Dr Prince A Ganai
Theoretical Physicist @NIT- Srinagar
Tuesday, December 2, 2008
Lets try to understand our universe.
Physics deals with the physical structure of our universe. In a broader sense, our universe is composed of space-time, matter and radiation. These fundamental constituents interact via known four forces. The basic problem of physics from last 100 years has been to unify the known interactions into a single consistent theory “Theory of everything”. The purpose of this Blog is to help my students to keep track of current happenings in physics. To help them to develop physics oriented brains so that they can take this subject seriously and would help in unlocking the mysteries of nature. The Blog is open to all Physics Lovers to paste their comments
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New light on 16th century explosion
NEW YORK: More than 400 years after Danish astronomer Tycho Brahe challenged established wisdom about the heavens by analysing a strange light in the sky, scientists say they have determined just what he saw.
It is no big surprise. Scientists have known the light came from a supernova, a huge star explosion. But what kind of supernova?
A new study confirms that, as expected, it was the common kind that involves the thermonuclear explosion of a white dwarf star with a nearby companion.
The research, which analysed a “light echo” from the long-ago event, is presented in Thursday’s issue of the journal Nature.
The story of what is commonly called Tycho’s supernova began on November 11, 1572, when Brahe was astonished to see what he thought was a brilliant new star in the constellation Cassiopeia.
The universe is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term universe may be used in slightly different contextual senses, denoting such concepts as the cosmos, the world or Nature.
Astronomical observations indicate that the universe is 13.73 ± 0.12 billion years old[1]. Its diameter is at least 93 billion light years, or 880 ×1024 (that is to say, 880 followed by twenty-four zeroes) metres. According to the prevailing scientific theory, the universe has expanded from a gravitational singularity known as the Big Bang, a point in space and time at which all the matter and energy of the observable universe were concentrated. Since the Big Bang, the universe has expanded to its present form, possibly with a "brief period" of cosmic inflation.[2] Several independent experimental measurements support this theoretical expansion and, more generally, the Big Bang theory. Recent observations indicate that this expansion is accelerating, and that most of the matter and energy in the universe is fundamentally different from that observed on Earth and not directly observable (cf. dark matter and dark energy). The imprecision of current observations has hindered predictions of the ultimate fate of the universe.
Astronomical models of the universe were proposed soon after astronomy began with the Babylonian astronomers, who viewed the universe as a flat disk floating in the ocean, and this forms the premise for early Greek maps like those of Anaximander and Hecataeus of Miletus.
Later Greek philosophers, observing the motions of the heavenly bodies, were concerned with developing models of the universe based more profoundly on empirical evidence. The first coherent model was proposed by Eudoxus of Cnidos. According to this model, space and time are infinite and eternal, the Earth is spherical and stationary, and all other matter is confined to rotating concentric spheres. This model was refined by Callippus and Aristotle, and brought into nearly perfect agreement with astronomical observations by Ptolemy. The success of this model is largely due to the mathematical fact that any function (such as the position of a planet) can be decomposed into a set of circular functions (the Fourier modes). However, not all Greek scientists accepted the geocentric model of the Universe. Aristarchus of Samos was the first astronomer to propose a heliocentric theory.
EINSTIEN SAID:The most comrehensive thing about this universe is, that it is incomprehensive
When space expands, galaxies move apart from one another. A value of 71 km/sec per Megaparsec for the Hubble constant means that a galaxy that is one Megaparsec from us moves away from the Earth at 71 kilometers per second (about 45 miles per second) and that a galaxy that is two Megaparsecs from us moves away at 142 kilometers per second, and so on. A Megaparsec is a million parsecs, which is about 3.3 million light years or 30 million-trillion kilometers....hahaha...
universe is expanding,so should be our knowledge about it....thnx sir
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