LEDs begin to dominate

Introduction and background

"God said that if there is light, there will be light. When God sees the light is good, he separates the light from the darkness." I am sure that most of us are very fond of the first two sentences in Genesis. Familiar, and whether you believe it or not, the fact remains that our world does have darkness and light. But what is it? Where does the light come from? How did it come about? What will it look like in the future?

These questions are very good, but in this article, I don't want to answer them one by one. I just want to review the brief history of light, from about 14 billion years ago to today. Why did it start 14 billion years ago? Because we know that according to the detection of the NASA Wilkinson Microwave Anisotropic Probe (-WMAP), 14 billion years is about the age of the universe. The detector is used to detect the universe with subtle accuracy and to detect the microwaves from the depths of the farthest universe, the cooling fireball formed by the Big Bang itself. Of course, our own solar system (including the sun and the earth) is much younger than the universe itself, only about 4.5 billion years old. Therefore, the main source of light on the earth is the sun. Later, about 4 billion years ago, the moon formed. No one knows exactly how the moon formed, although there are four main assumptions, namely fusion, capture, co-formation, and big impact (see Wikipedia for more information on these assumptions). However, no matter how the moon is formed, by reflecting the sun's photons back to the Earth's surface, the moon provides us with an extra source of light at night.

It is widely believed that humans (erects) appeared on Earth about 1 million years ago, and 1 million years in the galaxy of the universe is nothing more than a blink of an eye! Obviously, the sun is the main source of illumination for these early humans, Because it was not until a long time later that there was an artificial lighting source. In fact, many scientists believe that there is irrefutable evidence that early humans created a controllable fire about 125,000 years ago. That is, humans made torches, and torches became the first artificial light source. However, it was not until 17,000 years ago that prehistoric humans used lamps to illuminate them. These lamps are usually made of shells, rocks or animal horns filled with animal or vegetable oil and fueled with a fiber wick. After another 10,000 years, the fuel of these lamps included olives, nuts, sesame or fish oil. In the next 5000 years, the materials used in these lamps have undergone many changes. Then, around 500 BC, Pythagoras proposed the "particle" theory of light. The theory assumes that all visible objects emit a steady stream of particles that bombard our eyes. He further proposed that "light consists of rays, which are like tentacles. Rays travel from the eye to the object in a straight line. When these rays touch the object, they acquire vision."

It was not until 400 AD that the next advancement in the field of lighting emerged, that is, the invention of candles. For the next 1400 years, candles became the main source of illumination. However, an important discovery of great significance for modern lighting occurred in 1666, when Isaac Newton, who was only 23 years old, did his famous prism experiment. He noticed and recorded that the sunlight is white light, which contains all the colors of the spectrum. Similarly, in 1752, Benjamin Franklin made his famous experiment with a kite. He invented the lightning rod and explained the phenomenon of positive and negative electricity. Benjamin Franklin's work is important, and his inventions and principles were used when he invented incandescent bulbs about 100 years later. Next, in 1792, William Murdock produced gas by heating the coal and used it to illuminate his home and office in Cornwall, England. This is the first time that a gas has been used as a fuel to produce artificial light. Later, in the early 19th century, after the discovery of natural gas, gas lighting became the mainstream in homes, offices, factories and street lamps.

In 1877, Thomas Edison became interested in electric lighting and experimented. A year later, with the help of a friend, he founded the Edison Electric Light Company. The company's goal is: "Own, manufacture, and operate a variety of devices used to generate light, heat, or power through electricity. And to provide permission to use such devices." Although Edison did not invent the filament lamp, he did turn the theory into a practical form and was one of the first to successfully distribute incandescent lamps. The first patent covering incandescent lamps was actually submitted in 1874 by Henry Woodward and Matthew Evans, about five years earlier than Edison's development of electric lights. However, perhaps the German chemist Herman Sprengel was the first to invent the vacuum bulb, which he invented in 1865.