Re: But Russell said SR is easy

Mike wrote:
Paul B. Andersen wrote:
scintillator scintillator
| |
particle -> | |
| |
------ ------
| |
Instrument
The minimum seperation of the peaks you
can get is twice the delay in activating the measuring device.

This is NOT true. The instrument measures the TIME DIFFERENCE between the signals ARRIVING AT THE INSTRUMENT. Put the two scintillators right together and the instrument will measure the time interval to be zero regardless of the speed of the particle. Put them a distance D apart and the instrument will measure the time interval to be D/v for any velocity v>0, including v>c. This is COMPLETELY INDEPENDENT of the signal delay in the cables (the cables are constructed so their delays are equal).

This is not quite what Alvaeger et al did, but is conceptually the same. Their apparatus is indeed capable of measuring speeds greater than c. Note that their two peaks are NOT from each input as you seem to think, but rather each peak is the time difference between the inputs, for two different separations of the scintillators (translating their situation to this one). And like the above discussion, the signal delay in their cables is irrelevant (it must only remain constant, which it does to better than the accuracy required).


T1 is the time for the first peak is at dt (the delaay)
T2 is the time for the second peak and equals t+dt, the elapsed time
plus the delay.

You are confused. That is NOT what the instrument above measures, and that is NOT what the plot in Alvaeger et al displays. The instrument above displays the time BETWEEN its two inputs; Alvaeger et al plotted the corresponding time between their two signals, for two different separations. The delays in the cable are not seen by the above instrument at all, nor are they relevant in the plot of Alvaeger et al.


As I said before, it is valid to argue this is not a pure one-way measurement, as the round-trip speeds of signals in the cables are involved. But one cannot validly claim this system cannot measure v>c, because it CAN measure such speeds.

[To keep the resolution constant, for larger v one must
arrange to use larger D. But that is not the issue here.]


Tom Roberts
.

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