David Rawcliffe, house and monument steward at the National Trust's Chedworth Roman Villa cleans a Roman mosiac in the new environmentally-controlled conservation shelter on March 19, 2012 near Cirencester, England. Opened this month, the multi-million pound building allows visitors to walk on suspended walkways just above the 1600-year-old Roman floors and to see recently excavated mosaics not seen for 150 years, with more to be uncovered over the coming year. (Photo by Matt Cardy/Getty Images)

“A small British company with a dream of building a re-usable space plane has won an important endorsement from the European Space Agency (ESA) after completing key tests on its novel engine technology. Reaction Engines Ltd believes its Sabre engine, which would operate like a jet engine in the atmosphere and a rocket in space, could displace rockets for space access and transform air travel by bringing any destination on Earth to no more than four hours away”. – Chris Wickham via Reuters. Photo: Artist's impression of Skylon. (Photo by Reaction Engines Ltd)

Supporters of Ratko Mladic wave flags with his picture and reading in Serbian “Serbian hero” during a rally organized by the ultra nationalist Serbian Radical Party in front of the Parliament building on May 29, 2011 in Belgrade, Serbia. Some 7,000 supporters of the former Bosnian Serb army chief Ratko Mladic, who was arrested on Thursday in a village in Serbia after 16 years on the run, took to the streets of Belgrade, to hear speeches and protest Mladic's arrest. Mladic, who is facing extradition to the The Hague, is accused of war crimes, including the 1995 massacre of 7,500 Muslin men and boys in Srebrenica. (Photo by Srdjan Stevanovic/Getty Images)

Balloons participate in the Balloon Spectacular during Canberra Festival on March 10, 2012 in Canberra, Australia. The annual balloon festival in Canberra is considered one of the best in the world, and is unique in allowing patrons to float above Parliament, embassies and other government buildings. Canberra is celebrating its 99th birthday in 2012, with over 50 events in the 17 day Canberra Festival. (Photo by Cameron Spencer/Getty Images)

An Economic Freedom Fighters supporter shows a mock weapons during a demonstration in Pretoria on April 12, 2017 calling for South African President Jacob Zuma to resign. Tens of thousand demonstrators took part in the march to Union Buildings, the official seat of government, which was organised on Zuma's 75th birthday and came after nationwide rallies against the president last week. Zuma's recent sacking of respected finance minister Pravin Gordhan has fanned years of public anger over government corruption scandals, record unemployment and slowing economic growth. (Photo by Marco Longari/AFP Photo)

A heifer, tied with a rope, turns during “Toro de Cuerda” in the white village of Villaluenga del Rosario, southern Spain September 3, 2016. Dazzling clusters of cube-shaped houses perched on top of Andalusia's olive tree-studded mountains, the “Pueblos Blancos”, or white villages, of southern Spain are named for the lime wash the buildings are painted with to keep the interiors cool. The labyrinths of narrow alleyways are a throwback to when this region was known as Al-Andalus and was part of a medieval Muslim territory. While this region is stunningly beautiful and a big draw to tourists visiting the south of Spain, it is also one of the poorest areas in the country and has one of the highest unemployment rates in the European Union. (Photo by Marcelo del Pozo/Reuters)

In this Tuesday, August 2, 2016 photo released by Xinhua News Agency, people stand on a platform as the Transit Elevated Bus TEB-1 conducting a test run after it unveiled in Qinhuangdao, north China's Hebei Province. The 72-feet long and 25-feet wide Transit Elevated Bus (TEB) powered by electricity can carry more than hundreds passengers, is designed to go over the normal traffic to help ease traffic congestion without having to dig new tunnels or build elevated rail tracks. (Photo by Luo Xiaoguang/Xinhua via AP Photo)

Gymnast Ahmad al-Sawas performs gymnastic moves near damaged buildings in the rebel-held Bustan al-Qasr neighbourhood of Aleppo, Syria March 26, 2016. As Syrian gymnast Ahmad al-Sawas watched his country fall apart, his Olympic dream collapsed too. The last national champion before the fighting began, he knew that supporting the anti-government side in the five-year-old civil war would prevent him from being selected for the Rio Games. (Photo by Abdalrhman Ismail/Reuters)