Trip into black hole possible

April 10, 2003 at 12:18 PM

SALT LAKE CITY, April 10 (UPI) -- When it comes to spaceship jaunts through a black hole to a distant part of the cosmos or even another universe, new research suggests anything -- or anyone -- that dared such an attempt might not be destroyed outright.

"There are many science fiction stories where you see these scenarios," researcher Lior Burko, a theoretical physicist at the University of Utah, told United Press International. "While this does not guarantee you will survive, at least it still keeps the possibility open."

Black holes are pits in space and time. They are so dense that nothing can escape their gravitational pull, not even light -- hence their name. They are formed when giant stars run out of fuel -- first they explode in titanic blasts called supernovae, then their remnants collapse into black holes because their outward-pushing nuclear explosions no longer can offset their tremendous gravitational pull.

However, decades of research suggests, at the hearts of black holes, the fabric of reality might be distorted so much that portals to other universes are opened. Such portals could be used as instantaneous shortcuts through "hyperspace" to far-off corners of our universe, places that otherwise would require millions of years to reach, even at the speed of light.

"It's a thought-provoking scenario," Burko commented.

The catch to such intergalactic or universe-spanning trips, traditional physics holds, is the portals are choked off by singularities -- infinitely dense points where all a black hole's mass is concentrated. Where the moon's tidal pull on the Earth can draw ocean waves more than 50 feet high, a singularity could exert unimaginably powerful pulls on any "extended object," or non-point-like item, such as a molecule or larger. The singularity's gravity would stretch it "infinitely in one direction," Burko said. "Colloquially, it would be called 'spaghettified.'"

Yet scientists now suspect this picture is not complete, he explained.

For instance, when a black hole spins -- as many are believed to, because they are formed from whirling, dying stars -- it might form a phenomenon called a "hybrid singularity," sort of an Achilles Heel, a relatively weak zone that could exert only limited tidal forces.

There's a problem, though, Burko explained: such hybrids are unstable. Scientists have debated whether any energy or matter approaching the weak zone would cause the black hole's overwhelming destructive zone to expand and block off access to the weak zone. The entire known universe, for instance, is pervaded with microwave energy, a leftover from the Big Bang. The leftover energy could be enough to jam any black hole portals.

Burko's calculations suggest, however, as long as the energy or other disturbance -- such as a spaceship -- is weak, the portal might remain open and "you could navigate your spaceship to the weak part" and dive through relatively unscathed, he said.

"There is still much we do not understand, and it could well be in the future someone very clever will prove it is impossible after all," he added. "But the laws of physics as we currently understand them do not preclude that possibility."

Assuming such hyperspace journeys are possible, the most promising black holes for this purpose would be "supermassive ones, like those in the center of many galaxies," Burko said. A giant black hole, equivalent to some 2.6 million solar masses, lurks at the Milky Way galaxy's core. Other monsters, weighing a billion solar masses or more, are known to exist.

It might sound strange, but the smaller black holes pose more dangers for hyperspace missions. Their tidal forces -- a few times the mass of our sun -- are too powerful for any object to survive their grasp. The larger the black hole, however, the more spread out its gravitation becomes, and within selected zones "could even be smaller than at the surface of the Earth," Burko said.

To keep open the possibility of hyperspace travel, Burko explained, the universe would have to expand faster and faster over time, so the microwave energy left over from the Big Bang dilutes out, keeping low the overall energy pouring into the black hole.

This no longer seems so far-fetched, he continued. Recent observations have led many scientists to theorize "that the universe's expansion rate is accelerating over time."

Even if possible theoretically, navigating a spaceship into a black hole's safer zone would remain extremely difficult -- and far beyond existing Earthbound technologies. Geometry becomes a complicated matter near the distorted space and time of a singularity, Burko said. Any mistake in the angle, speed or time of entry could trap a spaceship forever, he added.

There are two other dangers: First, a black hole's gravitational pull is so powerful it can shorten wavelengths of light, turning any relatively harmless visible rays into deadly X-rays or gamma rays. "But you can shield against gamma rays. It's not necessarily a problem of principle. Tidal forces can't be shielded," Burko said.

Second, once anything -- matter or energy -- crosses a black hole's "event horizon," it cannot return. A hyperspaceship plunging into the event horizon could not communicate with anyone outside the attempt had succeeded.

Such communication would be possible only if and when the hyperspaceship ultimately reenters our universe. Even then, the ship would have to "take the long route around to let us know," Burko said.

Burko cautioned that more complicated theoretical models need to be constructed to simulate black holes more realistically. Perhaps then, scientists could determine with greater certainty whether such travel is possible.

"I think the exciting aspect of this work is the fact that (Burko) has demonstrated rather clearly, using a simple model, that indeed an extended object may be able to do hyperspace travel," gravitational physicist Gaurav Khanna, of Southampton College of Long Island (N.Y.) University, told UPI. "Overall, I think it is a rather excellent piece of research."


(Reported by Charles Choi, UPI Science News, in New York)

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