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الجمعة، 7 سبتمبر 2012

"Could There be Life in the Universe Far Older Than Ours?" --Planetary Building Blocks After Big Bang Suggest: "Yes"

"Could There be Life in the Universe Far Older Than Ours?" --Planetary Building Blocks After Big Bang Suggest: "Yes"
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September 02, 2012 "Could There be Life in the Universe Far Older Than Ours?" --Planetary Building Blocks After Big Bang Suggest: "Yes"

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The raw materials for building terrestrial planets were available very soon after the Big Bang, raising the possibility that there could be life in the Universe far older than we. Perhaps they reside around long-lived red dwarf stars, or have moved on from their home system after their star expired. Or, perhaps, we really are the first, which means that if life has happened just once throughout the entire history of the Universe, our existence must be a fluke and our planet very, very special indeed.

The Kepler Mission has changed the way we view exoplanets. Simply by observing so many all at once in its field-of-view, the space telescope is taking an unprecedented census of alien worlds. It has found 2,321 candidate planets to date, over a third of which are smaller, rocky planets (Jupiter-sized gas giants or larger make up just 11 percent, with the rest being Neptune-sized worlds of indeterminate nature), whereas before Kepler you could count the number of rocky exoplanets discovered on one hand. Follow-up studies of their host stars have since revealed a surprising discovery.

"We found that the existence of small planets does not depend as strongly on the metallicity of their star as is the case for the larger planets," says Lars Buchhave of the Niels Bohr Institute at the University of Copenhagen. Buchhave is lead author of a new study involving a multinational group of astronomers investigating the spectra of 150 stars that play host to 226 candidate planets found by Kepler. Their research was initially presented at the 220th meeting of the American Astronomical Society in Anchorage, Alaska this June, followed by a paper in Nature.

"At first glance it appears very counter-intuitive that gas giants should be the ones caring about metallicity and terrestrial planets less so," says Anders Johansen of Lund Observatory in Sweden, who was a co-author on the Buchhave paper. Only when you stop to consider how planets are constructed does it begin to make sense. The process of accreting hierarchically from smaller building blocks is termed core accretion, but there has been something of a debate surrounding gas giants like Jupiter. Can they condense straight out of the gas of the solar nebula like a star, or do they need a large seed around which to grow by rapidly gathering gas from the protoplanetary disc in a runaway process?

Findings that show rocky planets existing around stars irrespective of their heavy element abundances mean that larger areas of galaxies than thought could be potentially habitable.

The preference of gas giants for higher metallicity stars indicates that they formed through core accretion, building up a central rocky core ten times the mass of Earth that could dominate the protoplanetary disc and sweep up much of the gas before it dissipates after around ten million years. In lower metallicity systems there would not be enough heavy elements to build up large cores, leaving only small rocky worlds. Johansen suggests that one way of looking at terrestrial planets is to see them as failed gas giant cores.

Limits to Life Planetary systems around stars possessing a deficiency in heavy elements might prove to be attractive locales to search for life because, without the presence of gas giants, life might have an easier time of it.

Most of the extra-solar gas giants that we have discovered are so-called 'hot Jupiters' located very close to their stars and completing an orbit in just a few days. These planets were not born this close, instead they migrated in-system from their birth orbits. Johansen says that more and more astronomers are coming around to the idea that such migration is forced by the gravitational pull and dynamical friction of the gas, or by close encounters with other planets. These interactions with fellow constituents of the protoplanetary disc removed angular momentum from the planets, often causing them to spiral towards their stars. Any smaller planets unfortunate to be in their way are thrown out of the system by the marauding gas giant.

"If a Jupiter-type planet migrates and in the process scatters all the smaller planets away, one should probably look for terrestrial planets elsewhere," says Buchhave. Life may have had a more pleasant ride in the early Universe when, thanks to the lower metallicity, there were no gas giants – and the argument that Jupiter-sized planets are needed as a shield against comet impactors no longer holds water either. Life can do without gas giant planets. If Earth-sized planets do not require stars with high abundances of heavy elements, then that has huge implications, expanding the possible abodes for life throughout both space and time.

