Arrows would continue to fly forward forever in a straight line were it not for gravity, which brings them down to earth.

要不是重力使箭落向地面，它们将永远以直线往前飞行。

They deserve punishment which matches the gravity of their crime. [+ of]

应当根据罪行的严重性来惩治他们。

Not all acts of vengeance are of equal gravity.

并非所有的报复行为都同等恶劣。

There was an appealing gravity to everything she said.

她说的每句话都带着一种庄严，很能吸引人。