On 1/2/2014 10:01 AM, Edgar L. Owen wrote:
No, present moment time is NOT equivalent to the lengths of the paths traced by each twin through spacetime. Imagine the paths are drawn on graph paper, Sam's points directly above one another and Pam's in a curve off to the side from Sam's start point to Sam's end point. Present moment time is simply the horizontal lines on the graph paper that connect the two world lines.
That's what everyone else in the world calls "coordinate time". But how to choose what is "horizontal". You're obviously choosing it normal to Sam's world line. But relativity shows there is not special about Sam's world line. We could as well have chosen any inertial (i.e. straight) world line, say Bob's, where Bob is moving left at 0.2c. So, yes each choice defines present moments, but different present moments depending on the choice.
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