OUR PLACE IN THE UNIVERSE : The Universe, has for ages, captivated human imagination with its sheer scale of size - distance and time. We could at best observe around 9,600 stars in the open sky on a clear night with naked eyes. Using a dedicated 2.5 metre wide-angle Apache Point Observatory in New Mexico (US), the Sloan Digital Sky Survey (SDSS) has hitherto mapped 35% of the sky involving 250 million celestial objects. Recent precision measurements gathered by Hubble-based telescopes and the findings of the Wilkinson Microwave Anisotropy Probe (WMAP) suggest the Universe to be 13.75 billion years old. According to the controversial inflationary hot Big Bang model for the origin and nature of the Universe, the Big Bang, an offshoot of backward extrapolation of Einstein’s theory of general relativity, is a mathematically obscure state - a ‘singularity’ of zero volume that contained infinite density and infinitely large energy. It refers to the grand event at which not only matter but space-time itself was born. The exponential inflation(expansion) that followed in the immediate aftermath of Big Bang along with the phenomenon of quantum fluctuation have been primarily responsible for presence of whatever celestial structures we notice in the observable universe today. Apparently, the age of the Universe should be the product of the age of Universe and speed of light, meaning thereby that the diameter of the present Universe should be 27.5 billion light years (1 light year is the distance travelled by light in 1 year @ 300,000 km/sec). But it is not so. According to Einstein’s general theory of relativity, there is really expansion of space between the galaxies that dot the Universe. Taking the spatial expansion into account, the observable Universe is estimated to measure around 93 billion light years from one end to the other. More recent estimates, however, put the diameter of the Universe at 156 billion light years. Though largely empty, the Universe is studded with a staggering number of 1,000 - 4,000 billion galaxies. The spiral- shaped Milky Way Galaxy, our parent galaxy (measuring 100,000 light years across), in which the solar system is located, is estimated to contain around 1,000 - 4,000 billion stars, making the conservative estimates for number of stars in the observable Universe as mind-boggling one trillion trillion (1 followed by twenty four zeros, i.e. 1,000, 000, 000,000,000,000,000,000)- more than all sand grains on all the beaches on Earth as hinted at by the noted astronomer, Carl Sagan. Despite presence of stars on gargantuan scale in the observable Universe, stars make up very small fraction of our Universe constituting just 0.4 per cent of the mass of the Universe. Invisible dark matter and dark energy together constitute 96 per cent of the mass of the Universe. Vastness of space and time in the Universe could also be visualized from the fact that if the age of the Universe was condensed into one year, the written human history occupies just last 10 seconds of that year. Our mother planet, Earth that orbits the Sun, is just an ordinary member of the Solar system. The Sun, itself a humdrum star tucked in one of the lesser arms, known as ‘Orion arm’ of the Milky Way, is located about 28,000 light years from the Galactic Centre in Sagittarius. Our entire Solar system is less than one light-day across. The Sun accounts for almost the entire mass (99.87%) of the Solar system. The eight planets and the officially recognised dwarf planets along with 180 satellites contribute a smattering of just 0.13% out of which the four gaseous giants - Jupiter, Saturn, Uranus, and Neptune together alone contribute 99% of the aggregate mass of all the planets. Enormity of Sun could be gauged from the fact that it could accommodate 1.3 million Earths in its body, diameter of Earth being 12,756 km against Suns 1,392,000 km. The above fact is sufficient to give an impression about how insignificant our Earth is in terms of its size and scale in the Solar system, let alone its status in the Milky Way and the Universe by and large. It wont be out of place to mention here that our own Sun is dwarfed by a large number of stars in the Milky Way in terms of size. VY Canis Major, the largest known star in the Milky Way is a red hypergiant measuring about 3 billion km in diameter. It is billion times larger than Sun in terms of volume. It is so big that if our Sun were replaced by it, its surface would extend to (or may even surpass) the orbit of Saturn. In Earth terms, it would take 70,000,000,000,000,000 (70 quadrillion) Earths to fill up the VY Canis Major. If the Universe were of the size of Earth, the Earth could be smaller than carbon molecules. Our world is thus fraction of a speck in the vast cosmic tapestry of stars and galaxies. Here, on the planet Earth, we have sets of hierarchy that govern the mankind. The human society is ridden with discrimination of all sorts – caste, colour, creed, and gender. It is divided along several lines- cultural, linguistic, economic, and religious. Some section of the society considers itself to be more endowed and privileged, and displays unwarranted superiority over those who are poverty - stricken and less privileged. Our sense of pride and ego overtake realization of the human values. We fail to admit that despite our ego and false sense of superiority, we remain so inconsequential in the spectacular cosmic landscape of the celestial bodies that dot the Universe!
Posted on: Thu, 21 Aug 2014 05:18:45 +0000
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