Dark Energy On the Rise

The universe’s dark energy may be growing stronger with time, study suggests

While we aren’t really sure what dark matter and dark energy are, the final data released from ESA’s Planck mission confirms it apparently does exist. Buzz60

Dark energy, a mysterious invisible force believed to play a role in how the universe expands, may be growing stronger over time, according to a new study.

Dark energy, discovered 20 years ago by scientists measuring the distances to supernovas, or exploding stars, is described as an energy of empty space that never changes over space and time. Researchers believe it represents about 70 percent of the total universe.

The study published this week in the peer-reviewed British journal Nature Astronomyinstead measures the distances to quasars, bright celestial objects located in the center of galaxies.

Using data from NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton observatory, researchers found the expansion rate of the universe is different from the model using supernovas.

“We observed quasars back to just a billion years after the Big Bang, and found that the universe’s expansion rate up to the present day was faster than we expected,” Guido Risalti, a study co-author from the department of physics and astronomy at the University of Florence in Italy, said in a statement. “This could mean dark energy is getting stronger as the cosmos grows older.”

Elisabeta Lusso of Durham University in the United Kingdom said because this technique for assessing dark energy is new, researchers took extra steps to make sure it was a reliable way to measure. “We showed that results from our technique match up with those from supernova measurements over the last 9 billion years, giving us confidence that our results are reliable at even earlier times,” she said.

Researchers say they used quasars to measure because they have a much farther reach compared to supernovas.

Adam Riess, a professor of physics and astronomy at Johns Hopkins University, said while the discovery would be “a really big deal” if confirmed, quasars have not proven to be historically reliable.

“People have not really used them as precision measuring tools for the universe because they have a very large dynamic range,” said Riess. “We don’t have a lot of confidence when we see one, we know how luminous it ought to be.”

Robert Kirshner, a Clowes Research Professor of Science, Emeritus at Harvard University, said that while the results of the study could prove true, there is no other evidence to date showing dark energy has changed with time.

“The thing that’s attractive about (their work) is that quasars are brighter, so you can see them farther back,” said Kirshner. “But you do worry the quasars from the early universe are not quite the same as the ones nearby.”

from:    https://www.usatoday.com/story/tech/news/2019/01/31/dark-energy-mysterious-force-space-growing-stronger-study/2732772002/

Gravity & Dark Matter

Dutch scientist publishes new theory of gravity

Erik Verlinde

@erikverlinde / Twitter
University of Amsterdam scientist Erik Verlinde published a new theory of gravity which he debunks the existence of dark matter, NOS reports.

Astronomers often note in their observations that they observe more gravity in galaxies than the number of stars would suggest. This extra gravity is attributed to dark matter – an unknown substance believed to hold the galaxies together.

But in Verlinde’s new theory, he can calculate the movements of stars without including dark matter in the calculations. According to NOS, this is the first time that a scientist develop a theory that fits the observations of astronomers.

According to Verlinde, physisicsts are working on a revision on Einstein’s theory of relativity “Our current ideas about space, time and gravity urgently need to be re-thought. We have long known that Einstein’s theory of gravity can not work with quantum mechanics”, he said, according to NOS. “Our findings are drastically changing, and I think that we are on the eve of a scientific revolution.”

from:    http://nltimes.nl/2016/11/08/dutch-scientist-publishes-new-theory-gravity

Large Hadron Collector -Finding New Dimensions?

Large Hadron Collider Could Detect Extra Dimensions

March 19, 2015 | by Stephen Luntz

Photo credit: Mopic via Shutterstock. If gravity is draining out of tiny black holes into other dimensions, the LHC may find it

A paper in Physics Letters B has raised the possibility that the Large Hadron Collider (LHC) could make a discovery that would put its previous triumph with the Higgs Boson in the shade. The authors suggest it could detect mini black holes. Such a finding would be a matter of huge significance on its own, but might be an indication of even more important things.

Few ideas from theoretical physics capture the public imagination as much as the “many-worlds hypothesis,” which proposes an infinite number of universes that differ from our own in ways large and small. The idea has provided great fodder for science fiction writers and comedians.

However, according to Professor Mir Faizal from the University of Waterloo, “Normally, when people think of the multiverse, they think of the many-worlds interpretation of quantum mechanics, where every possibility is actualized,” he said to Phys.org. “This cannot be tested and so it is philosophy and not science.” Nonetheless, Faizal considers the test for a different sort of parallel universes almost within our grasp.

“What we mean is real universes in extra dimensions,” says Faizal. “As gravity can flow out of our universe into the extra dimensions, such a model can be tested by the detection of mini black holes at the LHC.”

The idea that the universe may be filled with minute black holes has been proposed to explain puzzles such as the nature of dark matter. However, the energy required to create such objects depends on the number of dimensions the universe has. In a conventional four-dimensional universe, these holes would require 1016 TeV, 15 orders of magnitude beyond the capacity of the LHC to produce.

