# General Relativity & Grav. Time Dilation Qn

• B
• IXWELL
In summary, the conversation is about a factor in the equation for gravitational time dilation, specifically ##\sqrt{1 -\frac{ 2GM}{rc^2}}##, and whether it has a specific name like the Lorentz factor. It is mentioned that this factor can also be referred to as the gravitational time dilation factor or the gravitational red shift factor, and the limitations of its applicability are discussed.

#### IXWELL

hello I'm korean high school student and sorry for my poor English.
I saw ## t_0=t_f\sqrt{1 -\frac{ 2GM}{rc^2}} ## in wikipedia.
does ## \sqrt{1 -\frac{ 2GM}{rc^2}} ## of this equation have name like lorentz factor ## \frac{1}{\sqrt{1 -\frac{v^2}{c^2}}} ##of ## t=\frac{t_0}{\sqrt{1 -\frac{v^2}{c^2}}} ## ?
or is it just called time dilation equation?
I just want to know if there is a word specifically referring to factor ## \sqrt{1 -\frac{ 2GM}{rc^2}} ##.

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You can read more about that factor here in the wikipedia article on Gravitational Time Dilation where they use the Lorentz factor and the escape velocity to get the ##\sqrt{1 -\frac{ 2GM}{rc^2}}## factor.

https://en.wikipedia.org/wiki/Gravitational_time_dilation

Here is the LATEX for the factor of interest:
# # \sqrt{1 -\frac{ 2GM}{rc^2}} # #

NOTE: Remove the spaces between "# #" to activate the web page mathjax latex rendering code.

Please take some time to learn LATEX for entering equations here. The cut/paste of images just doesn't work out well. There is a link to LATEX formatting in my signature section at the bottom of this post.

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You might call it the gravitational time dilation factor or the gravitational red shift factor. It doesn’t really have a name because it wasn't an independent discovery like the Lorentz factor, it's just a part of Schwarzschild's solution of Einstein's equations. It's also not particularly general because gravitational time dilation is only really applicable in some circumstances - it cannot be defined for things like a pair of orbiting black holes, for example

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• • jedishrfu, IXWELL and dextercioby