Aurion Mission: Aug 13, 2012

Monday, August 13, 2012

Black Hole Puts Dent In Space-time

A spinning black hole in the constellation Scorpius has created a stable dent in the fabric of spacetime, scientists say.
The dent is the sort of thing predicted by Albert Einstein's theory of general relativity. It affects the movement of matter falling into the black hole.
The spacetime-dent is invisible, but scientists deduced its existence after detecting two X-ray frequencies from the black hole that were identical to emissions noted nine years ago. The finding will allow scientists to calculate the black hole's spin, a crucial measurement necessary for describing the object's behavior.

   Scientists think that all spinning black holes emit two stable frequencies, and that the frequencies are closely tied to the black hole's mass and spin.                                                           

You Can't Travel Back in Time, Scientists Say

Date: 07 March 2007 Time: 04:01 AM ET
The urge to hug a departed loved one again or prevent atrocities are among the compelling reasons that keep the notion of time travel alive in the minds of many.
While the idea makes for great fiction, some scientists now say traveling to the past is impossible.
There are a handful of scenarios that theorists have suggested for how one might travel to the past, said Brian Greene, author of the bestseller, “The Elegant Universe” and a physicist at Columbia University.“And almost all of them, if you look at them closely, brush up right at the edge of physics as we understand it. Most of us think that almost all of them can be ruled out.”
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The fourth dimension
In physics, time is described as a dimension much like length, width, and height. When you travel from your house to the grocery store, you’re traveling through a direction in space, making headway in all the spatial dimensions—length, width and height. But you’re also traveling forward in time, the fourth dimension.
“Space and time are tangled together in a sort of a four-dimensional fabric called space-time,” said Charles Liu, an astrophysicist with the City University of New York, College of Staten Island and co-author of the book “One Universe: At Home In The Cosmos.”
Space-time, Liu explains, can be thought of as a piece of spandex with four dimensions. “When something that has mass—you and I, an object, a planet, or any star—sits in that piece of four-dimensional spandex, it causes it to create a dimple,” he said. “That dimple is a manifestation of space-time bending to accommodate this mass.”
The bending of space-time causes objects to move on a curved path and that curvature of space is what we know as gravity.
Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn’t share this multi-directional freedom.
“In this four-dimensional space-time, you’re only able to move forward in time,” Liu told LiveScience.
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Tunneling to the past
A handful of proposals exist for time travel. The most developed of these approaches involves a wormhole—a hypothetical tunnel connecting two regions of space-time. The regions bridged could be two completely different universes or two parts of one universe. Matter can travel through either mouth of the wormhole to reach a destination on the other side.
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Time Travel Tale
“Wormholes are the future, wormholes are the past,” said Michio Kaku, author of “Hyperspace” and “Parallel Worlds” and a physicist at the City University of New York. “But we have to be very careful. The gasoline necessary to energize a time machine is far beyond anything that we can assemble with today’s technology.”
To punch a hole into the fabric of space-time, Kaku explained, would require the energy of a star or negative energy, an exotic entity with an energy of less than nothing.
Greene, an expert on string theory—which views matter in a minimum of 10 dimensions and tries to bridge the gap between particle physics and nature's fundamental forces, questioned this scenario.
“Many people who study the subject doubt that that approach has any chance of working,” Greene said in an interview . “But the basic idea if you’re very, very optimistic is that if you fiddle with the wormhole openings, you can make it not only a shortcut from a point in space to another point in space, but a shortcut from one moment in time to another moment in time.”
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Cosmic strings
Another popular theory for potential time travelers involves something called cosmic strings—narrow tubes of energy stretched across the entire length of the ever-expanding universe. These skinny regions, leftover from the early cosmos, are predicted to contain huge amounts of mass and therefore could warp the space-time around them.
Cosmic strings are either infinite or they’re in loops, with no ends, said J. Richard Gott, author of “Time Travel in Einstein's Universe” and an astrophysicist at Princeton University. “So they are either like spaghetti or SpaghettiO’s.”
The approach of two such strings parallel to each other, said Gott, will bend space-time so vigorously and in such a particular configuration that might make time travel possible, in theory.
“This is a project that a super civilization might attempt,” Gott told LiveScience.  “It’s far beyond what we can do. We’re a civilization that’s not even controlling the energy resources of our planet.”
Impossible, for now
Mathematically, you can certainly say something is traveling to the past, Liu said. “But it is not possible for you and me to travel backward in time,” he said.
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However, some scientists believe that traveling to the past is, in fact, theoretically possible, though impractical.
Maybe if there were a theory of everything, one could solve all of Einstein’s equations through a wormhole, and see whether time travel is really possible, Kaku said. “But that would require a technology far more advanced than anything we can muster," he said. "Don’t expect any young inventor to announce tomorrow in a press release that he or she has invented a time machine in their basement.”
For now, the only definitive part of travel in the fourth dimension is that we’re stepping further into the future with each passing moment. So for those hoping to see Earth a million years from now, scientists have good news.
“If you want to know what the Earth is like one million years from now, I’ll tell you how to do that,” said Greene, a consultant for “Déjà Vu,” a recent movie that dealt with time travel. “Build a spaceship. Go near the speed of light for a length of time—that I could calculate. Come back to Earth, and when you step out of your ship you will have aged perhaps one year while the Earth would have aged one million years. You would have traveled to Earth’s future.”
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Related News
 Einstein's Warped View of Space Confirmed

