One string in each of the following pairs can be unraveled into a circle—the so-called unknot. Which one is it? Show puzzle solution The knots at the top left and the bottom right can be unraveled into circles: Challenge problem: The other two knots, which can’t be completely unraveled, can each be made to look… Continue reading Math Puzzle: Find the Unknot
Ukrainians: Resilient and More Confident
Despite limits on some U.S. aid and a mushrooming corruption scandal, Ukrainians appear more confident. Europeans are stepping up support. Ukraine is leading in drone innovation and Russia is seizing only slivers of land and cannot land a decisive blow, even if the eastern city of Pokrovsk falls. Although Western help is essential, Ukrainians now… Continue reading Ukrainians: Resilient and More Confident
Old ‘Ghost’ Theory of Quantum Gravity Makes a Comeback
The force we experience most intimately remains the most mysterious. Physicists understand how vast migrations of particles called photons light up our homes, and how swarms of “gluon” particles hold together the cores of our atoms. But they can’t say what gravity particles, if any, delight us as babies by enabling our spoons to plummet… Continue reading Old ‘Ghost’ Theory of Quantum Gravity Makes a Comeback
Can More British and French Nuclear Cooperation Help Deter Russia?
This commentary was originally published by War on the Rocks on September 30, 2025. As Europe continues to come to terms with both the Russian threat amid the war in Ukraine as well as the uncertainty surrounding the U.S. commitment to Europe, policymakers across the continent are urgently considering alternative deterrence arrangements. French President Emmanuel… Continue reading Can More British and French Nuclear Cooperation Help Deter Russia?
Poem: ‘Love Letter from Photograph 51’
September 16, 2025 1 min read Poem: ‘Love Letter from Photograph 51’ Science in meter and verse By Faith Paulsen edited by Dava Sobel & Clara Moskowitz Science History Images/Alamy Stock Photo “[c]learly Rosy had to go or be put in her place…. The thought could not be avoided that the best home for a… Continue reading Poem: ‘Love Letter from Photograph 51’
The Gaza Cease-Fire Deal Is Hardly the Total Victory Netanyahu Promised
Questions linger about whether the cease-fire between Israel and Hamas will hold, and how—or if—the parties will move on to the far thornier issues in the U.S.-sponsored plan that led to it. Still, it’s clear that this breakthrough signals the beginning of the end. That is, it is clear to most except the government of… Continue reading The Gaza Cease-Fire Deal Is Hardly the Total Victory Netanyahu Promised
Contributors to Scientific American’s October 2025 Issue
September 16, 2025 4 min read Contributors to Scientific American’s October 2025 Issue Writers, artists, photographers and researchers share the stories behind the stories By Jen Schwartz Chris GunnThe Lives of Dead Trees For almost 25 years Chris Gunn (above) worked as a contract photographer for NASA, where he shot precious objects such as moon… Continue reading Contributors to Scientific American’s October 2025 Issue
China Is Going to the Moon by 2030. Here’s What’s Known About the Mission—and Why It Matters
This commentary was originally published by The Conversation on November 11, 2025. More than 50 years after the last time humans walked on the Moon, China is working steadily towards landing its astronauts on the lunar surface. On October 30, 2025, a spokesman for China’s crewed space programme said the country was “on track” to… Continue reading China Is Going to the Moon by 2030. Here’s What’s Known About the Mission—and Why It Matters
Mixing Is the Heartbeat of Deep Lakes. At Crater Lake, It’s Slowing Down.
In the past, when summer nights grew cold, the lake released the day’s accumulated heat, causing surface water to become denser and sink. This phenomenon drives the shallow mixing that occurs in summer. As nights have warmed, however, this process has weakened, and mixing has slowed. Counterintuitively, as the layer of surface water has become… Continue reading Mixing Is the Heartbeat of Deep Lakes. At Crater Lake, It’s Slowing Down.
Germany’s €35 Billion Bet on Military Space Capability
Speaking at the recent Berlin Space Congress, German Defence Minister Boris Pistorius warned: “Our Achilles’ heel lies in space.” His statement pointed to an uncomfortable truth—modern societies are dependent on space, yet poorly protected against attacks beyond Earth’s atmosphere. In the 21st century, almost every aspect of our lives, from smartphones to online banking to… Continue reading Germany’s €35 Billion Bet on Military Space Capability