January 26, 2024: African fish that use electric fields to "see," you can calculate the distance to a horizon that recedes forever, and the bizarre life of the world's most prolific mathematician. —Andrea Gawrylewski, Chief Newsletter Editor | | | The elephantnose fish creates an electric map to navigate the murky rivers of western and central Africa. A specialized organ in its tail emits a weak electric field that radiates outward from its body in pulses. Tiny receptors on its skin detect distortions to the field caused by objects in the field.
Why this is so cool: The fish wiggles around to get electric images from multiple angles. Stacked together, those electric images help the fish decipher its surroundings in three dimensions. A new study found that with less room to maneuver–to dance–the fish lose some sense of location.
What the experts say: "It's just so complex, what they do, that we can't really model it with our greatest computers," says Stefan Mucha, a postdoc at the Humboldt University of Berlin. "But it's just a small fish!" | | | Credit: Paul Starosta/Getty Images | | | The horizon is a defined line between earth and sky. But as you move toward it, the horizon recedes indefinitely, making it more mirage than fixed place. Even though it is a specter of sorts, you can roughly calculate the distance to the horizon using a familiar geometric equation, writes astronomer and columnist Phil Plait.
How this works: Imaginary lines connecting your eyes, the horizon and the center of the Earth form a right triangle (see diagram below sketched by Plait). If you remember the Pythagorean theorem from 8th-grade math, you can calculate the length of any side of a right triangle using a^2 + b^2=c^2 where the distance between the center of Earth plus your height is c^2, or the hypotenuse (sorry, I know it's been a long week).
The takeaway: For someone with eyes about 1.5 m above ground, their horizon is about 4.4km away. The distance decreases the closer to the ground you are, and increases as you gain height–or altitude! If you're staring out the window of a commercial aircraft at cruising altitude, the horizon is closer to 360 km away. Slight caveat here, Earth's atmosphere has a lensing effect, so we can actually see slightly farther than the above calculations yield. | | | Credit: Phil Plait, restyled by Amanda Montañez | | | • After nearly three years soaring through the red skies of Mars, NASA's Ingenuity helicopter is permanently grounded. | 4 min read | | | • Paul Erdős, the most prolific mathematician in history, led an eccentric and nomadic life focused singularly on his work. | 5 min read | | | • Weight-loss drugs have taken the world by storm. And while early signs show they could have a large impact on rising global rates of obesity and even cardiovascular disease, the pharmaceutical industry stands to profit most, writes Arthur Caplan, professor of bioethics at NYU Grossman School of Medicine. If history is a guide, "pricing, proper medical supervision, responsible marketing and attention to underlying causes go out the window when the chance to make a fortune is all but guaranteed," he says. | 5 min | | | OUR MOST POPULAR STORIES OF THE WEEK | | | • Your Body Has Its Own Built-In Ozempic | 4 min read | • A Wild Claim about the Powers of Pi Creates a Transcendental Mystery | 6 min read | • There Are Quicker Ways to Board a Plane—So Why Don't Airlines Use Them? | 5 min read | | | For something so mercurial, the horizon can have a standout stabilizing effect on us, no? To encourage inspirational future thinking we advise others to "look to the horizon!" To settle queasy stomachs on sea voyages or long car trips, the advice again: "look at the horizon." That hard line between earth and sky isn't necessarily real in the physical sense, but philosophically it's as certain as things come. | Whatever horizon you can see, I hope you get lots of time to stare at it this weekend. Reach out anytime with thoughts or feedback: newsletters@sciam.com. See you on Monday! | —Andrea Gawrylewski, Chief Newsletter Editor | | Subscribe to this and all of our newsletters . | | | | Scientific American
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