Convex lenses can focus light. This optical phenomenon is known to modern children, but in the Han Dynasty, it seemed very magical.
Liu Xiang thought about words that would make them understand: "If the sun hits your body, you will feel warm. That means the sun is hot, right?"
"Yes." Zhao Aier nodded vigorously.
Zhao Jing and others also nodded, everyone knows this.
Fei Changfang didn't nod. He was listening attentively and carefully, trying to remember every word.
"This kind of lens with two convex sides can gather a lot of sunlight together and generate a lot of heat." Liu Xiang pointed to the convex lens made of ice: "Come on, put your hands under here and feel it."
Zhao Aier took two steps forward, put her hand under the lens, and a large spot of light fell on the white palm of her hand. She didn't feel any heat, but felt that the ice cube was cold.
"It's so cold, my hands are freezing."
Liu Xiang stretched out his hand and put it on her wrist. He pressed her hand and moved it downwards, looking for a focus. He did not withdraw his hand until the light spot in her palm gathered into a light spot.
"You'll feel the heat after a while."
Zhao Aier didn't feel any heat on her hands, only her ears felt warm, and she hurriedly lowered her head to hide her shyness.
But he didn't notice the guards and attendants surrounding him winking and smiling meaningfully.
Only Fei Changfang stared at the light spot in her palm extremely seriously, as if he had some realization.
But after looking at it for a while, I felt that the light spot was dazzling and very uncomfortable. There was always a black spot when I looked at things, just like looking directly at the sun and being blinded.
"The power of sky fire cannot be looked directly at, and this is evident from this." He muttered in a low voice, confirming that Liu Junhou had used ice to borrow the sky fire. He felt even more awed and thought about a lot of mysterious things in his mind.
After this period of relief, Zhao Aier finally came back to her senses. She felt like she was holding hot coals in her palms and quickly retracted her hands.
She turned to look at Liu Xiang in surprise: "It's so hot, as if it was burned by fire."
"This is the heat generated by gathering sunlight."
When the others saw Zhao Aier's reaction, they all stretched out their hands to feel it. They were all dumbfounded and felt it was extremely magical.
Liu Xiang continued to explain: "Concentrating sunlight produces heat, and the accumulation of heat ignites the tinder. This is the principle of convex lenses igniting fire out of thin air."
"Can tinder be lit without fire?" Zhao Aier was confused.
Liu Xiang nodded: "Yes, drilling wood to make fire and focusing light to start a fire both use the accumulation of heat to ignite the flame."
After saying this, everyone understood that using light to make fire would feel very magical, but everyone was familiar with making fire by drilling wood. Not only had they heard the myths and legends about Suiren's making fire by drilling wood, but they had also done it themselves.
Only Fei Changfang thought deeply and muttered: "The gathering sky fire should be regarded as fire in the sky, but it is made from water. This is a combination of obstacles and separation. This move must have deep meaning."
He actually had a more bold idea in his mind, but he didn't dare to say it out loud: The ancient Suiren clan drilled wood to make fire and became a god. This person can gather heavenly fire, so he has a great background!
Zhao Aier, who came to attend the class together, did not think about those magical things. She just felt that her mood was restless today and her desire to seek the truth was not firm. She was not like her usual self.
In order to firmly believe in the Tao, she silently picked up the wooden board and tinder to master the first spell in her life.
There was no trouble in the process, and the flame ignited smoothly.
A small flame spread among the tinder. Her heart was beating fast and her breathing was a little rapid. She turned to look at Liu Xiang excitedly and said happily: "I have learned a spell! Is this spell called Void Fire? Or is it called Fire in the Void?
Borrowing fire from heaven?"
"This is not magic, this is knowledge." Liu Xiang shook her head, feeling helpless. Such a senior superstitious person clearly told her the principle, but she still had to understand it in terms of gods and ghosts.
"It's knowledge, it's knowledge, I know it!" Zhao Aier nodded perfunctorily, whatever you say is fine, since she has learned magic anyway.
happy!
Looking at the increasingly handsome Liu Junhou, her heartbeat never slowed down.
"I've hosted a banquet, please, please." Liu Xiang was not going to go on. He couldn't let these two people know about the telescope.
He waved his hand to the craftsmen to carry the ice cubes down.
