The universe is not only expanding, but that expansion appears to be speeding up. And as if that discovery alone weren’t strange enough, it implies that most of the energy in the cosmos is contained in empty space — a concept that Albert Einstein considered but discarded as his “biggest blunder.” The new findings have been recognized as 1998’s top scientific breakthrough by Science magazine.
The magazine’s annual “Breakthough of the Year” section focuses on advances that have profoundly changed the practice or interpretation of science or its implications for society — something like a Time Man of the Year award for scientific ideas.
Last year’s top breakthrough related to Dolly the sheep, the high-profile result of cloning experiments. This year, the topic is a little more esoteric, involving technical discussions about Type 1A supernovae, redshift, “antigravity” and a curious factor known as the cosmological constant, or lambda in geekspeak.
But the bottom line touches on the ultimate fate of all that we see: Based on the observations so far, two teams of astronomers have concluded that the universe is fated to expand forever into virtual nothingness.
Writing in Friday’s issue of Science, James Glanz said the amazing results are changing the way people approach life’s grandest questions.
“Although the nature of the universe was once chiefly the realm of philosophers, in 1998 it seems that cosmology is grounded in data, as visions of distant supernovae revealed the true nature — and perhaps the future — of the cosmos,” Glanz said. “Scientists and philosophers both will be grappling with the implications for years to come.”
Supernova surprise
The flood of findings about the universe’s expansion rate is the result of about 10 years of study, said Saul Perlmutter, team leader of the Supernova Cosmology Project at Lawrence Berkeley National Laboratory. The results are turning out to be just the opposite of what astronomers expected to find.
In 1929, astronomer Edwin Hubble announced that the universe appeared to be expanding based on his observations of faraway galaxies. He noticed that the characteristic signature of starlight from distant sources appeared to be shifted toward the red end of the spectrum — meaning that the light waves had been stretched during their journey to Earth. The implication was that during the intervening time, the entire universe had been stretched by a corresponding amount.
Such “redshift” observations have been confirmed repeatedly in the nearly 70 years since then, cementing the idea of an expanding universe as a fundamental pillar of modern astronomy. But many theorists assumed that the gravitational attraction of all the matter in the universe would slow down an expansionary tide that came in the wake of the primordial Big Bang.
To shore up that assumption, scientists looked for a standard yardstick that could be used to measure the distance from a light source. Using such a yardstick, they could match up various known distances with redshift values and calculate how the expansion rate has changed over time. Light that started its journey from a relatively distant source — say, 10 billion years ago — might exhibit a redshift different from light that was thrown off just 1 billion years ago.
Perlmutter and others found such a yardstick in a particular kind of exploding star known as a Type 1A supernova. Over the course of several years, the astronomers developed a model to predict how bright such a supernova would appear at any given distance. Astronomers recorded dozens of Type 1A supernovae and anxiously matched them up with redshifts to find out how much the universe’s expansion was slowing down.
To their surprise, the redshift readings indicated that the expansion rate for distant supernovae was lower than the expansion rate for closer supernovae, Perlmutter said. On the largest scale imaginable, the universe’s galaxies appear to be flying away from each other faster and faster as time goes on.
“What we have found is that there is a ‘dark force’ that permeates the universe and that has overcome the force of gravity,” said Nicholas Suntzeff of the Cerro Tololo Inter-American Observatory, who is the co-founder of another group called the High-z Supernova Search Team. “This result is so strange and unexpected that it perhaps is only believable because two independent international groups have found the same effect in their data.”
Einstein revisited
To make sure they haven’t made a mistake somewhere, the two teams are double-checking their results and adding to their supernova database. Perlmutter said his team only recently discovered the most distant Type 1A supernova ever found, 10 billion light-years from Earth.
Meanwhile, theorists are puzzling over what this all means for their understanding of the universe. So far, the best way to make the equations come out right is to use the cosmological constant, a value often derided in the past as a cosmic fudge factor.
Einstein initially included the cosmological constant in his theory of gravitation, thinking it was needed to explain what kept gravity from crashing the universe into one big ball of matter. But as astronomers accepted the idea that the universe began with an explosive Big Bang, Einstein dropped the cosmological constant and called it his “biggest blunder.”
“Now it looks like maybe his biggest blunder was calling it his ‘biggest blunder,’” Perlmutter told MSNBC in a telephone interview from Paris, where he was attending an astrophysics conference.
Don't call it antigravity
The effect of the cosmological constant, or lambda, would account for a tendency of empty space in the universe to expand, he said. In fact, the data from the supernovae imply that this lambda effect accounts for 70 percent of the energy in the universe, with the other 30 percent consisting of matter.
But Perlmutter cautioned that it would be a mistake to refer to the lambda effect as “antigravity” — a term used in some of the reports about the supernova studies.
“People were using the term antigravity for it because it happens to be a tendency of empty space that works opposite to the way gravity works on empty space, but it’s not what we traditionally think of as a force,” he said. “And it’s not an antigravity force, in the sense that you couldn’t use it to levitate real things.”
Rather, the effect could be the result of quantum mechanics, involving the interactions of paired particles we can’t detect. Perlmutter said the cosmological constant could be part of the solution for other mysteries of the universe such as dark matter. Indeed, the effect already has been dubbed “dark energy.”
Even though we shouldn’t count on developing antigravity drives anytime soon, Perlmutter noted that “every time you learn a little bit more about your universe, you become a little bit more powerful.”
“So it’s possible that someday, by understanding a little bit more about how the world works, it will come back to help us in some other way that will be surprising,” he said.