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.

Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of the boundless four-dimensional continuum known as spacetime.

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 ...