Once electricity was discovered, it was used as a "postman", transmitting information at lightning speed. By wire transfer electrical signals learned, transfer telegrams and live human speech. It was a victory over the space! But telephone and telegraph wires will not last for a ship or plane, the train or car.
Bridge the space people helped radio (translated from the Latin word "radio" means "radiate", it has a common root with another Latin word - "radius" - "beam"). To send messages without wires need only radio transmitter and receiver, which are connected by electromagnetic waves, otherwise known as radio waves emitted by the transmitter and received by the receiver.
<span>The history of radio begins with the world's first radio that was created by the Russian scientist Alexander Popov Popov in 1895 constructed a device which, in his words, "to replace the missing man electromagnetic sense" and react to electromagnetic waves. First, the receiver can "feel" the only atmospheric electrical discharges - lightning. And then learned to accept and record on a tape telegrams transmitted by radio. His invention Popov summed up the work of a large number of scientists from several countries.</span>
4000÷2=2000( в месяц)
2000÷4=500( в неделю)
500÷7=71.4(71, если округлить)( в день)
71÷24=2.9( 3, если округлить)( в час)
ну и задача
Joan of Arc
Georgy Konstantinovich Zhukov
Mikhail Illarionovich Kutuzov
Steven Hawking