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September 8, 2025—Mammoth tooth microbes, the math of shuffling a deck of cards and a geological drip beneath the U.S. Midwest and Ohio Valley. —Robin Lloyd, Contributing Editor | | Ancient mammoth teeth, pictured here, contained DNA from 310 different species of bacteria. Love Dalén | | Deep underneath the U.S. Midwest and Ohio Valley, North America's geological core may be sinking, reports Scientific American senior news reporter Meghan Bartels. An ancient oceanic plate below the central block of the region's continental crust is siphoning away molten material and thinning its underside, a newly published model suggests. The current North American model of a stable continental crust, called a craton, and this craton's unusual deep, dripping descent into Earth's denser mantle only made sense when the researchers included the remnants of the oceanic slab, known as the Farallon plate. The plate stretched between the Pacific and North American plates in its hey-day, a time when large dinosaurs roamed. Its remains now linger in Earth's lower mantle. Why this is cool: Cratons typically are considered unchanging and resistant to plate tectonics. The North American craton has persisted for more than a billion years. But the long-lost Farallon plate might be eroding this craton right under our feet, the researchers say. What it found: The newly hypothesized role of the Farallon plate is "intriguing," says geophysicist Claire Currie, who was not involved in the new research. To be convinced of the finding, she would like to see more evidence of the cratonic drip, perhaps at the surface of the Earth. And she wonders exactly how the craton could be drawn into the mantle. It ought to float above this denser material. —Andrea Tamayo, newsletter writer | | ELabArts; Source: "Seismic Full-Waveform Tomography of Active Cratonic Thinning beneath North America Consistent with Slab-Induced Dripping," by Junlin Hua et al., in Nature Geoscience, Vol. 18; April 2025 (reference) | | It was once common for even a simple computer to fill an entire room. Today, computers can slip into our pockets. Now, a scientist has shown that the computer memory required to solve a problem is even less constrained than previously thought. The finding could enable computers that are even smaller and more space efficient, reports Max Springer, a Ph.D. candidate in applied mathematics. How it works: For decades, computational complexity theoreticians were only able to prove that if a problem takes a machine t steps to solve, it would require roughly t bits of memory—the 0s and 1s that a machine uses to record information. For example, if a task requires 100 times the steps of another one, say, you'd expect to need about 100 times the bits. In the new proof, MIT computer scientist Ryan Williams demonstrated that any problem solvable in time t only needs only about √t bits of memory. What the experts say: "This progress is unbelievable. Before this result, there were problems you could solve in a certain amount of time, but many thought you couldn't do so with such little space," says Mahdi Cheraghchi, a computer scientist at the University of Michigan. Williams's finding, he adds, is "a step in the right direction that we didn't know how to take." —Andrea Tamayo, newsletter writer | | | | |
- A free online resource developed by a team of psychology researchers, including Darwin A. Guevarra of Miami University, sends participants daily e-mails or texts with instructions for a five- to 10-minute short activity meant to increase one's feelings of joy. Examples include making a gratitude list. Participants across the globe and of various levels of social advantages report feeling more positive emotions and lower stress after performing these "micro-acts" for a short time, write Guevarra and colleagues. The so-called Big Joy project is showing benefits that match those of interventions that take more time, the team writes. | 5 min read
| | Amanda Montañez; Source: Hans-Karl Eder/Spektrum der Wissenschaft (reference) | | Prolific puzzle inventor Henry Ernest Dudeney published the following problem in his 1917 book Amusements in Mathematics.The current version of the U.K.'s Union Jack flag was introduced in 1801. This image is a simplified version of the Union Jack that just consists of lines. Try to trace the lines with a pencil while only going through each line once. You should also lift the pencil from the paper and place it somewhere else as rarely as possible. Is it possible to draw the line version of the Union Jack in one go? If not, how many times do you have to reposition the pencil at minimum? Click here for the answer. | | The Big Joy project, described above, is not the first research effort to look into inexpensive, accessible ways to help others feel better emotionally. Check out The Friendship Bench, The Happiness Project and the field of positive psychology, credited to Martin Seligman. The Big Joy researchers acknowledge the limitations to their findings: reliance on self-reports (rather than less subjective measures) and no control group as yet. Still, the team's sample is sizeable and diverse. Thinking about all these researchers and writers who are dedicating their careers to simple ways to improve global wellbeing? That makes me feel a little better too. | | —Robin Lloyd, Contributing Editor
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