Though sensationalized in movies like Donnie Darko, the multiverse is a hypothetical concept debated by many scientists, and two new studies up the ante on the fantastic idea of a multiverse: Perhaps, if our universe is just one among many alternative universes, life could be scattered across those universes, too.
“Stars and planets form as the result of gravity pulling clumps of matter together, but if there is too much dark energy, the universe expands too fast for this to happen,” the study’s co-lead author Richard Bower, a physicist at Durham University, tells Inverse. “A universe without stars is too dark and cold for life to exist.”
The research of Bower and others was published in two related papers on Sunday in the Monthly Notices of the Royal Astronomical Society.
Researchers in these new studies found more questions than answers about dark energy and the multiverse. By adding dark energy to models of the early universe, researchers tried to find a threshold for life. How much dark energy was too much to impact star formation? Too little?
Apparently, the threshold was much higher than researchers anticipated.
“Our simulations are able to follow the formation of stars in the universe much more accurately than was previously possible,” Bower explains. “Our simulations accurately reproduce the formation of stars and galaxies in our universe, and this gives us confidence that we are able to predict how many stars would form in a universe that had more dark energy. The surprising result is that the amount of dark energy can be much much larger than we observe, and yet the universe still forms plenty of stars.”
While the teams don’t suggest the multiverse idea “solves” the mystery of life in our universe (or others), this research serves as a stepping stone for future physics investigations. The teams propose a new law of physics might need to be created in order to help explain the small amount of dark energy on the universe.
“The multiverse was previously thought to explain the observed value of dark energy as a lottery — we have a lucky ticket and live in the universe that forms beautiful galaxies which permit life as we know it,” says Dr. Luke Barnes, a John Templeton Research Fellow at Western Sydney University. “Our work shows that our ticket seems a little too lucky, so to speak. It’s more special than it needs to be for life. This is a problem for the multiverse; a puzzle remains.”
Bower, the physicist at Durham University, says our universe might be something for its limited about of a dark energy, enabling life.
“The multiverse theory suggests that universes are born with random amounts of dark energy”
“The multiverse theory suggests that universes are born with random amounts of dark energy, with most universes having much larger values than we find in our own,” Bower tells Inverse. “If universes with larger values could not form stars, planets or life … our universe would be picked out as special.”
He continues: “Our work shows that this explanation doesn’t work! Our universe is far more special than this theory can explain. Our work suggests that a new theory of dark energy is needed,” making the weird plot of Donnie Darko only slightly less weird.
Models of the very early universe, including inflationary models, are argued to produce varying universe domains with different values of fundamental constants and cosmic parameters. Using the cosmological hydrodynamical simulation code from the EAGLE collaboration, we investigate the effect of the cosmological constant on the formation of galaxies and stars. We simulate universes with values of the cosmological constant ranging from Λ = 0 to Λ0 × 300, where Λ0 is the value of the cosmological constant in our Universe. Because the global star formation rate in our Universe peaks at t = 3.5 Gyr, before the onset of accelerating expansion, increases in Λ of even an order of magnitude have only a small effect on the star formation history and efficiency of the universe. We use our simulations to predict the observed value of the cosmological constant, given a measure of the multiverse. Whether the cosmological constant is successfully predicted depends crucially on the measure. The impact of the cosmological constant on the formation of structure in the universe does not seem to be a sharp enough function of Λ to explain its observed value alone.