The Stack Overflow podcast is back! Listen to an interview with our new CEO.

# Questions tagged [measurements]

The tag has no usage guidance.

833 questions
Filter by
Sorted by
Tagged with
65 views

### When did scientists first experimentally measure wavelengths of EM radiation? How?

When did someone first discover that short wavelength light has higher energy than long? And can gamma ray wavelengths be measured, even today?
12 views

### how to measure distance trough foil wrapping

I would like to measure the distance of wooden board through a plastic foil. The target accuracy is less than a mm. I thought about using triangulating a laser beam via a CCD array. I tested this with ...
23 views

### Error estimation with missed data

When I need to find an error in the value of some real physical quantity and I can have as many number of measurements as needed, then it is clear. For example, I have a metal rod 10 cm length and 1 ...
723 views

### Propagation of uncertainties

I have five values for the volume of sodium hydroxide needed to neutralise a fixed quantity of hydrochloric acid, each trial with an uncertainty of 0.05 mL. If I take the average of these five values, ...
44 views

### What can be measured in quantum mechanics and how?

This is a question about bridging reality to theory. In learning QM theory, we learn a bunch of stuff about observables, like their operators, that two quantities can be measured at once if their ...
26 views

### Significant figures in complex calculations

In my physics book it is written that ' In any involved or complex multi-step calculation, you should retain, in intermediate steps, one digit more than the significant figures and round off to proper ...
72 views

### 2019 Higgs Boson Mass?

Wiki, based on the 2018 Particle Data Group, gives the Higgs boson mass as $125.18 \pm 0.16$ GeV$/c^2$. OK. However, 2017 ATLAS gives a combined value of $124.98 \pm 0.28$ GeV$/c^2$. So what is ...
1k views

### How is the speed of nucleons in the nucleus measured?

This article claims that "nucleons in a dense nucleus exceed 25 percent of the speed of light". How do you measure or infer the speed of nucleons in the nucleus? Note added later: I'm looking here ...
15 views

### Is it possible to measure the amplitude of a magnetic field independent of the orientation?

The strength of a magnetic field can be measured as strength in a specific direction. We can calculate the strength of a magnetic field along the field lines from measuring the strength in x,y,z ...
28 views

### Light Polarizer for Photons

This is maybe a noob question. I read that if unpolarized light is passed through a polarizer that only allows vertical polarization, then if this light is passed through a diagonal polarizer, only ...
21 views

### Does a maximum thermometer assume a room temperature?

Consider a liquid-in-gas maximum thermometer. That is usually conventional thermometer designed for measuring body temperature. Wikipedia says: One special kind of mercury-in-glass thermometer, ...
136 views

### Why are speeds of different EM waves in vacuum not EXACTLY equal?

It is said in my textbook (reference below) that the different waves of the Electromagnetic Spectrum have velocities almost equal to each other. (Variations are within a few m/s according to my ...
84 views

### How to know that scientific instruments work?

While reading Zimring's book, What Science Is and How It Really Works, I came across some words on being skeptical about scientific instruments on p.183-184: "The extent to which such instruments ...
17 views

### Uncertainty and error in a measurement

I do not find a clear and simple explanation of the difference between uncertainty and error of a measurement. Basically, in a measurement, uncertainty is defined as the standard deviation of the ...
113 views

### The problem of measurement in general relativity

I am looking for a good selection of articles and books on the topic of measurements in general relativity. The only one I'm really aware of is Reichenbach's "The Philosophy of Space and Time", which ...
32 views

### Significant figures and precision

Which of these two measurements is more precise, 5.1 cm or 0.002 ? As per concept of significant figures 5.1 cm is more precise because it has two signicant figures while the other oone has just one
42 views

### Are interference patterns the basis for all other measurements of light frequencies and wavelengths?

The wavelength or frequency of monochromatic electromagnetic radiation is determined indirectly by calculations on the interference or diffraction pattern. These patterns are generated by gratings, ...
57 views

### What does “An experiment performed with certainty has results with uncertainty.” mean? [closed]

A physics book says: An experiment performed with certainty has results with uncertainty. What does this mean?
27 views

### Principle of a pyrometer

How does a pyrometer work? Especially how do I ensure that the temperature of a single spot is measured (where the laser points at)? Here is a scheme of the structure but I guess it's not really ...
182 views

### Decoherence Free Subspaces and how they stay this way, using the Zeno Effect

I am currently reading papers discussing the Zeno Effect, which discuss how measuring a system at high frequencies can almost freeze the state of a system, or keep the system in a specific subspace of ...
45 views

### Use of significant figures in lab report calculations

I am currently doing a lab report that involves multi-step calculations. The values σ(mean, visual) and σ(mean, auditory) are calculated to be 0.004051s and 0.004917s. Since the number of trials (27 ...
25 views

### Why does a photomultiplier tube (PMT) traditionally present better signal-to-noise ratio (SNR) than an avalanche photodiode (APD)?

