Here's why:

* Gravity is a force of attraction: It pulls objects towards each other. The Earth has a large mass, so it exerts a strong gravitational pull on objects near it.

* Gravity acts constantly: Whether an object is moving upwards, downwards, or stationary, it is still being pulled by gravity.

* Motion is relative to a frame of reference: An object might appear to be stationary, but it's still being acted upon by gravity.

Examples:

* A ball thrown upwards: While the ball is moving upwards, gravity is still acting on it, slowing it down. Eventually, gravity will overcome the upward momentum, and the ball will fall back down.

* A book sitting on a table: Even though the book isn't moving, gravity is pulling it downwards. The table exerts an equal and opposite force, preventing the book from falling.

In summary: Gravity is a constant force that acts on all objects with mass. It doesn't only act when objects are moving downwards.