The idea that spaceships might zip across the universe using
black holes as a high-speed portal is a well-worn sci-fi
cliché.
But the consensus among scientists of late is that black holes are
so destructive, spaceships would be torn to subatomic bits if they
tried such a thing.
Then again, maybe not. A new paper by University of Utah physicist
Lior Burko, building on earlier work, raises the possibility that
black holes may not annihilate everything, and that the potential
for hyperspace travel is still open.
"One possibility is that black holes may allow us to travel to very
remote places in the universe, or another universe entirely," said
Burko in a telephone interview from his office in Salt Lake City.
"It depends on the topology of the universe, which we do not know
very well.... I'm not arguing it's a practical thing to do, but
maybe in 1,000 years from now, maybe it would be simpler."
In Burko's scheme, black holes may be doorways to wormholes,
theoretical constructs equivalent to tunnels, or shortcuts, between
distant points of the universe, different points in time or even
parallel universes.
Burko's ideas aren't new. Wormholes were popularized by Caltech
physicist Kip Thorne in the 1980s, and were the interstellar
vehicle of choice in Carl Sagan's influential novel Contact.
But subsequent black hole studies have suggested it would be
impossible to use them as wormhole portals. The interiors of black
holes are so infinitely dense that they exert massively
destructive, "tide-like" distortions on approaching objects,
ripping them into their constituent subatomic particles.
In fact, this infinitely dense interior gives black holes their
potential for space and time travel. Inside a black hole, the very
fabric of the universe is collapsed into a point of infinite
curvature -- known as a "space-time singularity," where the laws of
physics no longer apply.
However, Burko, a 34-year-old physicist from Israel, has suggested
that some black holes may not be as destructive as others. Under
certain circumstances, black holes may have "Cauchy horizon
singularities," which may not be destructive but still act as
openings to a wormhole.
Earlier work by Burko and others suggested weaker singularities
were present in rotating black holes.
In a paper published in the March 28 issue of Physical Review
Letters, Burko suggests that under certain conditions, hybrid
singularities may exist. These hybrid singularities are composed of
a strong sector, which is destructive, and a weak sector, which may
not be. Any spacecraft entering the weak sector could possibly pass
through without being damaged.
It's all theoretical, but the possibility of a weaker singularity
doesn't rule out the potential of using black holes for
interstellar travel.
"At the moment, we dont have compelling evidence that this kind of
hyperspace travel is disallowed," said Burko. "It doesn't mean, of
course, it is allowed, but we dont have compelling evidence to the
contrary."
Princeton physicist Richard Gott, author of Time Travel in
Einstein's Universe, said he hadn't read Burko's latest paper, but
previous work on the subject reopened some interesting
possibilities.
"It's certainly one of the possibilities that you can have a weak
singularity," he said. "I characterize it like a speed bump. You
hit it, and you come out in a new region. It could be a region of
time travel, another universe or somewhere a great distance away.
These are interesting possibilities and should be investigated
further."
Burko noted that the theory rests on some unproven assumptions, and
further work could debunk it. In addition, he said so little is
known about quantum gravity -- the marriage of quantum physics and
classic theories of gravity -- that as-yet-undiscovered laws may
forbid hyperspace travel altogether.
Even if the idea of interstellar space travel through black holes
is possible, traveling to a suitable black hole to try it out would
be a problem.
Burko said the black hole at the center of the Milky Way may be a
candidate, but it's 26,000 light years away. Traveling at near the
speed of light -- the upper limit for an interstellar excursion --
the trip would take nearly 30,000 years!