Galaxies tend to evolve chemically from the inside out, with the highest abundances of heavy elements closer to the galactic center than in the outskirts of the spiral arms. Under the previous paradigm, the outer regions of the spiral arms were effectively the badlands, incapable of building planets or life. Yet when metallicity is no longer such a big issue, the galactic habitable zone – a region where environmental conditions including the metallicity and the rate of supernovae conspire to make habitable planets possible – suddenly widens to encompass much wider swathes of a galaxy.

The abundance of heavy elements in the Universe has grown over history. In the past the average metallicity would be quite a bit less. Again, under the previous paradigm this had been assumed to preclude rocky planet formation early in the Universe, but now we know that such planets could have been constructed in environments that contained much poorer levels of heavy elements.

This means that planets that could potentially have supported life may have formed eight, ten, maybe even twelve billion years ago. Surveys do detect a decrease in the number of planet-hosting stars with decreasing metallicity, but this drop is much shallower for terrestrial planets than it is for gas giants. Of course, the presence of some heavy elements during the planet-building phases is required, but the minimum level has not yet been determined.

"I expect there will be a lower limit," says Johansen. "Simply because below a threshold metallicity there is not enough building material to form Earth-mass planets." Clearly, a heavy element abundance a tenth of the Sun's or less would struggle to build any planets. However, each galaxy evolves differently and there is no way to say for sure when the Milky Way crossed this threshold, although it is likely to have been early in the history of the Universe, for the young cosmos was particularly adept at producing multiple generations of stars in quick succession.

Star-formation rates of 4,000 solar masses per year have been measured less than a billion years after the Big Bang, compared to the paltry ten solar masses of gas converted into stars each year in the Milky Way.

"A typical massive star that exploded and released heavy elements 10 to 12 billion years ago had a metallicity of about a tenth of the Sun," adds Johan Fynbo, Professor of Cosmology at the Niels Bohr Institute. "But whenever you have a new generation of stars then you start enriching the interstellar gas with heavy elements."

Rocky planets around more stars, across greater expanses of the Milky Way and going back deeper in time than we had ever dreamt adds more fuel to the fire of the Fermi Paradox. First voiced by the brilliant nuclear physicist Enrico Fermi in 1950, the Fermi Paradox questions why, given all the stars and planets out there coupled with the huge age of the Universe, have no alien civilizations encountered Earth yet? Where are they all?

The problem is made even worse when you consider that the first term in the Drake Equation – Frank Drake's method for estimating the number of intelligent civilizations in the Galaxy – is the star formation rate, which on average was much higher in the Universe 10 to 13 billion years ago when it seems planets could first begin forming. In the Milky Way today the average annual star formation rate is ten solar masses; an order of ten or one hundred greater has the effect of bumping up the product of the equation: the estimated number of civilizations.

One of the favorite counter-arguments to the Fermi Paradox was that the threshold metallicity takes time to build up, resulting in the Sun being one of the first stars at the required level and hence Earth would be one of the first planets with life. Now we see that planets and possibly life could have arisen at practically any point in cosmic history, undermining this counter-argument and once again forcing us to ask, where is everybody?

If life did first appear on worlds 12 to13 billion years ago, then intelligent civilizations (if indeed they survived all this time) would now billions of years ahead of us and their concerns may no longer include the happenings on a damp mudball somewhere in the galactic hinterlands. Perhaps civilizations that are many billions of years old instead spend their time siphoning energy from black holes or living inside Dyson Spheres.

There are, however, some twists in the tale. In 2010 researchers at the Max Planck Institute for Astronomy in Heidelberg, Germany, found a gas giant planet around a star so lacking in heavy elements that it must have formed very early in the history of the Universe. To add to the intrigue, the star, known as HIP 13044 and located 2,000 light years away, is part of a stellar stream that is all that remains of a dwarf galaxy that has been cannibalized by the Milky Way.

