On the enigmatic $\Lambda$ - a true constant of spacetime
  Had Einstein followed the Bianchi differential identity for the derivation of
his equation of motion for gravitation, $\Lambda$ would have emerged as a true
new constant of spacetime on the same footing as the velocity of light? It is
then conceivable that he could have perhaps made the most profound prediction
that the Universe may suffer accelerated expansion some time in the future!
Further we argue that its identification with the quantum vacuum energy is not
valid as it should have to be accounted for like the gravitational field energy
by enlarging the basic framework of spacetime and not through a stress tensor.
The acceleration of the expansion of the Universe may indeed be measuring its
value for the first time observationally.
