<em><u>Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart. One explanation for dark energy is that it is a property of space.</u></em>
Space has amazing properties, many of which are just beginning to be understood.
Another explanation for dark energy is that it is a new kind of dynamical energy fluid or field. Dark matter makes up about 27%.
An external force is a force that acts on an object within the system from outside the system. This type of force is different than an internal force, which acts between two objects that are both within the system. The net external force combines these two definitions; it is the total combined external force
