- #36
Mister T
Science Advisor
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NoahsArk said:That's the subtle point that I'm trying to wrap my head around, that my notion of "now" has changed, but so far have not been able to do.
I know that you think you've properly accounted for the delays due to the travel of light signals, but in fact you have only partially done so. Yes, you accept the fact that the delay exists, and that it has to be accounted for when an observer makes a claim as to when a distant event must have occurred, but you are ignoring the effect it has on simultaneity. It is the delay due to the transmission of information that accounts for the fact that the shift in the notion of a simultaneous distant event is unlike the shift in clock readings between distant events.
Think about the version of the twin paradox solution where at the turn-around point the traveling twin jumps from an outbound ship to an inbound ship. He makes his jump when the two ships pass each other. During that jump there's a shift in what he considers to be simultaneous events for his stay-at-home twin, but it's not a leap in the staying twin's clock reading.
Let's say the staying twin watches three television shows while his twin is traveling. Starting at 12:00 noon he watches the first three episodes of "Fun with Flags". Each lasts for 30 minutes. When he gets to the end of the first episode his clock reads 12:30. The traveling twin makes his leap when, according to him, it's 12:30 back at home. But when he lands on the inbound ship he reckons it's 1:00 at home, and his twin has finished watching the second episode. So what happened during that second episode? Did the staying twin's clock suddenly jump from 12:30 to 1:00, or did he spend a half hour watching the second episode? Of course he spent a half hour watching it. There was no sudden leap of 30 minutes according to the traveling twin, either. It's just that after allowing for the travel time of light signals, a person in the outbound ship reckons it's 12:30 when he passes the inbound ship, but a person in the inbound ship reckons it's 1:00 at home when he passes the outbound ship.