At the very bottom of the page they have that the straight line, using the definition of a vector as the derivative of the worldline is given as:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]P(0) + \lambda(\frac{dP}{d\tau})_o[/tex]

But since the worldline, [tex]P(\tau)[/tex] is paramtrized by [tex]\tau[/tex] andnot[tex]\lambda[/tex], then shouldn't the equation be:

[tex]P(0) + \tau(\frac{dP}{d\tau})_o[/tex]

?

Thanks in advance.

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# GRAVITATION by MTW: p.49, lambda or tau?

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