Every day is Earth Day here. Never miss a discovery! ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏
April 23, 2025—Check out mathematicians' favorite shapes. Plus, one Roman gladiator's very bad day; and why people are drawn to narcissistic leaders. --Andrea Gawrylewski, Chief Newsletter Editor | | Lesion on the left iliac spine of 6DT19."Unique osteological evidence for human-animal gladiatorial combat in Roman Britain," Thompson TJU, Errickson D, McDonnell C, Holst M, Caffell A, Pearce J, et al., in PLoS ONE, Vol. 20, No. 4, Article No. e0319847, Published online April 23, 2025 | | - Archaeologists have found the first physical evidence that Roman gladiators battled animals—a lion left a bite mark on a gladiator's pelvic bone. | 3 min read
- RFK, Jr., declared a U.S. ban on eight food dyes yesterday. This is what we know about how artificial food dyes affect human health. | 4 min read
- Only a (depressingly) small percentage of the plastics we recycle in household bins is given a second life. Here's why. | 5 min read
- The popular fantasy card game Magic: The Gathering has a new card related to prime numbers. Now fans are trying to use it to tackle one of the biggest problems in mathematics. | 5 min read
- In a new book called Slither, Stephen S. Hall takes a deep dive into the biology and history of one of the most reviled animals. On our podcast, Science, Quickly, he explains that throughout history people have not always hated snakes. | 16 min listen
| | Math's Favorite Shapes For mathematicians, shapes are more than just circles, triangles and squares. They encompass a vast universe of surprising forms, from one-dimensional loops to polytopes (geometric objects with flat sides that can exist in any desired dimension). Mathematicians use shapes and surfaces, which are collections of points that form boundaries in 3D space, to contemplate open questions, explore new ideas and make discoveries. We asked mathematicians to choose their favorite shapes and surfaces and tell us why they find them so exciting and intriguing. Here are two of their responses. Click through to read about many more, from loops to polytopes to permutahedrons. | | Ribbon Knots: Here's how such a representation is constructed: Take a finite collection of disks, cut slits into them, then add bands between the boundaries of the disks that are allowed to pass through these slits. If the boundary of the resulting picture is a single piece of knotted string, the result is what's called a ribbon disk, and a knot in 3D that bounds such a disk is called a ribbon knot. In the 4D space, which we think of as surrounding the 3D space, there is enough room to undo the insertion and recover a disk (without the slits). Therefore, a ribbon knot is an example of the simplest possible type of knot in 4D, and the process of making a ribbon disk gives us a 3D way to construct it. The slice-ribbon conjecture, a major open problem in low-dimensional topology, says every such simple knot in 4D comes from a ribbon disk. I find the shape fascinating because it is a simple construction that underlies a difficult—and impossible to fully visualize—process in 4D space. Because there is more room than in 3D space, a set of points in 4D that itself constitutes a disk may occupy the space in intricate ways when we view its projection in 3D. —Christine Ruey Shan Lee, Texas State University | | | | |
Hyperbolic pair of pants: My favorite shape—and one I think about every day—is called the hyperbolic pair of pants. It is a surface with the shape of a pair of pants, meaning it has three boundary components (a waist and two ankles) and genus 0 (no handle, as opposed to your coffee mug). What makes this shape so special is that to every three lengths a, b and c, we can associate one and only one hyperbolic pair of pants of boundary lengths a, b and c. Thus, the same way that you know how to draw "the rectangle of edges 2 and 3.5," it makes sense to talk about "the hyperbolic pair of pants of boundaries 1, 6 and 2.4." You can play and sew hyperbolic pairs of pants together. When you sew two pairs of jeans along their beltlines, an important decision is whether to line up their buttons and, if not, how much to twist. The amount of twisting is called the twist angle, represented by tau (τ). We can construct every hyperbolic surface by sewing together hyperbolic pairs of pants and describe all of them entirely in terms of the boundary lengths and twist angles in this decomposition. Therefore, hyperbolic pairs of pants are the perfect building blocks of hyperbolic geometry. —Laura Monk, University of Bristol, England | | Narcissistic leaders both fascinate and repel us, writes Eddie Brummelman, an associate professor at the University of Amsterdam. They can act charming and with an assertiveness that inspires confidence, but they also have a dark side that can include unethical, autocratic and aggressive behavior, he says. Brummelman's research with kids has found that narcissistic leaders emerge in classrooms, even though they are no better leaders than anyone else. "We hope that our research inspires educators and other professionals to take leadership development seriously. Kids can learn to lead democratically, feel responsible for the common good, and organize and inspire others toward making meaningful societal change." | 5 min read | | - So-called gain-of-function virology research has been controversial for years. Now it may be going away. | The New Atlantis
| | - A woodpecker in Cape Ann, Mass., has been cracking car side mirrors and window glass in attempts to assert his mating territory. | The New York Times
| | One reader asked me why I didn't mention anything yesterday about Earth Day. My response was that nearly every day this newsletter considers the planet and how human actions impact it. From the changing climate, to ways to encourage more pollinators in your lawn, to discovering how our favorite varieties of apples came about, science is the business of getting to know Earth, its place in the cosmos and how best to live here. Every day is Earth Day here. | | —Andrea Gawrylewski, Chief Newsletter Editor | | | | |
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