Theoretical physicists have a lot in common with lawyers. Both spend a lot of time looking for loopholes and inconsistencies in the rules that might be exploited somehow.
Valeri
P. Frolov and Andrei Zelnikov from the University of Alberta in Canada and Pavel Krtouš from
Charles University in Prague probably couldn't get you out of a traffic fine,
but they may have uncovered enough wiggle room in the laws of physics to send
you back in time to make sure you didn't speed through that school zone in the
first place.
Shortcuts through spacetime known as
wormholes aren't recognized features of the cosmos. But for the better part of a century,
scientists have wondered if the weft and warp instructed by relativity prescribe
ways for quantum ripples – or even entire particles – to break free of their
locality.
At
their most fantastic, such reconfigurations in the fabric of the Universe would
allow human-sized masses to traverse light-years to cross galaxies in a heartbeat
or perhaps move through time as quickly as one might move through their kitchen.
At
the very least, exercises that probe the more exotic side of spacetime behavior
could guide speculation over the mysterious meeting point of
quantum physics and the general theory of relativity.
Wormholes are, in
effect, little more than shapes. We're used to dealing with single-dimensional lines, two-dimensional drawings,
and three-dimensional objects in everyday life. Some we can intuitively fold,
mold, and poke holes in.
Physics
allows us to explore these changes in situations we can't
intuitively explore. On the smallest of levels,
quantum effects give distances and time some wiggle room.
On
much larger scales, spacetime can shrink and expand in relation to gravity in ways that are
impossible to appreciate without a whole bunch of equations to guide you. For
example, cram enough mass in one place (conveniently
ignoring any charge it might have, or if it spins around), spacetime will bend
in ways that give it two exterior surfaces. What connects them? A wormhole, of
course.
Matter
wouldn't be able to move across this mathematical structure, though some suspect
objects on either side that happen to be entangled would remain linked.
Over
the decades, the search has been on for scenarios – both possible and purely
theoretical – that could allow for quantum effects, and even whole particles, to journey through
exotic shapes of spacetime unscathed.
Frolov,
Krtouš, and Zelnikov's time warp proposal involves what's known as a ring wormhole, first described in 2016 by the
University of Cambridge theoretical physicist Gary Gibbons and University of
Tours physicist Mikhail Volkov.
Distinct
from spherical contortions of spacetime we might attribute to black holes, the ring wormhole
proposed by Gibbons and Volkov connects patches of the Universe (or different
universes, for that matter) that are what we call flat.
Considering
interactions of electrical and magnetic fields called duality rotations and
applying some choice transformations, ring-shaped masses could create some
interesting distortions in what would otherwise be flat spacetime.
And
voilà! A hole in the Universe that connects you to … well, somewhere not nearby.
Frolov,
Krtouš, and Zelnikov took this hole and ran it through different scenarios. Like, what effect
might another, non-moving mass have on the ring? And what if the entry ring and
exit ring are in the same universe?
The
solutions they uncovered included what's known as a closed timelike curve.
Just as it sounds, it describes an object or ray of light that travels along a
line, returning to the exact same point as before. Not only in space but time
as well.
Before
you pack for a paradoxical round trip to the future and back, many obstacles
could easily prevent such a loop. The late physicist Stephen Hawking certainly thought so.
But
who knows? With the right kind of cosmic lawyer, we just might be able to
appeal our sentence of a one-way trip into the future with a bit of help from a
massive pair of rings.
This research is available on preprint server arXiv and has been accepted to be published in Physical Review D.
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