The time span measured is dark adaptation time. 所计得的时间为其暗适应时间。
For many, approaching Tibet gradually by train will be preferable to flying in, as it will allow more time to acclimatise and reduce the chance of altitude sickness. 更好的是,与坐飞机相比,乘火车将是逐渐的抵达西藏,这样将使乘客有更多的适应时间和降低发生高山病的几率。