Exploration 3: More on the Twin "Paradox"

Pulses from Traveling Twin Pulses from Traveling Twin: ST Stationary Twin Actually Sees This

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In this Exploration we will be considering different aspects of the so-called twin paradox.  Restart.  At t = 0 years the traveling twin (represented by the green circle) heads out on her journey and then returns at t = 10 years (position given in lightyears).  In the top panel the spacetime diagram for the stationary frame is shown. 

Select Pulses from Traveling Twin and play.  Also shown are the stationary observer's clock and the clock that the moving observer's clock as seen by the stationary observer.

  1. What is the frequency of the moving twin's light pulse in the moving frame?
  2. What is the frequency of the moving twin's light pulse in the stationary twin's frame?   Consider both outbound and return trips.
  3. Are (a) and (b) the same?  Explain.

Select Pulses from Traveling Twin: ST and play.  One way to see what is going on with the twin's pulses is to see the pulses depicted as blue lines on the spacetime diagram.

  1. How many pulses are emitted by the moving twin during her outbound trip? During her return trip?
  2. Where was pulse A (received at t = 2 years) emitted?
  3. Where was pulse B (received at t = 4 years) emitted?
  4. What can you say from (e) and (f) regarding what the stationary twin actually sees of the moving twin?  The phrase "actually sees" means what a real (not omnipresent) stationary observer would see.

Select Stationary Twin Actually Sees This and play.  The orange circle and the orange trajectory on the spacetime diagram represent what the stationary twin would actually see accounting for the time delay (Therefore the orange trajectory on the spacetime diagram is not a true worldline).

  1. How fast does the moving twin appear to be moving on her outbound trip (measured in c)?
  2. How fast does the moving twin appear to be moving on her return trip (measured in c)?