Aliens slumbering for billions of years are out there – really?
来源：未知 作者：成倔鲇 时间：2019-03-15 05:18:00
gremlin/Getty The vastness of the universe suggests advanced alien civilisations, or at least evidence of them, ought to be out there. The signs – such as megastructures and communications – should be obvious. Instead, astronomers are confronted with a silent universe beyond our own planet. This “eerie silence”, as cosmologist Paul Davies puts it, inspired the great physicist Enrico Fermi to ask: “Where are they?” Many have proposed solutions, but now another is on the table. What if aliens are out there after all, only they are sleeping,