- Before Einstein, space and time were absolute quantities
- Postulates: *Speed of light is constant, *Relativity principles must hold true
- Couple thought experiments along with actual evidence to relativity (atomic clocks, or muons for time dillation)
Consequences of the constancy of the speed of light
*Time dillation
*Mass dillation
*Length contraction
*Law of Simultaneity
*Equivalence of Mass and energy
For example it could be said that length contraction and time dillation pose as benefits to space travel because at relativistic speeds, the astronauts will seem to age slower, and travel a shorter distance, this in turn makes long distance space travel a possibility. However the disadvantages would be that returning back to earth would see loved ones possibly aged significantly/or dead. Furthermore the implication of mass dilation means that approaching light speed would require a significant amount of fuel/energy due to the exponentially increase mass of occupants within the spacecraft.
Moreover, the constancy of speed of light means that the 'metre' can be defined universally as the distance light travels in 1/299 792 458 of a second. Since the light speed is constant and unaffected regardless of the position etc, the metre now has a standard definition.