Fei Changfang didn't want to waste time on banquets. He learned the principles of heaven and earth today, and thoughts were flooding in his mind. He wanted to retreat and meditate to understand the great road.
"Today I am fortunate enough to receive a sermon from you. I have learned a lot. I urgently need to calm down and understand. There is no need to have a banquet. Don't blame me."
Zhao Aier really wanted to have a drink and talk with Liu Junhou, but it was difficult to refute Master Fei's face.
The days are long, she can just visit her again later, she persuaded herself in her heart.
The two said goodbye and left.
Liu Xiang was very happy that he didn't have to waste time at the banquet, so he didn't try too hard to stay. After they left, he recruited the craftsmen back.
"Carve two lenses, one with convex sides and one with concave sides, one inch in size is enough. Then take two bamboo tubes, which can be put together and telescopically pulled. The lens must be inlaid on the bamboo tube."
All he has to do is make requests, and how to implement them is the craftsman's business.
The craftsmen summoned today are all carefully selected as supervisors, skilled in craftsmanship, and loyal and reliable. Such a simple request cannot stump them.
It's ready in a matter of seconds.
The thick bamboo tube is inlaid with a concave lens. The concave lens can diffuse the light and form an upright, reduced virtual image, making the image distance longer.
This is the objective lens.
The thinner bamboo tube is inlaid with a convex lens, which can magnify the image of the concave lens and make it easier for the human eye to receive.
This is the eyepiece.
The inner and outer walls of the two bamboo tubes have been polished and smoothed. They are set together and can be pushed and pulled back and forth to find the focusing position.
The telescope made of ice cubes and bamboo is very rough, the lens is not pure enough, and the vision is unclear.
There is no light-absorbing treatment inside the lens barrel, so there is reflection interference, which affects the visual effect.
The bamboo tube connection is not smooth and the feel is not good.
The gap is too large, causing light interference again.
Lots of problems.
However, no matter how rough it is, it is true that it can see distant scenery.
It worked.
It brings together jade craftsmen who are good at fine carving, mirror craftsmen who are good at grinding, and gold and silver craftsmen who are good at making exquisite jewelry.
Using bamboo tubes and ice cubes, he made the first version of a monocular telescope, which was also a retractable telescope with adjustable focus.
Standing on the watchtower of the high platform, using a primitive telescope, I looked at the figures on the south city wall and the blurry crowds at the market outside the city.
Liu Xiang was happy.
He stretched out his hand and handed it to the craftsmen, letting them see the effect and know what they had done.
Several craftsmen took turns to watch, and after going through several rounds of processes ranging from disbelief, wonder, to admiration, these craftsmen finally knew what they had made.
"clairvoyance!"
This is Zhao Jing's conclusion.
After the craftsman read it, it was finally Zhao Jing's turn who was already scratching his head with curiosity, and then he came to this conclusion.
"Clairvoyance, this is clairvoyance, the Lord will do clairvoyance!"
"Stop talking nonsense, it will be good if you can see for more than ten miles." Liu Xiang turned to look at several craftsmen and made a new request:
"Water jade is used as the lens, and brass is used as the lens tube. The two lens tubes must be tightly sealed to prevent light from entering. The inner wall of the lens tube must be painted black to prevent reflection and affect the observation effect. Can this be done?"
"General Qi, you can do it."
Although the telescope is beyond their knowledge, they have physical reference and with their craftsmanship, they are confident that it can be made exquisitely.
Liu Xiang has "guided" many craftsmen over the years, and this is the most specific one. He believes in the craftsmanship of Han craftsmen.
"How many sets of lenses can that piece of water jade cut?"
"At least eight groups." The jade craftsman relied on years of experience and judged that the piece of jade could be cut into sixteen rough blanks, enough to make eight pairs of concave and convex lenses.
Liu Xiang nodded and encouraged: "Go ahead and do it. If you do it well, I will not hesitate to reward you with military titles and money. It is in your own hands. Whether you can hold it firmly depends on your skills."
"We will do our best to create an exquisite clairvoyance for the general!"
Large rewards can always mobilize people's enthusiasm. This is a timeless truth.
"This matter must be kept secret, and no trace of it can be leaked. But if a few words are leaked to the outside, they will be severely punished."