Matter - Anti-Matter -

The Blinking On and Off

The Spaces Between

Antimatter Not As Tough As Matter -- Thus We Exist

July 6, 2001 - Reuters

Looks like antimatter is not all it's cracked up to be, a group of international physicists have announced in a finding which proves there is a good reason for our universe, made of matter, to exist.

The experiments set the stage for another debate, however.

After bashing a stream of antimatter particles against a stream of matter particles in mile-long tubes near Silicon Valley, scientists found themselves with some left over matter that the uninitiated would not have expected.

Matter and antimatter blow each other up when they meet, as any Star Trek fan knows, which has left physicists working hard to explain how our universe, made up of matter, could exist, since around the Big Bang which started things there apparently were equal amounts of matter and antimatter.

The answer is that matter is a bit tougher than antimatter, at least as far as the recent experiments on a particle called a B meson are concerned, the team working at the Stanford Linear Accelerator Center in Palo Alto, California, announced.

That confirmed results of another experiment on a similar particle that has haunted physicists for decades.

``For 37 years people have looked and they haven't found anything beyond the original one,'' said Princeton University physicist Stewart Smith, a spokesman for the group.

``Physicists now know that there are at least two types of subatomic particles that exhibit this puzzling phenomenon, thought to be responsible for the great preponderance of matter in the universe.''

The physicists drove electrons against positrons, a type of antimatter, in a 1.3 mile particle accelerator. A 1,200-ton detector, called BABAR, recorded how B mesons and their antimatter equivalents, anti-B mesons, were born and how they decayed, leaving a bit more matter than antimatter.


The work fits nicely with the current view of the universe, the Standard Model, which accurately predicted that B mesons and anti-B mesons would be slightly different, or asymmetrical.

``We don't have to invent new physics to explain our results,'' Smith.

Russian physicist and dissident Andrei Sakharov came up with the idea in 1967 that the universe of matter could exist because of the slight difference, also called charge-parity violation, or CP violation.

Sakharov in turn was explaining results of experiments with another particle, the K meson, which in 1964 showed the same behavior as particles in the Stanford-based experiment.

But in settling one debate physicists set the stage for another.

The Standard Model is missing something, even if it is correct as far as it goes. The amount of matter it predicts is only about one billionth as much as exists, Smith said.

``There is something major out there that we don't know,'' he said.

``Either there is some new set of ghostly particles, maybe they are just too massive to have been produced in accelerators... or there is some completely new phenomenon that we have not been able to see that is there to have catalyzed the evolution of the universe.''

A top candidate for a bit of asymmetry might be neutrinos, another fundamental particle that has not been studied much in this regard, Smith said, but those experiments await.

The Stanford-based tests were conducted by more than 600 scientists from 75 institutions in Canada, China, France, Germany, Great Britain, Italy, Norway, Russia and the United States, and the results have been submitted for publication in the Physical Review Letters journal.

Scientists Map Dark Matter, Prove Einstein Right

May 13, 2000 -

Eighty-four years after Albert Einstein introduced the world to his theory of general relativity, scientists are seeing that he was right all along about measuring what we now call dark matter.

Astronomers supported by the National Science Foundation have found the first evidence of an effect called cosmological shear, a phenomenon predicted by Einstein�s theory, in which light from distant cosmic objects bends due to gravitational forces. What�s more, the detection of cosmological shear has allowed astronomers to track down significant amounts of dark matter, non-luminous matter whose presence in the universe has been predicted, but scantly detected until now.

"This marks a totally new way of finding dark matter," said Max Tegmark, a physicist at the University of Pennsylvania. "It�s going to revolutionize our ability to map out where all the dark matter is."

The results on cosmological shear were published in this week's issue of the journal Nature.

