Practice question · Fill in the blanks
Complete the founding postulate of special relativity.
Special relativity begins from the postulate that ______ is the same for every observer, whatever their state of motion.
Word bank: the rate at which time passes · the length of a moving object · the speed of light · the mass of an object
Hints
- Exactly one quantity is held absolute; everything else is allowed to become relative.
- The other three options are precisely the things the theory makes observer-dependent.
Show the answer
Special relativity begins from the postulate that the speed of light is the same for every observer, whatever their state of motion.
Why
Holding light speed absolute is what forces time and length to become relative, the three distractors are the very quantities that had to give way. This inversion of what counts as absolute is the whole content of the theory.
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