Testing the Equivalence Principle to Support String Theory

Read the whole article for the details; basically, three groups of scientists are trying to find a very small deviation from the Equivalence Principle (which states that gravity affects all materials equally) that would support various forms of String Theory. These experiments need to be extremely accurate (to within at least one part in 10 trillion (10[sup]13[/sup]: the experimenters claim they'll detect deviations up to 1 quintillion (10[sup]18[/sup]), 1 quadrillion (10[sup]15[/sup]), and 100 quadrillion (10[sup]17[/sup])); and if a deviation is indeed found, String Theory would see some much sought-after experimental support. These are exciting times in theoretical physics; we may be a step closer to the Grand Unified Theory.

clipped from www.physorg.com "Some variants of string theory predict the existence of a very weak force that would make gravity slightly different depending on an object's composition," says Will. "Finding a variation in gravity for different materials wouldn't immediately prove that string theory is correct, but it would give the theory a dose of supporting evidence." This new facet of gravity, if it exists, would be so astonishingly weak that detecting it is a tremendous challenge. Gravity itself is a relatively weak force—it's a trillion trillion trillion (1036) times more feeble than electromagnetism. Theorists believe the new force would be at least ten million million (1013) times weaker than gravity. No experiment to date has detected this tiny difference. But now three groups of scientists are proposing space-borne missions that would hunt for this effect with greater sensitivity than ever before.

Pair-Instability Supernova May Be Brightest Ever

A pair-instability supernova, located in a galaxy in the Pegasus constellation 240 million light-years away, is believed to be the brightest supernova ever since the early days of the universe.

Ordinary supernovas fall into one of two types. All supernovas occur during the dying days of a star, after the hydrogen fuel has been turned to helium, and the helium to higher-order elements such as carbon and all the way up to iron; without supernovas such higher-order elements could not exist. The first type, found in white dwarf stars around one and a half times as massive as our sun, are uniform explosions of the stars matter. The larger, second type is found in more massive stars, which instead of exploding implode, creating a neutron star or black hole and exploding the outer bits of the star outward. Both types of supernova typically reach peak brightness within a week, and fade away within a couple of months.

A supermassive star such as the one being observed, which weighs in at 100-200 times the mass of our sun, is far, far greater and rarer. Indeed, such explosions were thought to have existed only with first-generation stars that should have all died out billions of years ago. In such a star, the inner heat becomes so great that matter-antimatter pairs are created in large amounts, which eventually leads to an explosion that scatters the remains of the star into the intergalactic medium. These explosions are far more efficient at dispersing the higher-order elements needed for life. This supernova has also lasted a long, long time; it began in September 2006, reached peak brightness in 70 days, and even now nine months later is still one of the brightest objects in the night sky.

clipped from www.berkeley.edu BERKELEY – An exploding star first observed last September is the largest and most luminous supernova ever seen, according to University of California, Berkeley, astronomers, and may be the first example of a type of massive exploding star rare today but probably common in the very early universe. Unlike typical supernovas that reach a peak brightness in days to a few weeks and then dim into obscurity a few months later, SN2006gy took 70 days to reach full brightness and stayed brighter than any previously observed supernova for more than three months. Nearly eight months later, it still is as bright as a typical supernova at its peak, outshining its host galaxy 240 million light years away.