Hungry Hungry Universe
It's broadly agreed that the universe is constantly expanding. The why of it all, though, is a little more mysterious. Most researchers agree that dark energy is responsible for our universe's ever-creeping growth. The problem with that: dark energy has never actually been observed by science — so far, we've only been able to infer its existence by the theoretical celestial stuff's effects on other objects.
Enter a study published December 2023 in the Journal of Cosmology and Astroparticle Physics, in which researchers from the University of Copenhagen and the Tokyo Institute of Technology argued that our universe could simply be swallowing "baby" parallel universes, leading to a sustained cosmic bloating.
Or as lead study author Jan Ambjørn, a physicist at the University of Copenhagen's Niels Bohr Institute, told LiveScience:
"The main finding of our work is that the accelerated expansion of our universe, caused by the mysterious dark energy, might have a simple intuitive explanation, the merging with so-called baby universes, and that a model for this might fit the data better than the Standard Cosmological Model."
In other words, our cosmos' expansion might not require dark energy as a constant, as the field's Standard Cosmological Model necessitates. It could just be out here... swallowing stuff. Like a cosmic Blob Monster consuming parallel worlds.
The paper is more or less a mathematical exercise, but pieces of it are compelling nonetheless. For one thing, as LiveScience points out, it accounts for the intense inflation that our universe experienced in the first few milliseconds after the Big Bang. The accepted theory is that a hypothetical field, commonly referred to as the "inflaton," was responsible; conversely, this new study suggests that our universe, then a "baby" itself, could have simply been blob-devoured by another, older universe.
That would explain immediate rapid growth — without the need for the hypothetical inflaton.
"The fact that the Universe has expanded … in a very short time, invites the suggestion that this expansion was caused by a collision with a larger universe," the researchers write in the study, "that is, it was really our Universe which was absorbed in another 'parent' universe."
Again, though, this is all just math. As the researchers themselves noted in the study, they don't have insight or detailed observations into what the mechanics of the universe-gobbling-universe process might fully entail, so their conjectures are as unproven as the rest.
Still, it's a fascinating reminder of how little we know about our cosmos — and how even some of astronomers' leading hypotheses remain just that.
More on worlds definitely colliding: Hubble Snaps Alarming Pic of Two Galaxies Crashing into Each Other