What might likely be affected by the existence of “dark matter”?

What would likely be affected if the dark matter exist is the life expanding of the universe. It is because of the dark matter, it could interfere with how the universe will expand and with their existence, a lot of things will be added on the universe and how it will be viewed and what more could a person discover.

Galileo, Copernicus and Kepler

Galileo was the first to use the telescope to observe the heavens, mainly observing the Moon, the Sun with its sunspots, Jupiter with its moons and Venus (in the early 1600s).  

In the specific case of Venus, he observed that it presented phases (such as those of the moon) together with a variation in size; observations that are only compatible with the fact that Venus rotates around the Sun and not around Earth.  This is because Venus presented its smaller size when it is in full phase and the largest size when it is in the new one, when it is between the Sun and the Earth.  

These images along with other discoveries were presented to the Catholic Church (which supported the geocentric theory for that time) as a proof that completely refutes Ptolemy's geocentric system and affirms Copernicus' heliocentric theory.

Years later, the astronomer Johannes Kepler refined the Copernicus' heliocentric theory with the introduction of elliptical orbits with the formulation of his three laws of planetary motion, finally explaining why planets orbited the Sun at different speeds at different times, because prior to this, the heliocentric model used only circular orbits.