Tuesday, July 03, 2007

The Big Bounce


What Happened Before The Big Bang?
Gazing Ball by qwerty

The idea that the universe erupted with a Big Bang explosion has been a big barrier in scientific attempts to understand the origin of our expanding universe, although the Big Bang long has been considered by physicists to be the best model. As described by Einstein's Theory of General Relativity, the origin of the Big Bang is a mathematically nonsensical state -- a "singularity" of zero volume that nevertheless contained infinite density and infinitely large energy.

Physicists at Penn State are exploring territory unknown even to Einstein -- the time before the Big Bang -- using a mathematical time machine called Loop Quantum Gravity. This theory, which combines Einstein's Theory of General Relativity with equations of quantum physics that did not exist in Einstein's day, is the first mathematical description to systematically establish the existence of the Big Bounce and to deduce properties of the earlier universe from which our own may have sprung. For scientists, the Big Bounce opens a crack in the barrier that was the Big Bang.
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"Einstein's Theory of General Relativity does not include the quantum physics that you must have in order to describe the extremely high energies that dominated our universe during its very early evolution," Martin Bojowald, assistant professor of physics at Penn State explained, "but we now have Loop Quantum Gravity, a theory that does include the necessary quantum physics."

Loop Quantum Gravity was pioneered and is being developed in the Penn State Institute for Gravitational Physics and Geometry, and is now a leading approach to the goal of unifying general relativity with quantum physics. Scientists using this theory to trace our universe backward in time have found that its beginning point had a minimum volume that is not zero and a maximum energy that is not infinite. As a result of these limits, the theory's equations continue to produce valid mathematical results past the point of the classical Big Bang, giving scientists a window into the time before the Big Bounce.

Quantum-gravity theory indicates that the fabric of space-time has an "atomic" geometry that is woven with one-dimensional quantum threads. This fabric tears violently under the extreme conditions dominated by quantum physics near the Big Bounce, causing gravity to become strongly repulsive so that, instead of vanishing into infinity as predicted by Einstein's Theory of General Relativity, the universe rebounded in the Big Bounce that gave birth to our expanding universe. The theory reveals a contracting universe before the Big Bounce, with space-time geometry that otherwise was similar to that of our universe today.

Bojowald found he had to create a new mathematical model to use with the theory of Loop Quantum Gravity in order to explore the universe before the Big Bounce with more precision. "A more precise model was needed within Loop Quantum Gravity than the existing numerical methods, which require successive approximations of the solutions and yield results that are not as general and complete as one would like," Bojowald explained. He developed a mathematical model that produces precise analytical solutions by solving of a set of mathematical equations.

In addition to being more precise, Bojowald's new model also is much shorter. He reformulated the quantum-gravity models using a different mathematical description, which he says made it possible to solve the equations explicitly and also turned out to be a strong simplification. "The earlier numerical model looked much more complicated, but its solutions looked very clean, which was a clue that such a mathematical simplification might exist," he said. Bojowald reformulated quantum gravity's differential equations -- which require many calculations of numerous consecutive small changes in time -- into an integrable system -- in which a cumulative length of time can be specified for adding up all the small incremental changes.

The model's equations require parameters that describe the state of our current universe accurately so that scientists then can use the model to travel backward in time, mathematically "un-evolving" the universe to reveal its state at earlier times. The model's equations also contain some "free" parameters that are not yet known precisely but are nevertheless necessary to describe certain properties. Bojowald discovered that two of these free parameters are complementary: one is relevant almost exclusively after the Big Bounce and the other is relevant almost exclusively before the Big Bounce. Because one of these free parameters has essentially no influence on calculations of our current universe, Bojowald colludes that it cannot be used as a tool for back-calculating its value in the earlier universe before the Big Bounce.

The two free parameters, which Bojowald found were complementary, represent the quantum uncertainty in the total volume of the universe before and after the Big Bang. "These uncertainties are additional parameters that apply when you put a system into a quantum context such as a theory of quantum gravity," Bojowald said. "It is similar to the uncertainty relations in quantum physics, where there is complimentarity between the position of an object and its velocity -- if you measure one you cannot simultaneously measure the other."

