Lorentz expanded his 1899 ideas in his famous 1904 paper, where he set the factor ε {\displaystyle \varepsilon } to unity, thus: m L = m e m ( 1 − v 2 c 2 ) 3 , m T = m e m 1 − v 2 c 2 {\displaystyle m_{L}={\frac {m_{em}}{\left({\sqrt {1-{\frac {v^{2}}{c^{2}}}}}\right)^{3}}},\quad m_{T}={\frac {m_{em}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}} , So, eventually Lorentz arrived at the same conclusion as Thomson in 1893: no body can reach the speed of light because the mass becomes infinitely large at this velocity.
Böylece : m L = m e m ( 1 − v 2 c 2 ) 3 , m T = m e m 1 − v 2 c 2 {\displaystyle m_{L}={\frac {m_{em}}{\left({\sqrt {1-{\frac {v^{2}}{c^{2}}}}}\right)^{3}}},\quad m_{T}={\frac {m_{em}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}} , Sonuç olarak Lorentz , Thomson 'un 1893 yılındaki sonucuyla aynı sonuca vardı : hiçbir madde ışık hızına ulaşamaz çünkü bu hızda kütle sonsuz büyüklüğe ulaşıyor.