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                                                                                                     R A D A R
Radar was first developed during World War II, around 1942/44. It changed air force behaviour during the war, because it could show airplanes coming from a very big distance giving time to prepare for defense. 
The development was difficult and took a long time. It was necessary to create a complex technology and the engineers were learning during the process. Making the rotating antenna and the screen image  work together and synchronized was a big challenge much more complex that it seems to us, who don’t know anything about electronics. After a long research it was a success. 
But how does it work? How can a machine show a flying object ? In principle its simple. The radar station sends a narrow beam of radio signal to the air. If the signal hits anything the signal is reflected back to the antenna producing a beep on the screen. It’s so precise that the operator can tell the distance, the altitude and the speed of the detected object. It has some limitations of course. If an object is flying close to the ground not higher than 30 meters, radar can’t detect it.
If you pay attention to the movies about war or military missions you will see an antenna spinning over the ship’s deck.

Today even smaller ships, like yachts and fishing boats need radar to navigate  safely. The Titanic sank because at that that time (1912) there was no radar yet. The ship hit an iceberg that would be detected by radar many miles away. Radar made it possible to measure the distance between Earth and Moon with an error of less than one meter.Airliners use radar as well as military planes for many different reasons. The main is to avoid storms and accidents. There are different kinds of radar for different applications and nowadays the digital electronics gave radar a precision never dreamed by its inventors in the 1940’s.

By the way: Did you know that bats use a natural radar for hunting insects at night? The bat sends a narrow ultra-sound whistle in the air and capture the small echo produced by a flying insect. Bats have done this for centuries and their precision is really amazing when we think on how small  insects are. But the bat is not just detecting things. It is trying to survive, and about survival mother nature never play games. 

Anyway, it’s really comfortable to now that the plane we are flying in has “eyes” to see many miles ahead and find a safe path in the sky, isn’t it?

Some words to help you:

Unkown = desconhecido

Beam = feixe

Safely = seguramente, em segurança

Deck = convés(do navio) Obs:há outros significados como “bandeja”  e”plataforma”

Sank (past of Sink)= afundou (do verbo sink= afundar)

Hit = acertar, bater, colidir

Airliner = avião de passageiros

Bat = morcego ( “Batman” lembra alguma coisa?)

Narrow = estreito

Amazing = espantoso(a). admirável

Path = caminho, trajetória

Whistle = assobio, apito (pronuncia-se “uissol”)

1- Radar is very recent technological invention.

2- Radar development was long and difficult.

3- Radar can detect any object in any situation.

4- Radar can detect even icebergs in the sea.

5-Radar was created after World War II.

6- There is an animal that uses radar principles for hunting.