We can not compare anything on earth to the biggest things known in space. The Alfa Lymann bubble is a bubble like structure containing countless galaxies – perhaps the largest object in the universe.
Regions of gas that emit radio called “radio lobes” could be even higher. Then there are the super clusters of galaxies that are hundreds of galaxies merged due to cosmic collisions.
Find out which is the largest planet, star, star cluster, constellation, black hole, volcano, galaxy, explosions, moon, storm, impact crater and the “empty” space.
Some people believe in UFOs, some do not. And there will always be “proofs of UFOs”, as much as there will always be people who think it is just another conspiracy theory...