James Clerk Maxwell in the 19th century was able to embody everything known about electric and magnetic fields into just 4 equations of electromagnetism (EM). These equations describe all the properties of light, which are EM waves. Light as waves was thought at the time to require a medium to vibrate, which was referred to as ether. If light traveled through vibrating ether, then an experiment to measure the travel times of light along Earth’s orbital motion would differ from that of light traveling along a perpendicular path. Efforts to measure the difference led to the Michelson-Morley interferometer and a quite famous experiment that produced the null results (no detection). After repeated efforts and changes to the experiment, always giving the null result, physicists were in a quandary. It appeared the wave properties of light via Maxwell’s equations were inconsistent with some observations.

Early in the twentieth century, it was also becoming obvious that all phenomena on the most microscopic scales obeyed the laws of quantum mechanics (QM), exhibiting both particle and wave properties, called the wave-particle duality. This is the point where Einstein genius came to bear. Einstein began thought experiments, asking questions such as if he were traveling at the speed of light or close to that speed, what would he observe? His quest produced Special Relativity, which revealed that time and the three spatial dimensions formed a single four-dimensional manifold and time and space dilations occurred for objects traveling near the speed of light. These are real distortions – for example, time itself is not independent of observer. It's not something distorting the functioning of the clocks, time itself differs. Moreover, General Relativity built on Special Relativity to account for the effects of gravity. The implications are: space itself and time are distorted under the right circumstances and everything was once again consistent with Maxwell’s EM. (Little of this makes sense to most people since few have first hand experiences in their daily lives. Some individuals go so far as to dismiss out of hand certain concepts.)

Going back to QM, physicists began building ever-bigger particle accelerators. First came cyclotrons, then synchrotrons requiring operational adjustment to account for the Relativistic effects experienced by the particles traveling close to the speed of light. This was one of several confirmation of Relativity and the distortions of time-space. Moreover, when ultra high-speed particles slam into stationary targets, a host of new particles are created in the process. Most particles are relatively short lived – some annihilating with their antiparticles, some decaying, and others simply escaping the accelerator. The combination of Relativity’s distortion of space-time plus the continually creation of particle-antiparticle pairs and other QM particle effects, indicates vacuum of space is something other than empty nothingness. Understanding the vacuum of space is the present-day goal of string theorists and particle accelerators such as Large Hadron Collider. It is also the goal of unified field theorists.