The idea of man journeying to unknown worlds in outer space, and intelligent extra-terrestrial beings regularly visiting earth appears weird, but is not entirely inconceivable. More than three decades ago man set foot on the moon. Today many artificial satellites are permanently orbiting the Earth. Manned missions to near-Earth orbits have become a regular feature. Scientists take off, conduct experiments in space, and come back. Many unmanned spacecraft have reached and landed on our sister planet Mars. Some have crossed the solar system and are hurtling away in deep space to destinations unknown. Plans are being made to land man on Mars in the coming years. The moon is under speculation for a possible future space station. It is, therefore no fantasy that all these efforts may culminate some day into construction of such space ships as would be capable of carrying researchers to the very distant world of stars and their planets for exploration of the universe. Before the time of large ships, it was not possible to cross the oceans. Those days, the different continents, living in isolation, were sort of unknown worlds to each other. Intrepid sea-voyagers like Columbus, Magellan, and Vasco-de-Gama crossed the oceans and discovered new continents. Airplanes have now bridged the distance between the far-flung landmasses on the earth. Similarly, space ships of the future might make regular inter-planetary or even inter-galactic travel possible. A related aspect of this theme is the phenomenon of UFOs mainly comprising flying saucers and fireballs. They have been reportedly sighted at so many places and by so many persons of undoubted credibility that they cannot be dismissed offhand. Scientists have so far been unable to arrive at a definitive conclusion about them either way. Under the circumstances, one should not deride if such phenomena are speculated upon as communicatory forays of extra-terrestrial origin. The flying saucers may be likened to space ships. The fire of electric balls could be intelligent beings from some distant celestial bodies. If, however, both are some sorts of special phenomena of nature, there must still be some causative factors involved. What are those factors, those forces and principles, which are working behind their mysterious appearance and disappearances? In either case, it is a fit case for comprehensive inquiry and deliberation. Miglay Byena and Manuel Cruz were two young Brazilian engineers engaged in researching the mystery of flying saucers. They had even built a laboratory for the purpose. It was August 1966. Very early in the morning, the two engineers left for Vintem hill. This hill is covered with dense woods and for the last many decades, flying saucers had regularly been sighted there. Almost everyday, some mysterious object from the sky was reported to land there, remain there for some time and then take off. It was the general impression that the extra-terrestrials had chosen this Brazilian hillock as their base station for exploration of the Earth. As the engineers were climbing the hill, some saucer-like object was seen descending; local citizens confirmed this event. The next day, some local boys out on a hunting expedition, found the two researchers lying dead atop the hill. Police investigation and autopsy failed to find any clue into the possible cause of death. Another character in the UFO saga is the fireball. Like its saucer counterpart, this too, has been doing the appear and vanish acts at many places. Eyewitnesses include persons of unimpeachable integrity who just cannot be put in the category of rumormongers. 15 March, 1963. 5:00 am. Eastern Airlines Flight No. 539 was on its way from New York to Washington. A fireball entered the plane at one end, traveled to the other end and vanished near the toilet. Many passengers saw this spectacle but none suffered any harm or injury. Only the air slightly smelt of sulfur or nitrogen oxide. The incident was reported in the magazine 'Nature'. Expert's proffered many possible theories and explanations but nothing definite could be framed. If it was really of the nature of fire or electric charge it ought to have left some effect on the things or persons there. NASA has compiled more than 600 reported sightings of these fireballs. These sizes range from 1 cm to 1 meter. Altogether, about 4,000 witnesses are available. But still no one knows why and how they suddenly appear and then vanish, all the time moving, running, and prancing about and still leaving everything completely unaffected by their visible energy outflow. Like flying-saucers, these fireballs, too, caused no harm to the persons whom they passed at close range or in whose body contact they momentarily came even as the latter could feel the reality of their energy substance. There is a distinct probability that this phenomenon reflects attempts by intelligent beings from some highly advanced extraterrestrial civilization to make some contact with the inhabitants of the earth and understand the local conditions. This friendly outreach should be reciprocated with a matching gesture on our side. The concept of black holes has some bearing. Black holes are big mysteries in space. They are extremely dense with such an unimaginably strong gravitational pull that even light cannot escape them. Hence no information can come out of there. The core and the surrounding region thus become one massive dark area of the dimension of billions of kilometers. Conceptually, it is possible for matter or 'passengers' in this area to travel smoothly from one point to another riding on the extremely strong pull operating there. The movement on this path will be completely effortless. Scientists think that in the black -hole zone the velocity of matter may exceed that of light. Then there are white holes too. These are vast expanses or gaps in the space devoid of any stars or galaxies. White holes are different from black holes. They have neither the gravitational pull of the latter nor any of its weird features. In dimension, of course, they are much larger. Scientists have so far identified more than 10 such white holes. The biggest one stretches across space for 30 trillion light years from one end to another. For all we know, such peculiar holes, in their miniature versions, might exist here on Earth itself. Through these presumed holes, ships and airplanes have been vanishing in the Bermuda triangle area of the Atlantic for a long time. Such sudden and mysterious disappearances of man or material are occasionally reported from other places too. These vanishing tricks remind one of the UFOs. All these mysterious happenings suggest that some sort of contact exists and is being forged between our Earth and other invisible worlds. The following incident is of July 1968. A 70-year-old tailor, Parfit, lived with his sister in an English Village, Sifton Mallet. He had been crippled in war and was so weak that he could hardly leave his bed. One day, he wished to sit near the door. His sister, with the neighborhood girl, put him on a chair and went upstairs. The door opened on the main road outside. When his sister returned after 15 minutes, Parfit was not there. Extensive search inside and outside, far and wide, failed to find him. Parfit had simply vanished as if in thin air. No clue has since been found that could shed light on the cause of his mysterious disappearance. October, 1920. British Labour M.P Victor Gresson was going from Liverpool to address a meeting. Many persons had come to the station to receive him. But Gresson was not on the train. Police inquiry later traced his bag to a London Hotel. The manager told that a man had deposited the bag there, but did not turn up again to collect it. But the manager's description of the man did not fit Gresson at all. Gresson could never be found. What causes people to suddenly vanish like this? Conjectures could be made. Are such phenomena linked with the experimental efforts of some invisible researchers who are engaged in making interstellar journeys possible? Or could it be that small black holes are roaming about hither and tither in the manner of fireballs and are pulling, snatching, and plucking people out of their worldly existence?