This view is based on a solution to Einstein's equations of general relativity found by German astrophysicist Karl Schwarzschild, who worked out his math during WWI while stationed at the Russian front. Schwarzschild sent his calculations to Einstein and died shortly thereafter. Theories based on his results have dominated the popular picture of black holes ever since.

"The singularity inside a Schwarzschild black hole is destructive, and any physical object which approaches it is necessarily and unavoidably pulverized by it," Burko explained in an e-mail interview. "Specifically, any such object is infinitely stretched in one direction and infinitely squeezed in two other directions. That is sometimes called 'spaghettification.'"

But some black holes have hybrid structures, theorists have long suspected. The new research shows that the hybrid singularity could contain both strong and weak sectors.

"It would allow the captain to navigate toward the sector where the singularity is weak," Burko said. "Experiencing only finite (and even small) effects (of stretching and squeezing), the spaceship could arrive at the singularity unharmed. While that still does not guarantee a peaceful traversing of the singularity, it keeps the possibility of doing so open. If that traversing becomes possible, it could open a 'tunnel' to another universe."

The highly speculative idea that such a journey might lead to another universe is based on certain solutions, developed in the 1960s, of Einstein's equations about time and space. The solutions allow for the possibility of multiple universes connected by black holes.

Burko arrived at his conclusion through a comprehensive analysis of how long-duration streams of radiation would affect a black hole's structure when falling inward. The results were published in the March 28 issue of the journal Physical Review Letters.

For an interuniversal journey, not just any size of black hole will do.

Stellar black holes, the variety created by the collapse of a star, are no good. Tidal forces -- similar to the effects of the Moon that lift tides on two sides of Earth at once -- "can overwhelm the resistance of our bodies to stresses if the mass of the black hole is small," Burko said.

With a supermassive black hole -- the one at the center of the Milky Way Galaxy would do, he says -- "the situation is much different, and tidal forces just on the boundary of the black hole can be very small, even smaller than on the surface of the Earth."

Other unknowns may thwart the journey. Weak sectors might still be too hazardous for travel, and no one has yet figured out if anything really exists on the "other side."

There is also the problem of getting to the center of the galaxy, a trip across 26,000 light-years that would require a really fast ship or a crew willing to die and spawn more than a few generations en route. Perhaps if they start now, Burko or some other theorist will have some firm answers about their ultimate prospects by the time they get there.