Objects do not fall into themselves due to gravity primarily because of the presence of other forces that counteract the force of gravity. These forces can include electromagnetic forces, electrostatic repulsion, or other forms of structural resistance.
When an object is at rest on a solid surface, the electromagnetic forces between the atoms and molecules in the object and the surface prevent the object from collapsing under its own weight. These forces create a "normal force" that acts perpendicular to the surface, balancing the force of gravity pulling the object downward.
In the case of celestial bodies like planets, stars, or moons, their spherical shape is a result of the gravitational force pulling matter inward from all directions. The object's mass and gravitational force are balanced by the internal pressure generated by the particles that make up the object, preventing it from collapsing under its own gravity.
Regarding escape velocity, it refers to the minimum velocity an object needs to escape the gravitational pull of a massive body without any further propulsion. If an object attains or exceeds the escape velocity, it can overcome the gravitational force and leave the vicinity of the massive body. The specific value of escape velocity depends on the mass and radius of the body.
In summary, objects do not fall into themselves due to the presence of counteracting forces, such as electromagnetic forces or structural resistance. Escape velocity can overcome the gravitational force of a massive body, allowing objects to break free from its gravitational pull.