This text goes through your eyes, to your head, back to your brain, and kindles a thought. A vague and unique thought. You predict what you will be reading next. What made you predict? Your brain could’nt have. Because all humans have a brain but not a similar thought process. Which brings me to the question, where are you? Your inner self fabricating these thoughts, giving you a unique life altogether? Where?
Enough psychology. It’s Science. It basically is that tiny nuclear matter in each of your cells. The DNA. Your DNA is unique to you, Science says. But what if it’s not, what if there is someone out there, a replica – you, reading this right now, pondering – just as you? Guess what? There might be.
How would this be possible? You have a certain volume. How many quantum states could describe this volume you occupy? How many alternatives are there? How many possible sets of DNA can occupy you? It is 101070. That’s quite large. This number is so big that it over rides the number of planck volumes in the observable universe. However, if someone were to explore further into the universe, farther than 101070 planck volumes, there is quite a chance he would see your doppleganger, an arrangement of atoms that matches you. Mind, the universe is just 4*10185 planck volumes across. It’s a long way to go.
Also note, For some one sitting on Earth waiting for you to get there, it will take 13.7 billion years. Of course the visible Universe will have gotten 13.7 billion light years bigger in that time.