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Image of an electron

An "image" is formed from lots of light rays leaving the same object. For instance, when your eye forms an image of a symbol on your computer screen, like this symbol, $$ \sum $$ what's ...
rob's user avatar
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Image of an electron

You can't see an electron with a microscope.
trula's user avatar
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Train example of special relativity

This is what you get for making a disordered SR problem in which the moving thing (the train) is stationary, and the stationary thing (the station) is moving. I always suggest we follow a protocol: ...
JEB's user avatar
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1 vote
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Train example of special relativity

If the lights on the train flash simultaneously in the frame of the train, then the light from each will arrive at Eric at the same time and he will raise his hand once. In that scenario in your ...
Marco Ocram's user avatar
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5 votes

GR contribution to time dilation when both clocks are falling freely

Option (2) is correct. The time dilation, both the "GR" and "SR" components, arises from applying the Schwarzschild spacetime interval to determine the proper time interval for one ...
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4 votes
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GR contribution to time dilation when both clocks are falling freely

Your statement (2) is correct. Gravitational time dilation is a function of gravitational potential, not of acceleration. The equivalence principle is true only locally, i.e. in the limit as the ...
Eric Smith's user avatar
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1 vote

In quantum mechanics, is there an actual difference between 'observation' and interaction?

A measurement is an interaction that records some information about the system being measured. The Elitzur Vaidman bomb tester (EVBT) fits into this way of thinking about measurement. In quantum ...
alanf's user avatar
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In quantum mechanics, is there an actual difference between 'observation' and interaction?

There are differences depending upon the interpretation of QM. The main difference being whether consciousness plays a role. However,in relational QM pioneered Rovelli in the mid 90s, there is no ...
Mozibur Ullah's user avatar
4 votes

Imagine a universe with only 2 objects:

If the electron is moving at a constant velocity, will the detector ever register a magnetic field? If a point charge (e.g., an electron) is moving at a constant velocity, the electromagnetic field ...
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Borde-Guth-Vilenkin (BGV) Theorem equation for the motion free falling observer

This can be seen from the variational principle $$ \delta \int\sqrt{-g_{\mu\nu}dx^\mu dx^\nu}=0 $$ and eq.(7) in the paper, i.e. $u_\mu u^\mu=-1$. From the Lagrange equations $$ \frac{d}{ds}\frac{\...
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Absolute rest in special relativity

No, your idea is incorrect. Time dilation is relative. If two objects are moving relative to each other, each object will be time dilated to the same extent relative to the other. If you perform your ...
Marco Ocram's user avatar
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Question regarding time dilation

In SR, if two people are moving relative to each other at constant velocity, each person will be equally time dilated in the frame of the other person. In those circumstances, the movements of the ...
Marco Ocram's user avatar
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Question regarding time dilation

Suppose you know that my clock currently says 3:00PM. Does that tell how anything about how fast it ticks? Answer: Of course not. No matter how fast or slow my clock runs, I can always set it to ...
WillO's user avatar
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-3 votes

Question regarding time dilation

Einstein himself answered this question in his paper here. What Einstein said pretty well contradicts with the other answers above. He says is that you cannot look at special relativity alone. You ...
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1 vote

Question regarding time dilation

Time dilation is indeed symmetric, since velocity is relative. But if a rocket ship turns around, it's definition of simultaneity changes, and it has to take that into account when calculating the ...
Eric Smith's user avatar
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Question regarding time dilation

This is basically the problem of the "twin paradox". It seems at first that there should be no difference between the observers on earth and those on the ship since there is symmetry between ...
Albertus Magnus's user avatar
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Question regarding time dilation

Suppose that there are several synchronized clocks in the Earth's frame along the ship's path. Each time that the ship passes by one of that clocks, the difference with respect to the clock inside the ...
Claudio Saspinski's user avatar

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