One of the greatest achievements of Imam Ja'far as-Sadiq was his Theory of Light. He said that light reflected by different objects comes to us, but only a part of the rays enter our eyes. That is why we do not see distant objects clearly. If all the rays of light that come from them entered our eyes, objects would appear near to us. If we make a device through which all the rays of light coming from the camels grazing at a distance of 3,000 zirah (one zirah is equal to 40 inches) entered our eyes we would see them grazing at a distance of only 60 zirah and all other objects would look 50 times nearer to us.
It was this theory, which helped Lippershey of Flanker's to make his first field glasses or binoculars in 1608. Galileo made use of these binoculars and invented his telescope on the 7th of January, 1610. When he directed his telescope towards the moon he was surprised to see that it has mountains, plains and valleys just as we have on the surface of the earth. It was at that time that he realized that earth was not the only world. The moon was also a world.
The period between the invention of the binoculars and the telescope was less than two years. Most probably the idea of making the binoculars and telescope entered the minds of Lippershey and Galileo at the same time, but it cannot be denied that Galileo leant a lot from the invention of Lippershey. He examined the binoculars, removed the defects which could possibly be removed at that time and made his telescope.
Galileo had studied in the University of Padua, Italy. After he completed his education he was appointed Professor of mathematics in the same university.
If Imam Ja'far as-Sadiq had not formulated his theory of light, binoculars and telescopes would not have been invented and made and Galileo could not have confirmed through visual observation the theories of Copernicus and Kepler that all planets including the earth, rotate around the sun.
The invention of telescope created so much excitement among the people of Italy that the President of the Republic and the senators became interested to see the solar system through it. Galileo took his telescope from the University of Padua to Venice and installed it on the steeple of a church. Aged senators, assisted by others, climbed the tower to observe the planets and stars.
When Galileo was asked why his telescope made heavenly bodies seems so near that they could see the mountains of the moon, he repeated the words of Imam Ja'far as- Sadiq and said, "This telescope collects all the rays of light coming from the heavenly bodies. When all the rays are concentrated, the objects which are at a distance of 3,000 feet away appear to us as if they were at a distance of only 60 feet. "
In the time of Ja'far as-Sadiq (as), the industry had made no progress to enable him to make a telescope and observe heavenly bodies himself. Nevertheless it does not, in any way, reduce the importance of his theory. Could Newton, who discovered the laws of Gravitation, send the apple which had fallen on the ground back to the sky and make it go round the earth?
The satellites which go to the moon, Venus and Mercury obey the laws of Gravitation discovered by Newton, but he himself could not send any satellite to the planets. Before the time of Imam Ja'far as-Sadiq, it was believed that light from our eyes falls upon different objects so that they could be seen. He was the first scholar who rejected that idea and said, "The rays of light from different objects come to our eyes and enable us to see them. The rays of light from our eyes do not go out and fall on other objects; otherwise we could have seen them in the darkness also. We see only those objects which are luminous. If they are not luminous themselves, they must reflect the light falling upon them from some luminous objects. "
He also put forward a very interesting theory about the speed of light. He has said that light is a kind of motion which is very fast. Since no technical aids were available he could not measure the speed of light, but what he said is quite in harmony with the modern theory of light.
It is reported that once, during the course of his lectures he said that a powerful beam of light could move heavy objects. The light which Moses saw at Mount Sinai was of that kind. It could have moved the mountain if God had so desired. It can be said that by making the above statement he laid the foundation of the theory of the laser.
The theory that a strong beam of light can move heavy objects was also mentioned in the past but the following theories are his own:
Rays of light are reflected by different objects and enter our eyes.
We do not see distant objects clearly because the rays of light coming towards us are scattered.
If the rays of light are concentrated by some device we can see distant objects distinctly.
Light is a kind of motion which travels as a very high speed. A strong beam of light can move heavy objects.
From time Immemorial, it was supposed that light could move heavy objects. In ancient Egypt it was believed that a very strong beam of light could pass through a mountain and even move it from its place. This view was shared by the followers of other ancient religions as well, but they did not explain how light could do that. Since sorcery and magic were parts of ancient religions they might have thought that light could do that by magic.
What Imam Ja'far as-Sadiq did not say about light is that it is a kind of energy otherwise there is no difference between his theory and the modern theory of light. He was definitely a leader and a pioneer in this field as well. He has said that light travels very fast. The speed of light has been measured to be 300,000 kilometers per second. It was very great speed by ancient standards, but is not considered as such today. A distance of 300,000 kilometers is a very short distance as compared to the astronomical distances between stars and galaxies.