- #1
Galadirith
- 109
- 0
Hi guys, I came across On the Electrodynamics of Moving Bodies while searching the net on relativity. I started reading it cause I thought It would be quite fun to do, not hoping to understand allot of it. I understand the basic (no-mathematical) concepts behind relativity, but I would like to understand the maths a bit better. What has been bugging me for ages is how is this step made:
[tex] \frac{1}{2} \left [ \ \tau (0,0,0,t) \ + \ \tau \left(0,0,0,t + \frac{x^\prime}{c - v} + \frac{x^\prime}{c+v} \right) \right ] = \tau \left(x^\prime,0,0,t + \frac{x^\prime}{c - v} \right) [/tex]
Hence if x' be chosen infinitesimally small
[tex] \frac{1}{2} \left( \frac{1}{c - v} + \frac{1}{c+v}\right)\frac{\partial\tau}{\partial t} = \frac{\partial\tau}{\partial x^\prime} \ + \ \frac{1}{c-v}\frac{\partial\tau}{\partial t} [/tex]
now I am still at A-level so havnt been to uni, don't know a whole lot on partial dirvatives, only what I have read in articles etc I can find online, so if peoples recomendation is leave this till I get to uni and then can do it there then that's fine, but from the looks of it this is a relatively easy step in the grand scheme of the paper, so if anyone could explain that step it would be really appreciated. Please don't flame me for asking this, I only ask because I want to understand, thanks guys :-)
[tex] \frac{1}{2} \left [ \ \tau (0,0,0,t) \ + \ \tau \left(0,0,0,t + \frac{x^\prime}{c - v} + \frac{x^\prime}{c+v} \right) \right ] = \tau \left(x^\prime,0,0,t + \frac{x^\prime}{c - v} \right) [/tex]
Hence if x' be chosen infinitesimally small
[tex] \frac{1}{2} \left( \frac{1}{c - v} + \frac{1}{c+v}\right)\frac{\partial\tau}{\partial t} = \frac{\partial\tau}{\partial x^\prime} \ + \ \frac{1}{c-v}\frac{\partial\tau}{\partial t} [/tex]
now I am still at A-level so havnt been to uni, don't know a whole lot on partial dirvatives, only what I have read in articles etc I can find online, so if peoples recomendation is leave this till I get to uni and then can do it there then that's fine, but from the looks of it this is a relatively easy step in the grand scheme of the paper, so if anyone could explain that step it would be really appreciated. Please don't flame me for asking this, I only ask because I want to understand, thanks guys :-)