亿年前

• At some time more than five billion years ago the universe started .
  在50亿年前的某个时候，宇宙开始形成。
• Yet oxygen gas did not begin to accumulate in the atmosphere until about 2 billion years ago .
  但是大约在20亿年前，氧气才开始在大气层中积累。
• Our solar system was formed 4 . 6 billion years ago
  我们的太阳系被形成了4 . 6十亿年前。
• The chrysanthemum stone was former 280 , 000 , 000 years ago
  菊花石形成于距今约2 . 8亿年前。
• The supernovae exploded between 3 . 5 and 10 billion years ago
  超新星爆炸时间在35 - 100亿年前。
• Lived in the early jurassic about 200 million years ago
  宽缘板蛇颈生活在侏罗纪早期约二亿年前。
• Then 65 million years ago they suddenly disappeared disappeared
  然而六百五十亿年前他们突然消失了。
• Lived in the early jurassic ( about 200 million years ago )
  宽缘板蛇颈龟生活在侏罗纪早期(约二亿年前) 。
• Billions of years ago the universe was too hot for life to exist
  数十亿年前，宇宙太热，不适合生命存在。
• It dates from 125 million years before biplanes were invented
  在双翼飞机问世之前的1 . 25亿年前，这种动物翱翔在天空。