Everywhere She Looks, It’s Bubbles in the Air : ‘Big Bang’ Idea May Be Revised

Even before Margaret Geller revealed evidence last week for a new concept about star clusters that may revolutionize man’s perception of the universe, she became fascinated with bubbles. “I looked at bubbles everywhere,” Geller said. “In the bath water, in the dishpan, everywhere.”

Geller’s latest fascination with bubbles grew out of new sky charts of distant galaxies that she and a colleague are preparing at the Whipple Observatory in Arizona. When she looked at the first of the charts, she saw giant structures that reminded her of the bubbles in her kitchen sink. Lots of them.

Geller’s latest observations convinced her and John P. Huchra, one of her colleagues at the Harvard-Smithsonian Center for Astrophysics, that galaxies behave very differently than previously thought. And their theory, buttressed by an unusual map they devised, was picking up support among astronomers last week at the American Astronomical Society meeting here.

Bubbles of the Universe

The three-dimensional map that Geller and Huchra are displaying shows that the universe is composed of gigantic “bubbles” on whose surfaces stars and galaxies, including the Milky Way, are gathered.

Until now, such “bubbles,” or voids, were believed to be quite rare.

But, according to Geller, “The universe is full of huge bubbles.”

The map shows a deeper region of galaxies than ever before, extending more than 300 million light-years from Earth, or twice as far as past charts.

Many other charts will have to be drawn before final conclusions can be reached, a process that could take up to 10 years.

But if Geller and Huchra are right, their view of the universe would support a theory that a multitude of vast, powerful explosions, rather than the forces of gravity and a single “big bang,” shaped the universe.

Geller and Huchra developed the map while in Arizona to chart 1,000 galaxies in a wedge of the sky stretching from horizon to horizon and about the width of a dozen moons.

Woven Pattern

It shows long fingers of galaxies, or “filaments,” that weave the fabric of the universe into a pattern somewhat like a crocheted bedspread. Astronomers have long known about the “filaments.” And they have recognized the universe as an irregular pattern with giant clusters of stars, called galaxies, traveling at high speeds--almost as if they were being pushed into sinewy strings of galaxies while under the control of some force, thought to be gravity.

The new sky chart produced by Geller and Huchra shows similar patterns, but it also shows giant circular voids as large as 150 million light-years across. A light-year is the distance light travels in one year, roughly 6 trillion miles.

Why, Geller and Huchra wondered, should such voids exist, and why do the galaxies seem to cluster around them?

The answer, they believe, is in the “bubbles.”

A cross section of the bubbles one might find on top of a dishpan full of water would show patterns similar to the sky chart. It would show, for example, voids inside the “bubbles,” but a lot of activity along the boundaries where the “bubbles” meet. “The striking thing is that there are vast, empty regions” where there are no galaxies, Geller said in an interview.

Grouping of Galaxies

The startling similarity in bubble patterns led Geller and Huchra to conclude that the universe is made up of something like giant, expanding “bubbles.” Galaxies group together along the edge of each “bubble” like water droplets on the outside of an expanding balloon.

But Geller cautioned against carrying the analogy too far, noting that the universe really is not a pan of dishwater and the “bubbles” of the universe are quite possibly expanding waves of energy created by giant exploding stars.

The theory is revolutionary because it challenges the idea that the universe began with a single big bang that sent cosmic debris flying off in an expanding universe. It suggests, instead, that there have been many “bangs,” each forming a “bubble” that pushed galaxies out, just as waves propel surfers.

The theory would also account for new evidence suggesting that clusters of galaxies are moving in many directions rather than as uniformly as would be expected with a single “big bang.”

Geller also cautioned, however, against drawing sweeping conclusions on the basis of a single sky chart. “That’s a little dangerous,” she said. “It’s like trying to figure out what the Earth looks like from a map of Rhode Island.”

Series of Explosions

Still, the chart by Geller and Huchra is the first real evidence to support a theory first advanced in 1981 by Jeremiah P. Ostriker of Princeton University and Lennox L. Cowie of Johns Hopkins University, who concluded that galaxy formations may have been triggered by giant explosions. The explosions, or series of explosions, would push galaxies out, causing them to group along the “shock wave” as they moved out.

The greatest concentrations would be found where the shock waves intersected, thus explaining the “filaments.” Or, as Geller put it:

“The clusters occur at the intersections of the bubbles.”

Astronomers have known about one of the largest voids, called “Bootes void,” discovered in 1981, but it was believed to be quite rare. The new, extended survey shows, however, that there are many voids, most of which form generally circular patterns.

The chart also suggests that the universe may be far less dense than believed, a suggestion that may lead to new insights into the eventual fate of the universe. Some astronomers believe the universe is so dense that it will eventually reach a point where gravity will overwhelm the force of expansion, causing the universe to collapse. That may not be the case, however, if the universe is as sparse as the new chart indicates.

Major Question

One of the main questions remaining on that issue is not easy to answer: What is at the center of the “bubbles?” Do the “bubbles” house dark galaxies or “shadow matter” that cannot be seen but which would add to the density of the universe?

It may be many years before that question can be answered.

Geller, Huchra and an associate, Valerie de Lapparent, also of the Harvard-Smithsonian Center for Astrophysics, will publish their findings March 1 in the astrophysical journal Letters.

They will continue their work at the Whipple Observatory, which is on Mt. Hopkins near Tucson. In about a month they hope to have another chart completed, and they will continue that process until they have a truly three-dimensional view of the universe.