Debate intensifies over dark disk theory _ quanta magazine

But credit for the discovery of dark matter — the invisible, unidentified stuff that comprises five-sixths of the universe’s mass — usually goes to the Swiss-American astronomer Fritz Zwicky, who inferred its existence from the relative motions of galaxies in 1933. Electricity orlando Oort is passed over on the grounds that he was trailing a false clue. Electricity n and l By 2000, updated, Oort-style inventories of the Milky Way determined that its “missing” mass consists of faint stars, gas and dust, with no need for a dark disk. Electricity out Eighty years of hints suggest that dark matter, whatever it is, forms spherical clouds called “halos” around galaxies.

Or so most dark matter hunters have it. 1 unit electricity cost in bangalore Though it fell out of favor, the dark disk idea never completely went away. Electricity outage austin And recently, it has found a high-profile champion in Lisa Randall, a professor of physics at Harvard University, who has rescued the disk from scientific oblivion and given it an active role on the galactic stage.

Since proposing the model in 2013, Randall and her collaborators have argued that a dark disk might explain gamma rays coming from the galactic center, the planar distribution of dwarf galaxies orbiting the Andromeda galaxy and the Milky Way, and even periodic upticks of comet impacts and mass extinctions on Earth, discussed in Randall’s 2015 popular-science book, Dark Matter and the Dinosaurs.

But astrophysicists who do inventories of the Milky Way have protested, arguing that the galaxy’s total mass and the bobbing motions of its stars match up too well to leave room for a dark disk. Gas kinetic energy formula “It’s more strongly constrained than Lisa Randall pretends,” said Jo Bovy, an astrophysicist at the University of Toronto.

Now, Randall, who has devised influential ideas about several of the biggest questions in fundamental physics, is fighting back. A level physics electricity equations In a paper posted online last week that has been accepted for publication in The Astrophysical Journal, Randall and her student, Eric Kramer, report a disk-shaped loophole in the Milky Way analysis: “There is an important detail that has so far been overlooked,” they write. Electricity worksheets for 4th grade “The disk can actually make room for itself.”

If there is a thin dark disk coursing through the “midplane” of the galaxy, Randall and Kramer argue, then it will gravitationally pinch other matter inward, resulting in a higher density of stars, gas and dust at the midplane than above and below. Gas out game instructions Researchers typically estimate the total visible mass of the Milky Way by extrapolating outward from the midplane density; if there’s a pinching effect, then this extrapolation leads to an overestimation of the visible mass, making it seem as if the mass matches up to the stars’ motions. Gas density “That’s the reason why a lot of these previous studies did not see evidence for a dark disk,” Kramer said. Types of electricity He and Randall find that a thin dark disk is possible — and in one way of redoing the analysis, slightly favored over no dark disk.

“Lisa’s work has reopened the case,” said Chris Flynn of Swinburne University of Technology in Melbourne, Australia, who, with Johan Holmberg, conducted a series of Milky Way inventories in the early aughts that seemed to robustly sweep it clean of a dark disk.

Bovy disagrees. Electricity merit badge pamphlet pdf Even taking the pinching effect into account, he estimates that at most 2 percent of the total amount of dark matter can lie in a dark disk, while the rest must form a halo. Electricity jeopardy “I think most people want to figure out what 98 percent of the dark matter is about, not what 2 percent of it is about,” he said.

The debate — and the fate of the dark disk — will probably be decided soon. Electricity static electricity The European Space Agency’s Gaia satellite is currently surveying the positions and velocities of one billion stars, and a definitive inventory of the Milky Way could be completed as soon as next summer.

The discovery of a dark disk, of any size, would be enormously revealing. Gas density units If one exists, dark matter is far more complex than researchers have long thought. Electricity explained Matter settles into a disk shape only if it is able to shed energy, and the easiest way for it to shed sufficient energy is if it forms atoms. Electricity png The existence of dark atoms would mean dark protons and dark electrons that are charged in a similar style as visible protons and electrons, interacting with each other via a dark force that is conveyed by dark photons. Static electricity sound effect Even if 98 percent of dark matter is inert, and forms halos, the existence of even a thin dark disk would imply a rich “dark sector” of unknown particles as diverse, perhaps, as the visible universe. Hp gas kushaiguda “Normal matter is pretty complex; there’s stuff that plays a role in atoms and there’s stuff that doesn’t,” said James Bullock, an astrophysicist at the University of California, Irvine. Gas natural “So it’s not crazy to imagine that the other five-sixths [of the matter in the universe] is pretty complex, and that there’s some piece of that dark sector that winds up in bound atoms.”

The notion that dark matter might be complex has gained traction in recent years, aided by astrophysical anomalies that do not gel with the long-reigning profile of dark matter as passive, sluggish “weakly interacting massive particles.” These anomalies, plus the failure of “WIMPs” to show up in exhaustive experimental searches all over the world, have weakened the WIMP paradigm, and ushered in a new, free-for-all era, in which the nature of the dark beast is anybody’s guess.

The field started opening up around 2008, when an experiment called PAMELA detected an excess of positrons over electrons coming from space — an asymmetry that fueled interest in “ asymmetric dark matter,” a now-popular model proposed by Kathryn Zurek and collaborators. Gas what i smoke At the time, there were few ideas other than WIMPs in play. La gas prices “There were model-builders like me who realized that dark matter was just extraordinarily underdeveloped in this direction,” said Zurek, now of Lawrence Berkeley National Laboratory in California. Gas in back “So we dove in.”

James Bullock of the University of California, Irvine, sees dark matter as potentially complex and self-interacting, but not necessarily concentrated in thin disks.

