# Questions tagged [measurements]

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### How to measure radius of the Earth in cloudy weather?

The two methods I know to measure Earth's radius — the method of Eratosthenes and the stopwatch method — require the Sun visible during measurement. But in my location such weather is quite rare: it's ...
2answers
95 views

### Is the choice of the automorphism of complex numbers relevant for Quantum Computing?

In Yale's paper, automorphisms on complex numbers $\mathcal{C}$ are shown to be wild, allegedly with cardinality $2^{\mathfrak{C}^{\mathfrak{C}}}$. There are two well-known ("trivial") automorphisms: ...
2answers
77 views

### Can observation affect the probability distribution of an event to occur?

It's already well know that in quantum mechanics the act of observation affects the outcome of an experiment making the wave function to collapse.Now in order to clear up my confusion about this topic ...
1answer
83 views

### Why do we call (the measurements we take in physics) approximations?

If a caliper takes the measurement to the 2 decimal points then is it not a correct measure to the 2 decimal points or is it still an approximation?
1answer
17 views

### How to Level Measure a fluid from under/inside/below the liquid? | Level Measurement Instruments

Level Measurement in liquids. I'm aware of all direct & indirect methods of measurement in Level Measurement. However, what are some methods that enable us to measure fluids from inside, or below ...
2answers
114 views

0answers
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### How does diameter of manometer affect the sensitivity of the manometer?

I have a physics question on How the sensitivity of the manometer will change if a narrower tube is used for the manometer. Logically speaking, it seems normal for the sensitivity of the manometer ...
1answer
479 views

### Standard deviation as uncertainty of a single measurement

If we have made the following several measurements of the quantity x that follow a normal distribution: 86, 85, 84, 89, 85, 89, 87, 85, 82, 85 The mean is 85.7 and the standard deviation(std) is ...
4answers
433 views

### How many significant figures should one give in stating an experimental uncertainty? [duplicate]

How many significant figures should one give in stating a experimental uncertainty? For this purpose I found three rules: Experimental uncertainties should be always stated to 1 significant figure. ...
2answers
61 views

### How should a hydrometer be read?

Probably due to surface tension the surface tends to curve near the hydrometer forming a meniscus. The question is whether it's correct to read the hydrometer at top of the meniscus or at the liquid ...
1answer
27 views

1answer
100 views

### How to construct a 12-micron thin layer of powder+epoxy?

Okay, this is more of an engineering tactic question perhaps, but any insight into any possible process will be very, very appreciated. So I'm mixing a powder with epoxy, making a pasty, fluid semi-...
1answer
208 views

### True white collimated light / nobody uses this?

Based on a previous question is this the difraction limit of our microscope? , I got the idea to use a true white parallel back light to illuminate an object for measurements (target accuracy is 1 ...
1answer
418 views

### How to estimate the frequency of the sample rate?

I'm studying for my class of physics laboratory and I need help with something: Let's say I need to deduce the constant of elasticity of a spring and I will do it using a dual-range force sensor, ...
4answers
667 views

### Definition of mass in Newtonian mechanics

I believe that for any physical quantity, to know what significance it has in any situation or that it's different from other quantities, we have to first start by assigning a value to it, or some ...
1answer
56 views

### Quantum Uncertainty in Measurement of Fundamental Quantities

Fundamental constants (such as electron rest mass or charge, which are stated with high precision and, I think, are believed to be certain), I believe are verified by measurements that involve some ...
2answers
123 views

### What happens if you make an observation of the spins of two entangled, far apart electrons at exactly the same time? [closed]

If we consider the spins of two, far apart, entangled electrons, what will happen if we make a measurement on both spins at exactly the same time (let's assume time is not discrete)? I see it as a ...
1answer
129 views

### understanding resolving power in QM

Consider the definition of resolving power of two states in quantum mechanics as being the absolute value of the difference between the probabilities of two states following the measurement averaged ...
5answers
305 views

### A non-metaphysical interpretation of measurement in quantum mechanics

In quantum mechanics, measurement plays a fundamental role and to me, its role is usually described in a rather odd way. The Copenhagen interpretation states thus When that device makes a ...
2answers
44 views

### Optimization problem and measurements

This is more of math problem, but my doubt is about the measurement units of the final answer so I figured I'd post it here. Problem: A lighthouse is located on a small island 3 km away from a ...
1answer
202 views

### If two commuting observables do not share eigenspaces, can't one measurement affect the other due to an extra wave function collapse?

When we learn quantum mechanics, we are told that the only way to extract information from a system is to conduct measurements. We are told that if two observables commute then performing one ...
1answer
80 views

### Is EMF/EMR additive (two devices produce twice the EMR)?

I'm interested in electromagnetic radiation radiated from home appliances. Wanted to know if I have two phones (for arguments sake assume that they are perfectly identical) and they both are in sync ...
0answers
56 views

### Measurement phrase: “determined to 1 cm precisely”, “centimeter-precision” [closed]

I'm not perfectly sure about the stated phrase (or similar ones since I had to translate it). Does it mean +-1 cm, or +-0.5 cm? I guess many people use it in the first way but only the latter will ...
2answers
3k views

### What are the problems with using spirit level experiment to prove the flat-earth theory?

Full disclosure: I do not believe the Earth is flat. However, a guy recently posted a YouTube video that purports to prove that the Earth is flat due to there having been no changes in the position ...
3answers
4k views

### How is temperature defined, and measured?

In questions like this one, temperatures of millions of degrees (Celsius, Kelvin, it doesn't really matter at that point) are mentioned. But, what does it mean exactly? What is measured, and how? As ...
1answer
9k views

### Dimensions of electric charge

I was studying dimensional analysis, which is a technique used in conversion of units, checking the homogeneity of equations and also sometimes deriving unknown equations, if we can guess the factors ...
2answers
96 views

### How do I measure loudness level of a device in environment?

I want to measure the individual loudness level of a device in environment. Fistly, I measure loudness level when the device is ON (95.5dB) Then I measure loudness level when the device is OFF (48....