Imam Jafar as-Sadiq has said that among the clusters of stars which we see at night, some are so bright that our sun, in comparison, is quite in - significant. Because of man's limited knowledge, many people during the Imam's time and centuries after him, considered this theory to be illogical, irrational and unacceptable. They could not believe that these small specks of light which are called stars, can have more light than the light of our big bright sun.
About twelve and a half centuries later, it was proved that what he said was quite correct. It has been discovered that there are stars in the universe, which are billions of times brighter than the sun. They are called quasars. The light of quasars is about quadrillion times (ten thousand billion times) the light of our sun. Some of them are at a distance of about 9000 million light years from the earth. The first such quasar was dis-covered in 1927.
Another important theory was that there are many worlds other than our own, that we cannot even count them. Their number is only in the know-ledge of Allah (swt). Just as we have living beings on this planet, there are living beings on many other planets in the universe where conditions are suitable.
Our telescopes are even today not powerful enough to enable us to see what is beyond the quasars. Therefore we do not know how vast the uni-verse is. It can only be surmised that in the universe there would be mil-lions and millions of worlds, which have existed for billions of years and shall continue to do so for billions of years to come. We must therefore accept aa Imam Jafar as-Sadiq has said, that, no one except Allah (swt) knows the number of large and small worlds.