Sam Wormley wrote:
<snippage here and there>
Science News, Week of Aug. 30, 2003; Vol. 164, No. 9
http://www.sciencenews.org/20030830/fob3.asp
As anyone falling into a black hole would tell you-if only they
could-the trip ends badly.
If you fell in feet first, the hole would pull harder on your toes
than your head, because the top of your body would lie farther from
the hole's center. Similarly, the uneven tug exerted by the hole
would compress your shoulders as though they were in a vise. Because
of these differences in gravity, you'd be simultaneously ripped apart
vertically and squeezed horizontally. From the instant these tidal
forces became too much to bear, death would occur in just under a
tenth of a second.
A "gripping" scenario...
Although death is unavoidable, is there any way to delay it and
shorten the agony?
According to two researchers who actually took the time to
contemplate the problem, the answer is yes. But you have to take
along the right equipment, assert Princeton University cosmologist J.
Richard Gott and Deborah L. Freedman of Harvard University. The
essential item resembles a life preserver-a thin ring massive enough
to counteract the black hole's tidal forces. The ring would have to
be as heavy as a large asteroid and could be as large as one of the
rings of Saturn, says Gott. The researchers have posted their
whimsical analysis online
(http://xxx.lanl.gov/abs/astro-ph/0308325).
Kept at waist level, the ring would exert an upward tug on your feet
and a downward pull on your head, counterbalancing the black hole's
uneven tug on different parts of your body. As the traveler
approached the black hole and the tidal forces from it increased, the
ring would shrink and exert correspondingly larger countertidal
forces. The massive ring would have to be electrically charged to
keep it from collapsing.
The ring counters the black hole's tidal forces up to a whopping
6,760 g's- 676 times the gravity a human body can withstand. That
would give a black hole diver an extra 0.09 second to remain in one
piece. It also means that tidal forces would begin to overwhelm the
explorer only during the last 0.00346 second of the journey, a time
so short "you'd never know what hit you," says Gott. The notion that
it's possible to even temporarily prevent tidal dismemberment of any
object that gets too close to a black hole is "something no one had
shown before," says Freedman.
ISTR Robert L. Forward mentioned this possibility
(without math) in one of the appendices to _Dragon's Egg_.
This intellectual exercise could have a practical application. In
venturing near a dense star called a neutron star, or touring the
outskirts of a small black hole, such a life preserver would enable a
space traveler to "venture closer than would otherwise have been the
case and still return safely home from the adventure," the
researchers note.
Forward describes this technique in _Dragon's Egg_ for
flattening spacetime near a neutron star so a manned
observatory can get into a frighteningly close orbit, except
he used a set of spherical masses rather than a ring. He
called them "compensator masses", and also included a pair
above and below the observatory.
"This idea could make a nice problem in a textbook . . . but will not
have much wider implications," says Avi Loeb of the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
If a neutron star comes whizzing out of Draco anytime
soon, it could even be practical.
Mark L. Fergerson
.
