...
2
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1answer
147 views

Problem on Einstein - de Haas experiment

I am a Physics student (4th year) and I'm trying to study the Einstein - de Haas effect in laboratory. That is what I got: a suspended Iron cylinder with about 5 cm height and a radius of 0.8 cm is ...
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0answers
57 views

measuring distances

We measure distances using half of the time of flight of light, 'a la Einstein'. What is the geometrical shape of the surface that is the locus of the points that are at a definite distance of an ...
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1answer
99 views

Do subatomic particles have finite size?

We know atoms are mostly "made" out of empty space, so the nucleus and all the subatomic particle are very small in compared to the magnitude of the atoms. We also know that atoms are incredibly ...
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0answers
19 views

How does one measure the power factor?

How does one measure the power factor? $$\text{power factor}\equiv\frac{\text{power}}{|V||I|}=\frac{R}{\sqrt{R^2+(1/\omega^2C^2)}}$$ for an RC circuit driven with $V(t)=V_0\cos{(\omega t)}$.
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2answers
177 views

Good way to compute the force of a hammer blow?

What is a good and easy way to compute and/or measure the force of a hammer blow, not using any fancy or specialized equipment? If the hammer is swung by hand through an arc, it is not obvious to me ...
4
votes
2answers
674 views

Do the copper connectors we used in measuring the resistance of a wire contribute to the said measurement?

We measured the resistance of a wire by setting the multimeter to ohmmeter mode and connected the ends of the ohmmeter to the ends of the wire; and we also calculated the theoretical value using a ...
0
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1answer
103 views

What is the difference between zero background radiation and field background radiation in Nuclear Physics measurements?

Can someone please explain the difference between these two terms (Zero Background Radiation and Field Background Radiation) used in radiometric prospecting measurements?
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5answers
133 views

The nature of measurement

Does the measurement of the particle change it's physical state? Or does it only seem to do that? Ex. if a particle was measured before the slits, would we see an interference pattern, or a particle ...
6
votes
1answer
359 views

How do bathroom scales measure body fat percent?

My bathroom scale has 2 metal strips each for a foot and the producer claims that it can measure body fat percent. There is a warning in the manual, that if I have heart problems (I guess pacemaker), ...
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0answers
37 views

What technologies are available to measure distance? [closed]

I'm a programmer, I really lack of physics knowledge, I'm trying to make some basic design for a distance measuring simple system, for a social project I'd take as hobby. Basically I would have many ...
21
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4answers
3k views

If the LHC-calculated mass of the Higgs is wrong, how long will it take to determine this with confidence? [closed]

After I watched "Particle Fever"--the movie about Large Hadron Collider (LHC) and the successful identification of the Higgs boson--I became a bit concerned with that team's handling of various ...
0
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1answer
72 views

Distinguishing between prepared and unprepared states Stern-Gerlach experiment

$ \newcommand{\bra}[1]{\left\langle #1 \right|} \newcommand{\ket}[1]{\left| #1 \right\rangle} \newcommand{\braket}[2]{\left\langle #1 \middle| #2 \right\rangle}$I have a problem and am confused as to ...
2
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0answers
118 views

Molecular structure correction factor in Mass Flow Controller

This question concerns device called Mass Flow Controller (or Mass Flow Meter). For a video explaining the principle: see https://www.youtube.com/watch?v=G62ma2IFh9o These devices are factory ...
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0answers
54 views

Justifying the use of real numbers for measuring length

I am not sure if this is the most appropriate place to post this but here goes nothing: Assume we were trying to come up with system of numbers $S$ to model our intuition of length. We want $S$ to ...
0
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1answer
49 views

Light speed measured by observing Jupiter moons [duplicate]

The famous discovery that the light has speed measures the times of the immersion and emergence of Io, one of Jupiter's moons. However, I still can't comprehend this. Even when the Earth is further ...
0
votes
1answer
42 views

How much time between measurements do you have in order to make the same measurement on a particle?

As I understand it, you can make a measurement on a particle and if you quickly carry out a second measurement you will get the same outcome as the prior measurement. If this is the case, how much ...
7
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5answers
949 views

Proving and demonstrating vacuum in container without breaking it

Let there be a hollow container made of glass or some other transparent material, roughly the size and shape of an apple. Let the walls be of sufficient thickness for the container to be safely ...
0
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2answers
81 views

How to calculate the error in measurments of derived quantities knowing the error in basic quantities?

I wonder how to calculate error of a derived quantity $z$ knowing the error of all quantities that $z$ depends on say $x$ and $y$. For example: Suppose I want to calculate the speed of a body ...
0
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0answers
31 views

What is the limit of directly detecting a resonance?

Some resonances are extremely short-lived. With a lifetime of $10^{-23}$ seconds, they would travel just about the size of the proton ($10^{-15}$ m) even if they traveled at the speed of ...
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0answers
72 views

Query about the proof why non-orthogonal states cannot be reliably distinguished

I have a query regarding the proof given in the book by Nielsen and Chuang on why two non-orthogonal states cannot be perfectly distinguished. The proof is given on page 87 of the 10th edition; here ...
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1answer
68 views

What are the methods of experimentally measuring the observables in quantum mechanics?

Perhaps due to the limited number of textbooks on quantum mechanics I have consulted, I have seen presented the fundamental principles related to observables, but have never seen a somewhat systematic ...
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4answers
223 views

How to measure the size of a laser dot?

I'm not a physicist, that's why I'm asking you if there is maybe an easy way (e.g. a mathematical law) to measure the size of a laser dot, or its diameter. The setup It contains a laser, a high ...
1
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1answer
46 views

How is the curvature of space measured on earth scale?

How do we measure the curvature of space due to earths gravity since we can't dig a hole through the centre of the earth and measure the actual diameter of earth which is slightly different (1.8cm) ...
4
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3answers
91 views

Can liquid contain information?

Is there any principle in physics that would allow liquid to contain some kind of information - could we, for example, in theory, use a glass of water to save information? For example digital photo ...
2
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2answers
73 views

How does a supersonic flight speedometer work? [closed]

I'm sure today they can use GPS and radar, but I was pondering the queation when I saw a film clip of a vintage analog dial labeled in mach number. I'm supposing that the usual way of measuring the ...
4
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2answers
73 views

Examples of (classical) measurements that are not independent?

What are some simple examples of measurements that are not statistically independent, i.e. with nonzero covariance? I'm looking for real examples that might reasonably come up in an undergraduate ...