Editing Snow (section)

===Sports and recreation===
[[File:Ski Famille - Family Ski Holidays.jpg|thumb|Alpine skiing]]
{{Main|Winter sport}}
Snow figures into many winter sports and forms of recreation, including [[skiing]] and [[sledding]]. Common examples include [[cross-country skiing]], [[Alpine skiing]], [[snowboarding]], [[snowshoe]]ing, and [[Snowmobile|snowmobiling]]. The design of the equipment used, e.g. skis and snowboards, typically relies on the bearing strength of snow and contends with the [[coefficient of friction]] bearing on snow.

Skiing is by far the largest form of winter recreation. As of 1994, of the estimated 65–75 million skiers worldwide, there were approximately 55 million who engaged in [[Alpine skiing]], the rest engaged in [[cross-country skiing]]. Approximately 30 million skiers (of all kinds) were in Europe, 15 million in the US, and 14 million in Japan. As of 1996, there were reportedly 4,500 ski areas, operating 26,000 ski lifts and enjoying 390 million skier visits per year. The preponderant region for downhill skiing was Europe, followed by Japan and the US.<ref>
{{cite book
 | last = Hudson
 | first = Simon
 | title = Snow Business: A Study of the International Ski Industry
 | publisher = Cengage Learning EMEA
 | series = Tourism (Cassell)
 | date = 2000
 | pages = 180
 | url = https://books.google.com/books?id=tGRLt8tG-kMC&pg=PA27
 | isbn = 9780304704712}}</ref>

Increasingly, ski resorts are relying on [[snowmaking]], the production of snow by forcing water and pressurized air through a [[Snowmaking#Snowmaking guns|snow gun]] on ski slopes.<ref>{{US patent reference|number=2676471|inventor=W. M. Pierce Jr.|title=Method for Making and Distributing Snow|issue-date=December 14, 1950}}</ref> Snowmaking is mainly used to supplement natural snow at [[ski resort]]s.<ref>[http://news.bbc.co.uk/onthisday/hi/dates/stories/march/25/newsid_2786000/2786871.stm On This Day: March 25] {{webarchive|url=https://web.archive.org/web/20110412010130/http://news.bbc.co.uk/onthisday/hi/dates/stories/march/25/newsid_2786000/2786871.stm |date=April 12, 2011 }}, [[BBC News]], accessed December 20, 2006. "The first artificial snow was made two years later, in 1952, at Grossinger's resort in New York, USA. "</ref> This allows them to improve the reliability of their snow cover and to extend their ski seasons from late autumn to early spring. The production of snow requires low temperatures. The threshold temperature for snowmaking increases as humidity decreases. [[Wet-bulb temperature]] is used as a metric since it takes air temperature and relative humidity into account. Snowmaking is a relatively expensive process in its energy consumption, thereby limiting its use.<ref>{{citation|url=http://bachler.cms1.ch/Portals/41/docs/energy_usage_for_snowmaking.pdf|title=Energy usage for snowmaking|author=Jörgen Rogstam|author2=Mattias Dahlberg|name-list-style=amp|date=April 1, 2011|url-status=live|archive-url=https://web.archive.org/web/20140201200900/http://bachler.cms1.ch/Portals/41/docs/energy_usage_for_snowmaking.pdf|archive-date=February 1, 2014|df=mdy-all}}</ref>

[[Ski wax]] enhances the ability of a ski (or other runner) to slide over snow by reducing its coefficient of friction, which depends on both the properties of the snow and the ski to result in an optimum amount of lubrication from melting the snow by friction with the ski—too little and the ski interacts with solid snow crystals, too much and capillary attraction of meltwater retards the ski. Before a ski can slide, it must overcome the maximum value static friction. Kinetic (or dynamic) friction occurs when the ski is moving over the snow.<ref name="Bhavikatti">{{cite book
| url = https://books.google.com/books?id=4wkLl4NvmWAC&pg=PA112
| title = Engineering Mechanics
| last = Bhavikatti
| first = S. S.
|author2=K. G. Rajashekarappa
| page = 112
| access-date = October 21, 2007
| publisher = New Age International
| isbn = 978-81-224-0617-7
| year = 1994}}</ref>