The universe began with a Big Bang.
宇宙是从一次大爆炸开始的。
That happened about 13.8 billion years ago.
那大约是138亿年前。
At first, everything was tiny and very hot.
一开始，所有东西又小又热。
Then it exploded and started to expand.
然后它爆炸并开始膨胀。
Stars and galaxies formed later.
星星和星系是后来才出现的。
The universe is still growing today.
宇宙直到今天还在变大。
The Big Bang is how our universe began.
大爆炸就是宇宙诞生的方式。
