Archive for December, 2008

Plate Tectonics May Have Begun 4.4 Billion Years Ago.

Wednesday, December 3rd, 2008 by Evan Finnes

A new study suggests that the Earth’s tectonic activity may have begun as many as 4.4 billion years ago. The evidence stems from tiny minerals called zircons found in rocks of the Jack Hills region of Western Australia. Zircons, or zirconium silicate (ZrSiO4), are amazing minerals because of the fact that they are very widespread, and can exist in igneous, sedimentary, or metamorphic rocks.

By analyzing tiny mineral inclusions found inside seven of the zircon crystals found in Western Australia ( seven out of 400 found) scientists were able to determine that there was tectonic activity in the earliest eon of our planet, the Hadean. These inclusions allowed the scientist to determine the temperature and pressures at which the zircons formed. Six of the seven bits of zircon contained inclusions composed of the mineral muscovite (KAl2(AlSi3O10)(OH)2). The Silicon to Aluminum ratio in these muscovite inclusions suggest that the rocks formed at depths of about 25 km beneath the Earth’s surface. Because of the amount of Titanium atoms present in the zircons, the scientists were able to determine that temperature of crystallization was between 665 and 745 degrees Celsius. The seventh inclusion consisted of a mineral known as hornblende ( (Ca,Na)2-3(Mg,Fe,Al)3Si6(Si,Al)2O22(OH)2) ). After analyzing the hornblende inclusions, (using methods similar to the above methods), scientists were able to confirm the determined results of the muscovite. However, because this discovery is based only on seven samples, there is some healthy criticism.

These temperatures and pressures indicate that the temperature flux during the zircon crystallization was approximately 75 mW/m2. This flux is slightly higher than what is observed on Earth today. Because the Earth was so much hotter during its first six hundred million years, a higher paleo-flux is expected. However, the calculated flux was also determined to be about 1/5 lower than the expected flux of the hadean eon. It is because of this abnormally lower than average flux of the hadean eon zircons, that it was determined that the plate tectonics had to have begun so early in Earth’s history.

On Earth today, fluxes much lower than average occur above subduction zones, where one plate subducts beneath another. It is hypothesized that these zircons were formed as the descending plate subducted, bringing liquid water with it, where it cooled the surrounding mantle enough for the zircons, and the inclusion minerals, to crystallize out of solution. Zircon contains uranium isotopes, which allowed the year of this crystallization to be calculated using radiometric dating techniques.

This could be an important discovery because it will help us understand the evolution of terrestrial planets. Plate tectonics play a very important role in recycling the gasses which make up our atmosphere, and therefore directly affect the ability of a planet to sustain life. With the right atmospheres, Venus and Mars could have been within the habitable zone of our solar system, however neither planet is believed to have developed plate tectonics.

Besides providing clues to the development of plate tectonics, the zircons also contain oxygen isotopes that suggest that water was also present on the Earth some 4.4 billion years ago. These Western Australian zircons are the oldest minerals on Earth, and have provided us with great insight into the dawning hours of our planet.

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Wednesday, December 3rd, 2008 by Terence Witt

Although Newton and Einstein were both brilliant individuals, far ahead of their time, this was not their defining attribute. What they, and most of the other truly great theorists of history have shared, is a genuine humility before nature. This is not the same thing as admitting to the incompleteness of the standard model of particle physics, for instance, nor is it the same thing as claiming that the deepest secrets of the universe remain shrouded in great mystery. Humility before nature is to stand in utter awe of the universe, listening with unshielded, unprejudiced ears to what it’s trying to tell you. This is not a mystical experience; this is a case of striving for total objectivity. The mental noise generated by our protracted simian ancestry clouds our thoughts with nonsensical egocentric ideas, and scientific progress is often the first casualty. Examples are too numerous to mention, so let’s just play the highlight reel.

