Harvard-Smithsonian Center for Astrophysics

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27 February 2007



I was dreamily thinking about 2006, as people often do on the final day of the year.  As part of this idle foolishness, I took a look at the Shaw Prize site.  This award, made to Brian Schmidt, Adam Riess, and Saul Perlmutter is a great thing and I am very glad to see that cosmic acceleration is being recognized. Everybody has a lot to be proud of.


But one point jumped out at me.  In his brief biography  Saul Perlmutter says that the Supernova Cosmology Project (SCP-Saul's team at Lawrence Berkeley Lab (LBL)) "first announced" the results. Then in his longer biographical statement Saul says the SCP announced the result that the Universe was speeding up at the January 1998 AAS meeting.  Brian and Adam were too polite to dispute this assertion of priority at the Shaw site.  Adam has a longer description of his work here.  And Brian has a description of his path to the Shaw Prize here.  Each has a personal account that shows there was no announcement by either team in January 1998.


As part of the High-Z team, I recognize that the accelerating universe was not discovered by us alone.  But Saul's version of events does not match the available facts.  If I learned one thing from writing The Extravagant Universe, it is that memory plays tricks.  You have to go back to the documents if you want to know what happened 9 years ago.  Since this claim of an announcement in January 1998 is confusing, even to experts, I've assembled the documents I could find on the announcement of the acceleration.  I've tried to be fairly complete and completely fair.


I think the evidence shows there were hints, but no "announcement" of acceleration of the Universe at the January 1998 AAS meeting.  That announcement was made by Alex Filippenko for the High-Z Team at the Dark Matter workshop in late February 1998.  More importantly, in my opinion, the refereed publication from the High-Z Team showing the evidence for cosmic acceleration was submitted in March 1998 and appeared in September 1998, while the comparable publication from the SCP was submitted in September 1998 and appeared in June of 1999.


The January 1998 press release from LBL for the AAS meeting is lengthy and carefully constructed, but it doesn't contain one word about cosmic acceleration.  Even the comment at the end attributed to Goobar, saying that when the new data are analyzed we may need to invoke the cosmological constant is both hypothetical and based on the subtraction argument:  if inflation implies Omega= 1, then a low value for Omegamatter implies the need for something else. No observation of acceleration in that.


If the SCP had wanted to make an announcement on January 8, 1998, there were 50 reporters in the room:  the press conference was the place and the press release was the means.  This did not happen.


Dennis Overbye wrote about the press conference in his book Lonely Hearts of the Cosmos.  He heard what Saul said for the SCP and what Peter Garnavich said for our High-Z team.  Both were reporting evidence, as published by the SCP in their January 1, 1998 Nature paper, and by us in our forthcoming February 1 1998 Ap.J. Letter (493, L53) that Omegamatter was low.  Or, as LBL put it in the press release, "we live in a universe that will expand forever."  


That Nature paper makes no claim of acceleration. But this new result pointed in the opposite direction from the recent July 1997 Ap.J. paper from the SCP, which had fit their data best with Omegamatter = 0.8. Both the January 1998 Nature paper and the LBL press release drew attention to a significant step in what turned out to be the right direction.  But announcing evidence for a low value of Omegamatter is not an announcement of acceleration. 


Overbye says (p.431)   "Only a year earlier in 1996, with seven supernovae in hand, Perlmutter thought he could see the first evidence that the universe was slowing.  At a conference in Santa Monica sponsored by UCLA, he was too cagey to venture a value for the deceleration parameter or a decision on whether the universe has a big crunch in its future, but he did announce to a cheering crowd, 'we do want to say it is very difficult to have an accelerating universe.  We live in a decelerating universe.' "


"These were historic words, but they were wrong...."


In the next paragraph Overbye goes on to say,


"At the January 1998 meeting of the American Astronomical Society in Washington, D.C., Perlmutter and Peter Garnavich of the Harvard-Smithsonian Center for Astrophysics, representing the other team, shared a stage and announced that the universe would expand forever and ever." 


