Today's globally networked media and communication system has its origins in the 19th century, when, for the first time, messages were sent electronically across great distances.
现代的全球网络媒体和通信系统起源于19世纪,当时信息第一次以电子方式远距离传送。
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A sensor on the aircraft records the time it takes to receive the backscattering of pulses, and that is used to compute distances to the forest canopy and to the soil beneath.