Observable matter takes up no more than about 10 percent of the total amount of matter predicted to exist in the universe. The rest � dubbed dark matter because it can�t be "seen" or detected in the same way that gas, dust, and other observable matter can � remains largely a mystery to astronomers precisely because it�s so difficult to find. Now, researchers have a new tool for uncovering the elusive stuff.

On the left is an optical image of a small cluster of galaxies. The center image shows a 1-degree image of the same field. The right image represents a mass map of the same patch of sky.

"The existence of dark matter has been known for a long time, and has even been mapped in various places over the past decade," explained astrophysicist David Wittman of Bell Labs, Lucent Technologies. "But the places that had been mapped were small areas of the sky. What�s new here is that we have studied a fair sample of the universe � and so were able to deduce some properties of the universe in general."

Cosmological shear helps astronomers "see" dark matter because it makes the light from distant galaxies appear distorted. A distant spherical-shaped galaxy, for example, will appear elliptical to astronomers back on Earth. This is because dark matter existing in the path between the galaxy and Earth exerts a gravitational pull on the light, causing it to bend.

Wittman and a team of researchers analyzed 145,000 distant galaxies in order to find evidence of cosmological shear, also known as "weak gravitational lensing." They used a special camera called a charged couple device or CCD and the 4-meter Blanco telescope at the Cerro Tololo Interamerican Observatory in Chile.

The recent observations have also shed new light on the eventual fate of the universe. Astrophysicists currently predict that the total amount of matter present in the universe will determine whether the universe will continue to expand, or whether it will eventually slow down, or even begin to contract. According to Wittman, the scientists� observations of cosmological shear have suggested that the overall density of matter in the universe is "too low to stop the expansion of the universe."

At the same time, astronomers admit that their new method for finding dark matter has not yet been tested enough to allow experts to make a definitive generalization about the fate of the universe. "Since our approach is new, it�s not very precise yet," said Wittman. "Really strict tests of the theory will come in the next few years as astronomers measure the [weak] lensing more and more accurately."

"Ultimately, we�d like to be able to map the whole sky to see just how much dark matter is out there," added Tegmark. For now, the use of cosmological shear to uncover dark matter in one region of the universe at a time will have to suffice. But as Bell Labs astrophysicist Anthony Tyson joked, "The future looks bright for dark matter."

Astronomers Map 'Dark Matter'

By analyzing the light from 200,000 distant galaxies, indicated above in blue, astronomers are creating a map of the interconnecting dark matter, the invisible material that keeps our universe together. This numerical simulation reveals filaments of dark matter, shown here in red and white, which are invisible even to the largest telescopes.

March 14, 2000 - Discovery

Trying to find invisible matter may seem an impossible task, but with scientific theory postulating that 90 percent of what makes up our universe is unaccounted for, the quest for so-called dark matter is far from academic.

A multinational team of cosmologists, astrophysicists, statisticians, technicians and other experts revealed they have developed a map of dark matter distributions across a 2-square-degree section of the sky.

To detect the undetectable, the scientists used a high-resolution, wide-field imaging camera on the Canada-France-Hawaii Telescope in Hawaii to analyze the light from 200,000 distant galaxies, looking for tiny distortions in the light caused by the gravitational effects of intervening dark matter.

The analysis showed a vast, interconnected web of dark matter, raising hopes that age-old questions about how the universe formed and what its ultimate fate will be may one day be answerable.

To build accurate mathematical models of the universe scientists need to have an idea of how much matter it contains, according to Yannick Mellier, of the Institut d'Astrophysique de Paris and the Observatoire de Paris.

"Since around 90 percent of this matter is invisible, it's hard for us to get a precise reading on this. Also, to test our models to see if they accurately describe the universe, we need to look at what is actually out there," says Mellier, who heads the French-based research team.

Telescope director Greg Fahlman called the team's results a preliminary view of what may be achieved with a new, more sensitive wide-field camera currently under development.

"Our goal is to help create the first distribution maps of dark matter across the sky, similar to the maps you currently see for galaxies," says Fahlman.