That you exist in the universe is pretty obvious, at least to yourself. But now researchers have used the fact that human observers are alive—and haven’t been zapped into oblivion by supernova explosions—to account for the puzzling weakness of dark energy, the mysterious force accelerating the expansion of the universe.
“This creates a new link between [dark energy] and astrobiology, which were previously considered to be vastly different fields,” says Tomonori Totani, an astronomer at the University of Tokyo and lead author of the new study.
Most people don’t think of dark energy—the all-permeating force driving apart galaxies—as particularly weak. But based on arguments from quantum mechanics and Albert Einstein’s equations for gravity, scientists estimate that dark energy ought to be at least 120 orders of magnitude stronger than it actually is.
If dark energy were that powerful, it would have quickly driven apart matter in the early universe, preventing the formation of galaxies, stars, and living beings. This has led some scientists to invoke what’s called the anthropic principle, which proposes that the laws of physics in our universe were fine-tuned to produce life.