The force that keeps the Earth in its orbit and prevents it from flying off into space is gravity.

Here's how it works:

* The Sun's Gravity: The Sun is a massive object with a strong gravitational pull. This pull acts on the Earth, constantly trying to pull it towards the Sun.

* Earth's Velocity: The Earth is moving very fast, orbiting the Sun at about 67,000 miles per hour. This velocity acts like a centrifugal force, pushing the Earth away from the Sun.

* Balance: The Earth's velocity and the Sun's gravity are perfectly balanced. If the Earth moved slower, it would fall into the Sun. If it moved faster, it would fly off into space. This balance keeps the Earth in a stable orbit around the Sun.

Imagine a ball tied to a string being swung around your head. The string represents the Sun's gravity, pulling the ball towards the center. The ball's velocity keeps it moving in a circle. This is a simplified analogy, but it illustrates how gravity and velocity work together to keep Earth in orbit.