{{Short description | Spherical object made from compacted snow}} {{Other uses}}
thumb|A snowball A '''snowball''' is a spherical object made from snow, usually created by scooping snow with the hands and pressing the snow together to compact it into a ball.<ref name="schmitz">{{Cite book | url = https://books.google.com/books?id=Y1ydBgAAQBAJ&pg=PA206 | page = 206 | title = Physical Chemistry: Concepts and Theory | first = Kenneth S | last = Schmitz | publisher = Elsevier | year = 2016 | isbn = 9780128006009 }}</ref> Snowballs are often used in games such as snowball fights.
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" 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.<ref>{{Cite web |last=Windham |title=Windham {{!}} Y Gaseg Eira |url=https://www.windham.club/dances/y-gaseg-eira |access-date=2023-09-22 |website=Windham {{!}} Y Gaseg Eira}}</ref> This method of forming a large snowball is often used to create the components needed to build a snowman.
The underlying physical process that makes snowballs possible is sintering, in which a solid mass is compacted while near the melting point.<ref>{{Cite book | isbn = 9781421402154 | title = Gliding for Gold: The Physics of Winter Sports | first = Mark | last = Denny | publisher = JHU Press | year = 2011 }}</ref> Scientific theories about snowball formation began with a lecture by Michael Faraday in 1842, examining the attractive forces between ice particles. An influential early explanation by James Thomson invoked regelation, in which a solid is melted by pressure and then re-frozen.<ref name="riley">{{Cite news | url = https://books.google.com/books?id=KDjf7u8ZcboC&pg=PA45 | title = A snowball's chance | first = Frank | last = Riley | date = 1988-01-14 | magazine = New Scientist }}{{Dead link|date=February 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>
==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.<ref name="schmitz"/> In addition, snowballs are difficult to form with dry powdery snow. In temperatures below {{Convert|0|°C|°F|0|abbr=on}}, there is little free water in the snow, which leads to crumbly snowballs. At {{Convert|0|°C|°F|0|abbr=on}} or above, melted water in the snow results in a better cohesion.<ref>{{cite conference |url=https://arc.lib.montana.edu/snow-science/objects/ISSW14_paper_P2.24.pdf |title=Granulation of Snow: Experiments and Discrete Element Modeling |first1=Walter |last1=Steinkogler |first2=Johan |last2=Gaume |first3=Henning |last3=Löwe |first4=Betty |last4=Sovilla |first5=Michael |last5=Lehning |date=2014 |conference=International Snow Science Workshop |archive-url=https://web.archive.org/web/20200328052228/https://arc.lib.montana.edu/snow-science/objects/ISSW14_paper_P2.24.pdf |archive-date=28 March 2020 |location=Banff |pages=733{{ndash}}737 |access-date=28 March 2020 }}</ref> Above a certain temperature, however, the snowball becomes slush, which lacks mechanical strength and no longer sticks together.<ref>{{Cite book | author = Morag Challenor | chapter = No-Ball Snow | page = 157 | title = Does Anything Eat Wasps?: And 101 Other Unsettling, Witty Answers to Questions You Never Thought You Wanted to Ask | editor = New Scientist | publisher = Simon and Schuster | year = 2006 | isbn = 9780743299176 }}</ref> 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.<ref>{{Cite journal | title= Developing Interfacial Phase Diagrams for Applications in Activated Sintering and Beyond: Current Status and Future Directions | first = Jian | last = Luo | journal = Journal of the American Ceramic Society | date = 2012-01-16 | volume = 95 | issue = 8 | pages = 2358–2371 | doi = 10.1111/j.1551-2916.2011.05059.x}}</ref>
==Natural snowballs== {{Main| Snow roller}} Under certain conditions, natural snowballs may form as a result of wind, without human intervention. These conditions are:<ref>[https://www.telegraph.co.uk/topics/weather/6950788/Snow-stories-rare-self-rolling-snow-balls-found-in-UK.html Rare self-rolling giant snow balls found in UK] {{webarchive|url=https://web.archive.org/web/20100112014558/http://www.telegraph.co.uk/topics/weather/6950788/Snow-stories-rare-self-rolling-snow-balls-found-in-UK.html |date=2010-01-12 }}, The Telegraph, January 8, 2010</ref>
* 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;<ref> {{Cite journal|author1=J. Nelson |author2=M. Baker |name-list-style=amp |title = Charging of ice-vapor interfaces|journal = Atmospheric Chemistry and Physics Discussions|year = 2003|volume = 3|pages = 41–73|url = http://www.atmos-chem-phys-discuss.net/3/41/2003/acpd-3-41-2003-print.pdf}}</ref> these wind-rolled frost balls are known as yukimarimo.
Under other rare circumstances, in coastal and river areas, wave action on ice and snow may create beach snowballs or ball ice.<ref>{{cite news |last1=Emerson |first1=Sarah |title=Thousands of Snowballs on This Siberian Beach Are Straight From a Fairy Tale |url=https://www.vice.com/en/article/thousands-of-snowballs-on-this-siberian-beach-are-straight-from-a-fairy-tale/ |access-date=8 November 2016 |work=Motherboard |publisher=Vice Media |date=8 November 2016 |url-status=live |archive-url=https://web.archive.org/web/20161109090438/http://motherboard.vice.com/en_ca/read/thousands-of-snowballs-on-this-siberian-beach-are-straight-from-a-fairy-tale |archive-date=9 November 2016}}</ref> <gallery> 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 </gallery>
==Snow lanterns== thumb|250px|Snowball lanterns {{Main|Snow lantern}} A snow lantern 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 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 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.<ref>University of Oxford libraries [http://solo-prd.bodleian.ox.ac.uk/primo_library/libweb/action/search.do?fn=search&ct=search&vid=OXVU1&vl(freeText0)=0340042230 Retrieved 14 September 2018.] {{Webarchive|url=https://web.archive.org/web/20201017232455/http://solo-prd.bodleian.ox.ac.uk/primo_library/libweb/action/search.do?fn=search&ct=search&vid=OXVU1&vl(freeText0)=0340042230 |date=17 October 2020 }}</ref>
==Gallery== <gallery> Pyramid of Snowballs Large.png|Collections of snowballs arranged in pyramid shape Venceslao Gennaio Castello Buonconsiglio Trento c1400 detail.jpg|A medieval image from Italy of people throwing snowballs ({{c.|1400}}) Ambrogio Lorenzetti 010.jpg|Ambrogio Lorenzetti's ''Winter'' ({{C.|1338–1340}}) </gallery>
==References== {{Wiktionary|snowball's chance in hell}} {{Commons category}} {{Reflist}}
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Ball Category:Play (activity)