Im working through a textbook section on particle kinematics. An example given is relating vertical velocity to horizontal velocity and states: $y$ has a constant velocity of $10 \ \rm [m/s]$ $y=(0.001x^2)\ \rm [m]$ when $y=100\ \rm [m]$ then $x=316.2\ \rm [m]$ and $t=10 \ \rm [s]$ Here comes my ...

Electromagnetic radiation (a photon) is generated by an oscillating charged particle. Therefore, is it possible to vibrate an object at say 585 THz and create a green light source? Alternatively: what's the highest frequency we've achieved on a macroscopic scale?

Studying the theory of open quantum systems, some textbooks start by introducing the notion of a semigroup for the time evolution operator $T_t$. The next step then usually is to impose that such a semigroup should be contracting, i.e. $||T_t|| \leq 1$ for every $t\geq0$. This can be found for ex...

Put a piece of cold pizza on top of a sheet of aluminum foil and then stick it in the oven to heat up. After about 10 minutes, the pizza should be nice and hot—the aluminum foil is the approximately the same temperature. You can pull the aluminum foil out with your fingers, but not the pizza. I r...