Cosmological Constant and the Colapse of the Universe

[NWH]

I was wondering if someone would mind talking a little about why the cosmological constant was introduced and what it actually means for the universe to collapse according to Einstein's Universe. I was reading up on Wikiepdia (not the greatest source, I know) in the Static Universe entry and it got me interested. Although it didn't go into too much detial on why this actually happened and what it meant. Any input is appreciated...

 

[mathman]

The essential point (when Einstein introduced the cosmological constant) was that a static universe would be an unstable equilibrium. To avoid either a collapse or an expansion he put it in. Later on Hubble discovered that the universe is expanding and more recently it was discovered that the expansion is speeding up. To explain this speeding up, most cosmologists have put the idea of a cos. constant back. This whole area is still open to further analysis.

 

[Entropia]

The cosmological constant was first introduced by Albert Einstein in 1917 as a term in his theory of general relativity. It was meant to counteract the effects of gravity and keep the universe in a static state. However, after the discovery of the expansion of the universe in the 1920s, Einstein abandoned the cosmological constant, calling it his "biggest blunder."

In simple terms, the cosmological constant is a value assigned to the energy density of empty space. It is often denoted by the Greek letter lambda (Λ) and is a fundamental constant in the equations of general relativity. It can also be thought of as a measure of the repulsive force of dark energy.

As for the collapse of the universe, this concept is based on Einstein's theory of general relativity, which describes gravity as the curvature of space and time caused by mass and energy. In this theory, the fate of the universe is determined by the overall density of matter and energy within it. If the density is high enough, the gravitational force will eventually overcome the expansion of the universe and cause it to collapse in on itself.

However, in the 1920s, astronomer Edwin Hubble's observations showed that the universe is actually expanding. This led to the abandonment of the static universe model and the introduction of the Big Bang theory, which suggests that the universe began as a singularity and has been expanding ever since.

Today, the cosmological constant is still a topic of debate and research in cosmology. It is believed to play a crucial role in the current accelerated expansion of the universe and the ultimate fate of the universe. While some theories suggest that the universe will continue to expand forever, others propose that it may eventually collapse in a "Big Crunch" or experience a "Big Rip" where the expansion becomes infinite.

In conclusion, the cosmological constant is a fundamental concept in our understanding of the universe and its evolution. Its discovery and subsequent abandonment by Einstein have greatly influenced our understanding of the universe and continue to be a topic of study and debate among scientists.