Einstein's Warped View of Space Confirmed

Date: 20 October 2004 Time: 01:00 PM ET
To pin down frame dragging, researchers included data on Earth's uneven gravity field, shown in this map by NASA's GRACE satellite. Fluctuations owe to mountains, trenches, and unseen sub-surface density differences. Red indicates high gravity; blue areas have low gravity.

Earth's spin warps space around the planet, according to a new study that confirms a key prediction of Einstein's general theory of relativity.
After 11 years of watching the movements of two Earth-orbiting satellites, researchers found each is dragged by about 6 feet (2 meters) every year because the very fabric of space is twisted by our whirling world.
The results, announced today, are much more precise than preliminary findings published by the same group in the late 1990s.
Frame dragging
The effect is called frame dragging. It is a modification to the simpler aspects of gravity set out by Newton. Working from Einstein's relativity theory, Austrian physicists Joseph Lense and Hans Thirring predicted frame dragging in 1918. (It is also known as the Lense-Thirring effect.)
Here's how it works:
Any object with mass warps the space-time around it, in much the same way as a heavy object deforms a stretched elastic sheet, explained study leader Ignazio Ciufolini of the Universit? di Lecce in Italy.
If the object spins, another distortion is introduced, "in the same way as the elastic sheet would be twisted by a spinning heavy wheel on it."
If the space around Earth is being frame-dragged, then satellites ought to be caught up in the deformation, scientists reasoned. Imagine how a second object on the elastic sheet would be moved by the scrunching motion created as the sheet is deformed.
Ciufolini's team analyzed millions of laser signals bounced off two satellites, called LAGEOS and LAGEOS 2. Both are highly reflective spheres not designed to do any work of their own. They look like 2-foot-diameter (0.6m) golf balls and contain no batteries or electronics.
The researchers say their result is 99 percent of the predicted drag, with an error of up to 10 percent. The details will be reported in the Oct. 21 issue of the journal Nature.
The analysis is "the first reasonably accurate measurement of frame-dragging," said physicist Neil Ashby of the University of Colorado in Boulder.
"Precise measurement of these effects predicted by relativistic gravity theories is crucial, as they have important implications for our view of the cosmos," Ashby writes in an analysis of the study for the journal.
Black hole applications
Specifically, the new results can be applied to black hole theory. In fact, it is with black holes -- typically much more massive than Earth -- that some of the first signs of frame dragging were spotted.

Precession in a spinning top.

LAGEOS satellite.
In observations of activity around black hole in 1997, researchers noted that gas spiraling into the black hole wobbled, or precessed, like a top. The precession was much greater than what could be described by basic mechanics of the setup.
And as early as 1996, Ciufolini's team saw signs of frame dragging on the Earth-orbiting satellites in their study, but the initial results had a high degree of error owing to the lack of knowledge about Earth's gravity field, which is not symmetric. A gravity map generated by NASA's new GRACE satellite made the latest analysis possible, he said.
Meanwhile, other studies have shown that black holes indeed spin, and that frame dragging plays an important role in spewing tremendous jets of material out of the environments around black holes. The whole setup can be likened to a giant gyroscope, Ciufolini told A jet can point in one direction for millions of years, other observations show.
"In other words," Ciufolini said, "an astrophysical gun was shooting for millions of years without changing direction: a fantastic gyroscope indeed."

Messing with space and time
This artist's concept illustrates the difference between a spinning black hole (right) and one that is not spinning (left). In both computer images, looking down from above, the central dark circle represents the black hole's point of no return, called the event horizon.
The surrounding blue and white rings are hot gas whirling around and toward the black hole, much like water near a bathtub drain. The green grid depicts space-time coordinates, distorted by the spinning black hole at right.