Earth Day, celebrated on April 22 each year, marks the anniversary of the birth in 1970 of the modern environmental movement in the United States.
每年4月22日的“地球日”(Earth Day)是1970年在美国诞生的现代环保活动纪念日。
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The first recording in Potsdam of such teleseisms on April 17, 1889 marks the birth of the study of the structure of the Earth by means of seismic waves ( see blog January 14, 2009).