Researchers Say Idea Can Be Tested.
A decade ago, a British philosopher put forth the notion that the universe we
live in might in fact be a computer simulation run by our descendants. While
that seems far-fetched, perhaps even incomprehensible, a team of physicists at
the University of Washington has come up with a potential test to see if the
idea holds water.
The concept that current humanity could possibly be living in a computer
simulation comes from a 2003 paper published in Philosophical Quarterly by Nick
Bostrom, a philosophy professor at the University of Oxford. In the paper, he
argued that at least one of three possibilities is true:
•The human species is likely to go extinct before reaching a “posthuman”
•Any posthuman civilization is very unlikely to run a significant number of
simulations of its evolutionary history.
•We are almost certainly living in a computer simulation.
He also held that “the belief that there is a significant chance that we will
one day become posthumans who run ancestor simulations is false, unless we are
currently living in a simulation.”
With current limitations and trends in computing, it will be decades before
researchers will be able to run even primitive simulations of the universe. But
the UW team has suggested tests that can be performed now, or in the near
future, that are sensitive to constraints imposed on future simulations by
Currently, supercomputers using a technique called lattice quantum
chromodynamics and starting from the fundamental physical laws that govern the
universe can simulate only a very small portion of the universe, on the scale of
one 100-trillionth of a meter, a little larger than the nucleus of an atom, said
Martin Savage, a UW physics professor.
Eventually, more powerful simulations will be able to model on the scale of a
molecule, then a cell and even a human being. But it will take many generations
of growth in computing power to be able to simulate a large enough chunk of the
universe to understand the constraints on physical processes that would indicate
we are living in a computer model.
However, Savage said, there are signatures of resource constraints in
present-day simulations that are likely to exist as well in simulations in the
distant future, including the imprint of an underlying lattice if one is used to
model the space-time continuum.
The supercomputers performing lattice quantum chromodynamics calculations
essentially divide space-time into a four-dimensional grid. That allows
researchers to examine what is called the strong force, one of the four
fundamental forces of nature and the one that binds subatomic particles called
quarks and gluons together into neutrons and protons at the core of atoms.
“If you make the simulations big enough, something like our universe should
emerge,” Savage said. Then it would be a matter of looking for a “signature” in
our universe that has an analog in the current small-scale simulations.
Savage and colleagues Silas Beane of the University of New Hampshire, who
collaborated while at the UW’s Institute for Nuclear Theory, and Zohreh Davoudi,
a UW physics graduate student, suggest that the signature could show up as a
limitation in the energy of cosmic rays.
In a paper they have posted on arXiv, an online archive for preprints of
scientific papers in a number of fields, including physics, they say that the
highest-energy cosmic rays would not travel along the edges of the lattice in
the model but would travel diagonally, and they would not interact equally in
all directions as they otherwise would be expected to do. “This is the first
testable signature of such an idea,” Savage said.
If such a concept turned out to be reality, it would raise other
possibilities as well. For example, Davoudi suggests that if our universe is a
simulation, then those running it could be running other simulations as well,
essentially creating other universes parallel to our own.
“Then the question is, ‘Can you communicate with those other universes if
they are running on the same platform?’” she said.