Existence: Why is there a universe?
来源：未知 作者：随窗垒 时间：2019-02-27 02:03:06
By Amanda Gefter Read more: “Existence special: Cosmic mysteries, human questions“ AS DOUGLAS ADAMS once wrote: “The universe is big. Really big.” And yet if our theory of the big bang is right, the universe was once a lot smaller. Indeed, at one point it was non-existent. Around 13.7 billion years ago time and space spontaneously sprang from the void. How did that happen? Or to put it another way: why does anything exist at all? It’s a big question, perhaps the biggest. The idea that the universe simply appeared out of nothing is difficult enough; trying to conceive of nothingness is perhaps even harder. It is also a very reasonable question to ask from a scientific perspective. After all, some basic physics suggests that you and the rest of the universe are overwhelmingly unlikely to exist. The second law of thermodynamics, that most existentially resonant of physical laws, says that disorder, or entropy, always tends to increase. Entropy measures the number of ways you can rearrange a system’s components without changing its overall appearance. The molecules in a hot gas, for example, can be arranged in many different ways to create the same overall temperature and pressure, making the gas a high-entropy system. In contrast, you can’t rearrange the molecules of a living thing very much without turning it into a non-living thing, so you are a low-entropy system. By the same logic, nothingness is the highest entropy state around – you can shuffle it around all you want and it still looks like nothing. Given this law,