A 2.75 inch sphere of ice weighs about 5.6 ounces.<\/p>\n
Thrown by hand it would sting. Fired down a tube at a steel instrument, it registered 3,252 pounds<\/strong> of force.<\/p>\n The same sphere, frozen 27 degrees warmer, registered 2,258.<\/p>\n Nothing about the ball changed except its temperature.<\/p>\n Not its mass, not its diameter, not the speed<\/strong> it was travelling.<\/p>\n Only how it broke.<\/p>\n Ice is not a constant. It sits close to its own melting point in almost every situation a person meets it, and materials near their melting point creep instead of snapping.<\/p>\n At 23 degrees Fahrenheit a hailstone still has a little give. On contact it deforms, spreads the touching area wider, and pays out its momentum over a slightly longer moment.<\/p>\n Take it down to 4 below and that give is gone. The ball is brittle, it fails all at once, and the whole load arrives in a shorter spike<\/strong>.<\/p>\n Glass does not care only about energy. It cares about how fast the energy shows up, because a sharp rise concentrates stress before the sheet has time to flex.<\/p>\n The measured stress rate for the middle size doubled with the cold, from about 74 to about 150 gigapascals a second.<\/p>\n Temperature is a hardness dial<\/strong>.<\/p>\n The rig sits in a materials lab in Mendrisio, in the Italian speaking south of Switzerland.<\/p>\n Compressed gas drives the sphere down a clear plastic tube cut to match each diameter. A laser at the muzzle clocks it on the way out.<\/p>\n Downrange stands the instrument, and it is the whole point of the setup. An aluminum bar, 1.2 inches<\/strong> across and about 5 feet long, wearing a strain gauge station partway along its length.<\/p>\n The bar does not break. That is what makes it useful, because a sheet of glass that shatters tells you only that it shattered.<\/p>\n The bar instead reports the entire force curve of a collision that is over in tens of millionths of a second, sampled a million times a second, with a camera running at 12,800 frames a second alongside it.<\/p>\n It measures the blow<\/strong>, not the wreckage.<\/p>\n Three diameters went down the tube, about 1 inch, 1.6 inches and 2.75 inches, each at two ice temperatures.<\/p>\n The smallest balls peaked at 191 pounds of force when warm and 325 when cold. The middle size went from 507 to 808. The largest went from 2,258 to 3,252.<\/p>\n Expressed as percentages the cold added 70, 59 and 44<\/strong> percent to peak force, in descending order of effect.<\/p>\n Time to peak moved the other way, falling 30 percent for the small balls and 21 percent for the middle ones.<\/p>\n Peak force also rose with size and speed, which surprised nobody and was never the point.<\/p>\n The warm ice was the gentle case<\/strong>.<\/p>\n Look again at that descending order, because it runs the opposite way to the worry.<\/p>\n Cold helps the ice most when the ice is small. For the 2.75 inch balls, the ones that actually threaten a module, the timing advantage of cold ice came out at 2 percent, which is inside the scatter, in the way that a wrong description<\/a> or a late flaw<\/a> hardens into a general rule<\/strong>.<\/p>\n Two more things deserve saying out loud. The team describes a rig reaching 313 miles an hour, but every result it published sits between roughly 49 and 86, so the top figure is a capability rather than a measurement.<\/p>\n And modules were indeed shot, yet no force, no velocity and no pass or fail was reported for them. What exists is a high speed sequence of glass cracking, which the published paper<\/a> calls preliminary throughout.<\/p>\n The work was paid for by the insurers<\/strong> themselves.<\/p>\n The mandatory test fires a 1 inch ball at about 50 miles an hour into eleven marked points on a module, with the ice held at about 25 degrees Fahrenheit.<\/p>\n That puts the certified stone at the soft end of the range this lab measured, and at one twentieth the weight of its largest ball. Swiss cantonal fire insurers already demand 1.2 inches and in practice ask for 1.6, and the lab is building a stand for 4 inch ice at 103 miles an hour.<\/p>\n Which leaves the geese, filmed near Toronto standing in a hailstorm with their bills aimed straight up. A biologist told the video report<\/a> that a few birds appeared to dodge individual stones.<\/p>\n Aldo Leopold wrote the same posture down in 1919, watching pintails on the Rio Grande, and concluded the vertical bill presented a surface that hail would simply deflect off.<\/p>\n A goose turns, but solar glass<\/strong> cannot.<\/p>\n It only gets thicker<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":" A 2.75 inch sphere of ice weighs about 5.6 ounces. Thrown by hand it would sting. Fired down a tube at a steel instrument, it registered 3,252 pounds of force. The same sphere, frozen 27 degrees warmer, registered 2,258. Nothing about the ball changed except its temperature. Not its mass, not its diameter, not the speed it was travelling. … Read more<\/a><\/p>\n","protected":false},"author":28,"featured_media":43787,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"rank_math_focus_keyword":"lab fired ice","rank_math_title":"A 2.75 inch ball of ice landed 1.6 tons of force on a sensor bar in a Swiss lab, while the mandatory test for solar glass uses a stone one twentieth that weight and warmer ice","rank_math_description":"A Swiss lab fires ice balls at solar panels to find their breaking point, a test that echoes how geese survive real hailstorms.","footnotes":""},"categories":[8],"tags":[],"class_list":["post-43460","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-energy"],"_links":{"self":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/43460","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/users\/28"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/comments?post=43460"}],"version-history":[{"count":4,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/43460\/revisions"}],"predecessor-version":[{"id":43788,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/43460\/revisions\/43788"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/media\/43787"}],"wp:attachment":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/media?parent=43460"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/categories?post=43460"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/tags?post=43460"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Why ice at 23 degrees behaves like a snowball<\/h2>\n
A 1.2 inch bar that refuses to break<\/h2>\n
191 pounds against 325 at the same size<\/h2>\n
The 2 percent that trims the headline<\/h2>\n
A 1 inch ball at 50 mph and 11 marked points<\/h2>\n