ECHOES OF BATS AND MEN 



than those facing a bhnd man or a bat, and human m- 

 genuity may eventually solve this type of problem along 

 with the others mentioned in previous chapters. 



Radar 



The detection of distant aircraft by echoes of radio 

 waves stands as one of mankind's major technical ac- 

 complishments. In miUtary results alone it has well re- 

 paid the billions of dollars spent on its development 

 and on manufacture of military radar systems. Not only 

 can ground- or ship-based radar systems detect airplanes 

 at hundreds of miles but smaller radars carried on air- 

 planes can locate other aircraft and also resolve a sur- 

 prising amount of detail on the ground below. Radar 

 systems developed for the purpose can draw crude but 

 highly useful maps of hundreds of square miles of ter- 

 rain in a fraction of a second. The maps are drawn 

 on specialized cathode-ray oscilloscope screens. Radar 

 echoes can also be used to locate and track clouds and 

 storms, birds and locusts, meteors, earth satelUtes, and 

 ballistic missiles. Shortly after World War II, radar 

 echoes were successfully detected from the moon. In 

 1958, for the first time, very faint echoes from the 

 planet Venus were detected. Although this book can- 

 not discuss radar thoroughly, certain basic similarities 

 are well worth considering, and it is even possible to 

 make a rough comparison of the performance and effi- 

 ciencies of radar systems and natural hving systems that 

 have evolved to enable bats to navigate and catch insects 

 in the dark. 



Relative Efficiency of Bats and Radar 



As with the sonar system we discussed, this compari- 

 son wiU be based on radar systems that served well in 



120 



