August 26, 2025—Is the universe expanding, contracting or something else entirely? Plus, humans are not as special as we think and new data on exoplanets around Proxima Centauri.
—Andrea Gawrylewski, Chief Newsletter Editor
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An artist’s impression of the Proxima Centauri system, with the planets Proxima b and Proxima d. Gabriel Pérez Díaz (IAC)
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Earlier this year, the Dark Energy Spectroscopic Instrument in Arizona provided evidence that dark energy may evolve over time, that is, it’s not a constant as physicists had thought for decades. This isn’t the first time that a reversal in thinking has threatened to strike cosmology.
The backstory: To astronomers in the 1990s, three facts seemed clear: all the matter in the universe is gravitationally attracting all the other matter in the universe; therefore, the expansion of the universe is slowing. In 1998, two independent research groups found the opposite: the universe’s expansion is not decelerating at all, it’s accelerating. Dark energy, which scientists believe constitutes about 70 percent of everything in the universe, was later predicted to be at the heart of this acceleration. How the latest dark energy finding will amend its role in cosmic expansion is the next question in physics.
Why this matters: Cosmology has often lent itself to assumptions that turn out to be dead wrong. Going back to the flawed assumption that the sun orbited the Earth, what seems obvious to our eyes is not necessarily true, and with the progress of technology scientists continue to gather data to reveal the nature of the universe. Reversals in cosmology are always possible, and should be expected.
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At the end of last year, Tahlequah the killer whale birthed a female calf. After only a few days the calf died, and Tahlequah was seen carrying her lost baby draped over her snout for at least 11 days in the Puget Sound. In 2018 the orca displayed similar behavior when she lost her previous calf. She carried the 300-pound body on her head for 17 days while swimming 1,000 miles. Researchers characterize the mother orca’s reaction to these losses as grief.
Why this matters: A 2023 study by researchers at Northeastern University found that human exceptionalism—the idea that humans are somehow separate from nature and not inherently linked to (or even like) nature— discourage environmental action and decreases how much humans value the natural world. In his book, A Sand County Almanac, Aldo Leopold urges humans to see ourselves not as conquerors but as members of ecological communities. Ethical consideration must extend to soils, waters, plants, animals—and prioritize the integrity, stability and beauty of ecosystems—not just human benefit, he says. “We abuse land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect.”
The Top Stories today are part of our 180th anniversary package, which is all about reversals in scientific thinking (180-degree turns. Get it?). Check out the rest of them here.
This week, our Science Quickly podcast explores some of the wildest U-turns in science. Listen here.
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