On Tue, Jan 24, 2012 at 11:27 PM, Stephen P. King <stephe...@charter.net>wrote:

Stephen P. King <stephe...@charter.net> Wrote:

 >  A "constant" that Einstein himself called the "greatest mistake of
> his life". The problem is that one can add an arbitrary number of such
> scalar field terms to one's field equations. Frankly IMHO, it is more
> "something from nothing" nonsense.

Yes, it amounted to a repulsive effect that came from space itself, and
you can set that constant to anything and mathematically the field
equations of General Relativity would still work. Originally  Einstein
saw no physical reason for that additional complication so he set it to
zero. But then he noticed that if it was zero the universe could not be
stable, it must be expanding or contracting; at the time everybody
including Einstein thought the universe was stable so he set it to a non
zero value and the cosmological constant was born. However just a few
years later Hubble found that the universe was expanding, so Einstein
thought the cosmological constant no longer had a purpose and said that
changing it from zero was the greatest mistake of his life.

In act 2 people working with quantum mechanics found that empty space
should indeed have a repulsive effect, but the numbers were huge,
gigantic astronomical, so large that the universe would blow itself
apart in far far less than a billionth of a nanosecond. This was clearly
a nonsensical result but most felt that once a quantum theory of gravity
was discovered a way would be found to cancel this out and the true
value of the cosmological constant would be zero.

In act 3 just a few years ago it was observed that the universe is was
not just expanding but accelerating, so now theoreticians must find a
way to cancel out, not the entire cosmological constant, but the vastly
more difficult task of canceling it all out EXCEPT for one part in
10^120. There are only about 10^90 atoms in the observable universe.

 John K Clark

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