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3

Consider a series of $i = 1, 2, ..., k$ measurements each with value $x_i$ and standard deviation $\sigma_i$. The best estimate for the overall mean is $ m_{best} = {\sum_{i = 1}^{k} x_i/\sigma_i^2 \over \sum_{i = 1}^{k} {1 \over \sigma_i^2}}$ and the best estimate for the standard deviation of the mean is $S_{best} = ({\sum_{i = 1}^{k} {1 \over \sigma_i^2}})...


0

All the answers/statements/videos are correct, just subtle differences in the experimental setup or in what in particular is being asked can lead to the misunderstanding/confusion. What Don Lincoln says is true, the patterns are being formed in his illustrated setup. Because he has 2 detectors off he is getting 2 patterns which happen to be complementary (...


2

If you have a scale measuring something like a mass to $1g$ you would have two measurements $1 \pm 1 \textrm{g}$ or $u=100\%$ and $100 \pm 1\textrm{g}$ or $u=1\%$. I doubt if you would give your scale a uncertainty of $50.5\%$. So I think it is not a good idea to take the mean value of errors in %.


0

as a metrologist, I wouldn't do that. Not because is not right, but because you could be undestimating your instrument's uncertainty. Usually what we metrologists do is take the greatest uncertainty, for the maximum entropy principle, because there's nothing more wrong than underestimating your unc


1

As far as I know, you only know the location an electron is when it interacts with something else. If you know where the other thing was, then you know where the electron was. The other thing might be the the element in a charge coupled device, an ionize gas molecule in a cathode ray tube, a droplet in a cloud chamber, or an ion on a photographic plate.


6

The question is, a $10^{-12}\rm\,N$ force applied to what. A force of $10^{-12}\rm\,N$ applied to a hydrogen atom, with mass $10^{-27}\rm\,kg$, would produce an acceleration $F/m = 10^{+15}\rm\,m/s^2$. A torsion pendulum is absolutely a way to allow very feeble forces to cause observable, macroscopic motion. My favorite underrated classic paper is Beth’s ...


0

You are aware of this issue of the conventionality of simultaneity or the definitions there in of what the actual one-way speed of light is. That we can define different values for it, making it anisotropic, but in a manner that gives rise to all the same observations that the Special Theory of Relativity ends up covering. The issue is much more deeper than ...


-1

According to Derek Muller from Veritasium, no: https://www.youtube.com/watch?v=pTn6Ewhb27k&ab_channel=Veritasium At this point in time, we are measuring the 'average' speed of the roundtrip of light. This is due to the problem of needing two points in space to measure speed: Speed = Distance/Time So you would need to send off a beam of light from Point A ...


0

I would say no. One of the most fascinating things in physics is time dilation. The speed of light is always the same but the speed of time varies. Not only may A and B be in different time frames as illustrated by others but also at different rates of time change. One way to visualize this is here on earth. It is scientifically theorized that the center of ...


5

In practice, yes. How much the time coordinate in a "reasonable" anisotropic coordinate system ("reasonable" meaning things like "things don't arrive before they leave") changes over a certain distance, compared to an isotropic coordinate system, can't be more than the spatial separation divided by c. In other words, suppose ...


17

Can we measure the one-way speed of anything at all? No, there is nothing unique to light in that respect. To measure a one-way speed of anything requires that you allow it to travel over a known distance with a start and stop time measured at the beginning and end of the known distance. Doing so requires that the start and stop clocks must be synchronized. ...


0

Measure the length of a finite segment of train track. Start your chronometer when you see the train enter the segment, stop it when it left the segment. If the train was travelling at constant speed you can determine it by calculating length/time. The reason why this does not work with the one-way speed of light is because light is the thing that you want ...


0

You are missing a vital piece of information, a datum which defines an angular separation. Suppose that I wanted to find the angular width of the Moon. I would set the telescope cross wire on the left side and then measure the angle through which the telescope has to be rotated to have the cross wires set on the right side of the Moon. The measured angle is ...


11

Here is a method that you could try. For an object that can be modelled as two pieces of mass $m_1$ and $m_2$, with a COM of each in an unknown position due to a possible variable density, in principle the values could be found like this. The blue numbers and $F_1$ are known, (numbers made up as an example), but the red numbers are unknown. Below $g$ and $\...


19

Use a balance to get the mass of the whole steel object. Then, fill a 100 ml graduate cylinder exactly to the 50 ml mark. Place the steel in the graduate cylinder, obtain the new reading, and subtract 50 ml from that reading to obtain the volume of the steel part. From that information, calculate the density of the steel as $\rho = \frac{m}{V}$. Next, tie ...


0

theoretically speaking least count decreases on increasing the number of divisions on the circular scale. Hence, accuracy would increase. Practically it may not be possible to take the reading precisely due to low resolution of human eye.


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The method that you have used to account for zero error in screw gauge makes no sense for screw gauge zero error. When the reading on the circular scale across the linear scale is more than zero (or positive), the instrument has a positive zero error as shown in case 1. When the reading of the circular scale across the linear scale is less than zero (or ...


0

The dew point temperature of an air parcel is the temperature at which the partial pressure of water vapor in the parcel is equal to the equilibrium vapor pressure of liquid water. The frost point temperature is the temperature which the partial pressure of water vapor in the parcel is equal to the equilibrium vapor pressure of ice. Above 0 C, the ...


0

I find that quantum lingo always tries to be so general that it sometimes makes the simple things seem complicated. In the case of a the experiment that you're referencing, the "pointer state" is the position of the photon when it hits the detector. Even more plainly, since we're dealing with a laser (ensemble of photons), the pointer is the ...


1

To help answering your question perhaps it's in order to remember ourselves why people use vacuum expectation values in the first place. Mathematically, the vacuum state is just another pure state. You could think of it as a basis element of $\mathcal{H}$ for a suitable basis, like the computational basis. It also has the property that when acting with its ...


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