You're absolutely right! The factor causing objects to change velocity (accelerate) towards Earth at a rate of 9.8 m/s² is gravity. Here's a breakdown:

* Gravity: A force of attraction between any two objects with mass. The more massive the objects, the stronger the gravitational force. The closer the objects, the stronger the force.

* Earth's Gravity: The Earth has a large mass, and therefore a strong gravitational pull. This pull affects everything near it, including objects falling from the sky.

* Acceleration due to Gravity: This is the rate at which an object's velocity changes as it falls towards Earth. On Earth's surface, this rate is approximately 9.8 meters per second squared (m/s²). This means that for every second an object falls, its downward velocity increases by 9.8 meters per second.

Let me know if you'd like to explore any of these concepts further!