Ice discs, ice circles, ice pans, ice pancakes [1] or ice crepes are a very rare natural phenomenon that occurs in slow moving water in cold climates. They are thin circular slabs of ice that rotate slowly on a body of water's surface.
Ice discs, ice circles, ice pans, ice pancakes [1] or ice crepes are a very rare natural phenomenon that occurs in slow moving water in cold climates. They are thin circular slabs of ice that rotate slowly on a body of water's surface.
Ice discs form on the outer bends in a river where the accelerating water creates a force called 'rotational shear', which breaks off a chunk of ice and twists it around. [2] As the disc rotates, it grinds against surrounding ice — smoothing into a circle. [3] A relatively uncommon phenomenon, one of the earliest recordings is of a slowly revolving disc spotted on the Mianus River and reported in an 1895 edition of Scientific American . [4] [5]
River specialist and geography professor Joe Desloges states that ice pans are "surface slabs of ice that form in the center of a lake or creek, instead of along the water’s edge". As water cools, ice crystals form into 'frazil ice' and can cluster together into a pan-shaped formation. [6] If an ice pan accumulates enough frazil ice and the current remains slow, the pan may transform into a 'hanging dam', a heavy block of ice with high ridges and a low centre. [7]
It is believed that ice circles form in eddy currents. [8] It has been shown that existing ice discs can maintain their rotation due to melting. [9]
Ice circles tend to rotate even when they form in water that is not moving. The ice circle lowers the temperature of the water around it, which causes the water to become denser than the slightly warmer water around it. The dense water then sinks and creates its own circular motion, causing the ice circle to rotate. [10]
An unusual natural phenomenon, ice disks occur in slowly moving water in cold climates and can vary in size, with circles more than 15 metres (49 feet) in diameter observed. [11] [12] [13] [14] Ice Circle of Vana-Vigala in Estonia is reported to have had a diameter of over 20 meters, [15] whilst one approximately 298 feet (91 meters) in diameter appeared in Westbrook, Maine in January 2019. [16]
Ice discs have most frequently been observed in Scandinavia and North America. An ice disc was observed in Wales in December 2008 and another one in England in January 2009. [17] [3] An ice disc was observed on the Sheyenne River in North Dakota in December 2013. An ice circle of approximately 15 m (50 ft) in diameter was observed and photographed in Lake Katrine, New York on the Esopus Creek around 23 January 2014. In Idaho, extreme weather led to a rare sighting of an ice disc on the Snake River on 22 January 2014.
On 14 January 2019, an ice disc approximately 298 feet (91 metres) wide on the Presumpscot River in Westbrook, Maine, United States drew wide media attention. [18] [19] [20] A smaller disc was reported by park rangers in Baxter State Park, in northern Maine, the same month. [21] In January 2020, an ice disc appeared on the Kennebec River in Skowhegan, Maine, United States [22]
In January 2021 a large ice circle was discovered via satellite imagery and on 23 February 2021, an ice disc estimated to be 196–202 metres (643–663 ft) wide was confirmed on the Taltson River, Northwest Territories (just below Tsu Lake). It was estimated to be rotating at approximately 20–25 minutes per rotation. [23]
Artificial ice circles have also been created by cutting a large circle in a sheet of ice. [24] These artificial creations are called "ice carousels". Record setting ice carousels are recorded by the World Ice Carousel Association. [25]
In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the left of the motion of the object. In one with anticlockwise rotation, the force acts to the right. Deflection of an object due to the Coriolis force is called the Coriolis effect. Though recognized previously by others, the mathematical expression for the Coriolis force appeared in an 1835 paper by French scientist Gaspard-Gustave de Coriolis, in connection with the theory of water wheels. Early in the 20th century, the term Coriolis force began to be used in connection with meteorology.
Disk storage is a general category of storage mechanisms where data is recorded by various electronic, magnetic, optical, or mechanical changes to a surface layer of one or more rotating disks. A disk drive is a device implementing such a storage mechanism. Notable types are the hard disk drive (HDD) containing a non-removable disk, the floppy disk drive (FDD) and its removable floppy disk, and various optical disc drives (ODD) and associated optical disc media.
Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called nutation. In physics, there are two types of precession: torque-free and torque-induced.
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path. The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating motion in the follower, which is a lever making contact with the cam. A cam timer is similar, and were widely used for electric machine control before the advent of inexpensive electronics, microcontrollers, integrated circuits, programmable logic controllers and digital control.
