P
Patriot Games
Guest
http://www.foxnews.com/story/0,2933,305996,00.html
Renegade Astronomers: 'Dark Matter' Is Bunk
Tuesday, October 30, 2007
Two Canadian astronomers think there is a good reason dark matter, a
mysterious substance thought to make up the bulk of matter in the universe,
has never been directly detected: It doesn't exist.
Dark matter was invoked to explain how galaxies stick together. The visible
matter alone in galaxies - stars, gas and dust - is nowhere near enough to
hold them together, so scientists reasoned there must be something invisible
that exerts gravity and is central to all galaxies.
Last August, an astronomer at the University of Arizona at Tucson and his
colleagues reported that a collision between two huge clusters of galaxies 3
billion light-years away, known as the Bullet Cluster, had caused clouds of
dark matter to separate from normal matter.
Many scientists said the observations were proof of dark matter's existence
and a serious blow for alternative explanations aiming to do away with dark
matter with modified theories of gravity.
Now John Moffat, an astronomer at the University of Waterloo in Canada, and
Joel Brownstein, his graduate student, say those announcements were
premature.
In a study detailed in the Nov. 21 issue of the Monthly Notices of the Royal
Astronomical Society, the pair says their Modified Gravity (MOG) theory can
explain the Bullet Cluster observation.
MOG differs from other modified gravity theories in its details, but is
similar in that it predict that the force of gravity changes with distance.
"MOG gravity is stronger if you go out from the center of the galaxy than it
is in Newtonian gravity," Moffat explained. "The stronger gravity mimics
what dark matter does. With dark matter, you take Einstein and Newtonian
gravity and you shovel in more dark matter. If there's more matter, you get
more gravity. Whereas for me, I say dark matter doesn't exist. It's the
gravity that's changed."
Using images of the Bullet Cluster made by the Hubble, Chandra X-ray and
Spitzer space telescopes and the Magellan telescope in Chile, the scientists
analyzed the way the cluster's gravity bent light from a background galaxy -
an effect known as gravity lensing.
The pair concluded that dark matter was not necessary to explain the
results.
"Using Modified Gravity theory, the 'normal' matter in the Bullet Cluster is
enough to account for the observed gravitational lensing effect," Brownstein
said. "Continuing the search for and then analyzing other merging clusters
of galaxies will help us decide whether dark matter or MOG theory offers the
best explanation for the large scale structure of the universe."
Moffat compares the modern interest with dark matter to the insistence by
scientists in the early 20th century on the existence of a "luminiferous
ether," a hypothetical substance thought to fill the universe and through
which light waves were thought to propagate.
"They saw a glimpse of special relativity, but they weren't willing to give
up the ether," Moffat told SPACE.com. "Then Einstein came along and said we
don't need the ether. The rest was history."
[Modified gravity may also help explain the Pioneer Anomaly - the puzzling
fact that the Pioneer 10 and 11 space probes, launched in 1972 and 1973, are
several hundred thousand miles from where the existing laws of physics say
they ought to be as they travel out of the solar system.
It could also do away with the hypothesis of dark energy, a fairly recent
concept which seeks to explain why the expansion of the universe appears to
be accelerating instead of staying constant or slowing down.]
Douglas Clowe, the lead astronomer of the team that linked the Bullet
Cluster observations with dark matter (and now at Ohio University), says he
still stands by his original claim.
For him and many other astronomers, conjuring up new particles that might
account for dark matter is more palatable than turning a fundamental theory
of how the universe works on its head.
"As far as we're concerned, [Moffat] hasn't done anything that makes us
retract our earlier statement that the Bullet Cluster shows us that we have
to have dark matter," Clowe said. "We're still open to modifying gravity to
reduce the amount of dark matter, but we're pretty sure that you have to
have most of the mass of the universe still in some form of dark matter."
Renegade Astronomers: 'Dark Matter' Is Bunk
Tuesday, October 30, 2007
Two Canadian astronomers think there is a good reason dark matter, a
mysterious substance thought to make up the bulk of matter in the universe,
has never been directly detected: It doesn't exist.
Dark matter was invoked to explain how galaxies stick together. The visible
matter alone in galaxies - stars, gas and dust - is nowhere near enough to
hold them together, so scientists reasoned there must be something invisible
that exerts gravity and is central to all galaxies.
Last August, an astronomer at the University of Arizona at Tucson and his
colleagues reported that a collision between two huge clusters of galaxies 3
billion light-years away, known as the Bullet Cluster, had caused clouds of
dark matter to separate from normal matter.
Many scientists said the observations were proof of dark matter's existence
and a serious blow for alternative explanations aiming to do away with dark
matter with modified theories of gravity.
Now John Moffat, an astronomer at the University of Waterloo in Canada, and
Joel Brownstein, his graduate student, say those announcements were
premature.
In a study detailed in the Nov. 21 issue of the Monthly Notices of the Royal
Astronomical Society, the pair says their Modified Gravity (MOG) theory can
explain the Bullet Cluster observation.
MOG differs from other modified gravity theories in its details, but is
similar in that it predict that the force of gravity changes with distance.
"MOG gravity is stronger if you go out from the center of the galaxy than it
is in Newtonian gravity," Moffat explained. "The stronger gravity mimics
what dark matter does. With dark matter, you take Einstein and Newtonian
gravity and you shovel in more dark matter. If there's more matter, you get
more gravity. Whereas for me, I say dark matter doesn't exist. It's the
gravity that's changed."
Using images of the Bullet Cluster made by the Hubble, Chandra X-ray and
Spitzer space telescopes and the Magellan telescope in Chile, the scientists
analyzed the way the cluster's gravity bent light from a background galaxy -
an effect known as gravity lensing.
The pair concluded that dark matter was not necessary to explain the
results.
"Using Modified Gravity theory, the 'normal' matter in the Bullet Cluster is
enough to account for the observed gravitational lensing effect," Brownstein
said. "Continuing the search for and then analyzing other merging clusters
of galaxies will help us decide whether dark matter or MOG theory offers the
best explanation for the large scale structure of the universe."
Moffat compares the modern interest with dark matter to the insistence by
scientists in the early 20th century on the existence of a "luminiferous
ether," a hypothetical substance thought to fill the universe and through
which light waves were thought to propagate.
"They saw a glimpse of special relativity, but they weren't willing to give
up the ether," Moffat told SPACE.com. "Then Einstein came along and said we
don't need the ether. The rest was history."
[Modified gravity may also help explain the Pioneer Anomaly - the puzzling
fact that the Pioneer 10 and 11 space probes, launched in 1972 and 1973, are
several hundred thousand miles from where the existing laws of physics say
they ought to be as they travel out of the solar system.
It could also do away with the hypothesis of dark energy, a fairly recent
concept which seeks to explain why the expansion of the universe appears to
be accelerating instead of staying constant or slowing down.]
Douglas Clowe, the lead astronomer of the team that linked the Bullet
Cluster observations with dark matter (and now at Ohio University), says he
still stands by his original claim.
For him and many other astronomers, conjuring up new particles that might
account for dark matter is more palatable than turning a fundamental theory
of how the universe works on its head.
"As far as we're concerned, [Moffat] hasn't done anything that makes us
retract our earlier statement that the Bullet Cluster shows us that we have
to have dark matter," Clowe said. "We're still open to modifying gravity to
reduce the amount of dark matter, but we're pretty sure that you have to
have most of the mass of the universe still in some form of dark matter."
