Thursday, February 24, 2005

Brightest Galactic Flash Ever Detected Hits Earth

Robert Roy Britt
Senior Science Writer
SPACE.com


A huge explosion halfway across the galaxy packed so much power it briefly altered Earth's upper atmosphere in December, astronomers said Friday.


No known eruption beyond our solar system has ever appeared as bright upon arrival.


But you could not have seen it, unless you can top the X-ray vision of Superman: In gamma rays, the event equaled the brightness of the full Moon's reflected visible light.


The blast originated about 50,000 light-years away and was detected Dec. 27. A light-year is the distance light travels in a year, about 6 trillion miles (10 trillion kilometers).


The commotion was caused by a special variety of neutron star known as a magnetar. These fast-spinning, compact stellar corpses -- no larger than a big city -- create intense magnetic fields that trigger explosions. The blast was 100 times more powerful than any other similar eruption witnessed, said David Palmer of Los Alamos National Laboratory, one of several researchers around the world who monitored the event with various telescopes.


"Had this happened within 10 light-years of us, it would have severely damaged our atmosphere and possibly have triggered a mass extinction," said Bryan Gaensler of the Harvard-Smithsonian Center for Astrophysics (CfA).


There are no magnetars close enough to worry about, however, Gaensler and two other astronomers told SPACE.com. But the strength of the tempest has them marveling over the dying star's capabilities while also wondering if major species die-offs in the past might have been triggered by stellar explosions.


'Once-in-a-lifetime'


The Sun is a middle-aged star about 8 light-minutes from us. It's tantrums, though cosmically pitiful compared to the magnetar explosion, routinely squish Earth's protective magnetic field and alter our atmosphere, lighting up the night sky with colorful lights called aurora.


Solar storms also alter the shape of Earth's ionosphere, a region of the atmosphere 50 miles (80 kilometers) up where gas is so thin that electrons can be stripped from atoms and molecules -- they are ionized -- and roam free for short periods. Fluctuations in solar radiation cause the ionosphere to expand and contract.


"The gamma rays hit the ionosphere and created more ionization, briefly expanding the ionosphere," said Neil Gehrels, lead scientist for NASA (news - web sites)'s gamma-ray watching Swift observatory.


Gehrels said in an email interview that the effect was similar to a solar-induced disruption but that the effect was "much smaller than a big solar flare."


Still, scientists were surprised that a magnetar so far away could alter the ionosphere.


"That it can reach out and tap us on the shoulder like this, reminds us that we really are linked to the cosmos," said Phil Wilkinson of IPS Australia, that country's space weather service.


"This is a once-in-a-lifetime event," said Rob Fender of Southampton University in the UK. "We have observed an object only 20 kilometers across [12 miles], on the other side of our galaxy, releasing more energy in a tenth of a second than the Sun emits in 100,000 years."


Some researchers have speculated that one or more known mass extinctions hundreds of millions of years ago might have been the result of a similar blast altering Earth's atmosphere. There is no firm data to support the idea, however. But astronomers say the Sun might have been closer to other stars in the past.





A similar blast within 10 light-years of Earth "would destroy the ozone layer," according to a CfA statement, "causing abrupt climate change and mass extinctions due to increased radiation."

The all-clear has been sounded, however.

"None of the known sample [of magnetars] are closer than about 4,000-5,000 light years from us," Gaensler said. "This is a very safe distance."

Cause a mystery

Researchers don't know exactly why the burst was so incredible. The star, named SGR 1806-20, spins once on its axis every 7.5 seconds, and it is surrounded by a magnetic field more powerful than any other object in the universe.

"We may be seeing a massive release of magnetic energy during a 'starquake' on the surface of the object," said Maura McLaughlin of the University of Manchester in the UK.

Another possibility is that the magnetic field more or less snapped in a process scientists call magnetic reconnection.

Gamma rays are the highest form of radiation on the electromagnetic spectrum, which includes X-rays, visible light and radio waves too.

The eruption was also recorded by the National Science Foundation (news - web sites)'s Very Large Array of radio telescopes, along with other European satellites and telescopes in Australia.

Explosive details

A neutron star is the remnant of a star that was once several times more massive than the Sun. When their nuclear fuel is depleted, they explode as a supernova. The remaining dense core is slightly more massive than the Sun but has a diameter typically no more than 12 miles (20 kilometers).

Millions of neutron stars fill the Milky Way galaxy. A dozen or so are ultra-magnetic neutron stars -- magnetars. The magnetic field around one is about 1,000 trillion gauss, strong enough to strip information from a credit card at a distance halfway to the Moon, scientists say.

Of the known magnetars, four are called soft gamma repeaters, or SGRs, because they flare up randomly and release gamma rays. The flare on SGR 1806-20 unleashed about 10,000 trillion trillion trillion watts of energy.

