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
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How come time does not commute with $i\hbar\dfrac{\partial}{\partial t}$ but it does so with $H$? [duplicate]
Are they not supposed to be the same operator according to Schrödinger equation?
$$
i\hbar\dfrac{\partial}{\partial t}\psi = H\left(\vec{r},-i\hbar\nabla,t\right)\psi
$$
Apparently $[t,i\hbar\dfrac{\...
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Intuitive explanation of COSMIC TIME?
I came across the following statement, while studying a Newtonian model for cosmic expansion:
"If $R(t)$ is the scaling factor, we can define the Hubble parameter as $H(t)=\frac{\dot{R(t)}}{R(t)}...
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Gravitational effects on a celestial body and the difference between a pendulum and a regular clock
Imagine a planet with the same properties as Earth, this time moving in an elliptical orbit around a heavy star of a large number of solar masses. Also imagine that the surface of this planet is as ...
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Can we define time as a field? [closed]
The main objective is, can we relate time in terms of a field, I know time differs in many properties from an usual field. But I always imagine time as an forward moving field and we all know it is ...
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Why is it that objects inside a moving train tend to move at the same speed as the train itself?
I mean I get people saying because it's Newtonian mechanics. Everything inside the train will have same speed as that of train but my question is why ? Why is it like that ? And How does that happen ?
...
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Can we consider that the photons that were not and will never be detected live in a zero-dimensional space? [closed]
According to Einstein’s theory of relativity, any particle traveling at the speed of light experiences no passage of time. It follows that if a photon travels through space then within any two points ...
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What is the branch of physics that asks the question 'what was before the Big Bang'?
What is the branch of physics that asks the question 'what was before the Big Bang', assuming the Big Bang is truly what happened at the beginning of the universe? If there could be a better model ...
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Planck time - what would I see? [duplicate]
Impossibly hypothetical, but to communicate the question: when the universe "ticks" a plank second, what does a particle do? I'd imagine the natural conception that it moves from position a ...
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Given a distance, and velocity as a function of time, how do I find the time taken to travel the distance? [closed]
Given the velocity of a particle as a function of time V(t), and a distance between two points on a straight line (from point A to point B), I would like to find the time it will take the particle to ...
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Does interactive measurement of a "particle" in a double-slit experiment affect what happened before that measurement
Yep, yet another question about the infamous "double-slit" experiment. I've read all the similar questions that pop up before submission of the question. I've read plenty :) over the years. ...
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Measurement of the velocity of a celestial body by means of (relativistic and classical) gravitational effects on clocks
Imagine a planet with the same properties as Earth, this time moving in an elliptical orbit around a black hole of a large number of solar masses. Also imagine that the surface of this planet is as ...
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Is spatial distance objective?
While reading some papers on Einstein's theory of relativity, seeing how the flow of time is not the same for everyone, a doubt occurred to me:
Let us imagine a photon moving in a well-defined space ...
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Common clock reference of Big Bang
Relativity tells us that there is no preferred reference frame, yet current cosmology does operate on the hypothesis that all points in the observable universe originate from the same big bang ...
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A ball dropped onto a rotating wheel of various frequencies experiment issues
I'm doing a experiment to find the relationship between the frequency of the rotating wheel and the horizontal distance travelled by the ball dropped onto it. I am manipulating the frequency of the ...
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Are astronauts really younger than the rest of us after their trips to space? [closed]
I have seen this commented in a million places on social media (see here as well as places like HowStuffWorks, Business Insider, and even Scott Kelly makes the claim in the Guardian. Their reasoning ...
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