This year, the same researchers found another low metallicity star with two gas giants. Based on its abundance of hydrogen and helium the star, known as HIP 11952, was born 12.8 billion years ago, a mere 900 million years after the Big Bang. Why gas giants have been able to form around these heavy-metal deficient stars is unknown, perhaps hinting at an alternative process for gas planet formation. On the other hand new results suggest that, in some regions of the Universe at least, gas giants have been able to form all along.

Elemental Abundance For some faint galaxies in the distant Universe, whose light is too feeble to allow a measurement of their spectra, it is possible to cheat by making use of natural backlights such as highly luminous quasars to probe faint foreground galaxies. When taking advantage of this method to study the chemical composition of a galaxy that existed 12 billion years ago, a team of astronomers including Johan Fynbo made a rather surprising revelation.

"We looked at a background quasar whose light was passing through a galaxy in front of it, where the light of the quasar was absorbed," says Fynbo. "This allowed us to see the absorption lines from oxygen, sulphur, carbon and all the elements that have been synthesized in the galaxy."

Twelve billion years ago the chemistry of galaxies should have been fairly primitive, yet in this one particular galaxy Fynbo and his colleagues, who reported on their findings in Monthly Notices of the Royal Astronomical Society, found abundances of heavy elements equivalent to the abundance in the Sun.

Such finds at high distances are not unusual in themselves, but they tend to occur within the hearts of quasars, across a very small area of a galaxy. In this instance, however, the quasar light was shining through the disc of the foreground galaxy revealing the solar levels of heavy elements 52,000 light years from the center, right in the outskirts.

Even today our own Milky Way isn't so heavily chemically processed to the edge of its spiral arms, so how did this distant galaxy become so enriched throughout its full extent so quickly? The best explanation so far is that a starburst – a ferociously rapid bout of star formation – within the inner regions of the galaxy has blown the heavy elements into the galactic outlands. This can be done simply though the gale force stellar winds of radiation emanating from hot, massive stars, or riding on the shock waves of supernovae.

Furthermore, the quasar light was reddened by intervening dust in the galaxy. Dust is the most basic building block of planet formation, coming together in conglomerations and clumps that build up into protoplanets. Dust is also a product of the violent bombardment phase endured by young planetary systems and is copiously manufactured in supernovae.

"In order to make planets you clearly need metals and that seems to be possible quite far out in a galaxy at a very early time, which is what surprised us," says Fynbo. However, such high metallicities enables gas giant planets to also form but, although Lars Buchhave has mentioned what difficulties gas giants can cause for habitable planets, they don't necessarily have to be a show-stopper and our Solar System with Jupiter and Saturn is not the only exception.

"In the Kepler-20 planetary system there are five planets," he says, "Three are Saturn-sized planets and two are terrestrial-sized, with the order being big–small–big–small–big. If the Saturn-mass planets migrated in, how can the small planets be in-between the larger ones?'

The image at the top of the page by Carter Roberts of the Eastbay Astronomical Society in Oakland, CA, shows the Milky Way region of the sky where the Kepler spacecraft/photometer will be pointing --equal to 1/400th of the galaxy. Each rectangle indicates the specific region of the sky covered by each CCD element of the Kepler photometer. There are a total of 42 CCD elements in pairs, each pair comprising a square.

Journal reference: Nature

The Daily Galaxy via Astrobio.net

Posted at 07:00 AM | Permalink

Comments

to answer your question about alien civilizations and given the age of the universe: first of all the aliens have been here many times or have you ever heard about jesus christ and the angels?? secondly you wouldnt be able to see them anyway in your mere mortal state let alone give rise to your stupid speculations. live long and prosper mr spock.

Posted by:phillip |August 31, 2012 at 08:21 PM

All the Haters and Jesus-Goons: Please go infest some other locale.

