accelerating expansion also puts a limit on what we can ever affect. If, today, you shine a ray of light out into space, it could reach any galaxy that is currently less than 16 billion light years away. But galaxies further than this are being pulled away so quickly that neither light, nor anything else we might send, could ever affect them.34 And next year this affectable universe will shrink by a single light year. Three more galaxies will slip forever beyond our influence.
