# Questions tagged [length]

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### Do solids also follow the reverse of this equation? [closed]

We all know the equation for linear thermal expansion on heating the solid $$\Delta L = \alpha L \Delta T$$ Now I know solids expand on heating, for example in railway tracks in summers but after ...
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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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### Length contraction speed of light

The Special Theory of Relativity tells us that a moving object eg spaceship measures shorter in its direction of motion as its velocity increases. At the speed of light it would have zero length, but ...
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### What is superconducting coherence length?

I'm an electronics student, and don't know much about some physics concepts. I was studying superconductivity and came to the London equation, Meissner effect and BCS theory. I kind of understood ...
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### If I cut a string, will its length be rational or irrational? [duplicate]

If I cut a string (lets say approximately halfway), will the length of each side (in inches) be rational or irrational?
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