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pervect is offline
Mar7-12, 05:45 AM
Sci Advisor
P: 7,433
Quote Quote by PAllen View Post
None of these are contradictory, though Thorne is at least misleading in an attempt a drama.

Let's take them one at a time:

"There is no such thing as a stationary clock at the event horizon." Here, you are rather naturally confused by ambiguity in English language. Pervect is here referring to stationary in the sense of motionless relative to distant observers, not rate of time flow on a clock. The two senses of stationary juxtaposed this way lead to false perception of contradiction. Sorry about that. English is a .... <forum rules> sometimes.
Yes, sorry if this wasn't clear. A stationary observer is basically an observer with constant r, theta, and phi Schwazschild coodinates.

In order to qualify as an observer, his worldline must be timelike. (Which is another technial term from special relativity). An photon isn't an observer, for instance.

Thorne's comments about "a direction you would have thought was spatial" and a "downwards direction" are misguided. The only one expecting this would be someone who interpreted coordinates according the letter used to name them rather than their physical characteristics.

I don't see why you say it's misguided. Though I think it may be confusing the OP, because Thorne's approach isn't based on the "clock slowing" paradigm.

My basic impression is that the OP is stuck in a Newtonian view of absolute time, and is also interpreting the whole "clock slowing" down thing as some sort of scalar function that modifies how fast absolute time flows at a given position.

And this is just not compatible with special relativity at all (mostly because of the absolute time idea).

At the risk of possibly causing more confusion, Thorne's view is more like saying that the time doesn't really "stop" (as per the stopped time idea), it's just bent to point in a spatial direction.

In standard Schwarzschild coordinates, the coordinate called 'r' is spacelike outside the horizon and timelike inside the horizon. This means nothing except that 'r' is a bad label for the coordinate inside the horizon. If you instead use the local Fermi-Normal coordinates of a infaller, all of this nonsense disappears.