weightlessnesses

Astronauts often feel weightlessness when their spacecraft orbits the Earth.

用法提示：此处 weightlessness 为不可数名词，表示“失重状态”，作 feel 的宾语。

The airplane's steep dive created a brief sensation of weightlessness for the passengers.

用法提示：weightlessness 在此指“失重感”，作为 of 的宾语，描述一种体验。

Scientists study how weightlessness affects muscles and bones during long missions.

用法提示：weightlessness 作主语，指“失重状态”这一物理现象，为抽象名词。