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We know that two ideal clocks permanently at rest relative to each other can be synchronized by means of the Einstein method.(1) Simply stated it means: measure the distance (d) between the clocks (Alpha and Beta); send a light pulse from Alpha to Beta at time t; when that pulse reaches clock Beta, set its time to t+d/c.
An equivalent method is to start with the two clocks in close proximity, set both to the same time and then slow-transport either Alpha or Beta (or both) to end up a distance d apart. Their synchronization can then be verified in both directions, using the above method, ensuring that they are indeed "Einstein-synchronized".
These two clocks were of Vulcan origin and Starship Enterprise performs a flyby at a (mild) speed of 0.6c. When adjacent to clock Alpha, Scotty records the time on its display and also the ship's clock's time. He does the same when adjacent to clock Beta, so that he could compare the elapsed time between the two flybys, as given by clocks Alpha and Bravo and by the ship's clock. To his surprise, Scotty finds that the elapsed time between the flybys according to the two clocks is larger than what the bridge clock has shown.(2)
At the debriefing Captain Kirk requests: "Right Mr. Scott, did we learn anything about the Vulcan clocks in this experiment?
Scotty: "Ay, Captain, we found that Vulcan clocks tick faster than our bridge clock".
Spock: "How can you say so, Mr. Scott? All Vulcan clocks conform to the United Federation of Planets standards of time. What is more, Starfleet physics predicts exactly the opposite. The Vulcan clocks were moving relative to our ship, so to us they will appear to tick slower than the bridge clock".
Scotty: "Sorry Mr. Spock, but I measured it and as Lord Kelvin once said: 'to measure is to know'."
Spock: "Captain, Mr. Scott never measured the rate of the Vulcan clocks".
Kirk cuts them short: "Scotty, I spot a difference of opinion here. Mr Spock, will the two of you please settle the issue off the bridge and then report back".
If you were Spock, how would you have resolved the disagreement?
-J
Notes
- "Permanently at rest relative to each other" implies free-fall in zero (or at least extremely weak) gravity and not too far apart.
- Take c as one foot per ns, the distance (d) between the clocks as 1000 ft in the Vulcan frame. Clocks Alpha and Bravo will then show an elapsed time of 1667 ns between the flybys, while the bridge clock will record the elapsed time as 1333 ns.
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