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Credit: No one willing to take responsibility for this one
Mar 24, 2006
A Dent in the Space-Time Fabric?
What does a
dent in the “fabric” of space and time look like? The cause in a
faraway place is invisible, scientists say. But theorists believe
its existence can be deduced from certain repetitive events.
In
January this year scientists reported that in 2005 two unusual X-ray
frequencies were detected coming from an extremely energetic light
source, GRO J1655-40. The source is seen in the constellation
Scorpius and it is estimated to lie about 10,000 light-years from
Earth. Astronomers say it is a “stellar black hole” about seven
times the mass of our Sun, gradually consuming the matter of a
companion star.
The emissions seemed strange because scientists had recorded identical
emissions nine years earlier—an improbable coincidence, they
thought. This got them to thinking, and the chain of reasoning that
followed led to a report given at a recent meeting of the American
Astronomical Society.
The
centerpiece of the story is a black hole, and black holes are said
to form in the death throes of massive stars as their fuel runs out
and their cores “implode into a point of infinite density”. The
“rebound” that follows produces a supernova explosion that blows
away the outer layers of the star. But the gravity of the collapsed
star is so great that, within a boundary called the “event horizon”,
nothing is able to escape, not even light. And that’s why we can’t
see a black hole, astronomers say.
Astronomers also say that the gravitational tug of a black hole is
sufficient to distort Einstein’s “space-time fabric”. And that means
it could affect the movement of matter falling into this celestial
glutton.
The X-ray emissions from GRO J1655-40 are sporadic—long periods of
relative calm followed by shorter periods of more intense activity
with emissions millions of times greater than during the quiescent
phase.
As reported on Space.com, some scientists began to wonder if the
blinking pattern of X-ray activity is “related to how matter
accumulates around the black hole”. The black hole is said to be
stealing gas from a companion into an “accretion disk” around the
super-dense relic, and the scientists suggested that as the mass of
the disk accumulates for several years, the black hole consumes very
little of the gas, and X-ray emissions are minimal.
“Every few years, however, something—scientists aren’t sure
what—triggers a sudden binge fest on the part of the black hole,
causing it to guzzle down most of matter in the disk within a period
of only a few months”. This is when the profusion of X-rays occurs,
the scientists suggested. (See “
Black Hole Puts Dent In
Space-time”, January 24, 2006),
But NASA’s Rossi X-ray
Timing Explorer recorded something curious. Among the
X-ray frequencies observed in 1996 were one at 450 Hz and one at 300
Hz. The same two frequencies were observed again in 2005.
"Because it’s very hard to get gas to behave the same way twice, it
argues strongly that these frequencies are being anchored by the
black hole’s mass and spin”, study co-author Jon Miller of the
University of Michigan told SPACE.com.
The scientists were reminded of the weird things predicted by
Einstein’s theory of general relativity. “Because the black hole is
so massive and spinning so fast, it warps spacetime around it”. And
the more massive the object, the more spacetime is distorted. “If
the massive object is also spinning, it causes spacetime to not only
bend but to twist as well”.
The authors suggest that the particles moving in “warped spacetime” near
the black hole exhibit two types of motions, each producing a unique
frequency. “One motion is the orbital motion of the gas as it goes
around the black hole. This produces the 450 Hz frequency. The lower
300 Hz frequency is caused by the gas wobbling slightly due to the
spacetime deformations”.
"If
spacetime were not curved, we’d probably just see one peak," said
study co-author Jeroen Homan from the Kavli Institute for
Astrophysics and Space Research at MIT.
The authors seemed confident that they were on the right track, and few
astronomers raised objections. "We can now begin to determine the
spin and thus, for the first time, more completely describe the
black hole," Miller said.
-----------------------------
Though
the photograph above is at best only marginally relevant, we have
tried to be as accurate as possible in paraphrasing the logic that
two scientists applied to the X-ray emissions from GRO J1655-40. Can
you track the number of speculations in their reasoning? Can you
separate what is known from what is imagined? If this seems
difficult, that is because the language used by scientific media
continually confuses fact and theory.
The light source in Scorpius is a fact. So are the sporadic X-ray
emissions. But it may surprise you to hear that everything else
discussed in the report is speculation, unsupported by anything we
can actually study in nature: the star running out of fuel, the
implosion, the rebound, the imploded star, its “infinite density”,
the “spacetime fabric”, the stellar black hole, the “event horizon”,
the companion star, the siphoning of the companion’s gases, the
“accretion” disk, the “sudden binge fest”, X-ray production by
accumulating matter, the calculated “spin-rate”, the simultaneous
“bending and twisting of spacetime”, X-ray frequencies linked to
orbital motion of gases, and X-ray frequencies linked to “wobbling”
of gases due to “spacetime deformation”.
So it
is not unreasonable to pose the question: Does the activity of GRO
J1655-40 really imply a “dent in the space-time fabric”? Or is there
a much simpler explanation based on accessible natural
phenomena?
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