Could there really be parallel universes? Whole other universes that exist somewhere,
somehow outside or alongside or within our own universe or in some mysterious
relationship to our universe? Can we find out anything about them? Can we
get to them? Can we communicate with sentient beings inside them? I believe your guess is as good as
anyone’s. Which is to say, I think no
one really knows. Which is also to say
all of the above might just be possible!
There are certain premises in science fiction that
are dead letters because they are
1. beaten-to-death
clichés, or
2. pernicious
because of what they imply, or
3. simply
stupid to speculate about because of what scientists have repeatedly shown
us. Among these are , faster than light
travel, time travel, and, in my opinion, as of 2019, space travel (see
my blog post).
You might think the parallel universe premise would fall into
at least one of the above categories. I
don’t think so.
Let’s examine the parallel universe premise from the
standpoint of the three criteria I’ve imperiously defined above. Are parallel universes dead horse clichés? They do show up a lot. They have featured in
some of the very best science fiction. If anything about P.K. Dick’s writing
can be described as a “staple,” it’s the parallel universe. In Dick’s writing,
people move between parallel universes, they create parallel universes (The World
Jones Made), and they join each other in secret trysts in the same parallel
universe by taking a certain drug at the same time (The Three Stigmata of
Palmer Eldritch). Dick’s parallel universes sometimes even bleed into each
other. One of Dick’s little-known
influences, Frederic Brown, spun out one of the best parallel universe stories in
his 1949 novel What Mad Universe. These
are some of my favorite science fiction stories of all time. These stories aren’t clichés because the
parallel universe is used as an effective literary device, providing
opportunities for characters to do things and compare things they otherwise
couldn’t. But the idea of a parallel
universe is not a cliché for another reason as well: it is such a broad idea. It’s not just an expedient like time travel. All fantasy worlds and alternate histories could
be considered parallel universes. A huge
variety of alternative reality stories have been written.1
Indeed, the very idea of writing a fictional story might be considered creation
of an alternative universe.
But the science fiction parallel universe I’m talking about,
in my opening paragraph above, is more limited.
It’s one that can have some kind of interaction with the reader’s
everyday universe. These universes are
“parallel” rather than simply “other” because they have some kind of
relationship to our own. That’s what is in Dick’s and Brown’s universes, and
those contemplated by Heinlein, Zelazny, Moorcock, Borges, Lewis Carroll and many
others. And even thus limited, there is
still a huge variety. Whole universes
worth.
Is there anything pernicious about promoting the idea of a
parallel universe? The idea of such a
universe is not pernicious in itself, as I believe promoting space travel
currently is, because the parallel universe idea encompasses so much territory.
Some might consider escapism pernicious, or at best a waste of time. Maybe so. But
in any case, the better parallel universe stories are not simply escapist. They
allow us to bring into focus contrasts among real things, and real potential
things, in unique ways.
What does science say about the reality of parallel
universes? To me, the most interesting
parallel universes are those that might be real instead of just effective
literary devices. Scientists working at the limits of what we can know, the biggest
things and the smallest things, have proposed two kinds of parallel
universe.
At the small end of things, the most fundamental interactions
of matter and energy, those among photons, atoms and their constituent parts
are governed by the equations of quantum mechanics. These equations come from the results of real
experiments (usually real expensive too) with these fundamental particles and
forces. They imply some bizarre things,
like instantaneous correlation of distant events, and things existing in two
mutually exclusive conditions until they interact with something else. One of the interpretations of quantum
behavior that is supported by some very reputable physicists is called the
“many worlds” theory.2 It is controversial because it has not been
either proved or disproved, yet it provides elegant solutions to the quantum
equations. Some highly respected physicists consider it plausible, if
bizarre. It postulates that every
physical interaction that has an element of quantum uncertainty generates
separate realities for each possible outcome.
That means an unfathomable number of separate universes. For science fiction, that means infinite speculation
territory.
At the biggest end of things there’s cosmology, the study of
the universe as a whole. We normally think of the universe as being everything,
including all space, matter, energy, thought, and all people. Cosmologists have reduced the universe we
know to a thing that can be looked upon from outside, in our imaginations. They
describe the whole thing’s behavior in a single equation.3
They measure a wide variety of things across the sky, from changes in stars’ light
spectrums that show they are all moving away from each other, to space-filling microwave
radiation that could only have come from the hot soup of electrons and nuclear
particles giving off energy as they cooled and settled into ordinary atoms in the
early universe, to the ratio of hydrogen and helium in stars and space, that
confirms how that hot soup formed the atomic nuclei that everything is made of.
The data show that the whole universe has been expanding and cooling since its
creation. Cosmologists, using their observations, trace the expansion back to a
very tiny and very hot space from which the whole universe exploded, and call the
explosion the big bang. They can trace
it back to an age of one trillionth of a second after creation, during which
time the entire universe expanded from less than a millimeter in size to about
the size of our current solar system, and had an average temperature of 10
quadrillion degrees Celsius.4 And using these same data, cosmologists propose
that the big bang, the beginning of this universe we know, may have spawned not
just the universe we know but a multiverse, an infinite number of co-existing universes.5
How could there be interactions with these hypothesized
parallel universes? At the quantum level, the many worlds seem to be blossoming
in some kind of very close proximity, since multiple realities are spawned by the
same microscopic events. Who is to say
there couldn’t be some collective interactions?
And for the separate universes of the multiverse, it’s been suggested
that they could each have different basic laws of nature than our own. Who can say this wouldn’t allow some kind of
interaction in specific cases? The point
here is we don’t know at all. There is
nothing that says how likely or unlikely interactions between parallel
universes could be. It’s wide open for
speculation.
Parallel universes are not hackneyed science fiction crutches as are space travel, time travel and faster-than-light travel. All of those crutches rely on assumptions which scientists tell us are highly unlikely. That’s not the case for parallel universes. Both the quantum many worlds idea and the cosmic multiverse idea are based on careful reasoning from experimental data and from cosmological observations, and have been vetted by many respectable scientists in these fields. The verdict for both is: plausible but unproven. Plausible but unproven is what science fiction is all about. There are so many ways to think about parallel universes.
Parallel universes are not hackneyed science fiction crutches as are space travel, time travel and faster-than-light travel. All of those crutches rely on assumptions which scientists tell us are highly unlikely. That’s not the case for parallel universes. Both the quantum many worlds idea and the cosmic multiverse idea are based on careful reasoning from experimental data and from cosmological observations, and have been vetted by many respectable scientists in these fields. The verdict for both is: plausible but unproven. Plausible but unproven is what science fiction is all about. There are so many ways to think about parallel universes.
[1]
The Wikipedia
Article on Parallel Universes is amusing and replete, to the extent
of irritating the Wikipedia editors.
[2] Penrose,
Roger, The Road to Reality
(2004), Section 21.11
[3]
The Friedmann equation, which uses Einstein’s general relativity theory to
describe the behavior of the entire universe.
See Weinberg, Steven, The First Three Minutes (1977), Chapter 11 The Expansion of the Universe. It’s old
but still valid and a good explanation.
[4]
Ryden, Barbara, Introduction to Cosmology, 2nd ed. (2017),
Chap. 10 Inflation and the Very Early
Universe.
