In order to transmit useful information to distant places as soon as possible, ancient China built many beacon towers on the road from the distant frontier to the capital. When there is a war or other emergency on the border, the bonfires will be lit one by one, and the information will be sent to the emperor of the capital. However, the beacon tower is expensive and needs someone to watch it all the time, but it can't convey the specific content of the information. So a lot of information has to be transmitted by manpower.
In 490 BC, the Greeks defeated the Persian army in the marathon and won the victory in defending their homeland. In order to let the people in the capital share this good news as soon as possible, without any means of transportation, the generals of the Greek army sent a soldier named Fidipi to walk from the marathon plain to Athens, the capital of Greece at that time. When Ferdinand reported the good news of victory to the people in the capital, he finally fell down and died because of extreme fatigue. In order to commemorate this hero forever, people listed the whole distance he ran (42 195 meters) as a long-distance race and named it a marathon. In ancient times, how difficult it was for people to transmit information. In ancient times, people tried their best to find the fastest way to transmit information. However, they can only create "clairvoyance" and "clairvoyance" in fairy tales to pin their ideals.
The ideal of "listening to the wind" was finally realized by an American painter, who was the inventor of the telegraph-Morse.
/kloc-One autumn at the beginning of the 9th century, on a sailboat, a group of passengers gathered around a doctor named Jackson and listened to him talk about the newly invented electromagnet: a horseshoe-shaped iron block with wires wound around it, which will be very attractive when electrified; As soon as the current is cut off, all the absorbed iron substances will fall down. Everyone is attracted by this new thing. Morse happened to be there then. Curious as he is, he thinks deeper and further than the people around him. He asked Jackson a question: does the current flow fast in the wire (it can be seen that Morse has no knowledge of electricity)? When he knew that the speed of current was so fast that it could pass through a wire several meters long in Qian Qian in an instant, a bold and novel idea came to his mind.
The encounter on the seagoing ship changed Morse's life path. He gave up his beloved painting career and began the arduous research work of inventing the telegraph. After more than ten years, he finally succeeded. He invented the telegraph and the code for representing information by stippling ── "Morse code" (one of the codes selected from the current primary school science textbooks), which made communication convenient.
Although telegrams can quickly transmit information content, the sender must first convert the information content into symbols and send the symbols to the receiver according to certain operating rules. After the receiver receives this symbol, it is still very troublesome to translate what it represents with code. It would be great if we could directly transmit language signals! Humans will never be satisfied. After the invention of the telegraph, they brought themselves new problems.
The first person to declare war on this difficult problem and win was Bell, an American teacher who studied deaf language. When Dambert began to study this difficult problem, he knew nothing about electricity. But in the process of studying human vocal cords, he believes that sound is produced by the vibration of vocal cords. Can this vibration be caused by the change of current intensity? Can you change the vibration of an object into a changing current, and then restore the changing current to the vibration of the object to make a sound? This is really a big problem.
In order to realize his dream, Bell came to Washington thousands of miles away to learn electrical knowledge from scratch. After three years of hard work, with the help of mechanic Watson, he finally made the world's first set of microphones and receivers at 1876. The ideal of spreading sound by electric current has come true. But at that time, the telephone noise was too loud and the transmission distance was too short, which was far from practical application.
1878, the great inventor Edison made great improvements to the telephone, which increased the communication distance to 100 kilometers.
19 15, Bell further solved a series of technical problems caused by long-distance telephone calls, and finally set up the first telephone line in the United States with a length of more than 6,000 kilometers this year.
Now, the telephone has become an indispensable communication tool in people's lives. In some developed countries, there is a telephone for every 1 ~ 2 people on average. There are more and more functions of the telephone: some phones can automatically record the message content of the other party on the tape when the owner is away; Some can transmit handwritten words or graphics at the same time besides talking; Some even allow callers to meet through the screen in front of the phone. This is more magical than the mythical clairvoyance and clairvoyance, because this kind of videophone has the dual functions of clairvoyance and clairvoyance at the same time.
2. A powerful bronze mirror
One day in 2 12 BC, the powerful Roman Empire launched an attack on the weak ancient Syracuse. The enemy troops approached Syracuse from the sea and land at the same time, and the whole country was in danger.
At that time, according to the king's order, Archimedes assumed the command to defend Syracuse.
Seeing the Roman fleet getting closer and closer, Archimedes still stood calmly on the castle, overlooking the distant bay. Suddenly, an idea flashed through his mind: "What a powerful sun! I hope your strength can help me save the good people of Syracuse. " He decisively ordered all women to pick up bronze mirrors and gather at the seaside.
At this time, the enemy saw many women in white robes gathered on the dock of the port, but they couldn't figure out what Archimedes was playing.
When the Roman fleet approached the dock step by step, it suddenly saw a bright beam coming from the opposite side. These beams kept moving, and finally, hundreds of beams focused on one point. That point, surprisingly bright and hot, landed on the big sail of the ship and caught fire.
The fire spread with the sea breeze, and suddenly, the whole fleet was in a sea of fire. Panicked Roman soldiers, covered in fire, jumped into the sea one after another.
The Syracuse women on the shore were all in high spirits, holding the mirror and cheering loudly: "The Romans were beaten back, the Romans were beaten back!" " "