Questions tagged [length]
The length tag has no usage guidance.
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Why does the line element expression contain only second order differential terms? [duplicate]
The general expression of the line element $ds^2$ is $$ds^2 = g_{ij}dX^{i}dX^{j},$$ where $g_{ij}$ is an element of the metric tensor.
Is there a rigorous proof of why there are no terms in the ...
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Are comoving distances time-independent?
A comoving reference frame expands along with the universe, factoring out the effect of the Hubble expansion. Suppose a galaxy has a redshift $z = 1$ and its comoving distance DM is $11 \,\mathrm{Gly} ...
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Is displacement vector always the shortest path?
I read that the displacement vector of a particle is the shortest path between its initial and final positions since it's a straight line joining the two points, this holds true for me till a 2D ...
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The length of four-force
Recently, I'm reading the FeynmanLecture II_26 https://www.feynmanlectures.caltech.edu/II_26.html
It says that the “length” of the four-vector is an invariant under what is called the “complete ...
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Is the meter relative to time?
Is the meter relative when we are near the speed of light?
I was reading a physics book and I found that the meter is the length that light travels for an amount of time, so since time is relative ...
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Has there been a big change in 1983 when the definition of the metre changed?
The metre was defined at the end of the $18^{th}$ century as the ten-millionth part of the quarter of the meridian (from the north pole to equator). Then, from $1983$ the definition changed for the ...
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In real life, we can have a pencil of length 2 cm. Can we have pencil of length $\sqrt{2}$ cm? [duplicate]
In real life, we can have a pencil of length 2 cm. Can we have pencil of length $\sqrt{2}$ cm?
My answer to that was no , we cannot even make 2 cm pencil.
My argument was that when are working ...
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If the electron has no spatial dimensions based on QM, does not it violate the Planck length as the minimum admissible length for physical entities?
I think the question is self-explanatory: Quantum mechanics insists that electrons have no dimensions as point-like entities, while there is a minimum (non-zero) boundary for length called the Planck ...
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Does a rubber band stretch evenly?
Suppose you have a rubber band, and a point is marked on the rubber band at the 1/3 point. If you now apply force to the two ends of the rubber band to stretch it, will the point maintain its 1/3 ...
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Translating plasma units into SI units
I am trying to compute the characteristic lengths and frequencies in a plasma, namely the electron plasma frequency and electron inertial length. From the NRL plasma formulary
$$\omega_{pe}\ [rad/s] = ...
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Can it be accurate to say that time is also a length?
So a type of measurement, in units, is length, position, mass, etc, and a unit is meters, kilograms, etc.
Is it accurate to say that "an hour" is a time measurement, but also a form of ...
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Parsec confusion
parsec is defined as the distance at which average radius of earth's orbit around sun would subtend an angle of 1''(second of arc). But suppose im looking at this star when earth is on one side of the ...
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What are light years? like you know how people measure some things in light years? what is light years [closed]
so basically you know how scientists measure how far things are but in space and they measure in light years well what are light years and how long are light years?
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How does the length of a double open-ended tube affect its frequency? [closed]
I am attempting to build a trumpet, and need to calculate the lengths of the piping for it. I have attempted to find information on this online, but have been unable to find something that can help me ...
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How accurately do we know how long a meter is?
A meter is, by definition, a specific fraction (1/299792458) of the distance light travels in a vacuum in one second. How accurately do we know how long this is? In principle, it's exactly defined, ...
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