Einstein’s special theory of relativity tells us how the Universe looks to
an observer moving at a steady speed. Because the speed of light is the same
for all such observers, moving clocks run slow, moving rulers shrink, and
moving masses become even more massive
ALTHOUGH it was Albert Einstein who developed the special theory of
relativity at the beginning of the 20th century, the principle of relativity
on which that theory is based goes back a further two centuries, to the time
of Isaac Newton. That principle holds that the same laws of physics apply for
all observers moving…