"The next biggest flare ever seen from any soft gamma repeater was peanuts compared to this incredible Dec. 27 event," said Gaensler of the CfA.

Monday, February 14, 2005

Was Tsunami caused by human hands trying to develop alternative energy from Tectonic plate frictions and movements?

Many in South Asia now believe that the Tsunami was created by some entity trying to develop alternate energy from Tectonic plate frictions and movements.
According to Geologists, Scientists and Thermodynamic experts, enormous amount of energy is involved in Tectonic plate frictions and movements. If that energy can be tapped, the world will be full of free energy.
It may make sense for some human hands to try and see if this enormous source of energy can be used to generate and use power – free energy!
The tsunami-battered Andaman and Nicobar Islands were on Sunday rocked by a series of eight earthquakes measuring 5 to 5.3 on the Richter scale, even as a slight tremor jolted Uttar Pradesh, India.
The quakes, classified as "moderate" by the India Meteorological Department, started occurring just after midnight Saturday and continued till 8.49 a.m. on Sunday.
The epicentres of the tremors were located off the east coast of Car Nicobar Island, off the north coast of Camorta and northwest of North Andaman Islands.
According to some Geologists in India the epicenter of the aftershocks are steadily moving northwards along a line. Still the aftershocks have strange gaps between them and the after shocks are not getting reduced in Richter scale.
The strangest thing observed is another smaller but very similar quake in Uttar Pradesh (a state in India), which is in the Northern India adjacent to the Himalayas.
When the epicenters of these quakes are joined with a straight line, it seems that the aftershock epicenter is moving along this line. The aftershocks are between 5.2 and 6.2 in Richter scale. After a series of aftershock there is approximately 78 hours of gap before the next series appears.
All these can be just a coincidence and is nothing unusual say some Geologists. But the continuation of this phenomenon for over a month cannot be just coincidental.
The sailors in Indian Ocean especially in the area of Andaman-Nicobar as well as Sumatra and in Bay of Bengal are weary of what is happening.

Thursday, February 03, 2005

Computers Learn from Google Search

From newscientist.com

Google's search for meaning

Computers can learn the meaning of words simply by plugging into Google. The finding could bring forward the day that true artificial intelligence is developed.

Trying to get a computer to work out what words mean - distinguish between "rider" and "horse" say, and work out how they relate to each other - is a long-standing problem in artificial intelligence research.

One of the difficulties has been working out how to represent knowledge in ways that allow computers to use it. But suddenly that is not a problem any more, thanks to the massive body of text that is available, ready indexed, on search engines like Google (which has more than 8 billion pages indexed).

The meaning of a word can usually be gleaned from the words used around it. Take the word "rider". Its meaning can be deduced from the fact that it is often found close to words like "horse" and "saddle". Rival attempts to deduce meaning by relating hundreds of thousands of words to each other require the creation of vast, elaborate databases that are taking an enormous amount of work to construct.

The "Google distance"
But Paul Vitanyi and Rudi Cilibrasi of the National Institute for Mathematics and Computer Science in Amsterdam, the Netherlands, realised that a Google search can be used to measure how closely two words relate to each other. For instance, imagine a computer needs to understand what a hat is.

To do this, it needs to build a word tree - a database of how words relate to each other. It might start with any two words to see how they relate to each other. For example, if it googles "hat" and "head" together it gets nearly 9 million hits, compared to, say, fewer than half a million hits for "hat" and "banana". Clearly "hat" and "head" are more closely related than "hat" and "banana".

To gauge just how closely, Vitanyi and Cilibrasi have developed a statistical indicator based on these hit counts that gives a measure of a logical distance separating a pair of words. They call this the normalised Google distance, or NGD. The lower the NGD, the more closely the words are related.

Automatic meaning extraction
By repeating this process for lots of pairs of words, it is possible to build a map of their distances, indicating how closely related the meanings of the words are. From this a computer can infer meaning, says Vitanyi. "This is automatic meaning extraction. It could well be the way to make a computer understand things and act semi-intelligently," he says.

The technique has managed to distinguish between colours, numbers, different religions and Dutch painters based on the number of hits they return, the researchers report in an online preprint.

The pair's results do not surprise Michael Witbrock of the Cyc project in Austin, Texas, a 20-year effort to create an encyclopaedic knowledge base for use by a future artificial intelligence. Cyc represents a vast quantity of fundamental human knowledge, including word meanings, facts and rules of thumb.

Witbrock believes the web will ultimately make it possible for computers to acquire a very detailed knowledge base. Indeed, Cyc has already started to draw upon the web for its knowledge. "The web might make all the difference in whether we make an artificial intelligence or not," he says.