8 25.3 consequences of Einstein's postulates Macroscopic clocks: In October 1977, Joseph hafele and richard Keating flew four portable atomic clocks twice around the world on commercial airline once in each direction. The prediction of the theory was verified within 10% A few years later, physicist at the university of Maryland carried out a similar experiment with improved precision (1%). 8 25.3 consequences of Einsteins postulates 2. Length contraction Lengths perpendicular to the direction of motion L. Measured using Measured using rulers at rest in rulers at rest in S 0 We can prove the sticks are the same length. 16
16 Macroscopic clocks: In October 1977, Joseph Hafele and Richard Keating flew four portable atomic clocks twice around the world on commercial airline, once in each direction. The prediction of the theory was verified within 10%. A few years later, physicist at the university of Maryland carried out a similar experiment with improved precision(1%). §25.3 consequences of Einstein’s postulates 2. Length contraction 1lengths perpendicular to the direction of motion We can prove the sticks are the same length. 0l x′ y′ o′ Measured using rulers at rest in S’ 0l x y o Measured using rulers at rest in S §25.3 consequences of Einstein’s postulates
8 25.3 consequences of Einstein's postulates Prove by contradiction: Make the hypothesis that a moving stick oriented perpendicular to the direction of motion is longer than stick at rest. An observer in reference frame s: lo rulers at rest in s 8 25.3 consequences of Einsteins postulates An observer in reference frame S l Measured using >lo rulers at rest in Measured using rulers at rest in S The two observer can compare their conclusions by communication, and find the results are contradictory, therefore, the hypothesis must be false
17 Prove by contradiction: Make the hypothesis that a moving stick, oriented perpendicular to the direction of motion, is longer than stick at rest. An observer in reference frame S: 0 l > l x′ y′ o′ Measured using rulers at rest in S’ 0l x y o Measured using rulers at rest in S §25.3 consequences of Einstein’s postulates An observer in reference frame S’: 0 l > l x′ y′ o′ Measured using rulers at rest in S’ 0l x y o Measured using rulers at rest in S The two observer can compare their conclusions by communication, and find the results are contradictory, therefore, the hypothesis must be false. §25.3 consequences of Einstein’s postulates