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Cosmological Constant and its Significance

Abdul Najeeb asked via Facebook:

Would you plz explain me what is a cosmological constant? When Einstein snubbed it as the "biggest blunder" in his life, what else is the real importance of the constant? Also what is cosmological acceleration and its’ effect on the constant…plz…but in simple words…plzzzz:)))))

Ans:

The cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe.

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Einstein abandoned the concept after the observation of the Hubble redshift indicated that the universe might not be stationary, as he had based his theory on the idea that the universe is unchanging.However, the discovery of cosmic acceleration in the 1990s has renewed interest in a cosmological constant.

{courtesy : Wikipedia}

More details will be added soon

Big Bang and the conservation of Mass

Harilal asked:

“During the big bang it is supposed that the small particles expanded in a very very small interval of time and there was nothing before that. If it is so, then how can it in be good agreement with law of conservation of mass?”

Ans:

After the Big Bang, the universe expanded rapidly. The big bang theory is not a theory which is completely resolved. There are many questions to be answered.

Further, mass alone is not conserved, it is mass+energy  which is conserved.

Energy can be converted into matter and vice versa. (E=mc^{2})

Dark Energy and Dark Matter are two widely discussed concepts in association with the Big Bang. These correspond to the mass (matter) and energy which we cannot account for by calculations and theory.

Further, BIGBANG is not the only possible cause of the Birth of Universe. There are many other possibilities.

Big Bang theory originated after the discovery that the universe is expanding. SO if we think in reverse direction, we can imagine that the entire universe was confined to an infinitesimally small (Compared to the present size of the universe) space. This idea started the theoritization of the Big Bang.

Please visit the following links for further reference:

http://www.aip.org/history/cosmology/ideas/bigbang.htm

http://www.aip.org/history/cosmology/ideas/journey.htm

http://en.wikipedia.org/wiki/Big_Bang

http://www.aip.org/history/cosmology/ideas/expanding.htm

 

(Comments and better answers are expected from visitors and experts visiting the site)

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