Westbrook is a city in Cumberland County, Maine, United States and a suburb of Portland. The population was 20,400 at the 2020 census, making it the fastest-growing city in Maine between 2010 and 2020. It is part of the Portland–South Portland–Biddeford, Maine metropolitan statistical area.
In fluid dynamics, a vortex is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in the wake of a boat, and the winds surrounding a tropical cyclone, tornado or dust devil.
A halo is an optical phenomenon produced by light interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky. Many of these appear near the Sun or Moon, but others occur elsewhere or even in the opposite part of the sky. Among the best known halo types are the circular halo, light pillars, and sun dogs, but many others occur; some are fairly common while others are extremely rare.
X-ray pulsars or accretion-powered pulsars are a class of astronomical objects that are X-ray sources displaying strict periodic variations in X-ray intensity. The X-ray periods range from as little as a fraction of a second to as much as several minutes.
A ring galaxy is a galaxy with a circle-like appearance. Hoag's Object, discovered by Art Hoag in 1950, is an example of a ring galaxy. The ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because most of a galaxy consists of empty space, this "collision" rarely results in any actual collisions between stars. However, the gravitational disruptions caused by such an event could cause a wave of star formation to move through the larger galaxy. Other astronomers think that rings are formed around some galaxies when external accretion takes place. Star formation would then take place in the accreted material because of the shocks and compressions of the accreted material.
Frazil ice is a collection of loose, randomly oriented ice crystals millimeter and sub-millimeter in size, with various shapes, e.g. elliptical disks, dendrites, needles and of an irregular nature. Frazil ice forms during the winter in open-water reaches of rivers as well as in lakes and reservoirs, where and when the water is in a turbulent state, which is, in turn, induced by the action of waves and currents. Turbulence causes the water column to become supercooled, as the heat exchange between the air and the water is such that the water temperature drops below its freezing point. The vertical mixing associated with that turbulence provides enough energy to overcome the crystals' buoyancy, thus keeping them from floating at the surface. Frazil ice also forms in oceans, where windy conditions, wave regimes and cold air also favor the establishment of a supercooled layer. Frazil ice can be found on the downwind side of leads, and in polynyas. In these environments, that ice can eventually accumulate at the water surface into what is referred to as grease ice.
The Ehrenfest paradox concerns the rotation of a "rigid" disc in the theory of relativity.
Anchor ice is defined by the World Meteorological Organization as "submerged ice attached or anchored to the bottom, irrespective of the nature of its formation". It may also be called bottom-fast ice. Anchor ice is most commonly observed in fast-flowing rivers during periods of extreme cold, at the mouths of rivers flowing into very cold seawater, in the shallow sub or intertidal during or after storms when the air temperature is below the freezing point of the water, and the subtidal in the Antarctic along ice shelves or near floating glacier tongues, and in shallow lakes.
Daytime as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. In direct sunlight the movement of the sun can be recorded and observed using a sundial that casts a shadow that slowly moves during the day. Other planets and natural satellites that rotate relative to a luminous primary body, such as a local star, also experience daytime, but this article primarily discusses daytime on Earth.
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface.
Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object. It may also describe other motions such as precession or nutation of an object's rotational axis. Prograde or direct motion is more normal motion in the same direction as the primary rotates. However, "retrograde" and "prograde" can also refer to an object other than the primary if so described. The direction of rotation is determined by an inertial frame of reference, such as distant fixed stars.
Arago's rotations is an observable magnetic phenomenon that involves the interactions between a magnetized needle and a moving metal disk. The effect was discovered by François Arago in 1824. At the time of their discovery, Arago's rotations were surprising effects that were difficult to explain. In 1831, Michael Faraday introduced the theory of electromagnetic induction, which explained how the effects happen in detail.
Higher performance in hard disk drives comes from devices which have better performance characteristics. These performance characteristics can be grouped into two categories: access time and data transfer time.
The ice circle of Vana-Vigala is a natural phenomenon appearing on the Vigala River in Estonia while the river freezes.
An ice carousel is a circular piece of ice made to spin like a carousel within a larger body of water, often a frozen lake. It is a man-made phenomenon, made by cutting the floating ice sheet, unlike the natural rotating ice circles.
El Ojo is an uninhabited circular rotating floating island located within a slightly larger circular lake in the Paraná Delta in the Buenos Aires Province, Argentina.
Officials at Baxter State Park in northern Maine shared a photo of an ice disk that's about 30 or 40 feet wide, located in wilderness more than 200 miles north of much larger disk that formed in Westbrook.
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