Similarly, Bojowald's study indicates that there is complementarity between the uncertainty factors for the volume of the universe before the Big Bounce and the universe after the Big Bounce. "For all practical purposes, the precise uncertainty factor for the volume of the previous universe never will be determined by a procedure of calculating backwards from conditions in our present universe, even with most accurate measurements we ever will be able to make," Bojowald explained. This discovery implies further limitations for discovering whether the matter in the universe before the Big Bang was dominated more strongly by quantum or classical properties.

"A problem with the earlier numerical model is you don't see so clearly what the free parameters really are and what their influence is," Bojowald said. "This mathematical model gives you an improved expression that contains all the free parameters and you can immediately see the influence of each one," he explained. "After the equations were solved, it was rather immediate to reach conclusions from the results."

Bojowald reached an additional conclusion after finding that at least one of the parameters of the previous universe did not survive its trip through the Big Bounce -- that successive universes likely will not be perfect replicas of each other. He said, "the eternal recurrence of absolutely identical universes would seem to be prevented by the apparent existence of an intrinsic cosmic forgetfulness."

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The Planck Scale from Bee @ Backreaction
Before the big bang from Universe Today
Against Bounces counterargument from Sean @ Cosmic Variance
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Wednesday, June 27, 2007

Event Horizon & BlackHoles


Astronomers May Have Solved Information Loss Paradox To Find Black Holes Do Not Form



"Nothing there," is what Case Western Reserve University physicists concluded about black holes after spending a year working on complex formulas to calculate the formation of new black holes.

The question that the physicists set out to solve is: what happens once something collapses into a black hole. If all information about the collapsing matter is lost, it defies the laws of quantum physics. Yet, in current thinking, once the matter goes over the event horizon and forms a black hole, all information about it is lost.
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Case physicists Tanmay Vachaspati, Dejan Stojkovic and Lawrence M. Krauss report in the article, "Observation of Incipient Black Holes and the Information Loss Problem," that has been accepted for publication by Physical Review D. "It's complicated and very complex," noted the researchers, regarding both the general problem and their particular approach to try to solve it.

"If you define the black hole as some place where you can lose objects, then there is no such thing because the black hole evaporates before anything is seen to fall in," said Vachaspati.
The masses on the edge of the incipient black hole continue to appear into infinity that they are collapsing but never fall over inside what is known as the event horizon, the region from which there is no return, according to the researchers.

By starting out with something that was nonsingular and then collapsing that matter, they were determined to see if an event horizon formed, signaling the creation of a black hole.
The mass shrinks in size, but it never gets to collapse inside an event horizon due to evidence of pre-Hawking radiation, a non-thermal radiation that allows information of the nature of what is collapsing to be recovered far from the collapsing mass.

"Non-thermal radiation can carry information in it unlike thermal radiation. This means that an outside observer watching some object collapse receives non-thermal radiation back and may be able to reconstruct all the information in the initial object and so the information never gets lost," they said.

According to the researchers, if black holes exist, information formed in the initial state would disappear in the black hole through a burst of thermal radiation that carries no information about the initial state.

Using the functional Schrodinger formalism, the researchers suggest that information about the energy from radiation is long evaporated before an event horizon forms.

"An outside observer will never lose an object down a black hole," said Stojkovic. "If you are sitting outside and throwing something into the black hole, it will never pass over but will stay outside the event horizon even if one considers the effects of quantum mechanics. In fact, since in quantum mechanics the observer plays an important role in measurement, the question of formation of an event horizon is much more subtle to consider."

The physicists are quick to assure astronomers and astrophysicists that what is observed in gravity pulling masses together still holds true, but what is controversial about the new finding is that "from an external viewer's point it takes an infinite amount of time to form an event horizon and that the clock for the objects falling into the black hole appears to slow down to zero," said Krauss, director of Case's Center for Education and Research in Cosmology.

He continued "this is one of the factors that led us to rethink this problem, and we hope our proposal at the very least will stimulate a broader reconsideration of these issues."

Adapted from a news release by Case Western Reserve University.

