We have established that time is relative and goes slower for objects in motion and we have experimentally proven with the ISS. A thought experiment: What if the ISS was moving at much higher speeds, let's say fast enough for the time differential to become more noticeable. So say it travels at 9...

A second on Earth is different from a second on the Sun and a second next to a black hole. Therefore speed, as measured in meters per second, is different in each of these locations. Is there an accepted and universal way to measure speed without the use of time, so that it can be understood by e...

I know that a quantum system can never have 0 energy due the Uncertainty Principle, and its lowest energy is called the Zero point Energy. However, Energy is a relative quantity (atleast in classical mechanics). What is this zero point energy relative to? When I calculate the energy for a harmoni...

In Newtonian gravity, what is the difference between the Poisson equation $\Delta(\Phi)$ and the expression $\Phi = -GM/r$ for the gravitational potential $\Phi$? Are both somewhat related?