The Liberty Bell, with its famous crack, hasn't been rung in 180 years, but that hasn't stopped scientists from pondering what the bell might have sounded like when tolling. In honor of the nation's 250th anniversary, researchers at Penn State University have modeled its acoustic properties, drawing on data collected from one of the bell's replicas. The work was first presented at a meeting of the Acoustical Society of America in Philadelphia earlier this year, followed by an article in Physics Today.

Historians aren't sure exactly when the Liberty Bell acquired its distinctive crack, just that it occurred sometime between 1817 and 1846. An 1846 account in the Public Ledger described the ringing of the bell on February 23 that year and mentioned that the bell had developed a crack, which someone had attempted to fix by filing the sides down. But it didn't work: The February 23 ringing extended the crack even more, so much so that "the old Independence Bell ... now hangs in the great steeple irreparably cracked and forever dumb." Nobody has heard it ring since.

This wasn't the first time the bell had cracked; the rim cracked shortly after it arrived in Philadelphia in 1752, the first time the clapper struck while testing the sound. It was recast by two local foundry workers, John Pass and John Stow, not once but twice, because the first recast produced a sound that one bystander likened to coal scuttles banging together.

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One reason plastics are used so often is that they’re chemically inert, meaning bags, food containers, and cups don't react with what we put in them. Yet they can still break down into microplastics, which turn up in drinking water, human blood, arteries, and brains. The consequences of that are uncertain.

“Whether microplastics can directly cause human disease is still being researched,” said Wei Min, a chemist at Columbia University. In a new Nature study, Min's team took a step toward answering this question by demonstrating that microplastics are likely not as chemically inert as we might expect.

Microdroplet chemistry

Min's lab has spent years working on microdroplet chemistry, studying how water broken into tiny droplets behaves at its boundary with air. These droplets have been reported to generate reactive oxygen species, or ROS, a family of harmful, oxygen-containing molecules. “ROS will essentially bump into proteins, lipids, DNA, and cause damage,” Min said. “You could break a DNA strand into segments. You could mutate DNA; you could misfold proteins.”

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Rocket Lab announced Wednesday that its Neutron launch vehicle won't fly until 2027, citing an issue discovered during manufacturing of the rocket's carbon composite structures.

The announcement was public confirmation of what nearly everyone inside Rocket Lab and the wider space industry already knew. The most recent official update from Rocket Lab in August suggested the company still held hope of delivering the first Neutron rocket to its launch pad at Wallops Island, Virginia, before the end of this year, a schedule that would have almost certainly pushed the first flight into 2027.

But Rocket Lab's statement Wednesday about Neutron's schedule suggests the company is still struggling with manufacturing the rocket's large booster stage. Neutron's reusable first stage is made of carbon composite structures, which offer low weight, high strength, and corrosion resistance. But carbon composites in aerospace are generally harder to manufacture than metallic structures.

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Coral-fringed tropical atolls are among the landforms most threatened by global warming, but many have a potential superpower: Healthy ecosystems may help them keep pace with rising seas.

Atoll islands with native vegetation and thriving seabird populations are “naturally active systems that can change and adapt to their environmental conditions if they are allowed to do so,” said Nick Graham, a marine ecologist at Lancaster University in the United Kingdom, who led an international team of scientists that studied island resilience across 28 atoll islands in the Pacific and Indian oceans.

Their paper, published Wednesday in Science Advances, shows that restoring atoll ecosystems reinforces their growth. Seabirds ferry nutrients from the open ocean and deposit them on the atolls as guano that nurtures land plants, marine life and coral growth. This provides more material for reef building, as parrotfish and other reef feeders turn dead coral into sand to maintain beaches, while native plants with extensive root networks stabilize sediments.

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