If black holes exist in the universe, the astrophysicists speculate they were formed only at the beginning of time.
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Saturday, April 21, 2007

The Universe in a flower


Blue_Morning_Glory - Click on Image to Enlarge
Image Credit copyright @ Xfg21042007/C5050Z


Like the Morning Glory in the picture, it is said the Universe started in an instant from a single node. In Time, Space (space-time) grew and unfolded outward like the funnel shape of the petals to arrive at where we are today. Sitting comfortably close to the fully open outer rim of the flower or Universe.

The light from the centre in the flower is pure white, the purples and blues are those wavelengths which are reflected, all other photons wavelengths and colours are trapped by the flower and held.

If we look at the body of the flower we could say the petals are like the sea of gravity or Space on which matter surfs and conglomerates into galaxies, and like droplets of rain water resting on the flower, which form into multiple shape and size bubbles, and by surface tension are bound.

As we reach the outer rim of the flower or Universe we are told, there, is to be found a cosmic event horizon or periphery. This of course we assume or perceive to be the boundary of the observable universe as it has come to be known.

While I was observing the flower, I couldn't fail to notice
the ant (and the bee) walking along the flower, walk right over the edge to the other side of the flower's boundary or periphery.

For you see, every flower, funnel shaped conical or pyramidal has a membrane or wall, which means it has an inner and outer wall. But of course to us sitting on one of these droplets in the inner wall of the flower Universe, the outside wall is hidden and as you can see, we cannot see beyong the periphery.

Fortunately for us all, the universe lasts a lot longer than the Morning Glory, which in all its majesty is here only for a day and its beauty gone in less than an hour shortly after the last sunray.

The flower typically lasts for a single morning and dies in the afternoon. New flowers bloom each day. The flowers usually start to fade a couple of hours before the petals start showing visible curling. They prefer full sun throughout the day.

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Morning glory is a common name for over a thousand species of flowering plants in the family the Convolvulaceae, belonging to the following genera:
Calystegia
Convolvulus
Ipomoea
Merremia
Rivea
As the name implies, morning glory flowers, which are funnel-shaped, open at morning time, allowing them to be pollinated by hummingbirds, butterflies, bees and other daytime insects and birds, as well as Hawkmoth at dusk for longer blooming variants. The flower typically lasts for a single morning and dies in the afternoon. New flowers bloom each day. The flowers usually start to fade a couple of hours before the petals start showing visible curling. They prefer full sun throughout the day, and mesic soils. In cultivation, most are treated as perennial plants in tropical areas, and as annual plants in colder climates, but some species tolerate winter cold.

Morning glory is also called asagao (in Japanese, a compound of 朝 asa "morning" and 顔 kao "face"). A rare brownish-coloured variant known as Danjuro is very popular. It was first known in China for its medicinal uses, due to the laxative properties of its seeds. It was introduced to the Japanese in the 9th century, and they were first to cultivate it as an ornament. During the Edo Period, it became a very popular ornamental flower. Aztec priests in Mexico were also known to use the plant's hallucinogenic properties to commune with their gods (see Rivea corymbosa).

Ancient Mesoamerican civilizations used the morning glory species Ipomoea alba to convert the latex from the Castilla elastica tree and also the guayule plant to produce bouncing rubber balls. The sulfur in the morning glory's juice served to vulcanize the rubber, a process pre-dating Charles Goodyear's discovery by at least 3,000 years.

Because of their fast growth, twining habit, attractive flowers, and tolerance for poor, dry soils, some morning glories are excellent vines for creating summer shade on building walls when trellised, thus keeping the building cooler and reducing air conditioning costs.

In some places such as Australian bushland morning glories develop thick roots and tend to grow in dense thickets. They can quickly spread by way of long creeping stems. By crowding out, blanketing and smothering other plants, morning glory has turned into a serious invasive weed problem.

Ipomoea aquatica, known as water spinach, water morning-glory, water convolvulus or swamp cabbage, is popularly used as a green vegetable especially in East and Southeast Asian cuisines.

The seeds of many species of morning glory contain d-lysergic acid amide, ergoline alkaloids better known as LSA. Seeds of I. tricolor and I. corymbosa (syn. R. corymbosa) are used as hallucinogens. They are about 5% to 10% as potent as LSD. Users also report the overall experience and some of the effects to be rather similar to those of LSD. However, caution must be taken as some commercial seed producers protect their seeds with a chemical that may cause vomiting, nausea and abdominal pain if the seeds are eaten.