Anthropic principle. This is one of my favorites; designing the universe in man’s image. The anthropic principle is perhaps the most egregious case of the tail wagging the dog in the history of organized thought. There is nothing; absolutely nothing, that is universally unique about the human form. I’ve often said that if the universe were different than it is, we would be different than we are. On reflection, however, the more accurate statement is if the Earth, the lovely blue-green speck floating amongst the hundreds of billions of stars in another speck – the Milky Way – were different than it is, we would be different than we are. Saying that the universe is designed to accommodate humans is like saying that the Earth has to be the way it is or else seagulls would be unable to fly. Ludicrous, yet the anthropic principle persists in many forms.

Conflating math with reality. Although America’s forefathers saw the wisdom of separating church and state, theoretical physics has failed to draw a clean line between math and reality. This is an occupational hazard of course. Without math, theoretical physicists would have little to do. Perhaps if enough theoretical physicists were immersed in engineering or applied mathematics, they would eventually come to the realization that our math is no more than a clumsy idealization of reality. It is the simplistic shadow that reality casts on our minds. Calculus, for instance, works because of the way reality is, not because of the way that calculus is designed.

Reality by consensus and aversion to new concepts. This is tribal activity at its best, and it does have a heavy evolutionary heritage. The shamans of thousands of years ago had jobs similar to the cosmologists of today – to answer questions for which there are often no good answers. The best way to do this is adopt a sweeping, agreed-upon liturgy that covers all the bases. It doesn’t even have to be self-consistent, it just has to be consistent. Getting the story straight, so to speak. In ancient times, the missing logical sequences were attributed to god; in modern times, the missing sequences are denigrated as philosophy. In both cases, the probing of logical inconsistencies is considered an attack, because these areas have already been labeled as out of bounds. “Foul!” they cry in unison. Since any genuinely new idea represents a change in the worldview, and since it takes so long to “get the story straight”, there is widespread resistance to original concepts. Hubris replaces humility, authority replaces curiosity, and science takes the fall…again.

Discovery by brute force. The LHC involves the work of literally thousands of scientists, with the oft stated and well-publicized goal of “probing nature’s deepest mysteries”. Yet it is all done to support a standard model of particle physics that contains a gaping schism near its core – the fundamental incompatibility between quantum mechanics and relativity. This is seen as a problem of course, but not really a pressing problem. Indeed, how could it possibly be in need of urgent attention? The schism has been in place for nearly a century. Full steam ahead, business as usual, damn the torpedoes. So, whereas a prudent airplane mechanic might be deeply concerned upon noticing a crack in a plane’s engine, theoretical physicists are convinced that they can unmask nature’s fundamental secrets by sheer force of will and accelerators so large that they need their own electrical generating plants.

These are only four of the dozens of implicit ways that science has been polluted by our needy, anthropocentric genes. While it is true that a progression of our worldview periodically occurs, it usually takes the form of observations kicking down the door and leaving us with no available recourse. It took a very long time for Earth to be demoted from “Center of Universe” to its current status as “Center of Intelligent Life”. It is entirely unclear how long it will take humankind to see the universe through eyes divorced from their heavily ego-dominated lenses, but this is the one and only path to scientific objectivity. Unfortunately (or perhaps fortunately, time will tell) we are quickly approaching a situation where the cost/benefit analysis of colliders larger than the LHC and telescopes beyond 20 or 50 m becomes simply indefensible. Either our worldview freezes and physics dies, or we go all the way back to where the cracks started forming in the current paradigms and we start using the most powerful tool of all – logic.

You might think that the author of a book as ambitious as Our Undiscovered Universe would be the last person to blog about humility and respect. And perhaps it might be easy to mistakenly conflate my book’s unbridled enthusiasm for the power of its new ideas with an author’s ego run amok. But as I continue the daunting task of developing and applying null physics, with its nonlinear four-dimensional geometry of particles and photons, and as I see single particle calculations that can effortlessly bring a supercomputer to its knees, humility is really my only option. Or as Yoda might say, “be beaten down by Mother Nature a thousand times in a thousand different ways for 30 years, humbled you will be!”

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Microquasars: Black Holes and Normal Stars an Interesting Mix

Tuesday, December 2nd, 2008 by Bellatrix

Astronomers using two different telescopes and two different systems have started learning about microquasars. They’re learning new things that can then hopefully be applied to full size quasars as well.

