Final answer:
Astronomical observations and the discovery of dark matter suggest Earth is not central in the universe, supporting a heliocentric model.
Step-by-step explanation:
One reason Earth being at the center of the universe is unlikely is because astronomical observations do not support it. Since the time of Copernicus and Galileo, telescopic evidence has shown that Earth orbits the sun, shifting the idea of a geocentric model to a heliocentric one.
Further research revealed that our Sun is just a regular star among billions in the Milky Way, which itself is not central in the cosmos. The discovery of dark matter reinforces this understanding, showing that the visible matter, including Earth and its solar system, is not even the most common in the universe.