The Earth's rotation is determined by its mass, shape, and angular momentum. While it might seem intuitive to think that increasing the Earth's rotation speed would cause everything to fly off into space, it's not the case due to the presence of gravity and the overall balance of forces.
Gravity is the force that keeps objects on the Earth's surface and prevents them from being flung off. The gravitational force between the Earth and any object on its surface depends on their masses and the distance between them. As long as the gravitational force is greater than the centrifugal force caused by the Earth's rotation, objects will remain on the surface.
Additionally, the Earth's shape plays a role in maintaining its stability. The Earth is not a perfect sphere but is slightly flattened at the poles and bulging at the equator due to its rotation. This shape, known as an oblate spheroid, contributes to the balance of forces and helps counteract the effects of centrifugal force.
Furthermore, the Earth's rotation has already reached a stable equilibrium where the gravitational force and the centrifugal force are balanced. If the Earth were to suddenly spin faster, it would disturb this equilibrium. However, the Earth's rotation rate is influenced by a variety of factors, including the distribution of mass, tidal forces from the Moon, and energy dissipation mechanisms such as atmospheric drag and tides. These factors tend to keep the Earth's rotation relatively stable over long periods of time.
In summary, the Earth's rotation speed is already at a point of equilibrium that allows objects to remain on its surface due to the counteracting forces of gravity and centrifugal force. The combination of these forces and the Earth's shape keep everything in place rather than causing objects to fly off into space.