A quasar is an extremely powerful, luminous and distant active galactic nucleus. While there was initially some controversy over the nature of these objects, there is now a scientific consensus that a quasar is a compact region surrounding the central supermassive black hole of a galaxy. Quasars show a very high redshift, meaning they are located a great distance from us. Quasars are active because the central black hole is accreting a lot of material. Near the black hole, intense magnetic fields in the disk accelerate material into tight jets that flow in opposite directions away from the hole.

Microquasars is a two-body system consisting of a stellar mass size black hole and a star, usually a red giant. The giant star is feeding material to the black hole. Which, needless to say creates some interesting dynamics. Astronomers have been looking at two systems, Swift1753.3-0127 and GX339-4, with the European Southern Observatory’s Very Large Telescope and NASA’s Rossi X-ray Timing Explorer to study microquasars. Microquasars are not only closer but change more rapidly, so a process that may take a normal quasar a year to undergo might only take a microquasar a few minutes.

Astronomers had thought that the visible light emission coming form microquasars was coming form far out in the accretion disk and thus did not give much information about the main actions going on. However, they were wrong. They now know that the optical and x-ray emission are intrinsically linked, probably by the same immense magnetic fields that hurl material into near light speed jets.

The data shows that light output typically drops just before x-ray output undergoes a large spike. The rapid variations in the x-ray and optical emission must have a common origin. The cool thing about discovering such patterns that stand out amidst chaotic fluctuations of light is that they give us a new handle on understanding the underlying physics. The best candidate is the strong magnetic fields as the dominant process behind it all.

So again what we once thought was wrong, we learned something new, but realize how much we don’t know yet. This data is a new clue about very mysterious and not yet understood systems. We still don’t know exactly what’s going on in these dynamic systems, but we have one more piece of the puzzle.

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ExtraSolar CO2

Monday, December 1st, 2008 by Evan Finnes

For the first time carbon dioxide has been found in the atmosphere of a planet outside of our own solar system. This is an important discovery because carbon dioxide is one the chemicals we would expect to find on a planet that harbors life, the other chemicals include: oxygen, water, and methane. Water vapor, along with carbon monoxide has previously been detected in the planet’s atmosphere.

Unfortunately, the discovery of carbon dioxide on this planet cannot be correlated to life. This Jupiter sized planet, which is located 63 light years from Earth, is known as HD 189733b. It has an orbital period of about 2.2 days and has a scorching surface temperature of about 1117 K. The close proximity of the planet to its host star may be responsible for the formation of carbon dioxide in the planet’s atmosphere. As the planet orbits, relatively close to its sun, it receives a high dosage of ultraviolet radiation. This radiation may have stripped apart other chemicals in the planet’s atmosphere while creating new chemicals, such as carbon dioxide.

The carbon dioxide was detected by analyzing the infrared spectrum of the planet. Because HD 189733b lies so close to its host star, the combined spectrum of the star/planet system had to first be analyzed and recorded. Scientists then waited for the planet to disappear behind its host star, so that the suns individual spectrum could be recorded. To obtain the planets individual spectrum, the spectrum of the star was subtracted from the star/planet system.

French astronomers discovered HD 189733b, in the constellation Vulpecula, on Oct. 5, 2005 by observing the transit of the planet across its host star. Since its discovery, the planet has reached a number of milestones. It was the first extrasolar planet to be mapped, it was the first found to contain water vapor and methane (which probably react in the high temperatures to form the carbon monoxide), and now it is the first exosolar planet known to contain carbon dioxide.

This discovery confirms our ability to detect the chemical compositions of planets outside of our solar system. If, and hopefully when, an Earth-like is discovered, analyzing the spectral signatures will be more difficult due to the small sizes of terrestrial planets. As we continue to develop our techniques by recording the spectral signatures of Jupiter-like planets, and super Earths, there should be little doubt that we will be ready to analyze the atmosphere of an Earth or Mars sized planet when the discovery occurs, bringing us one step closer to eventually detecting life on another planet.

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