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Question 1

3votes

1answer

166views

Is the age of the universe significantly different as viewed from the Earth's frame of reference than as viewed from the CMB frame?

The standard value given for the age of the universe is 13.79 billion years. But of course, that age depends on the frame of reference; that figure is given from the perspective of the comoving FLRW ...

tparker

52.3k

askedNov 16 at 21:01

Question 2

2votes

1answer

186views

Is Big Crunch time reversed Big Bang - before it there would be formed black or white holes?

Big Crunch is often presented as time reversed Big Bang, e.g. https://www.sciencealert.com/physicists-predict-when-the-universe-will-end-in-a-reverse-big-bangI wanted to ask how true is it especially ...

Jarek Duda

1,196

askedNov 15 at 5:17

Question 3

0votes

1answer

132views

Clock on a moving rocket

Let's say that there is a clock mounted outside a rocket that is moving at a constant velocity upwards as measured by an adjacent observer looking at the clock from a stationary platform. The clock's ...

Owlywolf

507

askedNov 12 at 15:47

Question 4

7votes

3answers

2kviews

Beating the uncertainty principle for musicians

https://www.phys.unsw.edu.au/jw/uncertainty.htmlThe musician's uncertainty principle as above states that tuning can be less precise in short notes. But when we have a string with knowing its ...

benito

111

askedNov 11 at 3:07

Question 5

1vote

0answers

67views

Can entanglement correspond to a state where the thermodynamic arrow of time becomes locally undefined?

While studying quantum entanglement and thermodynamics, I started wondering about a possible conceptual link between the two.In a bipartite pure entangled state we have:Total entropy: S_total ≈ 0...

fivelove8102

11

askedNov 5 at 6:36

Question 6

-3votes

1answer

148views

Are physical quantities like Time, Momentum and Energy really fundamental in universe? [closed]

Well I am not professional in physics but studied a bit of some theories ( especially Noether`s theorem , SR , GR , QM ) and did thought experiments and observed that momentum is meaningful due to ...

ARNAV Pandey

119

askedOct 28 at 10:32

Question 7

1vote

1answer

155views

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 ...

SwitchArio

135

askedSep 24 at 9:41

Question 8

12votes

4answers

836views

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 geometryWavefunction of electron is spread over large region such that difference in time ...

Karan Kumar Sinha

137

askedSep 21 at 10:37

Question 9

4votes

1answer

735views

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 ...

Ayush Kumar

49

askedSep 15 at 5:27

Question 10

0votes

1answer

100views

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 ...

Khushal

1,238

askedAug 26 at 14:48

Question 11

2votes

0answers

71views

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=...

Michael

21

askedAug 26 at 8:51

Question 12

4votes

0answers

247views

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 ...

CBBAM

4,856

askedAug 24 at 5:06

Question 13

0votes

1answer

193views

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 (...

cr_007

11

askedAug 23 at 13:17

Question 14

0votes

2answers

131views

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 ...

Alec Jason Weinberg

3

askedAug 23 at 5:38

Question 15

1vote

1answer

359views

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 ...

Peter

367

askedAug 22 at 14:53

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Stack Exchange Network

Questions tagged [time]

Is the age of the universe significantly different as viewed from the Earth's frame of reference than as viewed from the CMB frame?

Is Big Crunch time reversed Big Bang - before it there would be formed black or white holes?

Clock on a moving rocket

Beating the uncertainty principle for musicians

Can entanglement correspond to a state where the thermodynamic arrow of time becomes locally undefined?

Are physical quantities like Time, Momentum and Energy really fundamental in universe? [closed]

Why does the total differential include $q$ but not $t$ in Landau & Lifshitz’s treatment of the Hamiltonian formalism?

Does an electron have an indeterminate time like its position before measurement?

Can time be understood as the record of the universe’s changing positions?

Poincare Transformations on Vectors that are function of time

Problem with discrete time into spacetime models [duplicate]

How to rigorously define quantum fields at fixed time?

Material Derivative of Infinitesimal Line Element

When we look at the start of the universe, are we looking at particles that could become us? [closed]

Periodic real time and temperature

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