Empirically, a photomultiplier tube (PMT) is said to present better signal-to-noise ratio (SNR) than an avalanche photodiode (APD). Some materials say that it is attributed to the higher gain and ...
152 views

### Difference between unpolarized beam and half H+V polarized beam

Let's say that we have got two light beams. Beam A is not polarized at all. Beam B is composed of half H polarized photons + half V polarized photons. Is there any way to measure those two beams in ...
12 views

### Methods of Subnanometer Distance Measurement

How can one measure distances down to the ~0.01nm resolution using standard equipment such as LEDs, lasers, photodiodes, interferometers etc...? A pulsed diode could be used as a measurement device ...
22 views

### Is Bourdon tube affected by the cross sectional shape of the tube?

I've been searching for the working of pressure measuring tools , and i know that what makes the bourdon tube straighten is the distribution of the pressure on its walls .so my question is , in ...
315 views

### How does one compute the state of a quantum system following imperfect measurement?

Suppose I have a quantum system $S$ ("system") with Hamiltonian $H_S$ and initial density matrix $\rho_S(0)$. I allow $S$ to interact with another system $P$ ("probe"), which has Hamiltonian $H_P$ and ...
36 views

### Measuring acceleration due to gravity in the lab

I am measuring the acceleration due to gravity in the lab with an electromagnet apparatus. My textbook says to take the average time for a number of falls (keeping the height constant of course). ...
22 views

### How to measure the microscopic surface area of a textile?

How to measure the microscopic surface area of something like a piece of cloth? By microscopic, I mean on the level of fiber surface, not the area that would be measured by using a ruler on the piece....
14 views

### Transformation to get rid of distribution multiplets

Are there any well-known distribution transformations that account for doublets, triplets, higher multiplets due to time series independent peaks occasionally being too close to resolve? I feel like ...
55 views

### How to estimate the mass of an incoming asteroid?

A second galactic visitor has just been observed: see this link. For a mass which is small enough to have no noticable effect on other masses, is there any other way to infer the mass? Its own motion ...
47 views

### Changes to Planck constant historically [closed]

I looked all over to get the various accepted value of the Planck constant since 1900. But there is never any record about the history of this mysterious number.
36 views

### How to build a particle detector, given a desired probability of detection [closed]

Suppose that the average flux of cosmic rays at sea level on an horizontal surface is $$\varphi = 1\, {\text{cm}}^{-2}\,{\text{min}}^{-1}$$ and that we can take this value without error. What should ...
143 views

### How many worlds are there during branching in the many worlds interpretation?

Background and Question "Measurements are modelled as interactions between subsystems of the universe and manifest themselves as a branching of the universal state." - Wikipedia What is the ...
36 views

### How did people estimate the speed of light before modern technology? [duplicate]

I just read a wikipedia page on the speed of light. Apparently people have made pretty accurate estimates for almost 200 years. How did they do this? How did they measure any fundamental constant ...
42 views

### Does the length of wire affect?

I find the voltage of electric wire in between point 1 and point 2. I want to know if I use the differrent wire,long one and short one,the voltage will be equal or not?
136 views

### Probability of Obtaining a Certain Value (normal distribution)

In my textbook it says that the probability of obtaining a value (which its Gauss distribution is known) is simply $$\frac{1}{\sqrt{2\pi }} \cdot e^{\frac{(x_{1}-X)^{2}}{2\sigma ^{2}}} \text{d}x$$ ...
2k views

### Total and static pressure: which one is measured?

Which pressure is measure using measuring device in a pipe flow. My first intuition that it is the static pressure. This is confirmed by this Wikipedia article (link) The concepts of total ...
168 views

### Why nature rejects 100% accuracy in experiments? [closed]

I have never heard about any experiment performed which is 100% accurate (Sorry,if there is any).By the term accurate I mean accurate measurements involved in the experiment.Is it every time that an ...
56 views

### Strange anomaly in the calculation of the cosmological constant

I was trying to calculate the cosmological constant with two different methods proposed on the internet, that are apparently equivalent but they give different results and different dimensional ...
38 views

### Measurement of Changes in the Weight of a Heavy Object

I am searching for an elegant way to measure small changes in the weight of a heavy object (a potted tree) over the period of one year. However, I do not need to know the exact weight of the heavy ...
54 views