Why Is The Earth Moving Away From The Sun?

Photo: The sun and Earth are moving apart by about 15 cm per year - the culprit may be tides raised on the sun by our home planet (Image: NASA)

From New Scientist:

Skywatchers have been trying to gauge the sun-Earth distance for thousands of years. In the third century BC, Aristarchus of Samos, notable as the first to argue for a heliocentric solar system, estimated the sun to be 20 times farther away than the moon. It wasn't his best work, as the real factor is more like 400.

By the late 20th century, astronomers had a much better grip on this fundamental cosmic metric – what came to be called the astronomical unit. In fact, thanks to radar beams pinging off various solar-system bodies and to tracking of interplanetary spacecraft, the sun-Earth distance has been pegged with remarkable accuracy. The current value stands at 149,597,870.696 kilometres.

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The Day The Universe Froze: New Model For Dark Energy

The ultimate fate of the universe depends on the exact nature of dark energy. Depending on its properties, the universe may fly apart (the big rip) or the current expansion might reverse into contraction (the big crunch) or anything in between. (Credit: NASA/CXC/M. Weiss)

From Science Daily:

ScienceDaily (May 11, 2009) — Imagine a time when the entire universe froze. According to a new model for dark energy, that is essentially what happened about 11.5 billion years ago, when the universe was a quarter of the size it is today.

The model, published online May 6 in the journal Physical Review D, was developed by Research Associate Sourish Dutta and Professor of Physics Robert Scherrer at Vanderbilt University, working with Professor of Physics Stephen Hsu and graduate student David Reeb at the University of Oregon.

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Star Explodes, And So Might Theory

This artist's illustration provided by NASA shows what the brightest supernova ever recorded, known as SN 2006gy, may have looked like when it exploded. Photo: AP/NASA

From Live Science:

A massive star a million times brighter than our sun exploded way too early in its life, suggesting scientists don't understand stellar evolution as well as they thought.

"This might mean that we are fundamentally wrong about the evolution of massive stars, and that theories need revising," said Avishay Gal-Yam of the Weizmann Institute of Science in Rehovot, Israel.

According to theory, the doomed star, about 100 times our sun's mass, was not mature enough to have evolved a massive iron core of nuclear fusion ash, considered a prerequisite for a core implosion that triggers the sort of supernova blast that was seen.

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Ancient Meteorites Reveal Early Magnetic Fields

Image: New research suggests that some of the small rocky bodies that smashed together to form planets, called planetesimals, had magnetic fields. Damir Gamulin, courtesy of Benjamin Weiss

From Earth Magazine:

Even before the birth of the planets, our solar system was hardly a lonely place. Small rocky bodies, called planetesimals, filled the inner solar system, eventually colliding together to form the planets. Now a new look at a group of ancient meteorites shows that at least some planetesimals generated their own magnetic fields — a feat many scientists thought extremely difficult for such small astronomical bodies. The work also has scientists rethinking how planets formed.

Most meteorites don’t make it to Earth unscathed. After repeatedly smashing into other objects and traveling through Earth’s harsh atmosphere, they can be substantially altered before crash-landing on the planet. But not angrites — a group of 12 stony meteorites that, at an age of about 4.56 billion years old, are among the oldest-known rocks in the solar system and somehow “got here without being messed up,” says Benjamin Weiss, a planetary geologist at MIT in Cambridge, Mass. Because these meteorites are pristine, angrites retain information about the larger body from which they came.

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Big Bang or Big Bounce?: New Theory on the Universe's Birth

The universe may not have started off with a bang after all.
Pat Rawlings/SAIC

From Scientific American:

Our universe may have started not with a big bang but with a big bounce—an implosion that triggered an explosion, all driven by exotic quantum-gravitational effects

* Einstein’s general theory of relativity says that the universe began with the big bang singularity, a moment when all the matter we see was concentrated at a single point of infinite density. But the theory does not capture the fine, quantum structure of spacetime, which limits how tightly matter can be concentrated and how strong gravity can become. To figure out what really happened, physicists need a quantum theory of gravity.
* According to one candidate for such a theory, loop quantum gravity, space is subdivided into “atoms” of volume and has a finite capacity to store matter and energy, thereby preventing true singularities from existing.
* If so, time may have extended before the bang. The prebang universe may have undergone a catastrophic implosion that reached a point of maximum density and then reversed. In short, a big crunch may have led to a big bounce and then to the big bang.

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Physicists Create BlackMax To Search For Extra Dimensions In The Universe

Black holes are theorized to be regions in space where the gravitational field is so strong that nothing can escape its pull after crossing what is called the event horizon. BlackMax simulates these regions. (Credit: iStockphoto/Christophe Rolland)

From Science Daily:

ScienceDaily (Nov. 9, 2008) — A team of theoretical and experimental physicists, with participants from Case Western Reserve University, have designed a new black hole simulator called BlackMax to search for evidence that extra dimensions might exist in the universe.

Black holes are theorized to be regions in space where the gravitational field is so strong that nothing can escape its pull after crossing what is called the event horizon. BlackMax simulates these regions.

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Unknown "Structures" Tugging At Universe, Study Says

The so-called Bullet Cluster of galaxies lies 3.8 billion light-years away. It's one of hundreds that have been found to be carried along by a mysterious "dark flow," an October 2008 study says. The dark flow is caused by unknown clumps of matter outside the known universe, which are pulling our entire universe toward them, the study suggests. The report hints that, whatever may be beyond the known universe, it's like nothing we know. Image courtesy NASA/STScI/Magellan/U. Arizona/D. Clowe, et al

From The National Geographic:

Something may be out there. Way out there.

On the outskirts of creation, unknown, unseen "structures" are tugging on our universe like cosmic magnets, a controversial new study says.

Everything in the known universe is said to be racing toward the massive clumps of matter at more than 2 million miles (3.2 million kilometers) an hour—a movement the researchers have dubbed dark flow.

The presence of the extra-universal matter suggests that our universe is part of something bigger—a multiverse—and that whatever is out there is very different from the universe we know, according to study leader Alexander Kashlinsky, an astrophysicist at NASA's Goddard Space Flight Center in Maryland.

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Giant Simulation Could Solve Mystery Of 'Dark Matter'

A map of the dark matter in six halos similar to that of the Milky Way. The brighter colours correspond to regions of higher density and indicate where most of the gamma rays are expected to be produced. (Credit: Image courtesy of Durham University)

From Science Daily:

ScienceDaily (Nov. 6, 2008) — The search for a mysterious substance which makes up most of the Universe could soon be at an end, according to new research.

Dark matter is believed to account for 85 per cent of the Universe's mass but has remained invisible to telescopes since scientists inferred its existence from its gravitational effects more than 75 years ago.

Now the international Virgo Consortium, a team of scientists including cosmologists at Durham University, has used a massive computer simulation showing the evolution of a galaxy like the Milky Way to "see" gamma-rays given off by dark matter.

They say their findings, published in the prestigious scientific journal Nature (Thursday, November 6), could help NASA's Fermi Telescope in its search for the dark matter and open a new chapter in our understanding of the Universe.

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