1. Electrons and Protons
Every electron in the universe has the same charge, follows the same laws (orbiting the nucleus, shooting out a photon when it collides with another electron, for instance) and has a natural “life-span” of ten billion trillion years. A proton is 1836 times bigger than an electron but the two have equal yet opposite charges (proton=positive, electron=negative); the electron to proton mass ratio is the exact proportion required for molecules to form. Stephen Hawking notes that any difference in the charge of the electron would have meant that stars either could not (a) burn hydrogen and helium or (b) explode – both of which were required for life.