So enjoy Today and Every Day!
Here's wishing you All a fine Earth Day this Sun day.
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Radio Active Brown Dwarves are new class of Pulsar
Astronomers Make Detailed Image Of Giant Stellar Nursery
XMM-Newton Pinpoints Intergalactic Gas & Quasar Bubbles
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Sunday, April 08, 2007

Above and Below



Above
and
Below
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All of the observable universe is filled with large numbers of photons, the so-called cosmic background radiation, and quite likely a correspondingly large number of neutrinos.

The current temperature of this radiation is about 3 K, or -270 degrees Celsius.

A vacuum is a volume of space (empty space) that is essentially empty of matter, so that gaseous pressure is much less than standard atmospheric pressure.

A perfect vacuum with a gaseous pressure of absolute zero is a philosophical concept that is never observed in practice, not least because quantum theory predicts that no volume of space is perfectly empty in this way.

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Physicists often use the term "vacuum" slightly differently, to discuss ideal test results that would occur in a perfect vacuum, which is simply called "vacuum" or "free space" in this context, and use the term partial vacuum to refer to the imperfect vacua realized in practice.

The quality of a vacuum is measured by how closely it approaches a perfect vacuum. The residual gas pressure is the primary indicator of quality, and it is most commonly measured in units of torr, even in metric contexts. Lower pressures indicate higher quality, although other variables must also be taken into account. Quantum mechanics sets limits on the best possible quality of vacuum. Outer space is a natural high quality vacuum, mostly of much higher quality than what can be created artificially with current technology.

Much of outer space has the density and pressure of an almost perfect vacuum. It has effectively no friction, which allows stars, planets and moons to move freely along ideal gravitational trajectories. But no vacuum is perfect, not even in interstellar space, where there are a few hydrogen atoms per cubic centimeter at 10 fPa (10 to the minus 16 Torr). The deep vacuum of space could make it an attractive environment for certain processes, for instance those that require ultraclean surfaces, but for small scale applications it is much easier to create an equivalent vacuum on Earth than to leave the Earth's gravity well.

Einstein argued that physical objects are not located in space, but rather have a spatial extent. Seen this way, the concept of empty space loses its meaning. Rather, space is an abstraction, based on the relationships between local objects. Nevertheless, the general theory of relativity admits a pervasive gravitational field, with properties that vary from one location to another. Only, one must take care not to ascribe to it material properties like velocity, and so on.

Stars, planets and moons keep their atmosphere by gravitational attraction, so atmospheres have no clearly delineated boundary. The density of atmospheric gas simply decreases with distance from the object. In Low Earth Orbit (about 300 km altitude) the atmospheric density is about 100 nPa, (10 to the minus 9 Torr,) still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region, and they need to fire their engines every few days to maintain orbit.

Beyond planetary atmospheres, the pressure from photons and other particles from the sun becomes significant. Spacecraft can be buffeted by solar winds, but planets are too massive to be affected. The idea of using this wind with a solar sail has been proposed for interplanetary travel.

In 1913, Norwegian explorer and physicist Kristian Birkeland may have been the first to predict that space is not only a plasma, but also contains "dark matter". He wrote: "It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. We have assumed that each stellar system in evolutions throws off electric corpuscles into space. It does not seem unreasonable therefore to think that the greater part of the material masses in the universe is found, not in the solar systems or nebulae, but in "empty" space.

In 1930, Paul Dirac proposed a model of vacuum as an infinite sea of particles possessing negative energy, called the Dirac sea. This theory helped refine the predictions of his earlier formulated Dirac equation and successfully predicted the existence of the positron, which was discovered two years later in 1932. Despite this early success, the idea was soon abandoned in favour of the more elegant quantum field theory.

The development of quantum mechanics has complicated the modern interpretation of vacuum by requiring indeterminacy. Niels Bohr and Werner Heisenberg's uncertainty principle and Copenhagen interpretation, formulated in 1927, predict a fundamental uncertainty in the position of any particle, which, not unlike the gravitational field, questions the emptiness of space between particles. In the late 20th century, this principle was understood to also predict a fundamental uncertainty in the number of particles in a region of space, leading to predictions of virtual particles arising spontaneously out of the void. In other words, there is a lower bound on vacuum which is dictated by the lowest possible energy state of the quantized fields in any region of space. Ironically, Plato was right, if only by chance.

