Physics

Caltech physicist Sean M. Carroll has been wrestling with the mystery of time. Most physical laws work equally well going backward or forward, yet time flows only in one direction. Writing in this month's Scientific American, Carroll suggests that entropy, the tendency of physical systems to become more disordered over time, plays a crucial role. Carroll sat down recently at Caltech to explain his theory. What's the problem with time?

For two decades, Stanford University physicist Leonard Susskind battled cosmologist Stephen Hawking over the behavior of black holes. Hawking said that when black holes eat their fill, they disappear, taking with them everything they consumed over their billions of years of existence. Susskind found this idea so disturbing that he publicly declared war -- a conflict he describes in his new book, "The Black Hole War."

Dark matter is like a construction scaffold on a building, allowing visible matter to build stars and galaxies, according to the first three-dimensional map of the unseen stuff that is thought make up the majority of mass in the universe. The map, created with images from the Hubble Space Telescope, confirms theories that dark matter accumulates in the same regions as visible matter, giving it a kind of shell, or exoskeleton, to work within.

THE year was 1915. War and privation had come to Germany. Meanwhile, in Berlin, a solitary man struggled with the equations for a new theory of gravity. "I have been laboring inhumanly," Albert Einstein, then 36, wrote to a friend in his native German. "I am quite overworked."

The 2007 Nobel Prize in physics was awarded Tuesday to two European scientists who discovered a tiny magnetic effect that has revolutionized the storage of computerized information. France's Albert Fert and Peter Gruenberg of Germany independently discovered giant magnetoresistance, known as GMR, in 1988. The manipulation of weakly magnetized films of atoms allows iPods, computers and other digital devices to store vast amounts of information on ever-smaller hard disks.

Attempting to understand how heavy elements are formed inside stars and supernovas, Michigan scientists have created three unusually heavy isotopes of magnesium and aluminum, including one that has been sought for a decade and a second that current theory says should be impossible to produce.

Across the tapestry of the night sky, hundreds or perhaps thousands of stars are doing frantic dances of death, spinning wildly around each other and shooting off waves of invisible gravitational energy like interstellar beacons. In one of the most exotic observatories in the world, Fred Raab is waiting for those waves to wash up on the shoreline of Earth. When they do, they could change our understanding of the universe.

Two astrophysicists from Berkeley and NASA won the 2006 Nobel Prize in physics on Tuesday for their discovery of the strongest evidence to date that the universe began with a big bang, a feat the Nobel committee said "marked the inception of cosmology as a precise science." John C. Mather, 60, of NASA's Goddard Space Flight Center in Greenbelt, Md.

Finding a Jackson Pollock painting is the art world's equivalent of a winning lottery ticket. But proving a Pollock painting's authenticity isn't easy, which is why physicist Richard Taylor's theory that the famed artist's work can be identified using fractals has stirred such interest and controversy. Now, a graduate student is debunking Taylor's analysis, saying she can make a crude drawing in a matter of minutes that has all the fractal qualities of a Pollock masterpiece.