宇宙

The universe is everything. It is all of space and time, all of matter and energy, and all of the laws of physics that govern them. It is the grandest of all subjects, and the most humbling. When you look up at the night sky, you are looking across vast distances, and back in time, to see the light from stars and galaxies that may no longer exist. The universe is a place of extremes: unimaginable heat and cold, crushing gravity and near-perfect vacuum, and scales of size and time that defy human intuition. Our story begins with the Big Bang, the moment about 13.8 billion years ago when the universe as we know it began. …