New tombs found in Giza support the view that the Great Pyramids were built by free workers and not slaves, as widely believed, Egypt's chief archaeologist said on Sunday. Films and media have long depicted slaves toiling away in the desert to build the mammoth pyramids only to meet a miserable death at the end of their efforts. "These tombs were built beside the king's pyramid, which indicates that these people were not by any means slaves," Zahi Hawass, the chief archaeologist heading the Egyptian excavation team, said in a statement. "If they were slaves, they would not have been able to build their s tomb beside their king's." He said the collection of workers' tombs, some of which were found in the 1990s, were among the most significant finds in the 20th and 21st centuries. They belonged to workers who built the pyramids of Khufu and Khafre. In 2004, NASA's Opportunity rover found evidence in Martian soils that water Hawass had earlier found graffiti on the walls from workers calling themselves "friends of had once flowed across the surface there, buoying hopes that the red planet may Khufu" - another sign that they were not slaves. once have supported primitive life. The tombs, on the Giza plateau on the western edge of Cairo, are 4,510 years old and lie at But a new study throws some cold water, and a big pinch of salt, on those the entrance of a one-km (half mile)-long necropolis. hopes. "Liquid water is required by all species on Earth and we've assumed that water is the very least that would be necessary for life on Mars," said study team member Nicholas J. Tosca, a Harvard University postdoctoral researcher. "However, to really assess Mars' habitability we need to consider the properties of its water. Not all of Earth's waters are able to support life, and the limits of terrestrial life are sharply defined by water's temperature, acidity and salinity." Tosca and his team analyzed salt deposits in the 4-billion-year-old Martian rock investigated by Opportunity. The new analysis shows that the water that would have flowed across these ancient Martian rocks may have been exceedingly briny. "Our sense has been that while Mars is a lousy environment for supporting life today, long ago it might have more closely resembled Earth," said Andrew H. Knoll, also of Harvard and on the study team. "But this result suggests quite strongly that even as long as four billion years ago, the surface of Mars would have been challenging for life. No matter how far back we peer into Mars' history, we may never see a point at A number of years ago， I had the rather unique experience of being backstage in Madison Square Garden， in New York， during the Ringling Brothers Barnum & Bailey Circus． To say the least， it was a fascinating experience． I was able to walk around looking at the lion tiger giraffes and all the other circus animals． As I was passing the elephant I suddenly stopped， confused by the fact that these huge creatures were being held by only a small rope tied to their front leg． No chain no cages． It was obvious that the elephants could， at any time， break away from their bonds but for some reason， they did not． I saw a trainer near by and asked why these beautiful， magnificent animals just stood there and made no attempt to get away． “Well，” he said， “when they are very young and much smaller we use the same size rope to tie them and， at that age， it's enough to hold them． As they grow up， they are conditioned to believe they cannot break away． They think the rope can still hold them， so they never try to break free．” I was amazed． These animals could at any time break free from their bonds but because they believed they could not， they were stuck right where they were． Name Class Grade One of Australia's most remarkable natural gifts, the Great Barrier Reef is blessed with the breathtaking beauty of the world's largest coral reef. The Great Barrier Reef is the world's largest reef system[1][2] composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres (1,600 mi) over an area of approximately 344,400 square kilometres (133,000 sq mi). The reef is located in the Coral Sea, off the coast of Queensland in northeast Australia.The reef contains an abundance of marine life and comprises of over 3000 individual reef systems and coral cays and literally hundreds of picturesque tropical islands with some of the worlds most beautiful sun-soaked, golden beaches. The Great Barrier Reef is one of the seven wonders of the natural world, and pulling away from it, and viewing it from a greater distance, you can understand why. It is larger than the Great Wall of China and the only living thing on earth visible from space. which the planet really looked like Earth." The research was presented in February at the annual meeting of the American Association for the Advancement of Science in Boston. Halophiles, or organisms that can tolerate high-salinity waters, are known to exist in places on Earth, but they likely evolved from organisms that lived in purer waters, scientists think, making it unlikely that life would actually arise initially in extremely briny waters. The high salinity, however, "doesn't rule out life forms of a type we've never encountered," Knoll added, "but life that could originate and persist in such a salty setting would require biochemistry distinct from any known among even the most robust halophiles on Earth." Knoll and Tosca also say the finding doesn't rule out the possibility that less salty waters once flowed on the planet. 本文来源：https://www.wddqw.com/doc/5c89de59f56527d3240c844769eae009581ba2c3.html