Interesting article DG. I think the Fermi Paradox answer is that They have very effective Game-Keepers looking after this little nature reserve.

Posted by:qraal |September 01, 2012 at 12:04 AM

Thank you for this interesting, well written article.

Apart from visits, why don't we see any evidence with all the looking we have done over the years? Really, no radio transmissions at all seen with SETI for years? Even if they all move on to better technologies quickly, radio seems obvious and easy as a first step. so why not tons of noise out there? Editor's Note: Thanks.

Posted by:HDS |September 01, 2012 at 04:35 AM

الاثنين، 3 سبتمبر 2012

Dark Matter --Could It Play a Role in Creating Life in the Universe? (Today's Most Popular)

Dark Matter --Could It Play a Role in Creating Life in the Universe? (Today's Most Popular)
Dark Matter --Could It Play a Role in Creating Life in the Universe? (Today's Most Popular)The Daily Galaxy --Great Discoveries Channel: Sci, Space, TechFollow the Daily Galaxy Add Daily Galaxy to igoogle page

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August 30, 2012 Dark Matter --Could It Play a Role in Creating Life in the Universe? (Today's Most Popular)

Hubble-dark-energy-825x804

Dark matter makes up the majority of mass in our universe. However, we cannot directly measure the stuff as it doesn't interact with electromagnetic radiation (i.e. it doesn't emit or reflect any light), but we can indirectly observe its presence. In the Hubble Space Telescope image above, the distribution of mostly dark matter has been calculated and mapped. Basically, the location and density of anything with mass has been plotted in a 3D representation of the cosmos.

A 2011 study suggests that mysterious, invisible dark matter could warm millions of starless planets in regions such as Abell 1689 (image below) and make them habitable.

Scientists think the invisible, as-yet-unidentified dark matter which we know exists because of the gravitational effects it has on galaxies, makes up about 85 percent of all matter in the universe. Current prime candidates for what dark matter might be are massive particles that only rarely interact with normal matter.These particles could be their own antiparticles, meaning they annihilate each other when they meet, releasing energy. These invisible particles could get captured by a planet's gravity and unleash energy that could warm that world, according to physicist Dan Hooper and astrophysicist Jason Steffen at the Fermi National Accelerator Laboratory. Abell_1689-gravlens-hires-smex

Hooper and Steffen's propose that rocky "super-Earths" in regions with high densities of slow-moving dark matter could be warmed enough to keep liquid water on their surfaces, even in the absence of additional energy from starlight or other sources.The density of dark matter is expected to be hundreds to thousands of times greater in the innermost regions of the Milky Way and in the cores of dwarf spheroidal galaxies than it is in our solar system.

The scientists concluded that on planets in dense "dark-matter" regions, it may be dark matter rather than light that creates the basic elements you need for organic life without a star"

Dark matter, the team believes, could keep the surfaces of such warm for trillions of years, outliving all regular stars and may ultimately prove to be the "dark" bastion of life in our universe.

"I imagine 10 trillion years in the future, when the universe has expanded beyond recognition and all the stars in our galaxy have long since burnt out, the only planets with any heat are these here, and I could imagine that any civilization that survived over this huge stretch of time would start moving to these dark-matter-fueled planets," Hooper said in an interview with space.com.

