How do we know that fundamental constants don't slowly change in time?
9463
What is the proof that the universal constants ($G$, $\hbar$, $\ldots$) are really constant in time and space?
67609
How is acceleration measured if there is change only in the direction of velocity & not magnitude?
16786
Is there any case in physics where the equations of motion depend on high time derivatives of the position?
22090
Does the (relativistic) mass change? Why?
67127
Does the speed of light vary in non-inertial frames?
28062
Something special about energy eigenstates when it comes to time evolution?
47242
Time dilation due to change in speed
117791
Why does the frequency of a wave remain constant?
113249
Does time exist in a vacuum?
100760
How do we know that radioactive decay rates are constant over billions of years?
9016
How can time dilation be symmetric?
50289
The vacuum light speed: Is it really constant, i.e., independent of location in space-time?
38482
What is $\Delta t$ in the time-energy uncertainty principle?
104255
Can we know the fundamental nature of space and time?
13786
A question in Special Relativity
83672
Time dilation in a gravitational field and the equivalence principle
78717
Does velocity or acceleration cause time dilation?