Wednesday, August 22, 2007

Readings, 22 August 2007

It's all physics, astrophysics, and astronomy in this edition. Hope you find something interesting here.

The text following each item is quoted material, except for editorial comments, which are in color.

Dark matter

'Dark matter' doubters not silenced yet
Astro­no­mers have be­lieved for dec­ades that most of the mat­ter in the cos­mos is un­seen. It be­trays it­self only through its gravita­t­ional pull on vis­i­ble ob­jects, whose move­ments are of­ten hard to ex­plain with­out this “dark mat­ter.”

And the past year has seen in­creas­ingly bold claims that as­tro­no­mers have “proved” the stuff’s ex­ist­ence.

De­spite that, there’s a core of doubt­ers who are­n’t go­ing away. Many of them are stick­ing by an al­ter­na­tive the­o­ry that holds that tweak­ing our un­der­stand­ing of gra­vity could ex­plain things bet­ter than in­vok­ing some un­seen sub­stance un­like any we know.

However, the alternative theories have plenty of problems too.

Dark Matter—What's Out There?
For thousands of years, people have gazed at the stars and wondered, "What's out there?" But it wasn't until the 1930s that anyone realized there is much more out there than meets the eye. Recent observations have proven that about 22 percent of the universe is made out of a "dark matter" that is like the wind—although invisible, its influence can be seen. In a recent paper, SLAC Theoretical Physicist Michael Peskin provides an overview of how scientists are trying to unlock the mysteries of dark matter.

Researchers use high-tech machines to detect dark matter
In deep underground laboratories around the globe, a high-tech race is on to spot dark matter, the invisible cosmic glue that's believed to keep galaxies from spinning apart.

Whoever discovers the nature of dark matter would solve one of modern science's greatest mysteries and be a shoo-in for the Nobel Prize. Yet it's more than just a brainy exercise. Deciphering dark matter - along with a better understanding of another mysterious force called dark energy - could help reveal the fate of the universe.

Cosmic 'train wreck' defies dark matter theories
Disturbing evidence has emerged from the wreckage of an intergalactic pile-up suggesting that the already mysterious substance known as dark matter may be even less well understood than astronomers thought.

Additional articles about this research: here, here

Other things

Supercollisions on the horizon?
The project staggers the imagination: a machine that would stretch 20 miles through the bedrock 400 feet beneath Kane, DuPage and perhaps Will Counties. It could help physicists discover mysterious forces of the universe and new dimensions in the fabric of space and time.

But there are other mysteries to resolve before the first spade is turned for a proposed, multibillion-dollar International Linear Collider scientists hope to center under Fermi National Accelerator Laboratory's Batavia campus.

What would the neighbors think about subatomic particles being fired at nearly the speed of light under west suburban homes, back-yard pools and cornfields? And how to accommodate any criticisms in advance and bring folks onboard?

Something to read if you want to know a little about advanced particle accelerators, and a lot about the problems of getting one built.

Fears over factoids
Recent TV programmes have claimed that the Earth could be destroyed by black holes created in particle accelerators and that helium-3 from the Moon could be used for fusion energy. Frank Close warns that these "factoids" must be stamped out before they become accepted as facts

Here's an example of the kind of misinformation that can interfere with projects such as described in the previous item. Sadly, general scientific literacy being what it is, such misinformation spreads too easily.

Catching the Gravitational Wave
At first, Albert Einstein believed that gravitational waves existed, ripples small and large in the curvature of space and time. But he repeatedly changed his mind, first doubting their existence, then believing, and then changing his mind again.

In the end, after decades of debate, scientists confirmed every main point of Einstein's early theory of gravitational waves. In his new book, Traveling at the Speed of Thought: Einstein and the Quest for Gravitational Waves, published by Princeton University Press, University of Arkansas professor Daniel Kennefick traces the history of a theory that researchers believe will help them one day better understand some of the greatest mysteries in the universe.

Testing the elements of the Big Bang
Measurements of the amount of lithium in the universe combined with precision data from the cosmic microwave background are challenging our understanding both of stellar astrophysics and possibly even Big Bang nucleosynthesis itself, as Kenneth Nollett explains.

I wrote a little about this topic two months ago, here. And by the way, Ralph Alpher, who played a leading role in nucleosynthesis theory, died very recently, on August 12 – see next item.

Ralph Alpher, 86; pioneering physicist in cosmic research overlooked for a Nobel Prize
Ralph Alpher, the "forgotten father of the Big Bang" whose calculations provided the theoretical underpinning of the theory but were ignored when it came time to pass out Nobel Prizes, died Sunday at an acute care facility in Austin, Texas.

Other obituaries: here, here, here.

Indium arsenide may provide clues to quantum information processing
“We’re not saying we’ve built a quantum computer,” Andreas Fuhrer tells, “but this is an important first step towards spin manipulation via the spin-orbit interaction.”

Fuhrer, a scientist with the Department of Solid State Physics/Nanometer Consortium at Lund University in Sweden, points out that one way quantum information processing might come about is through the manipulation of spin states.

This is one example of how "spintronics" may make it possible to implement a quantum computer.

Scientists' galaxy quest yielding hundreds of new planets
It's boom time for planet hunters. Astronomers are bagging new worlds at an average rate of more than two a month.

As of July 20, the latest available date, 246 extrasolar planets had been detected circling other stars in the Milky Way galaxy. Among them are 25 alien "solar systems" consisting of two, three or four bodies orbiting single suns.

And the hits just keep coming, such as this, and this.


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