However, because Mercury has virtually no tilt to its axis, there are actually parts of the surface that never see sunlight at all.
FORBES: NASA Has Discovered Water Ice On Mercury
Because Earth's axis is tilted, all parts eventually get some darkness.
NPR: Space Probe to End Moon Mission with a Bang
On the horizontal axis of each graph, we have total traffic-related air pollution exposure, increasing in parts per billion (a part here would be a drop in a billion drops) from left to right.
FORBES: 5 Caveats About The Autism And Air Pollution Study
应用推荐
模块上移
模块下移
不移动