This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Let me be clear: Another Earth, opening July 22, is not a science-fiction film, despite its premise of the discovery of a planet just like our own.
And frankly, the little science that does exist in this otherwise remarkable indie film, by first-time feature director Mike Cahill, is laughable. For instance, Earth 2 can be seen hanging in the sky near Polaris, the north star, which would put its orbit perpendicular to the solar system's ecliptic—and ripe for discovery long ago. Plus, Earth 2 keeps getting bigger as the movie goes on, meaning that it gets closer without gravitationally disrupting our home's orbit.
In this movie, though, the existence of a second Earth is a metaphor, artistic leverage to explore what it means to confront yourself and your past, warts and all. The warts in this case belong to Rhoda Williams (played by co-writer and co-producer Brit Marling), a brilliant high school senior on her way to M.I.T. to study astrophysics. One evening, she makes the poor decision of driving after heavily drinking and plows into a car driven by John Burroughs (William Mapother, perhaps better known as "Ethan" from the TV series Lost ). The accident, which kills Burroughs's wife and young son, also occurs on the night when Earth 2 is discovered.
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Four years later, Rhoda is released from prison, but instead of picking up where she left off, she decides she still needs to do penance and takes a job as a school janitor. The lost and emotionally fragile Rhoda seeks out John, who never knew, or wanted to know, who destroyed his world. John, a once successful composer and master of the saw (you know, the musical instrument you can find at any Home Depot), has yet to come close to recovering from his heartbreaking loss. Compelled to make reparations, Rhoda inveigles her way into John's life without revealing her true identity (did I mention that she has poor decision-making skills?). The two damaged souls begin the road to recovery with each other's help, at least until Rhoda wins a chance to visit the other Earth, a prospect that fills Rhoda with hope but John with dread.
The speculative fiction in this film, which at this year's Sundance Film Festival won the Alfred P. Sloan Prize for the best film focusing on themes of science and technology and the Special Jury Prize for Dramatic Feature, might seem like something inspired by the multiverse theory. In fact, the movie was screened during the World Science Festival in June, where Columbia University physicist Brian Greene led a discussion about it one evening. But Cahill and Marling—both majored in economics at Georgetown University, and Marling was an analyst at Goldman Sachs—had not even heard of Greene's bestseller on the multiverse theory, The Hidden Reality (Knopf, 2011), until after the movie was done.
Cahill actually came up with the concept after listening to audio books of Pulp Physics by astrophysicist Richard Berendzen, who now directs NASA’s Space Grant Consortium. Berendzen makes an appearance as the expert interviewed on local news to explain the "broken mirror theory" that decouples the inhabitants of both Earths and sets them on different destinies.
And therein lies what might be the only part of the film relevant to the multiverse theory, at least as navel-gazing in the blogosphere is concerned. Some observers have commented that the multiverse has a moral dimension to ponder. In his Huffington Post blog, Clayton Naff worries how the general populace will interpret the multiverse theory. Basically, he reasons that if all possibilities happen infinitely, then what does it matter how we behave in this universe: "If we come to believe that choices do not matter, that any action is matched by its opposite somewhere, we risk losing our capacity for moral reasoning."
Another Earth touches on this moral dimension in the sense that the second planet gives you a second chance. You might not really have to live with the consequences of your decisions. And whatever moral reasoning you did to make the choice could have led your doppelganger to make the exact opposite choice.
Discussions of moral relativism came long before the idea of a multiverse, of course. Still, bloggers have found other upsetting moral aspects of multiverse thinking. John Horgan asked in a Cross-check blog post if speculation in the multiverse is as immoral as speculation in sub-prime mortgages. In a post on his Not Even Wrong blog, Peter Woit frets that the multiverse theory essentially promotes pseudoscience to the general public. (Caltech physicist Sean Carroll has a good review of these moral qualms in his Cosmic Invariance blog post here.)
The latter objections stem from an outright dismissal of the multiverse for its lack of scientific rigor; after all, astronomical observations cannot detect the alternate realities. And even if true, the multiverse fails to explain deep mysteries of nature. (See, for example, George Ellis's article in the August 2011 issue of Scientific American. ) In terms of the immorality of multiverse thinking, however, neither Horgan nor Woit convinces me, because so much of basic research explores concepts well removed from everyday practical experience and applications, and all science runs the risk of being misinterpreted and misused.
Some physicists do take the concept of the multiverse seriously; see the defenses of parallel universes by Alexander Vilenkin and Max Tegmark, who also notes that the theory might actually be testable. No doubt, an Earth hanging in our sky would be the most convincing evidence of all.