Our universe is 13.8 billion years old,. How do astronomers arrive at such an enormous number? more with Sabrina @qdteinstein @quickdirtytips at #365daysOfAstro

Our universe is 13.8 billion years old,. How do astronomers arrive at such an enormous number? more with Sabrina @qdteinstein @quickdirtytips at #365daysOfAstro