An article yesterday on Brookhaven National Laboratory's new heavy-ion collider inadvertently misstated the beam speed. It is 99.95 percent of the speed of light. (Published 09/14/99)

No, the scientists keep repeating, with weary resignation, the experiment will not tear our region of space to subatomic shreds.

Never mind the letter in the July issue of Scientific American warning that Brookhaven National Laboratory's new $365 million atom smasher could theoretically create a black hole that would end up "devouring the entire planet within minutes."

(One news operation recently called the lab to ask if a BNL black hole had swallowed up the airplane piloted by John F. Kennedy Jr.)

And forget about that July 18 headline in the Sunday Times of London: "Big Bang Machine Could Destroy Earth"--ostensibly by conjuring up a new kind of matter called "strangelets" that would transform everything they touched into "strange matter," sort of like The Blob in the old movie.

"If the universe were that unstable," said BNL Director John Marburger, "you would think that all of the violent processes you see in astronomy would have destroyed it long ago."

Nonetheless, Marburger asked a select panel of experts to review the safety issues involved in BNL's new Relativistic Heavy Ion Collider (RHIC), the purported doomsday machine designed to reproduce energy and density conditions a few millionths of a second after the Big Bang created our expanding universe some 13 billion years ago.

The report is expected soon, and few doubt that the panel will dismiss the apocalyptic concerns. "The really important question is whether we'll destroy the universe before or after we win the Nobel Prize," joked RHIC Project Director Satoshi Ozaki.

Of course, there are bound to be some bizarre effects later this year when BNL fires up RHIC (known as "Rick"). According to the project design plan, it is intended to open "unexplored territory" in which "there is ample room for the unforeseen."

That's the sort of language that understandably prompts fears.

But all such facilities are built precisely to pursue the unknown. RHIC exists because science needs to understand how the tiniest subcomponents of matter, called quarks, interact with one another. These entities make up way more than 99 percent of all the visible mass in the cosmos, yet their private behavior is still a mystery.

There are three quarks in every proton and neutron in every atom, tied to one another by force-carrying particles appropriately known as gluons. Gluons convey the "strong" force--the most powerful of the four fundamental forces in nature. But unlike gravity or electromagnetic force, the strong force does not decrease with increasing distance. In fact, it does just the opposite: It only drops off as quarks get extremely close together. As a result, a lone quark has never been seen.

But if physicists can create sufficient energy and density--even for RHIC's expected event duration of less than a billionth of a trillionth of a second--individual quarks would be hyper-excited and slammed very close together. In that so-far hypothetical condition, called a "quark-gluon plasma," the particles "can roam freely and interact as they wish," Ozaki said, undergoing a "phase transition" like what happens when liquid water turns to steam.

Boosting matter to such energies is typically accomplished by building colliders such as RHIC--devices that accelerate subatomic particles to nearly the speed of light in underground tunnels, then smash the particles into one another.

The energy released in those collisions, usually within a tiny fraction of a cubic inch, immediately congeals into new matter particles (including quarks), thanks to the eerie but profound principle expressed in Einstein's famous equation E=mc{+2}. That is, the more energy liberated in the smashup, the greater the variety and masses of the newly minted--and potentially unknown--particles produced.

Thus physicists at Fermilab, a national laboratory outside Chicago, finally discovered the elusive and long-sought "top" quark by engineering a collision between protons and their antimatter opposites, antiprotons, at unprecedented energy levels.

Compared to those collisions, RHIC is like running a demolition derby with 747s. Instead of slamming single protons and antiprotons into one another, RHIC is designed to accelerate whole nuclei of gold atoms, each containing 197 protons and neutrons.

Two beams of those nuclei will scream around a 2.4-mile ring in opposite directions at 99.95 times the speed of light. At impact, conditions will resemble what the universe was like in the first few microseconds of its existence after the Big Bang, long before the incandescent soup of primordial quarks and gluons condensed into simple protons and neutrons.

In doing so, RHIC will create densities and energy levels that might seem reasonably sufficient--even to some scientists--to create a black hole. That notion "is not credible," Marburger said, and calculations show that drastically higher collision energies are necessary. "It's the strangelet scenario that is kind of interesting," Marburger said. "But generally speaking, these things just don't happen."

In fact, "I now believe that there is no question that it is not going to happen," said Robert L. Jaffe, director of the Center for Theoretical Physics at MIT and widely regarded as the world's leading expert on strangelets.

What makes the idea of "strange matter" plausible is that there are six kinds of quarks. Two garden-variety types--called "up" and "down"--make up all the ordinary matter in the cosmos. The four others ("charm," "strange," "top" and "bottom") can appear in high-energy events, but their products are usually so unstable that they decay into other particles in a fraction of a second.

However, if several "strange" quarks were created and then somehow penetrated and lodged in a normal atom's nucleus (producing a hybrid strangelet), there are certain conditions under which the strangelet would exist in a lower energy state than plain old up or down quarks. Because nature favors situations in which the least amount of energy is expended (which is why water flows downhill and shoelaces don't re-tie themselves), a strangelet could be stable.

However, Jaffe said, "just because it's stable in bulk doesn't mean that it's stable in small droplets" formed in a collider. "There's a tendency for quark matter to be come unstable in smaller units."

Even if it were stable, calculations indicate that a strangelet fortunately would have a positive charge. Thus even if one formed, it would just suck up an extra electron from somewhere and appear as a heavy but non-threatening isotope of some element.

If it had a negative electrical charge, it would be attracted by other nuclei, with their positive charges. That would overload the nucleus, making it unstable. So it would break up, leaving the strangelet free to destroy another nucleus. The process, Jaffe said, would create "an endless loop that would give off endless amounts of energy and would be catastrophic."

But theoretical arguments aren't the only evidence, many experts agree, because, as Jaffe put it, "cosmic rays have been carrying our RHIC-like experiments for billions of years" in unimaginable numbers.

Many of these "rays"--which are actually particles and atoms--are extremely massive and traveling at the same speeds the RHIC would achieve. By one estimate, about 10 trillion collisions with more energy and higher mass than RHIC's gold nuclei have occurred on the surface of the moon alone since it formed. And Earth's satellite has not been transformed into strange matter. "Or green cheese," Jaffe noted.