We wake up in the morning and see the lights all around us. If the light was not reaching then I would not be able to see anything. All was dark. Again, if it happened suddenly the sun stopped shining. It means that if someone switches off a light, it will take 8 minutes for the people of the world to understand it. When we turn off the light it turns off immediately but when the sun stops shining why does it take 8 minutes to turn off? It takes about 8 minutes and 20 seconds for light to reach Earth from the Sun. The speed of light is great, but not infinite. How was the speed of light first discovered? who did it?
Einstein’s famous special laws of relativity are based on light (especially the speed of light). But what is light or what is it made of, and how does it behave, scientists, are still struggling to answer these questions. The behavior of light also seems to be different in different tests. As a result, different scientists talk about light in different ways.
Scientist Newton said that ‘light’ is made up of numerous small particles and these particles have no weight. The name of this particle is ‘Photon‘. From any source these particles i.e. photons come out in swarms and spread all around.
Physicist Huygens said that ‘light’ behaves like a wave.
Meanwhile, Max Planck said another thing. According to him, ‘light’ travels in the form of bunches or packets of packets (called the quantum theory of light).
We know that light travels in a straight line. That is, it continues straight in the same direction as it exits from the source. Bending does not go in any other direction. But when light passes near a strong magnetic field, it bends slightly toward that magnetic field.
Light has a definite speed and that is about 300,000 kilometers per second in a vacuum, meaning it will travel at 300,000 kilometers per second from a source.
Light always travels faster in a vacuum. The denser the medium, the slower the speed of light. For example Light travels through water at three-fourths of the speed it travels in a vacuum. That is, the speed of light in water is 3/4*300000=225000 kilometers per second or two lakh 25 thousand kilometers. And the speed of light in glass is only two-thirds of the speed of a vacuum.
How the speed of light is measured:
In 1675, Professor Wolf Römer of the University of Copenhagen, while working in Paris, first determined the speed of light by observing the eclipse of one of Jupiter’s satellites. And this is called Romer’s Astronomical Method.
But the telescope he uses to do this work, i.e. to observe the satellite of Jupiter, was invented by Galileo and the most interesting thing is that the satellite he used to observe this work was also discovered by Galileo (the satellite is called ‘Io’).
Galileo discovered one on February 7, 1610, and continued to observe Jupiter through it. It was at that time that he discovered the four satellites of Jupiter. The four moons are named ‘Io’, ‘Europa’, ‘Ganymede’, and ‘Callisto’ and are the largest moons of Jupiter so far.
Let’s say a ball is placed on a table far away from us. We are looking at it with a powerful telescope. The ball suddenly fell off the table. The exact moment the ball falls, but we cannot see the ball fall. Because, when the ball falls, the light that will come from the ball towards us will take time to travel that long distance. That is, when the light at the moment of falling crosses that path and reaches our eyes, we will see the scene of the ball falling.
What Romer did this time is to find out the extra time by calculating the time of the eclipses of ‘Ior’ when the minimum and maximum of Earth and Jupiter are at these two positions or distances.
And at this time the additional distance that was increased, i.e. the distance from ‘A’ to ‘B’ was already known (because it is the diameter of the earth). If you divide the extra distance by that extra time, you get how far the light travels in a single time i.e. one second. And this is the speed of light.
According to his calculation, the extra distance is 29,90,00,000 plus 1000 seconds, which when divided is 2,99,000 kilometers or 186,000 miles per second.