Science One Physics Lesson 20 Length Contraction Relativity of Simultaneity Recap and Preview Last class • Α constant speed of light in all frames means time and distance stop making sense. • Most people would be deterred, but Einstein was like “No, our notion of space and time is broken.” This class • A clickertastic adventure through time and space • Length contraction • Relativity of Simultaneity Time Dilation 2 Muons Created in Upper atmosphere Frisch-Smith Experiment (1963) Experimental Evidence Experimental Evidence Length Contraction Length Contraction Twin Paradox One resolu*on is that in the frame of the ship the distance between the planets is contracted, so the journey takes less *me on the spaceship. The Ladder Paradox You watch your friend, who is travelling at near the speed of light, carry a ladder into a garage. When they’re inside the garage, the doors close for an instant, so the ladder just fits. The doors then open to let you friend out. What happens in your friend’s frame? B) In the frame of the train, observers see the light hit the front and the back of the train exactly at noon. In the frame of the track, shown above, what can we say about the time on clock at the front of the train when light hits the back of the train. A) The clock at the front reads 12:00. B) The clock at the front reads earlier than 12:00. C) The clock not he front reads later than 12:00. In the frame of the train, observers see the light hit the front and the back of the train exactly at noon. In the frame of the track, shown above, what can we say about the time on clock at the front of the train when light hits the back of the train. A) The clock at the front reads 12:00. B) The clock at the front reads earlier than 12:00. C) The clock not he front reads later than 12:00. In the second picture, the back clock reads noon, but the front clock reds earlier than noon, since the light hasn’t hit it yet. Spacetime Drawings Frame of train Spacetime Drawings Frame of track Relativity of Simultaneity The Ladder Paradox Barn Frame Ladder Frame Simultaneous events in the barn frame are not simultaneous in the ladder frame. Principle of Relativity.