You wrote;
> We all know that Einstein got rid of the cosmological constant
> because there was no evidence for it, but if that's the case, why did
> he put it in in the first place? What was his original concept?
This might help;
If he were alive, no one would be more bemused by this turn of events
than Albert Einstein. Soon after he formulated his general theory of
relativity in 1915, Einstein was unsettled to find it demanded that the
universe either expanded or contracted over time. But like nearly all
scientists at the time, he assumed the universe was static, neither
expanding nor contracting.
What to do? To compensate for what he considered a flaw in his theory,
Einstein introduced the idea of the cosmological constant, symbolized in
equations by the Greek letter lambda. The repulsive energy force would
presumably counteract gravity and make the universe in his theory stand
still. Soon after Edwin P. Hubble discovered the expanding universe in
1929, Einstein renounced the cosmological constant as the greatest
blunder of his career.
For years, scientists agreed, dismissing lambda as "that fudge factor."
In the last decade, however, they reluctantly dusted it off as a means of
balancing the books on the matter, and other forces that are required to
support the favored interpretation of Big Bang theory.
In this model, called the inflationary Big Bang, the universe should
contain a critical density of matter, just enough to slow expansion to a
halt, given infinite time. Scientists express this condition of critical
density as omega equals one. Too little mass -- if omega equals less than
one -- and the universe would expand forever, growing ever more tenuous.
If omega equals more than one, then the universe would collapse of its
own weight, contracting in what is called the Big Crunch.
So far, astronomical observations and other research have established
that the mass density of the universe amounts to no more than 30 percent
of the preferred critical value. That includes the mass from ordinary
matter in galaxies and a large component of mysterious exotic particles,
invisible and still hypothetical. Despite this matter deficit,
cosmologists clung to the inflation theory because it had passed many
tests and provided a satisfying explanation for early conditions in the
universe.
-- Jerry W. Decker / jdecker@keelynet.com http://keelynet.com / "From an Art to a Science" Voice : (214) 324-8741 / FAX : (214) 324-3501 KeelyNet - PO BOX 870716 - Mesquite - Republic of Texas - 75187