Even an ideal vacuum, thought of as the complete absence of anything, will not in practice remain empty. One reason is that the walls of a vacuum chamber emit light in the form of black-body radiation: visible light if they are at a temperature of thousands of degrees, infrared light if they are cooler. If this soup of photons is in thermodynamic equilibrium with the walls, it can be said to have a particular temperature, as well as a pressure. Another reason that perfect vacuum is impossible is the Heisenberg uncertainty principle which states that no particle can ever have an exact position. Each atom exists as a probability function of space, which has a certain non-zero value everywhere in a given volume. Even the space between molecules is not a perfect vacuum.

More fundamentally, quantum mechanics predicts that vacuum energy can never be exactly zero. The lowest possible energy state is called the zero-point energy and consists of a seething mass of virtual particles that have a brief existence. This is called vacuum fluctuation. While most agree that this represents a significant part of particle physics, it is a concept that would benefit from a deeper understanding than currently available. Vacuum fluctuations may also be related to the so-called cosmological constant in the theory of gravitation, if indeed this entity were to be observed in nature on a macroscopic scale. The best evidence for vacuum fluctuations is the Casimir effect and the Lamb shift.

In quantum field theory and string theory, the term "vacuum" is used to represent the ground state in the Hilbert space, that is, the state with the lowest possible energy. In free (non-interacting) quantum field theories, this state is analogous to the ground state of a quantum harmonic oscillator. If the theory is obtained by quantization of a classical theory, each stationary point of the energy in the configuration space gives rise to a single vacuum. String theory is believed to be analogous to quantum field theory but one with a huge number of vacua - with the so-called anthropic landscape.

Deep space is generally much more empty than any artificial vacuum that we can create, although many laboratories can reach lower vacuum than that of low earth orbit. In interplanetary and interstellar space, isotropic gas pressure is insignificant when compared to solar pressure, solar wind, and dynamic pressure, so the definition of pressure becomes difficult to interpret. Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre. The average density of interstellar gas is about 1 atom per cubic centimeter.

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Still begs the question what is outside the observable universe.
Laser-cooling Brings Large Object Near Absolute Zero from MIT
LHC cooler than outer space by John @ Cosmic Variance
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Friday, April 06, 2007

Quantum Universe


Science Tunnel - Max Planck Society

Nothing in the physical sciences predicts the phenomenon of consciousness. Yet its reality is apparent to each and every one of us

Consciousness is as fundamental as matter - in some ways, more fundamental. Advances in physics, psychology, and philosophy have shown that reality is not what it seems.

Take vision, for example. When we look at a tree, light reflected from its leafs is focused onto cells in the retina of the eye, where it triggers a cascading chemical reaction releasing a flow of electrons.

Neurons connected to the cells convey these electrical impulses to the brain’s visual cortex, where raw data is processed and integrated. Then — in ways that are still a complete mystery — an image of the tree appears in our consciousness.

It may seem that we are directly perceiving the tree in the physical world, but what we are actually experiencing is an image generated in our mind.

The same is true of every other experience. All that we see, hear, taste, touch, smell and feel has been created from the data received by our sensory organs. All we ever know of the world around are the mental images constructed from that data. However real and external they may seem, they are all phenomena within our mind.

Peter Russell
The Universe as a hologram by Michael Talbot
Play the quantum lottery by John @ cosmicvariance

The human brain stores and processes its information at the level of single organic molecules and is a single macroscopic quantum system. Acts of consciousness may be viewed as incorporating quantum events.
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Thursday, March 15, 2007

GRBs & Magnetars


Gamma-ray Birth Cries Suggest Massive Magnetic Engines

Swift's Burst Alert Telescope (BAT) detected the GRB in the constellation Pictor on 29 July 2006.

