The speed of light in a vacuum, about 300,000 kilometers per second, is one of the few values in physics that appears the same to every observer regardless of motion. This counterintuitive fact, established by Einstein in his 1905 special theory of relativity, forces strange consequences: clocks run slower at high speeds, and lengths contract along the direction of motion.
Which choice best states the main idea of the text?
- A
Clocks are unreliable at high speeds.
- Bcheck_circle
The constancy of light's speed across observers is the foundation of special relativity's surprising consequences.
- C
Light travels at 300,000 kilometers per second.
- D
Einstein worked in 1905.
Explanation
The passage's central point is that the constancy underlies the strange consequences — A. B and C are facts; D misreads.