Talk:Eddington–Finkelstein coordinates

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Not a stub?

Why is this article considered to be a stub? What would you like to enlarge? I volunteer to do it!

René

Well, it was Hillman who marked it as a stub. You would have to ask him what he wants, although he claims to have left Wikipedia. He also added the {{expert}} tag with the edit summary: Expert: add figures of charts with light cones, clarify ingoing-outgoing, link with articles on other charts for Schwarzchild. I certainly agree that this article could use some figures with good explanations. -- Fropuff 18:15, 8 December 2006 (UTC)[reply]

Tortoise coordinate

Where did that name come from ? MP (talk) 16:11, 26 December 2005 (UTC)[reply]

I found this name used in "Gravitation" (paragraph 25), written by Ch. W. Misner, K. Thorpe and J.A. Wheeler. The authors relate the name to the ancient paradox of Achilles and the tortoise, where the faster running Achilles could never overtake the tortoise because it moved an (ever smaller) distance ahead. This keeps on going forever (of course the time involved decreases to zero), which correlates quite well with the behaviour of r* when r approaches 2GM. But that's just my guess. The authors - Wheeler actually, and Regge - have introduced the tortoise coordinate in two articles written in 1955 and 1957 (Phys Letters IIRC); I suppose there one could find the answer. Arjunah (talk) 21:38, 16 October 2008 (UTC)[reply]

Wrong Diagram

The diagram [1] just mirrored the part from r>2 ro r<2, but that's not how it's done. The dt/dr for a light ray is calculated via ds=0, that gives dr/dt=±(r-2)/r, which is infinite in the limit of r→0, so the world lines should be horizontal there as they are at [2] and [3] -~~ — Preceding unsigned comment added by 178.165.176.195 (talk) 20:29, 22 November 2022 (UTC)[reply]