Questions tagged [time]
Time is defined operationally to be that which is measured by clocks. The SI unit of time is the second, which is defined to be "the duration of $9, 192, 631, 770$ periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium $133$ atom."
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Why does the total differential include $q$ but not $t$ in Landau & Lifshitz’s treatment of the Hamiltonian formalism?
In Landau & Lifshitz, Classical Mechanics, §40 (Hamilton’s equations), p.132-133, it is said that when writing the total differential of the Lagrangian and of the Hamiltonian, one ignores the time ...
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Does an electron have an indeterminate time like its position before measurement?
Consider the case of quantum entity :
If electron is present in region of high curvature of spacetime geometry
Wavefunction of electron is spread over large region such that difference in time ...
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Can time be understood as the record of the universe’s changing positions?
I’ve been exploring a way to think about time in relation to the motion of all objects in the universe. The Earth moves around the Sun, the Solar System orbits within the Milky Way, and the Milky Way ...
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Poincare Transformations on Vectors that are function of time
I have a spacetime 4 vector $P^{\mu}(t)$ that is a function of time. I want to understand how a generic boost $\vec{\beta}$ would change this 4-vector. But since the implicit time coordinate also ...
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Problem with discrete time into spacetime models [duplicate]
Is this the essential problem of discrete time: suppose you decide that time is discrete, e.g. it only comes in integer "ticks". So an observer at rest says that event happened at times $𝑡=...
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How to rigorously define quantum fields at fixed time?
Let $\Phi$ be a quantum field, for simplicity we can take it to be a scalar spin zero Bosonic field. Mathematically a quantum field is defined as the map $f \mapsto \Phi(f)$ which is an operator ...
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Material Derivative of Infinitesimal Line Element
I am trying to self-learn fluid dynamics from online resources because I am interested in its application to astrophysical environments. I found lecture notes on astrophysical fluid dynamics on arXiv (...
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When we look at the start of the universe, are we looking at particles that could become us? [closed]
Suppose we had the time and ability to track one particle from the start of the universe until now.
Suppose that particle is currently part of earth.
We would watch it over billions of years, and see ...
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Periodic real time and temperature
Suppose we have an imaginary time path integral then partition function is
$$ Z = \mathrm{Tr}\left [ \mathrm{e}^{-\beta \hat{H}} \right ]=\int_{x(0) = x(\beta)} \mathcal{D}[x(\tau)] e^{-S_E[x]}$$
and ...
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Energy eigenstates in time dependent potential
Suppose the potential of the quantum particle is time dependent , $V(x,t)$ . Therefore the hamiltonian can be written as :-
$$\hat H=-\frac{\hbar^2}{2m}\frac{\partial^2}{\partial x^2}+V(x,t)$$
And we ...
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What's meant by "the flow of time"? [duplicate]
I was watching https://closertotruth.com/video/time-at-sea/ (full video at https://www.youtube.com/watch?v=AZ87SypBstc), hosted by https://fqxi.org/, where one of the contributors (sorry, don't recall ...
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How does the area under the Velocity-Time graph represent the magnitude of displacement? [closed]
For constant velocities where $a=0$ the area is simply given by the area of the rectangle enclosed between the velocity and the time (i.e. $v * t = x$).
And for accelerated bodies we simply imagined ...
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What is conformal time?
The Wikipedia pages for the Particle horizon of the universe has the following statement:
"Due to the expansion of the universe, it is not simply the age of the universe times the speed of light ...
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How Can a Physical Theory Make Predictions Without Time? [closed]
I am not a physicist or a mathematician, so it's hard for me to understand a theory like the Wheeler–DeWitt equation.
But there is something I can explain without the need for deep mathematics.
As far ...
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Clarification on time difference for synchronized clocks in General Relativity
I am having some trouble interpreting the time difference in clocks synchronisation in general relativity. I will expose the way I understood it and hope somebody can confirm whether I understood ...
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