{"product_id":"schumanns-note-plate-094-physics-poster","title":"Schumann's Note – Plate 094 Physics Poster","description":"\u003cp\u003ePlate 94 speaks for itself: \u003cem\u003e“Lightning rings the planet at 7.8 hertz.”\u003c\/em\u003e\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eThe ground and the ionosphere form a spherical cavity. Lightning excites its resonances, the lowest near 7.8 Hz, a wave whose wavelength is about Earth's circumference.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003ef_n = (c \/ 2πR) √(n(n + 1))\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003ef_n: ideal mode frequency, Hz\u003c\/li\u003e\n\u003cli\u003ec: speed of light, m s⁻¹\u003c\/li\u003e\n\u003cli\u003eR: Earth radius 6.371×10⁶ m\u003c\/li\u003e\n\u003cli\u003en: mode number, integer\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eThe ideal lossless cavity gives f₁ ≈ 10.6 Hz. Observed modes are ≈ 7.8, 14.3 and 20.8 Hz.\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e Losses in the ionosphere pull the observed frequencies below the ideal formula.\u003c\/p\u003e\u003ch3\u003eSources\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eW. O. Schumann, Z. Naturforsch. A 7, 149 (1952).\u003c\/li\u003e\n\u003cli\u003eM. Balser, C. A. Wagner, Nature 188, 638 (1960).\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eOn the poster\u003c\/h3\u003e\u003cp\u003ePlate 094, “Schumann's Note”: the pixel-art plate with its slogan “Lightning rings the planet at 7.8 hertz.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.\u003c\/p\u003e","brand":"Printify","offers":[{"title":"9'' x 12\" (Vertical) \/ Matte","offer_id":50962715148391,"sku":"21652190590873604154","price":19.99,"currency_code":"USD","in_stock":true},{"title":"9'' x 12\" (Vertical) \/ Fine Art","offer_id":50962715181159,"sku":"68991938725820654187","price":29.99,"currency_code":"USD","in_stock":true},{"title":"9'' x 12\" (Vertical) \/ Semi Glossy","offer_id":50962715213927,"sku":"24396929769072308338","price":19.99,"currency_code":"USD","in_stock":true},{"title":"18″ x 24″ (Vertical) \/ Fine Art","offer_id":50962715246695,"sku":"13460530080957800894","price":44.99,"currency_code":"USD","in_stock":true},{"title":"18″ x 24″ (Vertical) \/ Semi Glossy","offer_id":50962715279463,"sku":"33469719150486142837","price":29.99,"currency_code":"USD","in_stock":true},{"title":"18″ x 24″ (Vertical) \/ Matte","offer_id":50962715312231,"sku":"27099185722434615070","price":29.99,"currency_code":"USD","in_stock":true},{"title":"36'' x 48\" (Vertical) \/ Matte","offer_id":50962715344999,"sku":"26923734909854196031","price":69.99,"currency_code":"USD","in_stock":true},{"title":"36'' x 48\" (Vertical) \/ Fine Art","offer_id":50962715377767,"sku":"52448966753544439988","price":119.99,"currency_code":"USD","in_stock":true},{"title":"36'' x 48\" (Vertical) \/ Semi Glossy","offer_id":50962715410535,"sku":"17173969422151718437","price":69.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/811781754080871518_2048.jpg?v=1793637944","url":"https:\/\/pixelatedphysics.com\/it\/products\/schumanns-note-plate-094-physics-poster","provider":"Pixelated Physics","version":"1.0","type":"link"}