Existential threats to humanity range from urgent, to a distant possibility. One such remote threat is the accelerating expansion of the universe. While most wouldn’t consider this a real threat, particle physicist, Dan Hooper, at the Fermi National Accelerator Laboratory, points out why it is a threat we should consider.
He points out that things beyond the cosmic horizon—the maximum distance that light can travel to us within the age of the universe—are beyond our ability to study, or influence. Stars, galaxies, even civilizations are beyond the cosmic horizon, and beyond our ability to contact or see them. According to an article in MIT Technology Review discussing Hooper’s theory, the cosmic horizon is changing and this will affect our neighborhood in the universe, which astronomers call the Local Group. The Local Group (50 nearby galaxies bound to the Milky Way) will be humanity’s home for the foreseeable future. But these galaxies may not always be within our reach to possibly colonize, as the accelerating expansion of the universe sends galaxies over the horizon at a rate that’s increasing.
As Hooper explains, “over the next approximately 100 billion years, all stars residing beyond the Local Group will fall beyond the cosmic horizon and become not only unobservable, but entirely inaccessible.” This eventuality would interfere with humanity’s ability to exploit ever more stars for energy. However, Hooper believes there is a way to mitigate the effects of an expansion. He believes that an advanced civilization could build a Dyson sphere that emits waste radiation in a specific direction to accelerate the sphere—and the star it contains—in the opposite direction of the acceleration. Over time, this technology could be used to gather stars as a source of energy, keeping them inside the cosmic horizon. So, potential problem solved? Well, as the article acknowledges, first the assumption that the expansion of the universe is accelerating would have to be correct.