На реке в штате Мэн засняли Луну

Instagram / Popular Science

Жители американского города Уэстбрук (штат Мэн) засняли на местной реке Пресумпскот уникальную 90-метровую льдину, похожую сверху на Луну. Такая льдина появилась в результате редкого процесса – замерзания водоворотов, сообщает британская телерадиокомпания BBC.

На опубликованных ниже кадрах запечатлена "лунная льдина", как будто нарисованная для съемок фантастического фильма.


Behold this giant spinning ice disk!
❄️ The image above might suggest someone dropped a small planet in the middle of the Presumpscot River in Westbrook, Maine, but (shocker) that’s not the case. It’s actually a big disk made of ice that’s slowly rotating in place, filled with fascinating physics. ❄️ It would be reasonable to think the river's current is propelling that rotation, but research suggests the object may be spinning on its own. Giant disks like this form not infrequently during the cold winter months, and in 2016 physicists got to the bottom of the phenomenon. The group created a miniature ice disk and floated it in a tank, where they determined that the rotational force was generated by a vortex that formed beneath the disk. Water is at its most dense at 4°C (that’s 39.2°F). As the ice of the disk cools down the fluid surrounding it, that water reaches the four-degree mark and sinks. It flows down and horizontally, creating a swirling vortex. And the larger the temperature gradient—meaning the warmer the river water is compared to the frozen disk—the faster the cooling water will sink. That means the disk spins faster, too. it’ll spin because the cooling water will sink faster. ❄️ That also means spinning disks like this wouldn’t necessarily happen in any body of water. Some lakes may already be at 39.2°F or colder when water starts freezing, which means the cooled water next to the ice wouldn’t sink at all, and thus there wouldn’t be a vortex to rotate the disk. ❄️ The same phenomenon also happens when you place an ice disk on a solid surface, such as a plate of aluminum. If the plate is warmer than the ice, it melts and creates a miniature vortex inside the pooled water beneath. ❄️ Hit the #linkinbio to watch a video of the disk spinning 👉 @popsci 📷 Tina Radel / City of Westbrook

A post shared by Popular Science (@popsci) on Jan 15, 2019 at 1:08pm PST

Физик из университета Гарварда Джон Хут рассказал, что льдина, скорее всего, превратится в диск, так как вода в водовороте течет медленнее основного течения, а значит, скоро окончательно замерзнет.

"Лунную льдину" уже нарекли местной достопримечательностью, ее снимки выложили в соцсети сотни жителей Уэстбрука.


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