# Special Relativity Basics

I'm on my first pass through special relativity and I can't remember the math that would take me from:

(∂τ/∂x') + (ν/(c22))(∂τ/∂t) = 0

To

τ = φ(ν)(t - (ν/(c2 - ν2))x')

Any help would be appreciated.

Also, sorry for the terrible format, but I haven't taken the time to figure out how to do equations the right way. Any tips in that direction that would apply to an iPhone would be much appreciated as well... :)

PeterDonis
Mentor
Any help would be appreciated.

Where are you getting these equations from?

Here:
http://fourmilab.ch/etexts/einstein/specrel/www/
Sorry about that. It's an adaptation of the 1905 Einstein paper On the Electrodynamics of Moving Bodies. I followed the math through section 3 up until the derivation of the first equation in my post, but I can't remember why an assumption of linearity would allow me to transform the first equation in my post into the second.

PeterDonis
Mentor
I can't remember why an assumption of linearity would allow me to transform the first equation in my post into the second.

Linearity means that ##\partial \tau / \partial x'## and ##\partial \tau / \partial t## must be constants--i.e., they cannot be functions of ##x'## or ##t##. (They can still depend on ##v##, because ##v## is not a function of any of the coordinates.) So we must have ##\tau = k_1 t + k_2 x'##, where ##k_1## and ##k_2## are constants. The first equation in your OP then lets you find the values of ##k_1## and ##k_2##, up to an unknown function of ##v## (the ##a## in the second equation).

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Perfect. Thanks!