# derive-it.com

• ## Finite Differences

Here are a few notes about the symbol $\Delta$. This symbol appears frequently in physics. Let $\alpha$ be a real number. This statement is equivalent to $\alpha \in \mathbb{R}$. Then $\Delta \alpha$ can be defined as follows. Definition 1 Define a finite difference as $\Delta \alpha \equiv \alpha_2 – \alpha_1$.…

• ## Remarks on the Lorentz Transformation and One Question

This is a summary of the second part of Appendix A in Albert Einstein’s book [1]. By second part, I mean the part immediately after the derivation of the Lorentz transformation. If there is no relative motion between the coordinate systems with respect to the $y$ and $z$ axis of $K$, then…

• ## The Lorentz Transformation

This is an attempt to clarify the brief derivation of the Lorentz transformation in Albert Einstein’s book [1]. Suppose that the speed of light, $c$, is the same regardless of whether a coordinate system is or is not translating with a nonzero speed.Next consider two coordinates systems.The first is called $K$ and…