That's it.  Nothing about acceleration.  He goes on to talk about "the buzz" about the cosmological constant, but that wasn't something he heard Saul announce at the press conference.


In his October 1999 Astronomy piece, James Glanz points out that he was not at the press conference, but that he cornered Saul later.  But even under individual pressure from this forceful and brilliant guy to say more to him than he had to the others, Saul stuck to his cautious formulation of possibility.  Glanz quoted Saul as saying: "If [the results] hold up, that would introduce important evidence that there is a cosmological constant."  This careful and conditional statement made privately to one person is a long way from "announcing" that supernova data show the universe is accelerating.


Of course, the possibility of acceleration was in the air, because it was in the data, and Glanz made the most of it.  Probably he didn't hear Saul say that the data were also consistent with no acceleration.  As the impatient Glanz says in his Astronomy article,


"Perlmutter cautioned that the group was still correcting for possible dimming of the light by dust and that the conclusions could still change.  But I folded my steno pad and hurried away in pursuit of another conference participant..."


Even so, the account by Glanz in Science on January 30, 1998 is carefully couched in tentative tones- he says, " a preliminary analysis may provide the first evidence that the universe could be permeated by a large-scale repulsive force." This is significantly different from "announcing" we live in an accelerating universe.


The report by John Noble Wilford based on public statements was much more typical of reports from the January 1998 AAS meeting.  He quoted Saul as predicting a reliable measurement of cosmic deceleration by the year 2000:


"'The field is moving very quickly,' Dr. Perlmutter said at the news conference. He had just returned from the Keck Observatory in Hawaii with more data. By the beginning of the new millennium, he predicted, the extent to which the universe has decelerated, if at all, should be known."


You can look at the AAS meeting reports from the Philadelphia Inquirer, the Boston Globe, the Toronto Globe and Mail, The Independent (London), The Irish Times, the Cleveland Plain Dealer, the Sydney Daily Telegraph.  Like the NY Times story, they have no whisper of cosmic acceleration.


There is a whisper in Kathy Sawyer's story in the Washington Post.  In the 13th paragraph, without attribution to any particular person of the five presenters at the news conference, she says "the findings also appear to breathe fresh life into the theory that there is a so-called cosmological constant..."


The only reporter who heard the message of cosmic acceleration was Charles Petit, of US News & World Report.  He starts his story by saying that bleakness lies ahead and "after slowing steadily since its birth...{the universe} is speeding up again, an accelerating expansion into darker and darker decay."  He attributes the evidence to Neta Bahcall, and to Saul, saying, "Strong signs that the expanding universe is actually starting to speed up come from astronomers using ground-based and orbiting telescopes to chart supernova exploding stars in galaxies, a gauge of how fast the universe has expanded so far.  Says Saul Perlmutter of the Lawrence Berkeley Laboratory, a leader of the effort: 'No big crunch.  The galaxies out there seem to be accelerating outward.  Not much, but they are not turning around, either.'"


If that had been the only report from the meeting, it would support the claim that the SCP concluded there was cosmic acceleration and said so in January 1998.  What makes this less convincing is that it contradicts all the other reports, that Perlmutter continued to say publicly that the evidence to draw a firm conclusion was not yet in, and that in January and in February of 1998, Saul repeatedly explained why they had not made an announcement in January.


For example, in the February 16 Pittsburgh Post-Gazette, there's a story by Byron Spice on Bob Nichol's claim that Omegamatter = 1 based on X-ray clusters. The writer says,


"One international study, headed by Saul Perlmutter of Lawrence Berkeley Laboratory in California, studied a series of exploding stars, called supernovae, to calculate how the universe's expansion rate had changed over time.  They not only found no sign that the expansion was slowing, but picked up hints that something might somehow be nudging the expansion faster.