The Daily Galaxy via astrophysical journalPosted at 11:30 AM | Permalink

Comments

A highly speculative essay with no basis has been chosen to postulate that life in visible matter originated due to the effect of extremely dense dark matter in the neighborhood! Life on Earth has come about only in the last 50,000 years while the Earth got formed as a planet of our Sun about some millions years back and the Universe itself came into being 14 billion years ago. From the start both dark and visible matter have existed as two components of creation. What dark matter is is as yet not scientifically understood except that it has got repulsive gravity towards visible matter component. One needs to go to the nature of primordial matter and how it converted into small 5 % visible matter and rest 95 % dark matter/energy remains not understood! Yes, conjectures have been made that dark matter may well be consisting of initial primordial matter that remained while a small part got converted into visible matter as we know it today. To me 6 quarks and 6 leptons as per Standard model form the basis for visible matter and taking that analogy backward, we may postulate that dark matter may consist of the predecessors of visible matter constituents that could not decay into the basic constituents of visible matter. These may well be some kind very much heavier quarks that we do not see anymore in our visible world. These may well be existing in free state if we can observe our Universe as it was during its first billion years of existence, about close to 13 billion years away!! Appears impossible to see in any cosmological experiment conducted today! However, these may appear as nascent particles if we develop still higher energy machines like LHC where such material particles may appear along with so-called Higg's bosons with still heavier mass compared to the Higg's! It appears foolish to follow such costly adventures in life at present.

Posted by:Narendra Nath |August 30, 2012 at 05:33 PM

Narenda: "Life on Earth has come about only in the last 50,000 years...."

What???

Posted by:Melissa Keiper |August 30, 2012 at 06:08 PM

Narenda, you need to check your facts; you come across as someone spouting something they copied and pasted. "the Earth got formed as a planet of our Sun about some millions years back and the Universe itself came into being 14 billion years ago."

Um, the sun formed 4 billion years ago....

Posted by:Rob |August 30, 2012 at 07:42 PM

Sun was formed six billion years ago, the earth more or less cooled down to its (much larger) state four billion years ago, and life.. glorious glorious life formed about one and half or two billion years ago. The rise of multicelluar organisms and its myriad complexity started about 600 million years ago. The crocodile was born about here. Several disasters of the ecological, volcanic and asteroidal kind later (The last major asteroid impact was 60 million years ago.) A little shrew about smaller than those tiny field mice diversified and made lots and lots of different mammals big and small. A couple of million years ago, evolution or the Flying Spaghetti Monster made some standup comedians who found it funny to rub sticks together and bash things with rocks. Couple million years later, Homo Sapiens outcompetes the Neadanthals which is about 20,000 years ago. Ice age comes and goes, record of human civilization begins at approximately 10,000BC.

Please read and respout approiately. People will be impressed how spot on you get it...

*mutters 'fricking life was made 50,000 years ago' my arse*

Posted by:David |August 31, 2012 at 12:25 AM

The majority of matter in the universe is made up of Dark Matter, but we can not see it? If Dark Matter and Dark Energy does exist, why does it only exist out there somewhere else. We can see the effect on the universe, on other galaxies, but not here. We want to explain the shift in the expansion of the universe, based on some unseen force of nature. It is like the question of whether the world is flat or round. We want to see the universe as being the only one of its kind, but what if the universe is not alone? It is a known fact that there are large galaxies, small galaxies and dwarf rogue galaxies that cluster around larger galaxies. What would happen if universe act in the same manner, and we are a dwarf rogue universe? What would happen if the sum of universes is infinite, and time has no beginning and no end. Fourteen billions years would be a drop in the bucket. If we are a rogue dwarf galaxies being cannibalized by a larger universe, what would this look like to the observer in the galaxies being consumed? What does space look like at the edge of our universe? Maybe we would see what lies beyond our little island called Earth, and this is not all that there is and always will be.

Posted by:kristi276 |August 31, 2012 at 01:00 AM

Answer to the Q:
No, fictional entities by definition cannot play a role in reality.

Posted by:Roman |August 31, 2012 at 03:31 AM

Well, where to start?

Life only got started about 50,000 years ago? Humans have likely been around this long in even just our current form. Pre-sapiens humanoids have been around at least twice as long, probably much more!

Dark matter has repulsive gravity??! Erm...no it doesn't. There is no such thing as repulsive gravity (except for maybe dark energy but seeing as the world's greatest scientific minds don't even know this, I imagine you're confused.)

The earth is millions of years old?! Sounds a bit creationist to me! Any half decent geologist will tell you it's about 4.56 billion years old, only a little younger than the Sun. The Universe is about 13.7 billion years old.

