Why does E = mc2 ?

Let's derive the most equation in physics, E = mc^2, intuitively. This is Albert Einstein's original 1905 derivation. Here we will see exactly where the c^2 in the mass energy relation really comes from. We will do each part step by step. We will also derive the expression for the relativistic doppler effect.

Chapters:
00:00 Introduction
00:27 Counting energy lost by the atom
03:31 Relativistic doppler effect animation
06:35 Recounting energy from moving frame
07:20 Discovering Mass - Energy connection
09:47 How mass - energy relation comes from constant speed of light!
12:43 Rearranging the equations - (1)
13:43 Deriving relativistic doppler effect equation - intuitively
20:05 Substituting in equation (1)
22:40 Summarising the result so far
23:19 Final substitution
26:25 The climax - E = mc^2 derived
26:50 The summary