The universe is a dynamic, evolving organism.
It is commonly defined as the totality of everything that exists.
It had a beginning, probably a sudden, massive expansion of matter, and it may have an end.
We don’t really know.
Meanwhile, it grows by means of further expansion; galaxies move farther and farther away from each other.
The universe is filled with activity and motion.
Stars explode into existence and expand and contract throughout their lives. Planets revolve around stars. Galaxies spin and tumble. Comets and asteroids streak through solar systems. Elements, atoms, molecules, and particles constantly interact, creating change.
Electromagnetic waves are everywhere.
Yet, for all we can see out there, it may be that most of the universe is made of dark matter, which we have not been able to find.
