Quite possibly the biggest question posed by eusocial primates. The need to know encouraged our forebears to climb down from the treetops. To brave the savannahs in hopes of sighting distant forests, or making meaningful contact with other clever apes. Over the millennia humans crossed oceans to new lands in hopes of deepening their gene pool, or their pockets. Unlike Alexander the Great, we do not weep when we see the breadth of our domain, knowing there are no more worlds to conquer. Instead we turn our gaze to the stars in hopes of expanding our real estate portfolio, and perk our ears heavenward to eavesdrop on aliens.
More esoterically, cosmologists and mathematicians propose the existence of parallel universes. If it happens we are the sole inhabitants in this dimension, maybe one day we can ping nearby branes of other universes, and hear what our parallel peers have to say about the human condition. The math seems to bear out the many-worlds interpretation, but where’s the evidence?
Back in 2010, Stephen Feeney and pals performed the first observational tests of eternal inflation. They combed WMAP’s 7-year survey of the cosmic microwave background radiation (CMB) for evidence of cosmic collisions. Their theory predicts our universe exists inside a single bubble within an expanding multiverse. Other universes exist within their own bubbles, sometimes ‘bruising’ ours. Bringing us to Roger Penrose and Vahe Gurzadyan detecting concentric circles in the CMB. These patterns could be indicative of a cyclical universe, with each incarnation ending with a big bang. The subsequent universe contains each of the previous universes, presenting a cosmological model akin to a Matryoshka doll. Feeney did note with the volume of data from WMAP, “[I]t is rather easy to find all sorts of statistically unlikely properties in a large dataset like the CMB.”
More observations would be needed to support these theories. WMAP’s successor, the Planck observatory, was up to the task. More sensitive than its predecessor, Planck left behind reams of data after its decomissioning in 2013. Ranga-Ram Chary took it upon himself to renew the search. His Spectral Variations of the Sky: Constraints on Alternate Universes describes bright anomalies in the CMB, possibly from our universe bumping into others. Chary’s method was to subtract the CMB, dust, gas, and stars from Planck’s data which should’ve left nothing but random noise. At the frequency of 143 GHz he found some parts of the sky were significantly brighter than others, proposing they’re evidence of those bumps. With such outlandish claims, there’s a high burden of proof to support them. Chary proposes two explanations outside of alternate universes. He suggests the bright spots may be carbon monoxide in the foreground interstellar medium (ISM) from stellar nurseries. Something similar happened with BICEP2’s data when scientists crowed about last year’s detection of gravity waves. Instead, those waves turned up being dust in the ISM. Ranga-Ram goes on to say carbon monoxide in the ISM is highly unlikely, since the lines aren’t as strong as they ought to be. Therefore a multiverse is a distinct possibility. At least ’til NASA’s Primordial Inflation Explorer, or PIXIE, launches in 2016 to disprove these theories.
Bringing us back to Feeney’s eternal inflation model. Once inflation starts it doesn’t stop, producing smaller pocket universes within the multiverse. Most of these bubbles would have their own physics and composition, some tearing themselves apart in the blink of an eye. Others would be more or less indistinguishable from our own. Some, like Edward Harrison and John Gribbin, posit this is evidence of why our universe is so stable.
[Harrison] says that there are three possible answers. First, that God designed it, though he argues that this answer precludes further rational inquiry. Second, the anthropic principle, but he finds this unsatisfactory. His third answer is that our Universe was created by life of superior intelligence existing in another physical universe. How does he arrive at that conclusion? First, he picks up on the above suggestions of black holes as the birthplaces of new universes. Second, he argues that due to the rapid evolution of intelligence (which we currently see in humanity) there is every reason to expect that a time will come when we will be able to design and create our own universes. Thus, the fine tuning of this Universe is to be explained as an engineering project of superior beings. They have created this Universe out of a black hole. He calls it a ‘natural creation theory’, and claims that it also explains why the Universe is intelligible to us. It is created by minds similar to our own, who designed it to be that way. cite
What if all those brief-lived universes are failed experiments? The product of graduate students pursuing their masters or doctorates, conjuring up each universe like a game of SimCity just to see what works. Or beings from another universe planning the ultimate exit strategy, abandoning their universe for another. Take Marvel‘s Galactus. Formerly known as Galan of Taa, his universe collapsed on itself. In the ensuing big bang, he was reborn as Galactus: Devourer of Worlds. In Stephen Baxter’s novel Ring, an alien race called the Xeelee hopes to escape the heat death of the universe via the Great Attractor. It’s the ultimate big dumb object, created by the Xeelee using cosmic strings as an escape hatch to other universes where physical laws aren’t so familiar.