XRT picked up GRB 060729 (named for the date of its first observation) 124 seconds after the BAT detected it. Normally, XRT monitors an afterglow for a week or two until it fades to near invisibility. But GRB 060729's afterglow started off so bright and faded so slowly that XRT could regularly monitor it for months, and the instrument still was able to detect it in late November. The burst's relatively close proximity to Earth, about 5 billion light-years, also was a factor in XRT's ability to monitor the afterglow for such an extended period.

The slow fading of the X-ray afterglow has several important ramifications for our understanding of GRBs. "It requires a larger energy injection than we normally see in bursts, and may require continuous energy input from the central engine," says astronomer Dirk Grupe of Penn State University, in University Park, Pennsylvania, who is lead author of the international team that reports these results in a paper scheduled to appear in the June 20, 2007 issue of the Astrophysical Journal.

One possibility is that the central engine, perhaps an accreting black hole, ejected multiple shells of material at near light speed. Forward shells may have decelerated when they slammed into interstellar gas, allowing back shells to catch up and slam into them with tremendous force. The resulting shock waves could have powered the afterglow and made it shine brightly in X-rays.

But another possibility is that the GRB's central engine was a magnetar -- a neutron star with an ultra-powerful magnetic field. The magnetar's magnetic field acts like a brake, forcing the star's rotation rate to spin down rapidly. The energy of this spin-down can be converted into magnetic energy that is continuously injected into the initial blast wave that triggered the GRB. Calculations show that this energy could power the observed X-ray afterglow and keep it shining for months.
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NASA Mission Finds Link Between Big And Small Stellar Blasts
New Panorama Reveals More Than A Thousand Black Holes
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"Quantum events are taking place all around us. They are very, very small. Some of these small quantum events caught up in the process of rapid expansion of space became galaxies along the way. During inflation, quantum fluctuations can produce not only galaxies, but also new parts of the universe. An infinite number of worlds could exist with different types of physical laws operating among them." - Andrei Linde
Cosmologist speaks of mind-bending dynamics from Stanford University
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Monday, February 19, 2007

Dark Galaxies

Ghostly galaxies speckle the universe. Unlike normal galaxies, these extreme systems contain very few stars and are almost devoid of gas. Most of the luminous matter, so common in most galaxies, has been stripped away, leaving behind a "spectral" shadow.
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These intriguing galaxies-known as dwarf spheroidals are so faint that, although researchers believe they exist throughout the universe, only those relatively close to Earth have ever been observed. And until recently, no scientific model proposed to unravel their origin could simultaneously explain their exceptional content and their penchant for existing only in close proximity to much larger galaxies.

Using supercomputers to create novel simulations of galaxy formation, Kazantzidis and his collaborators found that a "dark matter" dominated galaxy begins life as a normal system. But when it approaches a much more massive galaxy, it simultaneously encounters three environmental effects - "ram pressure," "tidal shocking" and the cosmic ultraviolet background-that transform it into a mere shadow of its former self.

About 10 billion years ago, when the gas-rich progenitors of "dark matter" dominated galaxies originally fell into the Milky Way, the universe was hot with a radiation called the cosmic ultraviolet background. As a small satellite galaxy traveled along its elliptical path around a more massive galaxy, called the host, this radiation made the gas within the smaller galaxy hotter. This state allowed ram pressure - a sort of "wind resistance" a galaxy feels as it speeds along its path - to strip away the gas within the satellite galaxy.

Simultaneously, as the satellite galaxy moved closer to the massive system, it encountered the overwhelming gravitational force of the much larger mass. This force wrenched luminous stars from the small galaxy. Over billions of years of evolution, the satellite passed by the massive galaxy several times as it traversed its orbital path. Each time its stars shook and the satellite lost some of them as a result of a mechanism called "tidal shocking". These effects conspired to eventually strip away nearly all the luminous matter gas and stars, and left behind only a shadow of the original galaxy.

The remaining matter, on the other hand, was nongaseous and therefore unaffected by the ram pressure force or the cosmic ultraviolet background, the scientists posit. It did experience tidal shocking, but this force alone was not strong enough to pull away a substantial amount of the remaining matter or "dark matter".

