the speed of light

Light

To know the speed of light at best, we must understand the light: it is an electromagnetic radiation visible to the human eye, whose wavelength varies between 380 and 750 nm.

Electromagnetic radiation is generated in the form of light by vibratory changes of electrically charged particles, such as parts of "hot" particles or electrons in the atoms (both processes play a role in the incandescent filaments of incandescence, while the latter occurs in fluorescent lamps). .

Electromagnetic radiation extends from rays and X-rays to radio waves and long waves. This is often called the "electromagnetic spectrum"

The light moves from sun to earth after traveling 149 million kilometers. It is estimated at 186,000 miles per second, which means that the light we see now is still very far out in the sun 8 minutes ago and that it is about twice as long to go from the sun to the earth than to prepare a cup of coffee.

the speed of light

Is the speed at which light waves propagate through different materials. Its importance is much broader than its role in describing the properties of electromagnetic waves

Since the dawn of time, philosophers and scientists have sought to understand light and to know its fundamental properties (particles or waves) and to accurately measure their speed of movement until they understand the light and the importance of their light. role in physics, astronomy and cosmology.

The speed of light (1.07 billion) at 1,079,252,848.8 km at the same time is 299,792,458 miles per second or 670,616,629 mph, a fixed speed. Traveling at the speed of light is like turning around the world seven and a half times a second.

Meanwhile, a person flying at a speed of about 800 km / h (500 mph) will take more than 50 hours to circle the planet once. On the astronautical plane, the distance from Earth to the Moon is 38,439.25 km (238,854 miles) and the light travels in about one second.

The distance between the sun and the Earth is approximately 149,597,886 km, while the light takes only 8 minutes to make the journey. Light has imaginary speeds, the fastest moving object in the universe, which is why the speed of light is used as a measure of astronomical distance.

History of the discovery of the theory

• The Greek philosopher Aristotle was the first to speak of the speed of light. He explained the movement of light with the Greek world Imbedox: "The light moves and will take time to travel, says Aristotle to oppose it: this light moves immediately.
• In 166 Galileo Galileo arrested two people on a plateau less than two kilometers away, each carrying a lantern covered and revealing the first lantern which, once seen, revealed its lantern. By observing the time required for the light to appear from the first lantern carrier (taking into account reaction times), Galileo thought he could calculate the speed of light. Unfortunately, Galileo's dimensions were too small for him to be able to see the difference. It is therefore only able to determine that the light is ten times faster than the sound.
• In 1670, the first real measure of the speed of light by the Danish astronomer Eul Romer was the trajectory of Jupiter's moon eclipse and a few months later, when Ayo pbaded behind the giant gas planet Romer discovered that the eclipse had arrived too late. Expectations were more right over the months. It was determined that light took time to move from Ayu to Earth and that eclipses slowed further when Jupiter and Earth were at the highest point. It was at the scheduled time when they were at the nearest point. He found that it took 10 to 11 minutes to light to move from the sun to the Earth. This estimate is exaggerated because it actually takes 8 minutes and 19 seconds. But finally, the scientists had a number to take into account – its calculation of the speed of light of 125 000 km / s (200 000 km / s).
• In 1728, the physicist James Bradley tried to measure the change in the stars due to the rotation of the earth around the sun. The speed of light was set at 185,000 km / h (301,000 km / s) accurately, so the error does not exceed 1%.
• In the mid-nineteenth century, two experiments challenged the controversy. French physicist Hippolyte Fizeau projected rays of light onto the wheel of a fast-moving sled and a mirror five miles (5 km) to reflect the light at its source.
• The different speed of the wheel allowed the physiologist to calculate the time that light travels to move out of the hole to the neighboring mirror and back through the space. Another French physicist, Leon Foucault, used a rotating mirror instead of a wheel and the two independent methods resulted in a result close to about 1,000 km / s of measured measured light velocity aujourd & # 39; hui.
• Albert Michelson (born in Prussia and growing up in the United States) restored Foucault's style in 1879 by using a longer distance, as well as high-quality mirrors and lenses. The result of 186,355 mpg (299,910 km / s) was accepted as a more accurate measure of the speed of light for 40 years, when Michelson recounted it.

Light formula

The properties of light show the relationship between the speed of light, the wavelength and the frequency. Is a very simple but important relationship, and the formula lies in the following equation: C = λ. F

• C = Speed ​​of light
• λ = Length of light wave, usually measured in meters or ngngströms (1 = = 10 -10 m)
• F = Frequency transmitted by light waves, measured in units per second (1 / s)
• The speed of light is always constant, so it always has the same value.

But if something changes wavelength or frequency, the other thing must also change, but in the opposite direction. That is, the low wavelength increases the frequency, and vice versa