He argues that radarastronomy, which is used to probe things like asteroids and the surface of Venus, already gives off signals that could be picked up by aliens.
他认为，人类运用雷达天文学探测小行星和金星等天体，早已经发射出可以被外星智慧生物接收到的信号。
2
The technique has been highly successful in radio astronomy, and in both satellite and aircraft borne radar.
该技术在射电天文学、卫星雷达和机载雷达上均获得了巨大成功。
3
This article put a stress on the principle of Doppler effect and its application to astronomy, radar, transportation, medical treatment, etc.