light year
光年
例句与用法：
A light year is the distance which light travels at 186,000 miles per second in one year, namely 6 million million miles.
1光年是以每秒186000英里的速度走过一年的距离，约为6万亿英里。
The distance of a light year boggles the imagination.
一光年的距离大得令人难以想象。
详细释义：
=light-year