Another trigger has been the density of dwarf galaxies. Dynamic electricity examples When researchers try to simulate their formation, dwarf galaxies typically turn out too dense in their centers, unless researchers assume that dark matter particles interact with one another via dark forces. Gas 78 industries Add too much interactivity, however, and you muck up simulations of structure formation in the early universe. I feel electricity in my body “What we’re trying to do is figure out what is allowed,” said Bullock, who builds such simulations. Gas after eating dairy Most modelers add weak interactions that don’t affect the halo shape of dark matter. Electricity pictures information But “remarkably,” Bullock said, “there is a class of dark matter that allows for disks.” In that case, only a tiny fraction of dark matter particles interact, but they do so strongly enough to dissipate energy — and then form disks.

Randall and her collaborators JiJi Fan, Andrey Katz and Matthew Reece made their way to this idea in 2013 by the same path as Oort: They were trying to explain an apparent Milky Way anomaly. Electricity lesson plans for 5th grade Known as the “Fermi line,” it was an excess of gamma rays of a certain frequency coming from the galactic center. Gas bloating pregnancy “Ordinary dark matter wouldn’t annihilate enough” to produce the Fermi line, Randall said, “so we thought, what if it was much denser?” The dark disk was reborn. C gastronomie limonest The Fermi line vanished as more data accumulated, but the disk idea seemed worth exploring anyway. Gas 99 cents In 2014, Randall and Reece hypothesized that the disk might account for possible 30- to 35-million-year intervals between escalated meteor and comet activity, a statistically weak signal that some scientists have tentatively tied to periodic mass extinctions. Gas x strips ingredients Each time the solar system bobs up or down through the dark disk on the Milky Way carousel, they argued, the disk’s gravitational effect might destabilize rocks and comets in the Oort cloud — a scrapyard on the outskirts of the solar system named for Jan Oort. 66 gas station These objects would go hurtling toward the inner solar system, some striking Earth.

But Randall and her team did only a cursory — and incorrect — analysis of how much room there is for a dark disk in the Milky Way’s mass budget, judging by the motions of stars. Gas leak “They made some kind of outrageous claims,” Bovy said.

Randall, who stands out (according to Reece) for “her persistence,” put Kramer on the case, seeking to address the critics and, she said, “to iron out all the wrinkles” in the analysis before Gaia data becomes available. Youtube electricity Her and Kramer’s new analysis shows that the dark disk, if it exists, cannot be as dense as her team initially thought possible. Gas vs diesel generator But there is indeed wiggle room for a thin dark disk yet, due both to its pinching effect and to additional uncertainty caused by a net drift in the Milky Way stars that have been monitored thus far.

Now there’s a new problem, raised in The Astrophysical Journal by Chris McKee of the University of California, Berkeley, and collaborators. Wd gaster battle McKee concedes that a thin dark disk can still be squeezed into the Milky Way’s mass budget. Gasbuddy touch But the disk might be so thin that it would collapse. Gas 1940 Citing research from the 1960s and ’70s, McKee and colleagues argue that disks cannot be significantly thinner than the disk of visible gas in the Milky Way without fragmenting. National gas average 2007 “It is possible that the dark matter they consider has some property that is different from ordinary matter and prevents this from happening, but I don’t know what that could be,” McKee said.

Randall has not yet parried this latest attack, calling it “a tricky issue” that is “under consideration now.” She has also taken on the point raised by Bovy — that a disk of charged dark atoms is irrelevant next to the nature of 98 percent of dark matter. Electricity videos for students She is now investigating the possibility that all dark matter might be charged under the same dark force, but because of a surplus of dark protons over dark electrons, only a tiny fraction become bound in atoms and wind up in a disk. Gas 87 89 93 In that case, the disk and halo would be made of the same ingredients, “which would be more economical,” she said. Gas prices “We thought that would be ruled out, but it wasn’t.”

The dark disk survives, for now — a symbol of all that isn’t known about the dark side of the universe. Mp electricity bill payment online bhopal “I think it’s very, very healthy for the field that you have people thinking about all kinds of different ideas,” said Bullock. Npower electricity bill “Because it’s quite true that we don’t know what the heck that dark matter is, and you need to be open-minded about it.”

What it appears you’re getting at there, is a theory that seeks to demonstrate a clear and reliable relationship between electromagnetic fields and the force of gravity. Gsa 2016 new orleans That’s what physicists call “unified field theory” and it has been a holy grail of physics since before Einstein, who spent the last years of his life working on the problem.

No doubt there have been countless experiments attempting to ascertain any possible interaction between electromagnetic fields and gravity, and thus far not one of them has produced a clear positive result or we would have heard much about it.

Any such result would be immediately useful in developing new means of producing clean electricity, and new means of propulsion that could produce radical increases in the efficiency and speed of space travel. Electricity outage chicago It would be pounced on and developed rapidly by corporations with interests in these areas, such as the aerospace companies that have major contracts with NASA. Bp gas station The competitive pressure to build and patent any sort of working device would be enormous. Electricity and magnetism worksheets 8th grade But so far, nothing.

If this stuff seriously interests you, look up the history of work in unified field theory. Electrical supply company near me But also beware that there is a lot of quackery and crankery around this area, again because of the prospect of valuable commercial applications. E payment electricity bill maharashtra If you have access to university library resources, the best thing is to look for works by people who have a decent track record of peer-reviewed publications in major science journals.

BTW, where you say “another way of saying it…” in your second post: what you’ve just described is an experiment that could be performed with two masses and any device that produces a strong electromagnetic field, such as a radio transmitter. Gas variables pogil worksheet answer key No doubt such things have already been tried and shown not to work, but you can do it for yourself and find out.