因为普通圆珠笔在有重力的情况下方可工作。主要是重力作用油墨，使圆珠在球座内滚动，带出笔芯内的油墨或墨水，以达到书写的目的。

Because ordinary pens rely on gravity, while you write, gravity forces the ink down onto the ball, which rolls inside its socket and spreads the ink on your writing surface.

youdao

因为普通圆珠笔在有重力的情况下方可工作。主要是重力作用油墨，使圆珠在球座内滚动，带出笔芯内的油墨或墨水，以达到书写的目的。

Because ordinary pens rely on gravity, while you write, gravity forces the ink down onto the ball, which rolls inside its socket and spreads the ink on your writing surface.

youdao