潮汐现象是海水在天体(主要是月球和太阳)引潮力作用下所产生的周期性运动。为什么一天会涨两次潮呢?笔者上网查了一下,查到的解释都很简略,有的地方甚至还很不严谨。在此,笔者借助理想化的质量分布均匀的刚体地球和月球的模型,利用离心加速度与月球引力加速度这两个概念解释这一现象。在月球与地球间的万有引力的作用下,地球与月球绕共同的质心近似做匀速圆周运动(为简便起 Tidal phenomenon is the periodic movement of seawater under the tidal force of celestial bodies (mainly the moon and the sun). Why one day will rise twice tide it? I checked the Internet, found the explanation is very simple, and some places are still not very rigorous. Here, I use the idealized uniform mass distribution of the rigid Earth and the moon model, the use of centrifugal acceleration and lunar gravity acceleration of the two concepts to explain this phenomenon. Under the universal gravitation between the Moon and the Earth, the Earth and the Moon revolve around a common centroid to make uniform circular motion (for simplicity