Check facts before spouting!

Posted by:Badgerchap |August 31, 2012 at 04:08 AM

I'm a little skeptical of this claim about DM annihilation powering life. Life doesn't need energy: it needs gradients of energy. Without that, the energy is just heat. The DM annihilation puts any nascent life in an isotropic bath of similar temperatures. The gradient from the interior of the planet to space will be relatively shallow, since a single planet can't clump DM *that* much.

On earth, life has never (to my knowledge) *directly* taken advantage of shallow thermal gradients to power life chemistry. Life has used black smokers, which are geological concentrations of thermal energy.

Posted by:Randal Cox |August 31, 2012 at 06:13 AM

I'm a little skeptical because there's no such thing as dark matter or dark energy. If you look at the evidence for the non-constancy of the (so-called) gravitational constant, you will find that this makes a much better theory than the dark-matter, dark-energy everywhere (but not anywhere near us) theory.

Posted by:criego |August 31, 2012 at 01:56 PM

Is dark matter just the gravitational waves of particles keeping everything in the galaxy held together. Kinda like how gravity is so weak here on earth. Well, same thing with gravity in a black hole. And the missing mass is the super-massive black holes in the center, and the medium black holes we can't see, but now are finding them. And the super-massive black holes were created from tons and tons of ,matter/anti-matter in the beginning of the formation of galaxies. So that you can't take all the matter in the galaxy, and throw it at the center and open up the black hole with enough energy to do anything personal. And the gravitational waves that pull the galaxies together and repulse them is dark energy. Spit-balling here, What else could dark matter be?

Posted by:Justin |August 31, 2012 at 10:21 PM

Maybe when a super-massive black hole sucks up energy from stars and stuff, it turns it into this really fine energy of particles, and the particles collect over time creating new matter, but since light is running from us, we can't see it happening. So the singularity really creates matter to the finest detail and over time, it accumulates into matter, but we don't see it because time for us is well, running away. Just thinking aloud.

Posted by:Justin |August 31, 2012 at 10:28 PM

الثلاثاء، 14 أغسطس 2012

The Discovery of Graphene in Space --Could It Revolutionize Our View of Space-Time? (Today's Most Popular)

In 2011, a team of astronomers, using the Spitzer Space Telescope, reported the first extragalactic detection of the C70 fullerene molecule, and the possible detection of planar C24 ("a piece of graphene") in space. Letizia Stanghellini and Richard Shaw, members of the team at the National Optical Astronomy Observatory in Tucson, Arizona, described how collisional shocks powered by the winds from old stars in planetary nebulae could be responsible for the formation of fullerenes (C60 and C70) and graphene (planar C24).

The team was led by Domingo Anibal Garcia-Hernandez of the Instituto de Astrofisica de Canarias in Spain and includes international astronomers and biochemists.

Planetary nebulae originate from stars similar to our Sun that have reached the end of their lives and are shedding shells of gas into space. In this case, the planetary nebulae are located in the Magellanic Clouds, two satellite galaxies to our own Milky Way, that are best seen from the Southern Hemisphere. At the distance of the Magellanic Clouds, planetary nebulae appear as small fuzzy blobs.

However, unlike planetaries in our own Milky Way Galaxy whose distances are very uncertain, the distance to planetaries in the Magellanic Clouds can be determined to better than 5%. With such accurate distances, the research team determined the true luminosity of the stars and confirmed that the objects are indeed planetary nebulae and not some other object in the astrophysical zoo.

Fullerenes, or Buckyballs, are known from laboratory work on Earth and have many interesting and important properties. Fullerenes consist of carbon atoms arranged in a three dimensional sphere similar to the geodesic domes popularized by Buckminster Fuller.

The C70 fullerene can be compared with a rugby ball, while C60 is compared to a soccer ball. Both of these molecules have been detected in the sample. Graphene (planar C24) is a flat sheet of carbon atoms, one atom thick, that has extraordinary strength, conductivity, elasticity and thinness.