Scientists elucidate the origin of the darkest galaxies in the universe
from Stanford University news (Image courtesy of Stanford University)


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Stem cells determine the daughter cells' fate
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Intestinal stem cells (ISCs) in the gut of the fruit fly, Drosophila melanogaster, directly determine the fate of their daughter cells. The signaling protein called Delta, seen here in red, determines what type of cell the ISCs will produce.

Large amounts of Delta signal the daughter cells to become gut-lining enterocytes (left panel), while small amounts of Delta signal them to become hormone-generating enteroendocrine cells (see image). (Credit: Images used with permission of the American Association for the Advancement of Science, Science, February 16, 2007)
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From roundworm to human, most cells in an animal’s body ultimately come from stem cells. When one of these versatile, unspecialized cells divides, the resulting “daughter” cell receives instructions to differentiate into a specific cell type. In some cases this signal comes from other cells. But now, for the first time, researchers at the Carnegie Institution’s Department of Embryology have found a type of stem cell that directly determines the fate of its daughters.

Stem cells can participate actively in determining what type of cell their daughters will become right at the moment of stem cell division, suggesting that tissue stem cells might not just be a source of new cells, but could actually be the ‘brains’ of the tissue - the cells that figure out what type of new cell is needed at any given moment.

Because they truly can become any cell in the body, “embryonic” stem cells tend to receive a lot of attention. Yet “adult” stem cells remain in fully-developed organisms, where they replace specific cell types lost to age or disease.

Read more Stem Cells Determine Their Daughters' Fate

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arxiv find dark matter from Sean @ Cosmic Variance
In Search of Dark Matter Galaxies from Centauri Dreams
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Saturday, February 17, 2007

Universal Feast


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Photo thanks to Jimmy James @ Under The Ledge click image to enlarge


Logic would dictate that just as there is space time, there is Space outside TIME.

In spacetime we can take a snapshot and freeze time, we can even rewind a film on video or dvd, but we do this travelling forward thru time. Even when we look at the distant stars and galaxies in the universe, we are looking at the light that reaches us on Earth, from a time long past.
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Time (and even Space) as we shall see is relative to the observer, and as humans we are travelling thru time (and ageing over time).

It is movement that creates the impermanence of time, but there must be a Space outside Time where motion (or movement) is possible without decay, ageing, disease, suffering or death - among the multiverses that Leonard Susskind & Alex Vilenkin would like us to be aware of (see or imagine) - they seem to have ommited the one Above All where Time itself does not exist.

Just for a moment imagine yourself looking at a film of yourself on a 2D or 3D screen, now take a further step back and look at yourself in 3D+T (from outside Time).

Quasar9

Stephen Hawking has worked on the basic laws which govern the universe. With Roger Penrose he showed that Einstein's General Theory of Relativity implied space and time would have a beginning in the Big Bang and an end in black holes.

These results indicated it was necessary to unify General Relativity with Quantum Theory, the other great Scientific development of the first half of the 20th Century. One consequence of such a unification that he discovered was that black holes should not be completely black, but should emit radiation and eventually evaporate and disappear.

Another conjecture is that the universe has no edge or boundary in imaginary time. This would imply that the way the universe began can be completely determined by the laws of science.

Stephen Hawking

We live in the aftermath of a great explosion. This awesome event, called somewhat frivolously the big bang, took place about 14 billion years ago. We can actually see some of the cosmic history unfolding before us since that moment—light from remote galaxies takes billions of years to reach our telescopes on earth, so we can see galaxies as they were in their youth.

But there is a limit to how far we can see into space. Our horizon is set by the maximum distance light could have traveled since the big bang. Sources more distant than the horizon cannot be observed, simply because their light has not yet had time to reach Earth.

And if there are parts of the universe we cannot detect, who can resist wondering what they look like? Until recently physicists thought that the answer to this question is rather boring: it’s just more of the same – more galaxies, more stars. But now, recent developments in cosmology have led to a drastic revision of that view.

According to the new picture, distant parts of the universe are in the state of explosive, accelerated expansion, called “inflation”. The expansion is so fast that in a tiny fraction of a second a region the size of an atom is blown to dimensions much greater than the entire currently observable universe. The expansion is caused by a peculiar form of matter, called “false vacuum”, which produces a strong repulsive force.