But Perlmutter says it will take another couple years of work to prove his findings are correct."


Dennis Overbye goes on in his 'Afterword' to give an account of the first announcement of cosmic acceleration, made in February.


He says (p.433), describing the February 1998 Dark Matter meeting:

"A month later, Schmidt's team beat Perlmutter's to the punch and went public with the new information.  At the same yearly meeting in Los Angeles at which, two years before, Perlmutter had said the universe was decelerating, Alexei Filippenko announced that the universe was instead accelerating under the influence of a mysterious force, a sort of cosmic repulsion or antigravity.  The announcement predictably riled Perlmutter's group, who were quick to point out they had far more data but had been proceeding more cautiously."


Glanz broke this story in Science on 27 February saying, "As team member Alex Filippenko of the University of California announced at a meeting near Los Angeles last week, 'the dimness of the supernovae-pointing to unexpectedly large distances-implies that cosmic expansion has actually sped up in the years since the stars exploded.' "


This announcement caused a stir: CNN sent a TV crew over the Bay Bridge to interview Adam Riess, then Adam appeared on PBS on the News Hour, and I did a phone interview with an in-your-face interviewer from the BBC.  [Something along the lines of, "Isn't it true, Professor Kirshner, that this discovery makes not a farthing's difference to anybody in their daily life?" ]


In an article in the New York Times, on March 3, 1998, John Noble Wilford wrote "Dr. Perlmutter's group, the Supernova Cosmology Project, has studied 40 distant supernovas in detail.  Describing their results in January, Dr. Perlmutter acknowledged that the evidence strongly suggested a cosmological constant, but went no further. 'We were trying to be very conservative until we had more observations,' he said last week."


In a later, longer article that Wilford wrote in April 1998, he says about the February events: "...the Schmidt team grew bold and reported even more stunning results, which both teams had been hinting at for months.  At a meeting of astrophysicists in February, Dr. Alexei V. Filippenko, an astronomer at the University of California at Berkeley, announced that supernova data strongly suggested that the universe's expansion was speeding up.


He goes on to say, "The announcement rankled members of the Perlmutter group, who said they had the same results from a larger store of data but felt it was premature to go public yet."


In the following paragraph Gerson Goldhaber  says, "They had only 14 supernovas, and we had 40.  But they won the first point in the publicity game." 


Ted Anson's book  Bold Science says that he was at the January AAS press conference where Perlmutter explained that "the universe would expand forever into a lonely infinite night." Then he goes on to say, "[Perlmutter] chose to play down their more spectacular results...For the rest of their lives, however, some in his small group would question their caution."


On p.116 of his book, Anson describes the situation prior to the Marina Del Rey meeting in February.   He says, "The problem for the Perlmutter team was that their margin of error, or error bars, were still too great, they felt, to make such a stupendous announcement." 


"Then Alex Filippenko rose to address the group. Well, he began, savoring the moment, either you have a discovery or you don't.  We have evidence, and our error bars are much smaller and better understood.  We have for the first time real evidence of a new 'antigravity' force at work in the cosmos.

"Afterward, a commotion broke in the conference room..."


Reporters are not perfect (Overbye spelled my name wrong! He doesn't know Marina Del Rey from Santa Monica!), but these people are professionals who were paying close attention to what was said in public.  There was no January 1998 announcement of cosmic acceleration.


Finally, for those with a rarefied taste for refereed publications, the facts speak for themselves.  Our High-Z paper was submitted to the Astronomical Journal on March 13, 1998 and it appeared in the September 1998 issue.  The SCP paper was submitted to Astrophysical Journal on September 8, 1998, and it appeared in the June 1999 issue. 


"Announcements" are one thing, publications another.  Everybody has a lot to be proud of.  Both teams made major contributions to this discovery, but whether you like announcements or publications, the SCP wasn't first.



Robert Kirshner

Harvard College Professor of Astronomy

Clowes Professor of Science