had been open to the world for races, cultures, and ideas to intermix with one another, along with the fact that this blend of both locals and outsiders from diverse backgrounds that were open to accepting cultural differences. Nation-building and modernity reduced the role of trade through the sea and increased the reliance on trade through the land and the air in economic and social exchange. Even though Singapore, Bangkok, and Hong Kong are still vibrant and available to the world, similar to their early modern counterparts serving functions such as tourism which is unrelated to foreign trade, only a few ports are as economically crucial today as they had been in the past. Inland trade moved both by water, and overland itself. For example, shipping in small boats went along the coasts of India, but inland waterways were readily available to use to transport goods throughout many parts of India, especially in the south. Caravans that contained numbers from ten, all the way to up forty thousand pack or draft animals moved overland at a time. Combinations of these forms of transportation carried throughout the subcontinent and were therefore transshipped to and from long-distance maritime trade. The majority of all of the port cities were in symbiosis with the caravan routes to and from their related hinterland interiors, and sometimes even with distant transcontinental regions. This is especially true in Central Asia - and it is suggested that the continental trade over both the land and the ocean maritime trade should be viewed not as separate or competitive, but rather as mirror images of one another. Air Humanity's desire to fly likely dates to the first time man observed birds, an observation illustrated in the legendary stories of Daedalus and Icarus in Greek mythology, and the Vimanas in Indian mythology. Much of the focus of early research was on imitating birds, but through trial and error, balloons, airships, gliders and eventually powered aircraft and other types of flying machines were invented. Kites were the first form of man-made flying objects, and early records suggest that kites were around before 200 BC in China. Leonardo da Vinci's dream of flight found expression in several designs, but he did not attempt to demonstrate flight by literally constructing them. During the 17th and 18th century, when scientists began analysing the Earth's atmosphere, gases such as hydrogen were discovered which in turn led