2, air conditioning, 1902, Dr. willis carrier invented the first scientific air conditioning system.
3. Internet, which began in America 1969. Under the ARPA (ARPA) protocol, the US military first used it for military connection, and then connected four main computers of UCLA, Stanford University Research Institute, UCSB (University of California) and the University of Utah in the southwestern United States.
4, mobile phone, 1973, Motorola engineer marty cooper invented the world's first commercial mobile phone.
5. The nylon developed by Carothers, an outstanding American scientist, and his research team is the first synthetic fiber in the world.
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