Peering into a clear sky on a starry night, one can experience and marvel at the unique beauty of the universe around us in the harmonious space of three dimensions. This observed space is filled with familiar heavenly objects - planets, stars, the Milky Way and much more. The mystifying spectacle of the night’s firmament has evoked a myriad of questions in the mind of the Homo sapiens during more than two hundred thousand years of its existence on earth. The earliest answers to these questions derived from superstition, philosophy, religion and fear abound in the literature and folklore of all peoples. But, it was not until the Renaissance period that scientific methods were applied and theories developed to explain the motion of stars and planets.
The early Greeks postulated that planets and other observable heavenly bodies move around a fixed earth that is located at the center. This was the concept of a geocentric universe. Around 300 B.C., Aristarchus of Samos floated the idea that the sun was fixed and the planets including the earth were in circular orbits around the sun. This was the first attempt of a heliocentric concept of the universe. This concept, however, was too revolutionary for the time and was rejected, and the geocentric theory continued to be the accepted theory. In the second century A.D., Claudius Ptolemaeus ( Ptolemy), a Greek astronomer to whom the geocentric concept is generally attributed, farther amplified the geocentric theory of the universe.
In 1543, Nicolaus Copernicus (1473-1543), a Polish astronomer of German descent, published De revolutionibus orbitum coelestium (On the Revolutions of the Heavenly Spheres) and reintroduced the idea of a heliocentric universe. Although there were inaccuracies in his theory, it was a major advance in concept.
Johannes Kepler (1571-1630), a Viennese mathematician and an assistant to Danish nobleman astronomer Tycho Brahe (1546-1601), analyzed his own observations and those of Tycho Brahe and arrived at three laws of planetary motion known as Kepler’s Laws that form the basis of modern celestial mechanics.
Galileo Galilei (1564-1642), an Italian physicist, astronomer and philosopher, who is considered the father of scientific method, was the first observer using a star gazing telescope and he lent credence to the Copernican model of the universe.
Sir Isaac Newton (1643-1727), British physicist, astronomer, mathematician, alchemist, and inventor actively pursued the theories of the “modern” scientists such as Copernicus and Kepler. In 1661, he joined Trinity College, Cambridge where he became a Professor. In 1666 he took an 18-month “sabbatical” as Cambridge closed due to Plague epidemic and proceeded to develop the basis for:
- Laws of motion
- Laws of Gravity
- Modern Optical Theory
- Differential Calculus
In 1687, Newton published Philosophiae Naturalis Principia Mathematica (“Mathematical Principles of Natural Philosophy”) also known simply as Principia. In Principia, Newton established his three laws of motion regarding Inertia, Acceleration and Action/Reaction. He also enunciated the law of gravitation that every mass attracts every other mass by a force directed along the line connecting the two. This force is proportional to the product of the masses and inversely proportional to the square of the distance between them.
Whereas Kepler described how planets move around the sun, Newton’s laws gave the mathematical basis for doing so. Newton’s discovery catapulted astronomy into a new era and opened the avenue for computing trajectories and orbits of man-made satellites.
The foregoing discourse mainly pertains to the near earth space where lies the more practical and immediate interest of mankind. Man has made significant strides in utilizing this space for a multitude of benefits—both civil and military. The near earth space is indeed the next logical frontier for adventure of mankind. This space presents the ultimate high ground for humanity from which to control its own destiny. This is the space where man has begun travel. Travel to the moon has already been accomplished and manned travel to the planet Mars is being contemplated. Artificial earth satellites packed with ultra sensitive sensors for multitude of missions are now hurtling through space in elliptical orbits around the earth gathering and/or transmitting data. In the process, our understanding of our own planet and the rest of the universe is leapfrogging and communication and entertainment through radio and television media has precipitated a global village environment. The Hubble Space Telescope, the Gamma Ray Observatory and the Chandra X-Ray Observatory are all armed with sensors operating far beyond the range of human senses. Results of observation made by these instruments from the vantage point of space unperturbed by the blanket of atmosphere that envelops the earth, have revolutionized our understanding of the cosmos. The International Space Station moving at a near earth orbit at an altitude of about 250 statute miles is now serving as a manned outpost in space to facilitate a variety of activities in a unique free fall environment.
Furthermore, one cannot overemphasize the military implications of utilization of space. During the last quarter of a century, the star war scenario has been visualized. When the Chinese destroyed one of their own satellites recently using a rocket, lot of eyebrows were raised around the world. Similarly, a recent successful destruction of a defunct satellite by USA using rockets by precision strike of the hydrazine propellant tank of the satellite, also proved how space can be militarized if wanted. Today, global military and battlefield communication is dependent on satellites. Debilitating these satellites will wreak havoc on strategy of military planners.
An indispensable part of the space exploration is the delivery vehicles which lift off with space deliverables to place them at the right place in space. Variety of rockets like Atlas and Delta series of USA, Soyuz of Russia, Long March of China, Ariane of Europe, H-Series of Japan and PSLV & GSLV rockets of India are now all delivering space articles. For more than a quarter century now, Space Shuttles that will be retired in 2012, have been regularly making rendezvous with the International Space Station (ISS) to deliver man and material.
Trying to understand the nature of the universe unto its furthest realm is the other strong urge of mankind regarding space. The universe as we know today consists of billions of galaxies including our own Milky Way Galaxy of which Sun is a part. The size of the universe is mind boggling-at least 93 billion light years across meaning that it will take light wave traveling at a speed of 186,000 miles/sec, 93 billion years to travel from one end of the universe to the other. According to the well-accepted Big Bang Theory, the universe began at one cosmic moment about 13 .73 billion years ago from a single point of infinite mass and energy when there was nothing else around. Initially the universe was small and dense. With time it expanded and the current thinking is that it is expanding at a ever faster rate meaning that the galaxies are moving farther apart from one another. The question then is what is the destiny of our universe? There does not seem to be an answer yet.
Umesh C. Tahbildar
- Log in to post comments