According to: https://en.wikipedia.org/wiki/Cosmic_microwave_background the CMB (Cosmic Microwave Background) "is faint cosmic background radiation filling all space" Also, https://en.wikipedia.org/wiki/Vacuum#Outer_space says "no vacuum is truly perfect, not even in interstellar space, where th...

Obviously some things, such as the speed of light in a vacuum, are defined to be a precise value. The kilogram was recently defined to have a specific value by fixing Plank's constant to $6.62607015\cdot 10^{−34}\frac{m^2 kg}{s}$. In particular, in the case of the latter, we held off on definin...

Consider a damped pendulum whose equation of motion is given in general by $$m\ddot{x}=-\mu\dot{x}-kx$$ where $\mu,k>0$ Rewrite this equation as $$\ddot{x}+2\gamma\dot{x}+\omega^2x=0,$$ where $2\gamma = \frac{\mu}{m}$ and $\omega^2 = \frac{k}{m}$. If $\gamma>\omega$, the roots of this equati...