Cited as the thinnest substance known, graphene was first synthesized in the lab in 2004 by Geim and Novoselov for which they received the 2010 Nobel Prize in physics. "If confirmed with laboratory spectroscopy - something that is almost impossible with the present techniques - this would be the first detection of graphene in space," said team member Garcia-Hernandez.

The team proposed that fullerenes and graphene are formed from the shock-induced (i.e., grain-grain collisions) destruction of hydrogenated amorphous carbon grains (HACs). Such collisions are expected in the stellar winds emanating from planetary nebulae, and this team sees evidence for strong stellar winds in the ultraviolet spectra of these stars.

"What is particularly surprising is that the existence of these molecules does not depend on the stellar temperature, but on the strength of the wind shocks," said Stanghellini.

The Small Magellanic Cloud is particularly poor in metals (any element besides hydrogen and helium, in astronomers' parlance), but this sort of environment favors the evolution of carbon-rich planetary nebulae, which turns out to be a favorable place for complex carbon molecules.

The challenge has been to extract the evidence for graphene (planar C24) from Spitzer data. "The Spitzer Space Telescope has been amazingly important for studying complex organic molecules in stellar environments," said Stanghellini. "We are now at the stage of not only detecting fullerenes and other molecules, but starting to understand how they form and evolve in stars." Shaw adds,

"We are planning ground-based follow up through the NOAO system of telescopes. We hope to find other molecules in planetary nebulae where fullerene has been detected to test some physical processes that might help us understand the biochemistry of life."

Horava has developed a new theory of quantum gravity that reflects the need understand what happened immediately after the big bang or what's going on near the event horizon of black holes, where the gravitational fields are massive.

in the physics of condensed matter, specifically in graphene, a carbon atom one atom thick, whose electrons ping around the surface like balls in a pinball machine and can be described using quantum mechanics. Because the graphene atoms are moving at only a fraction of the speed of light there is no need to take relativity into account.

But cool graphene down to near absolute zero and something extraordinary happens: the electrons speed up dramatically. Now relativistic theories are needed to describe them correctly. It was this change that sparked Horava's imagination. What struck Horava about graphene is that Lorentz symmetry isn't always apparent in it.

Could the same thing be true of our universe, he wondered. What we see around us today is a cool cosmos, where space and time appear linked by Lorentz symmetry - a fact that experiments have established to astounding precision. But things were very different in the earliest moments. What if the symmetry that is apparent today is not fundamental to nature, but something that emerged as the universe cooled from the big bang fireball, just as it emerges in graphene when it is cooled?

Horava tweaked Einstein's equations in a way that removed Lorentz symmetry: a property that keeps the speed of light constant for all observers, no matter how fast they move, time slows and distances contract to exactly the same degree. This led Horava to a set of equations that describe gravity in the same quantum framework as the other fundamental forces of nature: gravity emerges as the attractive force due to quantum particles called gravitons, in much the same way that the electromagnetic force is carried by photons. He also amended general relativity to include a preferred direction for time, from the past to the future -the way the universe as we observe it appears to evolve.

"All of a sudden, you have new ingredients for modifying the behaviour of gravity at very short distances," Horava said in an interview with New Scientist.

By breaking asunder the symmetry between space and time, Horava's theory alters the physics of black holes - especially microscopic black holes, which may form at the very highest energies, which means for the formation of these black holes, and whether they are what they seem to be in general relativity "is a very big question."

Horava gravity might also help solve one of the great unsolved mysteries of modern cosmology: the puzzle of dark matter if the equations of motion derived from general relativity are slightly off this could explain the observed speeds of the stars and galaxies without dark matter playing a role.

"It is possible that some fraction of the dark matter picture of the universe could be coming from corrections to Einstein's equations," Horava says.

