Second postulate of special relativity

Definition

The second postulate of special relativity states that the speed of light in a vacuum is constant and independent of the motion of the light source or observer. This implies that all observers, regardless of their relative velocities, will measure the speed of light as approximately 299,792 kilometers per second.

5 Must Know Facts For Your Next Test

1. The second postulate challenges classical mechanics by asserting that the speed of light remains constant irrespective of the relative motion between source and observer.
2. It is a cornerstone of Einstein's theory of special relativity, fundamentally changing our understanding of space and time.
3. This postulate leads to the conclusion that time and length are not absolute but depend on the relative motion between observers (time dilation and length contraction).
4. Experimental evidence, such as the Michelson-Morley experiment, supports this postulate by showing no variation in the speed of light due to Earth's motion through space.
5. The constancy of the speed of light implies that nothing can travel faster than light in a vacuum.

Review Questions

• What does the second postulate say about the speed of light?
• How does this postulate affect our understanding of time and space?
• What experimental evidence supports the second postulate?

Related terms

Special Relativity: A theory formulated by Albert Einstein which posits that laws of physics are invariant for all non-accelerating observers and introduces concepts like time dilation and length contraction.

Time Dilation: A phenomenon predicted by special relativity where time passes more slowly for an observer in motion relative to a stationary observer.

Michelson-Morley Experiment: An experiment conducted to detect Earth's movement through aether; it provided evidence supporting the constancy of the speed of light, leading to challenges against classical physics theories.