Skeleton involves a person riding a small sled down a frozen track while lying face down. The sport is a more intense form of luge because skeleton competitors leap onto the sled and slide downhill head first. Skeleton athletes can reach up to 80 mph on straightaways, causing forces up to 5g, so the helmet is a critical component for attitude as well as safety.

A mass pillow fight in Trafalgar Square in central London on April 5, 2014 on International Pillow Fight Day. (Photo by Jane Scanlan)

The competition, which is run by the Royal Observatory Greenwich in association with BBC Sky at Night Magazine, is now in its sixth year and has received over 2,500 entries. Photo: Centre of the Heart Nebula by Ivan Eder (Hungary). Situated 7500 light years away in the “W”-shaped constellation of Cassiopeia, the Heart Nebula is a vast region of glowing gas, energized by a cluster of young stars at its centre. The image depicts the central region, where dust clouds are being eroded and moulded into rugged shapes by the searing cosmic radiation. (Photo by Ivan Eder)

Revellers celebrate "Ash Monday" by participating in a colourful "flour war", a traditional festivity marking the end of the carnival season and the start of the 40-day Lent period until the Orthodox Easter,in the port town of Galaxidi, some 215 km (134 miles) north west of Athens, March 18, 2013. The revellers "fight" by throwing coloured flour, charcoal dust and powder painting until they essentially run out of supplies. (Photo by Yannis Behrakis/Reuters)

“News of a ceasefire is greeted by wild celebrations on the streets of Gaza, whilst Israeli residents of Jerusalem and Tel Aviv are more cautious in their support for the peace deal”. – Reuters

Photo: Palestinian gunmen hold a poster of late Ahmed Jabari, head of the Hamas military wing in Gaza City, while they celebrate the cease-fire agreement between Israel and Hamas in Gaza City, Wednesday, November 21, 2012. Israel and the Hamas militant group agreed to a cease-fire Wednesday to end eight days of the fiercest fighting in nearly four years, promising to halt attacks on each other and ease an Israeli blockade constricting the Gaza Strip. (Photo by Adel Hana/AP)

Pope Benedict XVI arrives at the Santa Sabina Basilica for the Ash Wednesday service on March 9, 2011 in Rome, Italy. Ash Wednesday opens the liturgical 40-day period of Lent, a period of prayer, fasting, penitence and alms giving leading up to Easter.

Members of the Black Hebrews community celebrate the Shavuot harvest festival on June, 19, 2011 in Dimona, Israel. The community, who call themselves the African Hebrew Israelites of Jerusalem, moved to Israel in 1969 from the United States and have since maintained a vibrant culture which includes a communal lifestyle and a vegan diet. They are not recognized as Jews by Israel despite their belief in the Torah, but were granted permanent resident status in 2003. (Photo by Uriel Sinai/Getty Images)

Fireworks explode around the London Eye wheel, the Big Ben clock tower and the Houses of Parliament to mark the beginning of the New Year in London, Britain, January 1, 2016. (Photo by Toby Melville/Reuters)