Eric Cloedia aged 14,  for his question:

How does Radar work?

An old sailing ship sent a man aloft in the rigging, His job was to scan the horizon for land, passing ships and gathering storms. Today, a great ship carries, a more dependable lookout. It looks like a huge wire bowl held on its side by a mast. A spike sticks horizontally from Its center. In port, the ribbed disc rests pointing in one direction,

At sea, the disc swings constantly around on its mast like a giant eye scanning the horizon. Which is exactly what it is. It is the ships radar scanner„ Through densest fog and darkest night it reports what it sees to a radar screen below. And it sees everything worth seeing. Land, islands, mountains, ships, planes, and reports~all solid objects as far as the horizon.

Radar is coined from the words radio, direction and ranging. It is powered with a beam of high frequency radio ‑ maybe ten . thousand million cycles a second. Such power is generated from electric impulses and magnetism. The power is beamed out from the antenna. The antenna pulses for maybe a millionth part of a second. Then it rests for perhaps a thousandth part of a second, Then it pulses again. The position of the silhouette of a solid object on the screen gives its direction. The time between impulse and picture give its distance.

The beam from the antenna travels in a straight line until it meets a solid, or fairly solid object. _It travels at 186,000 miles a second. When it hits something solid it does a right about turn. It bounces off clouds, ships and landmarks and returns with an echo to its ending station. The echo arrives back between the sending impu1ses. The further the object, the longer the echo takes to return. The echo of a plane 93 miles away returns in a thousandth part of a second. The beam and the return echo take that much time to make the round trip of 196 miles.

The radio echoes are translated into beams of light. These build the light and dark pictures that appear on the radar screen. The silhouette pictures sweep around the screen in time with the spinning antenna like the fast second hand on a watch.

Different objects form different shadings on the radar screen, A plane can use radar to get an accurate picture of a coastline even when the pilot can see only a carpet of clouds below him, Ground radar can guide a plane to safe landing even in a pea soup fog. Army planes can use radar to spot certain buildings they want to bomb. Submarines can be spotted when only their periscopes show above the water,

There is no knowing how far these powerful scanning beams can pierce the skies. In 1946„ we waited around the radio to hear a strange Pip; A radar beam had been directed at the moon. It bounced off the moons hard face and echoed back to earth with a Pip; This was the first sound to reach us from out of this world ‑ a message from the moon.