Ditto for dark energy: theories of particle physics predict the strength of dark energy to be about 120 orders of magnitude larger than what is observed, and general relativity cannot explain this enormous discrepancy. But Horava's theory contains a parameter that can be fine-tuned so that the vacuum energy predicted by particle physics is reduced to the small positive value that is in line with the observed motions of stars and galaxies.

The ultimate answers of course will come with Improved observations of supermassive black holes, which contain regions of intense gravity, which could reveal the necessary corrections to general relativity and prove Horava's theory of quantum gravity, in much the same way that unexplained measurements of Mercury's orbit showed that Newton's laws were incomplete, opening the door for Einstein.

The Daily Galaxy via via newscientist.com and spacedaily.com

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الاثنين، 13 أغسطس 2012

Could a return to the back four of 2011 end LA’s defensive woes?

Could a return to the back four of 2011 end LA’s defensive woes? | LA Galaxy #bg { background: #2a2d51 url(http://www.lagalaxy.com/sites/losangeles/files/la-WEB_BACKGROUND_v2.jpg) no-repeat scroll center top !important; } Castfire.html5ify({ ios_ext: "adaptive.m3u8", // Profile for iPhone, iPod touch, iPad h264_ext: "640.mp4" // Profile for Android, webOS, Blackberry }); Skip To Content

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CARSON, Calif. – Last week’s stunning 4-0 defeat to the Seattle Sounders brought up many questions in the LA Galaxy camp, but one rose above all others.

Is it time to reunite the defense of 2011?

Last season, the defense anchored by goalkeeper Josh Saunders, right back Sean Franklin, center backs A.J. DeLaGarza and Omar Gonzalez and left back Todd Dunivant formed one of the fiercest backlines in MLS history.

However, this season, injuries—particularly to Gonzalez and Dunivant—have kept the 2011 group from suiting up together even once in 2012. But with Gonzalez and Dunivant both healthy and an important match against Chivas USA looming this Sunday, head coach Bruce Arena admits that the club is considering tinkering the backline.

“We haven’t had our back four together this year. That’s a long time not to have your back four back,” said Arena after training on Thursday. “It’s made for a lot of tinkering and obviously as we’re getting healthy, we’re able to go with a more consistent group. It’s all part of it, nothing you can do about it.”

Tinkering may be necessary for Arena after a difficult performance against the Sounders. In particular, rookie left back Bryan Gaul and defender David Junior Lopes struggled against a dynamic Seattle attack leading to calls for the a return of the back four of 2011.

Defensive struggles have become a main talking point this season as the Galaxy have conceded 39 goals in 24 games. By comparison, LA notched 22 competitive shutouts and allowed just 28 goals in 34 league matches in 2011. During the Galaxy’s run to the MLS Cup, the back four of Franklin-DeLaGarza-Gonzalez-Dunivant was the backline of choice, with the quartet starting 17 matches last season including all four playoff games.

“Obviously, we did well last year so fans are hoping that we can do that again. Whatever way that we go though, we have to do better than in Seattle,” said DeLaGarza. “I’d love to be back with Omar, but wherever Bruce sees me fit to be, I’ll be there, whether that’s in the middle or out right or on the bench, which ever.”

Gonzalez was quick to echo the sentiments of his longtime teammate.

“There has been some chemistry issues, Gaul’s new back there, Lopes is new back there and me and A.J. were the only guys that have played together,” said Gonzalez, who has played with DeLaGarza since their days at the University of Maryland. “Of course, I’d love playing with him. I’ve been saying it for the past three years and even before that I love playing with him. I’d like to see it again.”

With LA embroiled in a heated chase to qualify for the postseason, Gonzalez believes that a return to the back four of 2011 may be enough to stabilize the club’s defense heading into the final months of the season.

“It’ll be nice to see the old back line together so maybe sometime soon, we’ll be able to see it,” said Gonzalez. “You know if it ain’t broke then don’t fix it; we ended on a high note last year so maybe we should get the back line together.”

Adam Serrano is the LA Galaxy Insider. Read his blog at LAGalaxy.com/Insider

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