“It’s a testament to Rickman’s talent as an actor that we are able to see the multiple layers of Snape’s character with simply the flash of his eyes. So much emotion and pain radiate from their depths thus making Snape’s character suddenly very real but also human. To be able to convey so much without dialogue further emphasizes the genius of Rickman’s acting. Very few can claim to possess that same kind of power on the silver screen.”
When you separate an entwined particle and you move both parts away from the other, even at opposite ends of the universe, if you alter or affect one, the other will be identically altered or affected.