On Jan. 31, 1958, Explorer 1 became the first satellite launched by the United States. Its primary science instrument, a cosmic ray detector, was designed to measure the radiation environment in Earth ...

In late winter, the zodiacal light is visible in the evening in the Northern Hemisphere (false dusk) and in the pre-dawn morning in the Southern Hemisphere (false dawn). In early autumn, the timing ...

Petroglyphs on sandstone at a national park in Chad bear witness to wildlife that once roamed the area before the continent’s ...