A snowball is a

spherical A sphere (from Ancient Greek, Greek , ) is a surface (mathematics), surface analogous to the circle, a curve. In solid geometry, a sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...

object made from

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

, usually created by scooping snow with the hands and pressing the snow together to compact it into a ball. Snowballs are often used in games such as

snowball fight A snowball fight is a physical game in which Snowball, balls of snow are thrown with the intention of hitting somebody else. The game is similar to dodgeball in its major factors, though typically less organized. This activity is primarily play ...

s. A snowball may also be a large ball of snow formed by rolling a smaller snowball on a snow-covered surface. The smaller snowball grows by picking up additional snow as it rolls. The terms "

snowball effect A snowball effect is a process that starts from an initial state of small significance and builds upon itself (an exacerbating feedback), becoming larger (graver, more serious), and also perhaps potentially more dangerous or disastrous (a vicio ...

" and "snowballing" are derived from this process. The Welsh dance " Y Gasseg Eira" also takes its name from an analogy with rolling a large snowball. This method of forming a large snowball is often used to create the components needed to build a

snowman A snowman is an Anthropomorphism, anthropomorphic snow sculpture of a man often built in regions with sufficient snowfall and is a common winter tradition. In many places, typical snowmen consist of three large snowballs of different sizes wit ...

. The underlying physical process that makes snowballs possible is

sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plas ...

, in which a solid mass is compacted while near the melting point. Scientific theories about snowball formation began with a lecture by

Michael Faraday Michael Faraday (; 22 September 1791 – 25 August 1867) was an English chemist and physicist who contributed to the study of electrochemistry and electromagnetism. His main discoveries include the principles underlying electromagnetic inducti ...

in 1842, examining the attractive forces between ice particles. An influential early explanation by James Thomson invoked

regelation Regelation is the phenomenon of ice melting under pressure and refreezing when the pressure is reduced. This can be demonstrated by looping a fine wire around a block of ice, with a heavy weight attached to it. The pressure exerted on the ice s ...

, in which a solid is melted by pressure and then re-frozen.

When and how

When forming a snowball by packing, the pressure exerted by the hands on the snow is a determinant for the final result. Reduced pressure leads to a light and soft snowball. Compacting humid or "packing" snow by applying a high pressure produces a harder snowball, sometimes called an ice ball, which can injure an opponent during a snowball fight. Temperature is important for snowball formation. It is hard to make a good snowball if the snow is too cold. In addition, snowballs are difficult to form with dry powdery snow. In temperatures below , there is little free water in the snow, which leads to crumbly snowballs. At or above, melted water in the snow results in a better cohesion. Above a certain temperature, however, the snowball becomes

slush Slush, also called slush ice, is a slurry mixture of small ice crystals (e.g. snow) and liquid water. In the natural environment, slush forms when ice or snow melts or during mixed precipitation. This often mixes with dirt and other pollutan ...

, which lacks mechanical strength and no longer sticks together. This effect is used in the rule that, in skiing areas, there is a high risk of avalanche if it is possible to squeeze water out of a snowball.

Natural snowballs

Under certain conditions, natural snowballs may form as a result of wind, without human intervention. These conditions are: * The ground must have a top layer of ice. This will prevent the snowball from sticking to the ground. * That ice must have some wet and loose snow that is near its melting point. * The wind must be strong enough to push the snowballs, but not too strong. In Antarctica, small windblown frost balls form through a different process that relies on

electrostatic attraction Coulomb's inverse-square law, or simply Coulomb's law, is an experimental law of physics that calculates the amount of force between two electrically charged particles at rest. This electric force is conventionally called the ''electrostatic f ...

; these wind-rolled frost balls are known as yukimarimo. Under other rare circumstances, in coastal and river areas,

wave action In fluid dynamics, a wind wave, or wind-generated water wave, is a surface wave that occurs on the free surface of bodies of water as a result of the wind blowing over the water's surface. The contact distance in the direction of the wind is k ...

on ice and snow may create beach snowballs or ball ice. File:Jää on kulmunud pallideks (Looduse veidrused). 05.jpg , Ball ice File:Yukimarimo_south_pole_dawn_2009.jpg , Yukimarimo File:Snow roller (30 January 2014) (Newark, Ohio, USA) 53 (46107487244).jpg , Wind-rolled snowball File:Spongy ice ball Lake Street.jpg , Beach snowball showing signs of denivation

Snow lanterns

snow lantern A snow lantern is a hollow cone built of snowballs into which a light is put, usually a candle or a Japanese stone garden lantern ''Yukimi Gata''. People lighting their own snow lanterns is one of Sweden's, Finland's and Norway's Christmas trad ...

is a decorative structure made from snowballs, typically shaped into a hollow cone. It is commonly used as a housing for a light source, such as a

candle A candle is an ignitable candle wick, wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a Aroma compound, fragrance. A candle can also provide heat or a method of keeping time. ...

or a Japanese stone garden lantern known as ''Yukimi Gata''. Snow lanterns are part of winter traditions in countries such as Sweden, Finland, and Norway, where they are created and lit during the

Christmas Christmas is an annual festival commemorating Nativity of Jesus, the birth of Jesus Christ, observed primarily on December 25 as a Religion, religious and Culture, cultural celebration among billions of people Observance of Christmas by coun ...

season. These structures illuminate the winter landscape and are associated with festive celebrations in snowy regions.

Literary allusion

A snowball that turns into a child is a protagonist in a 1969 children's fantasy novel, '' The Snowball'', by

Barbara Sleigh Barbara Grace de Riemer Sleigh (1906–1982) was an English children's writer and broadcaster. She is remembered most for her Carbonel series about a king of cats. Family and career Barbara Sleigh was born on 9 January 1906 in Birmingham, the d ...

.University of Oxford librarie
Retrieved 14 September 2018.

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References

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Ball A ball is a round object (usually spherical, but sometimes ovoid) with several uses. It is used in ball games, where the play of the game follows the state of the ball as it is hit, kicked or thrown by players. Balls can also be used for s ...

Play (activity)