There are many theories about galaxy formation.
Most of the theories contain the basic notion that there must have been gravitational seeds, regions that had more mass, and, hence, more gravity, than everything around them.
Those seeds evolved into the galaxies of today.
Early discussions of the big bang theory included the idea that all matter initially expanded in a uniform, smooth manner because nothing existed to interrupt its journey.
Scientists have since theorized that before subatomic particles combined to form hydrogen and helium, the first two elements, particles may have clumped together, that there were in fact variations in the distribution of matter.
These clumps of the most basic particles would have had more mass and hence more gravity than non-clumping particles.
They would have attracted more and more matter, eventually creating stars.
The stars’ gravity would attract other stars, forming galaxies.
Another interesting theory postulates that at the beginning of the big bang, there existed energy fluctuations called cosmic strings.
These fluctuations would be similar in nature to the energy transition of water to ice. Water and ice have the same atomic structure, but represent different forms of energy.
The cosmic strings would disrupt the otherwise uniform energy of the big bang.
Just as the clumps mentioned above could act as seeds for galaxies, so could the cosmic strings.
The word galaxy comes from the Greek term for our own galaxy, “galaxias”, or kyklos galaktikos, meaning “milky circle” for its appearance in the sky.
In Greek mythology, Hera sprays the night sky with her milk, producing the faint band of light known as the Milky Way.