The word “false” refers to the fact that, unlike the normal “true” vacuum, this type of vacuum is unstable and typically decays after a brief period of time, releasing a large amount of energy. The energy ignites a hot fireball of particles and radiation. This is what happened in our cosmic neighborhood 14 billion years ago – the event we refer to as the big bang.

With inflation, the two competing processes are the decay of the false vacuum and its “reproduction” by rapid expansion of the inflating regions. My calculations, and those of Andrei Linde, show that false-vacuum regions multiply much faster than they decay, and thus their volume grows without bound.

At this very moment, some distant parts of the universe are undergoing exponential inflationary expansion. Other regions like ours, where inflation has ended, are also constantly being produced. They form “island universes” in the inflating sea of false vacuum. Because of inflation, the space between the islands rapidly expands, making room for more island universes to form.

Inflation is thus a runaway process that has stopped in our neighborhood, but still continues in other parts of the universe, causing them to expand at a furious rate and constantly spawning new island universes like our own. This never ending process is referred to as “eternal inflation”.


The role of the big bang in this scenario is played by the decay of the false vacuum. It is no longer a one-time event in our past: multiple bangs went off before it in remote parts of the universe, and countless others will erupt elsewhere in the future.

Analysis shows that the boundaries of island universes expand faster than the speed of light. (Einstein’s ban on super-luminal speeds applies to material bodies, but not to geometric entities such as the boundary of an island.) It follows that, regrettably, we will never be able to travel to another island, or even send a message there. Other island universes are unobservable, even in principle.

In the global view of eternal inflation, the boundaries of island universes are the regions where big bangs are happening right now. Newly formed islands are microscopically small, but they grow without limit as they get older. Central parts of large island universes are very old: big bangs once took place there long time ago. Now they are dark and barren: all stars have long since died there. But regions at the periphery of the islands are new and must be teeming with shining stars.

The inhabitants of island universes, like us, see a different picture. They do not perceive their universe as a finite island. For them it appears as a self-contained, infinite universe. That dramatic difference in perspective is a consequence of the differences imposed by the ways of keeping time appropriate to the global and internal views of the island universe. (According to Einstein's theory of relativity, time is not fixed, but instead is observer dependent.)

Perhaps the easiest way to see this is to count galaxies. In the global view, new galaxies are continually formed near the expanding boundaries, so as time passes, we have an infinite number of galaxies in the limit. In the internal view, all this infinity of galaxies exists simultaneously (say, at time 14 billion years). The implications are extraordinary.

Since each island universe is infinite from the viewpoint of its inhabitants, it can be divided into an infinite number of regions having the same size as our own observable region. My collaborator Jaume Garriga and I call them O-regions for short. As it happens, the most distant objects visible from Earth are about 40 billion light-years away, so the diameter of our own O-region is twice that number.

Quantum fluctuations in the course of eternal inflation ensure that all possible values of the constants are realized somewhere in the universe. As a result, remote regions of the universe may drastically differ in their properties from our observable region. The values of the constants in our vicinity are determined partly by chance and partly by how suitable they are for the evolution of life. The latter effect is called anthropic selection.

Another recent application of the principle of mediocrity, unrelated to string theory, is to the amount of dark matter in the universe. As its name suggests, dark matter cannot be seen directly, but its presence is manifested by the gravitational pull it exerts on visible objects. The composition of dark matter is unknown. One of the best motivated hypotheses is that it is made up of very light particles called axions. The density of axionic dark matter is set by quantum fluctuations during inflation and varies from one place in the universe to another.

Alex Vilenkin

However, it is clear that just as photons can be in many possible places but are only actually in one, we as humans though we can potentially be in many places are only actually ever in one, and that one place will be wherever we happen to be in 1) our physical body, and 2) our mind or mental state.

All our other states in Vilenkin's multiverses are effectively or conceptually in a different time frame, or outside Time - but they are unlikely to be at the same time. After all we can talk to many people in an auditorium or through tv, but we can only ever hold a one to one with one person at a time, and a dialogue or conversation with a few at most - even during video conferencing.

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The multiverse is like a flower from Dialogues of Eide
Quantum Phase Transitions from Science Daily releases
Universe offers 'eternal feast' by alinde@stanford.edu
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