How was the speed of light first measured?
The light journey of science: from Al Hazen to Einstein
Egypt is the gift of the Nile. That blue river flooded Egypt every year. That trend has been going on for ages. The Egyptian caliph of the tenth century wanted permanent relief from that flood. For this he took refuge in the Iraqi scholar al-Hasan ibn al-Haysam. Latin and European scientists know him as Al Hazen. Hazen came to Cairo. After observing the flood situation, he undertook a project to build a dam. Hazen checked a lot and saw that it was not possible to build a dam. But he did not speak to the caliph. Instead, he kept asking for time day after day. There are many benefits to being a Raj Pandit. Research can be done as desired, there is no shortage of money.
It is not possible to build a dam, so Al Hazen started scientific research by enjoying that money and royal benefits. He did some basic work on the light. The famous Greek philosopher and mathematician Euclid thought that light came out of the human eye. That light falls on the object. Then people see that object. Euclid's idea is wrong, even the school children here understand it. But in the tenth century it was not so easy to understand. Greek scholars in world science were then the seat of the gods. In the second century, Ptolemy established most of Aristotle's views with one misinterpretation after another. Light is no exception. Euclid kept it at bay for ages with misinterpretations of misconceptions. Al-Hazen axed the idea. He said that we see the object only when the light is reflected from the object and falls on our eyes, not from the human eye. Many then rushed in, He shouted that he was born. How dare any Al-Hazen to throw out Wickleid-Ptolemy's theory! Hajen was then supported by two famous Arab scholars, Ibn Sina and al-Biruni.
Al-Hazen researched light with the money to build the dam
Al-Hazen could not build the dam. So the caliph went mad at one time. It is said that Hazen remained in Egypt pretending to be insane. Secretly researched light. Kitab al-Manazir, a huge book of seven volumes, has written about light. The English translation is called the Book of Optics. In this book, Hazen says that when light travels from a dense medium to a light medium, its speed decreases. Earlier people thought the speed of light was infinite.
Hazen's idea was later inspired by the famous thirteenth-century French scholar Roger Bacon. He agrees with al-Hazen that the speed of light is too high. More than words, but speed is not infinite. Then there was another theory about the speed of light. Scholars thought that the speed of light through zero was infinite, but the light slowed down as it passed through the air medium.
Al-Hazen's theory also inspired the famous German scientist Johann Kepler in the seventeenth century. He also wrote a famous book on optics called Optics. That book feeds Newton's light research. One of the foundations. In that book, Kepler writes that there is no impediment to the movement of light through zero.
1829 The Dutch philosopher Isaac Beckmann proposed an experiment. A ray of light coming out of a cannon, it has to be reflected in a mirror one mile away. If it takes time for the reflection to return, then it can be confirmed that there is a limit to the speed of light. But no one tried that test.
Recently, the Italian physicist Galileo Galilei did one such experiment. However, Galileo did not know about Beckman's proposal. Galileo saw that light does not take time to cover distances. That was Galileo's mistake. The speed of light is too high. 1 lakh eighty six thousand miles per second. So it would take only a fraction of a hundred and eighty-six thousandths of a second for light to be reflected from a mirror one mile away. Galileo did not have the technology to measure such a small amount of time. So he didn’t realize it took time for the light to go on.
Al-Hazen researched light with the money to build the dam
French astronomer Giovanni Cassini. At some point in the middle of the seventeenth century, he noticed an amazing event. We know that the planets in the solar system revolve around the sun. Everyone has a specific orbit. Orbits are not round. Elliptical. So its planets are not always at equal distances from each other. The same thing happens with Earth and Jupiter. Cassini was observing the eclipses of Jupiter's satellites. The eclipse of Jupiter's satellite can be predicted in advance. And that's very easy. Cassini observed that at a time of year when Jupiter is very close to Earth, the eclipse can be seen a few minutes ahead of the previously estimated time. At the same time of year when Jupiter is farthest from the Sun, the eclipse is seen a few minutes after the estimated time. What does this mean? Cassini did not have an explanation. That's when Dennis astronomer Ole Christensen Romer came forward.
When light from an object or source hits the retina of our eye, we see that object. The difference between the two eclipses of Jupiter is due to the fact that it takes two different times for light to come from two places. Roma thought it meant one thing. The action of light is not an instantaneous event. That is, light has a certain speed. However, the speed of light is very high.
