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slowly we began to like it. We began to care what the universe was like. This is not altogether healthy. You like to think you're just a dispassionate observer—an eagle-eyed umpire: "I call 'em the way I see 'em." But we were drifting into becoming believers, or at least fans of the cosmological constant. It was a time for less propaganda and more data.

the smoking gun?

By the beginning of 1999, the case for an accelcrating universe had acquired some traction. The high-z team results were published in the The Astronomical Journal and the Lawrencc Berkeley Lab results were widely circulated as preprints and conference reports, both pointing to the same conclusion. Consistent results from two independent teams made the cvidencc more credible, though there was still an outside chance wc were both making identical mistakes. But if wc were making a mistake, it was a subtle one. As far as either team could tell, distant SN la were just like the nearby SN la. Although age, composition, and dust were possible complicating factors, their effects seemed to be small, and we were working hard to detcct and limit them. The decisive test, though, would be to look for supcrnovac at even higher rcdshift.

For any combination of the dark energy, fiA, and the dark matter density, £lni, we could predict what to expcct as wc looked to redshift one and beyond. After the Big Bang, there should be cosmic deceleration causcd by £2m followed by cosmic acceleration due to fiA. Somewhere out beyond redshift one, supernova observations should reach well into the deceleration zone, and we should start to see the supernovae appearing a little brighter than otherwise. If the supernovae showed extra dimming instead, that would point to a systematic problem and we would be forced to retreat

Figure H.I. The work on the acceleratir^g universe was Science Magazine's "Science Breakthrough of the Year" for 1998. Reprinted with permission from SciencE, vol. 282. December 18, 1996 IIlustration. John Kascht, Albert Einstein™ represented by the Roger Richman Agency, Inc , Beverly Hills, CA Copyright 1998 American Association for the Advancement of Science.

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