Einstein's special relativity, established in 1905, unified space and time into a four-dimensional continuum. It relies on two core principles: Galileo's relativity and the constancy of light's speed.

It is unnecessary to conceive the four-dimensional space-time of the relativists as so filled. If space-time is empty, is space also empty?

Definition:4D Scanning Transmission Electron Microscopy (4D-STEM) is an advanced imaging technique that combines high-resolution electron microscopy with diffraction pattern analysis over a ...