New atomic clocks are more accurate than those used to define the second, suggesting the definition might need to change ...

从古埃及的日晷到现代的原子钟，人类对时间测量的精度不断提升。而如今，光学钟的精确度已超越了当前以铯-133原子跃迁定义的“秒”。这引发了一个关键问题：我们是否应该重新定义时间的基本单位？本文将系统解析当前时间计量的框架、光学钟的革命性突破，以及重新定 ...

The DRC illustrates how millions of people in fragile, violent and conflict-affected parts of the world are at risk of disaster.