雅思阅读 108: Dark Energy Survives a Challenge (暗能量闯过一次考验)

改编自 University of Southampton / Monthly Notices of the RAS（2026年6月）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.southampton.ac.uk/news/2026/06/universe-expansion-still-accelerating-say-astronomers.page

Reading Passage

A. For nearly three decades, one of the most startling facts in science has stood without serious challenge: the universe is not merely expanding, as physicists have known since the 1920s, but expanding at an ever-faster rate. The agent driving this runaway growth is a mysterious, repulsive influence dubbed dark energy, which overwhelms the inward tug of gravity on the largest scales. The discovery, made independently in 1998 by two teams observing a special class of exploding stars, won the 2011 Nobel Prize in Physics. It also handed cosmology its central puzzle: the cosmos is being pushed apart by something no laboratory has ever detected, and no theory fully explains. Everything else in the standard picture of the universe — its age, its eventual fate, the relative amounts of matter and radiation it contains — is, in one way or another, built on top of that single observation. If it were to wobble, textbooks would have to be rewritten, research programmes redirected and careers that had rested on the standard model set adrift. That is why the small band of astronomers who in 2025 suggested that the wobble might already have begun caused such unusual alarm.

B. The observation rests on "standard candles": Type Ia supernovae, the thermonuclear explosions of white-dwarf stars that, because they all reach nearly the same peak brightness, allow astronomers to infer vast distances. By comparing the distance of such a supernova with the speed at which its host galaxy recedes, researchers can reconstruct how the expansion of the universe has changed over time. In 1998 that comparison revealed that distant supernovae were fainter — and therefore farther away — than a universe slowing under gravity ought to place them. The universe, the teams concluded, had begun speeding up. Two and a half years ago, however, a separate group of astronomers dropped a bombshell. They argued, also from supernova data, that the bright standard candle was not as constant as everyone assumed: as the universe aged, they claimed, these explosions reached systematically different peak luminosities. If so, astronomers had been fooled into seeing an acceleration that was not really there, and dark energy might be weakening — or even vanishing. The paper was taken seriously because it came from respected researchers using the same instruments and the same data that everyone else relied on.

C. The claim, had it held up, would have dismantled almost thirty years of progress. It suggested that the methods behind the 1998 discovery were fundamentally flawed, and that the cosmos might actually be decelerating, pulled back by ordinary gravity. A new team, led by the University of Southampton and including two of the original Nobel laureates, set out to test the extraordinary claim with particular care. Their reanalysis, published in the Monthly Notices of the Royal Astronomical Society, concluded that the earlier result was an artefact of measurement, not a discovery about the universe. When the supernovae were re-calibrated, taking account of the different environments and stellar populations in their host galaxies, the evidence for accelerating expansion came back just as strong as before. The debate that followed, the lead author noted, was the result of a scientific misunderstanding rather than a crack in the cosmos itself. The dissenting group had been honest and careful, but they had leaned on an assumption about their standard candles that the wider community had long since learned not to make.

D. Where exactly did the dissenting team go wrong? The new analysis points to a subtle error in how the age of each exploding star was estimated. The earlier work had, in effect, assumed that the age of a host galaxy was the same as the age of the particular white dwarf that exploded inside it. Galaxies, however, are crowded metropolises of stars born at different times; a single supernova can flare in an old galaxy from a star that was itself born much more recently. Compounding the mistake, the 2025 paper failed to apply a routine correction that modern cosmology has long used — adjusting for the mass of the host galaxy, which is known to affect how bright a Type Ia explosion appears. Once both effects were properly accounted for, the supposed trend in supernova brightness with cosmic age evaporated, and the standard picture reasserted itself. The lesson, the authors say, is not that bold challenges are unwelcome — quite the contrary — but that extraordinary claims must clear an especially high bar, and that a measurement which everyone has used for a quarter of a century is usually, in the end, measuring something real.

E. The episode is not, however, to be dismissed as mere noise. Challenging accepted theories is, by design, how science advances, and the failed challenge has pushed researchers to scrutinise their own assumptions about how these stars explode and how best to use them as cosmic rulers. What remains is the original mystery in all its force. The measurements are sound, the Southampton team insists, but that only restores the question that provoked the chase in the first place: why is the universe accelerating at all? Dark energy's existence is now more secure, yet its nature — a constant vacuum energy, an evolving field, or something stranger still — is as opaque as ever. Future surveys, mapping millions of galaxies and their supernovae, will narrow the possibilities further, but they are unlikely to settle what the thing actually is. For the moment, the cosmos has been confirmed to do what everyone thought it did, and astronomers can return to the harder task of explaining a universe that refuses, even in its expansion, to behave as plain gravity would predict. A crisis has been averted; the puzzle, thank heavens, has not.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. The standard candles — and the bombshell of 2025 ii. How the 2025 claim went wrong iii. Why the discovery of acceleration matters iv. The failed challenge that restored the standard picture v. The mystery that remains vi. The history of the Hubble Space Telescope vii. How white dwarfs are formed

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why are Type Ia supernovae useful to astronomers? A. They are the brightest objects in the solar system. B. Their near-uniform peak brightness lets researchers estimate cosmic distances. C. They never change their luminosity. D. They are found only in our own galaxy.

6. What did the 2025 study claim? A. Dark energy was getting stronger over time. B. Supernova peak brightness changes with cosmic age, possibly mimicking acceleration. C. The universe had stopped expanding entirely. D. Dark matter did not exist.

7. According to the new analysis, what was the main error in the 2025 work? A. It used telescopes on the wrong side of the Earth. B. It equated a host galaxy's age with the age of the exploded star, and ignored host mass. C. It forgot to observe any supernovae. D. It measured distances with a defective ruler.

8. What does the Southampton team conclude about the evidence for acceleration? A. It has collapsed entirely. B. It remains strong once host environments are properly accounted for. C. It is weaker than in 1998. D. It can never be tested again.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. The discovery of accelerating expansion was awarded the 2011 Nobel Prize in Physics.
10. The 2025 study claimed that the universe might actually be decelerating.
11. The Southampton team includes two of the original Nobel laureates.
12. The new study proves that dark energy is a constant vacuum energy.
13. Type Ia supernovae are the explosions of giant red-giant stars.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

The 2025 work incorrectly assumed that the age of a host (14) __________ was the same as the age of the star that exploded. It also failed to adjust for the (15) __________ of the host galaxy, a routine correction in modern cosmology.

答案与解析

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