Could be a number of things.
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The title text in Wiki Answers sums it up quite well: "Black holes are regions in space created by the death of stars. Their gravitational field is so strong that even light cannot escape from it."The strong gravitational field is caused by stars collapsing, into a very small space.
Everywhere in the universe. Gravitational fields are steeper and more intense around very massive objects such as stars and planets.
Potential energy is created from a gravitational field. This energy is stored in an object based on its position in a gravitational field and is released when the object moves closer or further from the source of gravity.
a region of space having a gravitational field so intense that no matter or radiation can escape.
for apex its: a quantum field, a gravitational field
The formula for gravitational field intensity is given by ( g = \frac{F}{m} ), where ( g ) is the gravitational field intensity, ( F ) is the gravitational force, and ( m ) is the mass of the object experiencing the gravitational field.
The area where objects feel a gravitational force is called a gravitational field. This field is created by the presence of mass in space and determines the strength and direction of the force experienced by objects within it.
The mass of an object in a gravitational field is called the object's "mass".The presence or absence of a gravitational field has no effect on the mass.
Weight is defined as the force that an object of mass M experiences in a gravitational field. Where mass comes from and why it is the quantity which interacts via the gravitational force is a more fundamental and unanswered question in physics.
Expanding and collapsing of a magnetic field
That is Einstein's theory of relativity.
Jupiters gravitational field strength is 25 Nkg^-1