String theory, on the other hand, proposes 10 dimensions, six of which have been wrapped up so we can’t experience them. Attempts to model such a universe suggest that the energy required to make these tiny black holes would be a great deal smaller, so much so that some scientists believe they should have been detected in experiments the LHC has already run.

So if no detection, no string theory? Not according to Faizal and his co-authors. They argue that the models used to predict the energy of the black holes in a 10-dimensional universe have left out quantum deformation of spacetime that changes gravity slightly.

Whether this deformation is real is a rapidly developing question, but if it is, the paper argues that the black holes will have energy levels much smaller than in a four-dimensional universe, but about twice as large as that detectable for any test run so far. The LHC is designed to reach 14 TeV, but so far has only gone to 5.3 TeV, while the paper thinks the holes might be lurking at 11.9 TeV. In this case, once the LHC reaches its full capacity, we should find them.

Such a discovery would demonstrate the microscale deformation of spacetime, the existence of extra dimensions, parallel universes within them and string theory. If found at the right energy levels, the holes would confirm the team’s interpretation of a new theory on black hole behavior named gravity’s rainbow, after the influential novel. Such an astonishing quadruple revelation would transform physics, although the researchers are already considering the most likely flaws in their work if the holes prove elusive.

 

from:    http://www.iflscience.com/physics/large-hadron-collider-might-reveal-extra-dimensions

Of Gamma Ray Bubbles and Dark Matter

MILKY WAY’S GAMMA RAY BUBBLES SHAPED BY DARK MATTER?

Amy Shira Teitel
Analysis by Amy Shira Teitel
Tue May 8, 2012 11:37 AM ET

Gamma-ray-bubbles

Dark matter, the elusive stuff that makes up a substantial portion of all the mass in the universe, is largely a mystery to astronomers. They’ve tried finding it and creating it, but so far no conclusive proof as to what exactly it is though most theories state that we interact with it through gravity.

But Christoph Weniger, of the Max Planck Institute for Physics in Munich, has a different theory to explain new possible evidence for dark matter. By carrying out statistical analysis of three and a half years worth of publicly available data from NASA’s Fermi Space Telescope, he’s found a gamma ray line across the sky that he says is a clear signature of dark matter.

Astrophysicists generally think that supermassive black holes, like the one at the center of the Milky Way, release jets that interact with surrounding dark matter. This interaction is thought to be the source of high-energy gamma rays that satellites like Fermi can detect. What satellites can see are the photons produced when these jets interact with dark matter.

Weniger looked for signs of such an interaction in about three and a half years worth of gamma-ray observations carried out by the Fermi satellite’s Large Area Telescope (LAT).

To increase his chances of success he only considered data from those regions of the Milky Way that should generate the highest ratios of dark-matter photons to photons from background sources. He was looking specifically for a peak in energy, a sign that a photon was produced by the collision between and annihilation of two particles; the photon left over should have the same mass as one dark matter particle. This energy would theoretically appear as a very narrow peak, a line in gamma-ray spectra, distinct from the broad energy distribution seen across the visible universe.

That’s just what he found — a line in the gamma ray spectrum.

But he’s quick to admit it’s a provisional result. His data points come from about 50 photons and he’ll need a lot more to prove conclusively that his line is related to dark matter. It’s possible the line he observed is from a known, though no less mysterious, astronomical phenomenon: the pair of enormous gamma-ray-emitting bubbles extending outwards from the plane of the Milky Way.

In December 2010, scientists working with the Fermi Space Telescope found two giant lobes extending from the black hole at the center of our galaxy.

Twenty-five thousand light years high, each bubble spans more than half of the visible sky reaching from the constellation Virgo to the constellation Grus and may be relatively young at just a million or so years old.

The bubbles are a recent find, normally masked by the fog of gamma rays that appears throughout the sky that is a result of particles moving near the speed of light interacting with light and interstellar gas in the Milky Way. Scientists only found the bubbles by manipulating the data from the LAT to draw out the striking feature.

The manipulated images show the bubbles have well defined edges, suggesting they were formed as a result of a large and relatively rapid energy release — the source of which is still unknown. Interestingly, the energy cutoff of the bubbles corresponds to the gamma ray line Weniger found, the one he’s associating with a dark matter signature.

It’s possible the bubbles and the line have the same origin. Or, dark matter might be the cause of the bubbles’ defined endpoint.

Whether or not the two observations turn out to be linked — which of course hinges on conclusive proof of Weniger’s gamma ray line — both are very cool and part of the fascinating and mystery nature of our corner of the universe.

Image credit: NASA-Goddard

from:   http://news.discovery.com/space/dark-matter-and-gamma-ray-lobes-light-up-the-visible-universe-120508.html