Participants climb over a wall at the “Tough Mudder” endurance event series in Arnsberg September 6, 2014. Competitors who took part in the endurance event saw themselves having to overcome various military style obstacles. (Photo by Ina Fassbender/Reuters)

Some are in it just for the money, others to help buy a meal. Then there are those who trade for fun or to spend time among friends. Millions of investors – pensioners, security guards, high-school students – dominate China's stock markets, conducting about 80 percent of all trades. Retirees gather in brokerage houses dotted around China also to enjoy some company and savour the air conditioning on hot days. Some start as young as 13, trading from home with an eye on future careers in finance. Winning isn't guaranteed. This year, among the most turbulent in China's financial history, its stock markets more than doubled in the six months to May, only to crash amid concerns that growth in the country, which makes everything from cars to steel, is slowing faster than previously thought. (Photo by Aly Song/Reuters)

Back dropped by planet Earth the International Space Station (ISS) is seen from NASA space shuttle Endeavour after the station and shuttle began their post-undocking relative separation May 29, 2011 in space. After 20 years, 25 missions and more than 115 million miles in space, NASA space shuttle Endeavour is on the last leg of its final flight to the International Space Station before being retired and donated to the California Science Center in Los Angeles. Capt. Mark E. Kelly, U.S. Rep. Gabrielle Giffords' (D-AZ) husband, has lead mission STS-134 as it delivered the Express Logistics Carrier-3 (ELC-3) and the Alpha Magnetic Spectrometer (AMS-2) to the International Space Station. (Photo by NASA via Getty Images)

Lightning strikes the Willis Tower (formerly Sears Tower) in downtown on June 12, 2013 in Chicago, Illinois. (Photo by Scott Olson/Getty Images)

A man transports the carcass of a car on a two- wheeled carriage in a neighborhood in Abobo, a suburb of Abidjan, Côte d’Ivoire on December 1, 2017. (Photo by Issouf Sanogo/AFP Photo)

A sign that reads “No more massacres LGBT” is seen to remember the victims of the Pulse nightclub mass shooting in Orlando, near the U.S. Embassy in Mexico City, Mexico, June 14, 2016. (Photo by Edgard Garrido/Reuters)

A worker looks at Spring Festival decorations ahead of Chinese Lunar New Year festivities in Beijing, China on January 12, 2023. (Photo by Thomas Peter/Reuters)

Twin brothers Keith (L) and Deano Stapleton (R) interact with one another as people gather to witness the winter solstice on December 21, 2022 in Newgrange, Ireland. Crowds are gathering at Newgrange in Co Meath, this morning for the winter solstice – the astronomical phenomenon that marks the shortest day and the longest night of the year. Newgrange is a Stone Age (Neolithic) monument in the Boyne Valley, County Meath, it is the jewel in the crown of Ireland's Ancient East and was constructed approximately 5,200 years ago (3,200 B.C.) which makes it older than Stonehenge and the Great Pyramids of Giza. (Photo by Charles McQuillan/Getty Images)