The concept of "great cosmic voids" refers to vast regions of space that appear to contain significantly fewer galaxies and matter compared to surrounding areas. While these voids have a lower density of matter, they are not completely devoid of it. They still contain some amount of matter, including gas, dust, and occasional sparse galaxy clusters or filaments.
Gravity is a fundamental force that acts over long distances, and it exists everywhere in the universe, including cosmic voids. However, the gravitational pull within a cosmic void is relatively weaker compared to regions with higher matter density. This is because gravity depends on the mass of objects and their proximity to each other.
If an Earth-sized particle were placed in the middle of a cosmic void, it would experience gravitational forces from the surrounding matter, albeit much weaker than if it were located in a denser region like a galaxy cluster. The exact behavior and movement of the particle would depend on the distribution of matter within the void and the initial conditions of the particle's motion.
In general, the particle would likely move under the influence of gravitational forces towards regions of higher matter density, such as nearby galaxies or filaments. However, the timescales for any noticeable motion or interactions would be extremely long, given the vast distances and the relatively weak gravitational forces within voids.
It's important to note that our understanding of cosmic voids is still evolving, and ongoing research continues to explore their properties and the dynamics of matter within them.