宇宙起源之谜。三级自拍视频

　　The universe began with a massive expansion, billions and billions of years ago, and it continues to expand with every passing second. The idea that the universe, and man's very existence, began with a "Big Bang" is no longer a topic of debate among most scientists--it is essentially taken as fact. How has man come to this conclusion, and how has our knowledge evolved so that w... (展开全部)