# Naked Science Forum

## On the Lighter Side => New Theories => Topic started by: talanum1 on 27/04/2021 16:39:48

Title: Is this Video in Error?
Post by: talanum1 on 27/04/2021 16:39:48
Is this video in error:

It says at timestamp: 1:52:22 that a pole moving relative to a barn has a clock on it's front end that goes slower than a clock on the rear end. Isn't this in error?
Title: Re: Is this Video in Error?
Post by: Halc on 27/04/2021 17:55:17
It says at timestamp: 1:52:22 that a pole moving relative to a barn has a clock on it's front end that goes slower than a clock on the rear end. Isn't this in error?
The video doesn't say that, so it is you that is in error.

The video says that the clocks at either end of the pole are not in sync relative to the barn frame. No indication was given as to how those clocks are synchronized, but presumably they're in sync relative to the pole frame, in which case, yes, the lead clock lags the trailing one in the barn frame, which is different than saying that they run at different rates.

Both inertial clocks are moving at identical speeds in any inertial frame, so one isn't going to 'go slower' than the other in either frame. Their rates are only different if the pole is accelerating, which isn't the case in this scenario.
Title: Re: Is this Video in Error?
Post by: talanum1 on 28/04/2021 10:45:41
Why would one clock lag the other in the barn frame?
Title: Re: Is this Video in Error?
Post by: Halc on 28/04/2021 15:16:01
Why would one clock lag the other in the barn frame?
Clocks in sync relative to one frame are probably not in sync relative to another. Surely this is discussed very early in the video when introducing relativity of simultaneity (RoS). Watch the video, since it seems very much paced for the lay audience and not physics students.

The guy seems to be going into a needlessly complicated explanation of the barn-pole scenario, dragging clocks into a situation that is quite simply explained without them.  There are only two events that matter, A: when the trailing end of the pole crosses the first threshold (door) of the barn, and B: when the leading end of the pole crosses the second threshold.  Those two events are ordered A-then-B relative to one frame, and B-then-A relative to the other. That is RoS in its most basic form, without need of quantification with clocks, dilation, or length contraction and such.
Title: Re: Is this Video in Error?
Post by: talanum1 on 28/04/2021 15:34:07
O.K. Thank you.