Astronaut Force Base. Astronauts is training must learn how to control and fly the Space Shuttle and, it is vital that they are familiar with the International Space Station so they know what they must do when they get there. Mission Specialist Educators, or "Educator Astronauts", were first selected in 2004, and as of 2007, there are three NASA Educator astronauts: Joseph M. Acaba, Richard R. Arnold, and Dorothy Metcalf-Lindenburger. Barbara Morgan, selected as back-up teacher to Christa McAuliffe in 1985, is considered to be the first Educator astronaut by the media, but she trained as a mission specialist. The Educator
Chinese as a foreign language neutral (轻声，denoted as no-mark in Pinyin) although the official name of the tones is Four Tones. Many other Chinese dialects have more, for example, Cantonese has six (often numbered as nine, but three are duplicates). In most Western languages, tones are only used to express emphasis or emotion, not to distinguish meanings as in Chinese. A French Jesuit, in a letter, relates how the Chinese tones cause a problem for understanding: Moser also stated that tones were a contributing factor to the difficulty of learning Chinese, partly because it is difficult for non-native learners to know how to convey emotion