In Newtonian physics, time and space were absolute, and bodies moving through space and time experienced them similarly. Then along came Einstein… and everything changed. In his theory of special relativity, time and space became relative. Clocks (or people) moving at various velocities now measured time differently, and even measured distances (lengths) differently. Space and time were now equivalent. So were matter and energy.
Einstein then went on to develop a more general theory of relativity, after realizing that inertial forces and gravitational forces were equivalent – one could not tell the difference between the experience of weight on the Earth and an upward acceleration of a rocket in space. One also could not differentiate between being in free-fall in the presence of gravity and moving at a constant velocity out in space far from any gravitational effects. In a moment of pure genius, through a leap of imagination, Einstein saw the relationship between gravity and geometry. To Einstein, gravity was nothing more than the curvature of space-time. Things became weirder and weirder. Space-time became warped in the presence of massive of objects (and smaller objects too, except that the effects are too small to be observable). Time slowed down in the vicinity of large gravitating objects. The only thing that remained absolute was the speed of light in vacuum, c.
These ideas may seem counter-intuitive with regards to everyday experience, but they have so far withstood a whole series of rigorous observations and experiments. Einstein’s theories of relativity have revolutionized our view of the universe – leaving behind a legacy of expanding universes, black holes, gravitational waves and other exotica such as worm-holes and time-travel.
I am no expert in philosophy, but it is rather interesting to note that the rise of modernity, with its absolutism and rationalism, roughly coincided with the rise of Cartesian and Newtonian worldviews. Postmodern philosophy on the other hand, with its deconstruction of objectivity, grew in parallel with the development of Einstein’s relativity and the other scientific revolution of the 20th century – quantum mechanics (with its uncertainty, unpredictability, messiness and craziness). Which influenced which? Or did both scientific and philosophical revolutions arise concurrently due to some other social factors?