Science for Ukraine provides an overview of labs offering a place for researchers and students who are affected to work from, as well as offers of employment, funding, and accommodation:.

Personally, I have found the messages of support from scientists everywhere to be truly heartfelt, and I would like to highlight some of the community initiatives I’ve seen here: We also want to use our platform to highlight the response from the scientific community.

This is the main idea behind the inertial observer concept and no if there are also other systems which can see forces. The spacetime of this falling observer would appear to be flat (curvature equal zero) although in reallity it is not flat, but what imports is that we can calculate things. The principle of equivalence allows to do it locally, only locally neglecting tidal forces, because for a falling observer the whole forces can be made zero. Mathematically the frames which see straight lines are inertial and in principle we always can reach one of them just using Lorentz transformations. This is easy to achieve in Classical Mechanics (Newton's law of motion) and in Electrodynamics (Lorentz' law), but in General Relativity the things are not so easy if we think in Einstein's equations of motion and in general we have a curved spacetime. with constant velocity v and therefore no forces act upon them. The idea of inertial system is very simple and intuitive: the objects move without acceleration, i.e.

Freefall position physics