The distance between Jupiter and Earth is a lot. The difference in distance between the two different times of the year is not less. So the eclipse of Jupiter's satellite proves that the speed of light is fixed. Roma measures the speed of light by one hundred and forty-four thousand miles per second. It is much less than modern measurements. But at that time the speed of light was not so fine. So this value measured by Romer is very important.
In the seventeenth century, Christian Higgins said, light, like sound, travels in waves. Earlier, Newton said that light is actually a collection of moving tiny particles. The medium is needed to move in waves. Let's catch the word. The sound makes waves in the chest of the wind. Then the wind shook and he spread around. What does the wave of light make waves on? There is no question of making waves in the air. If so, what is the medium of light movement?
Then scientists imagined an invisible medium. The name is its ether. It is assumed that ether exists even in empty space. But the problem remained. If light travels through the ether, that ether key is everywhere. Light rays from distant stars also travel through the medium of ether? Or is the whole universe immersed in ether?
In 175 the Scottish physicist James Clark Maxwell established his famous electromagnetic equations. This equation is called light electromagnetic waves. Coming out of Maxwell's equations, no medium of light wave is needed to move. Dynamic magnetic fields give rise to electric or electric conditions and dynamic electric fields give rise to magnetic states. It is from this idea that Maxwell's theory of electromagnetism was born. And this theory raises doubts about the concept of ether. Because out of here came a certain value of the speed of light. And that is one lakh eighty six thousand miles or three lakh kilometers per second.
The problem is with the ether. Maxwell could not accept the matter of ether. The sound waves in the air. The sound wave lasts as long as it can hold the minimum power. We see that sound waves cannot run continuously. At one point it was forced to stop due to wind obstruction. If ether is such a medium of light, then it is able to stop the light at once! But the light can never be stopped. Maxwell shared his ideas with the editor of the Royal Society's journal, Proceedings of the Royal Society. But the editor did not find Maxwell's idea reasonable. The American physicist Albert Michelson was inspired by Maxwell's ideas.
In 18 he conducted an experiment with another American scientist, Edward Morley. Michelson-Morley tested the speed of light twice relative to the Earth. Once the speed of light is determined towards the speed of the earth. From a light source, Michelson and Morley twice sent two rays of light into two mirrors. Twice they found the speed of light to be exactly the same. This test proved that the speed of a moving train at the station is different from that of any other moving bus or train, this does not happen in the case of lighting.
If there were ether waves, two results could be obtained twice. But Michelson-Morley got the same result. If so, what was the ether barrier? The Michelson-Morley experiment proved that there is no such thing as ether. The test is, the proof is. But the explanation was not. However, the existence of ether broke down. We have to wait for this for a long time.
That is, the existence of ether broke down. But many scientists could not accept that. They set up various projects to overcome the complexities of ether. Some scientists in particular were reluctant to exclude ether. So they took a different approach to retaining the ether. One of these was the project of the Irish scientist Fit Gerald. He said it would take longer for the light sent in the direction of motion to return, but the length of the interferometer had shrunk due to the motion. That is, the direction of light has decreased. This trajectory decreases as much as the light sent along the north-south can return at the time it returns. The amount of compression will depend on the velocity of the object. Here the interferometer is moving at the speed of the earth. He calculated that if an object 1 m long traveled at half the speed of light, its length would be reduced to 0.6 m.
Based on his project, the Dutch scientist Hendrik Anton Lorenz undertook another project. Fitzgerald and Lorentz co-founded the Fitzgerald-Lorentz project. How many equations do they use in this project? Maxwell's electromagnetic equations can be used in two different contextual structures through the Fitzgerald-Lorentz project. Einstein used these formulas in his theory of relativity. But Fitzgerald and Lorentz wanted to use the equations to save the ether and prove that the speed of light is not constant. Einstein used them to prove the constant speed of light. In relativity, Einstein replaced Galileo's transformation equations with Lorentz's transformation equations.
These problems emerge from the Michelson-Morley experiment. But they could not solve. The solution came in 1905. Holding Albert Einstein's hand. The constant of the speed of light came out. Einstein added that there could be no object faster than the speed of light. Einstein's theory still reigns supreme in the natural sciences. Source: New Scientist
