Why Nothing Outruns Light
The speed of light is not a speed limit in the way a motorway sign is. It is built into the geometry of space and time — which is why approaching it does strange things to clocks.
7 min readPublished November 1, 2026
It started as a measurement problem
Nineteenth-century physics assumed light travelled through a medium called the ether. The Michelson-Morley experiment tried to detect Earth's motion through it and found nothing. Instead of a small correction, the result pointed at something enormous: the measured speed of light did not change no matter how the observer moved.
The fix that became a theory
Einstein took that result at face value in 1905. If the speed of light is the same for every observer, then time and distance must adjust to keep it so. Moving clocks run slow relative to stationary ones, and moving objects contract along their direction of travel. These are not optical illusions; they are measurable, and they are accounted for in GPS satellites every day.
Why the limit holds
Accelerating an object adds energy, but that energy increases its momentum ever more slowly as it approaches c. Reaching c would require infinite energy. Light manages it because photons have no rest mass. Nothing with mass can be accelerated to that speed — which is a statement about the structure of spacetime, not about engineering.
Sources
References point to third-party sources. Esurranty summarises them in its own words; check the original for the full argument.