Overview of Dark Energy on Penn Staet U site

 http://hetdex.org/dark_energy/what_is_it/vacuum_energy.php

dark energy is the leading explanation for the expansion of the universe. It is a repulsive force in opposition of gravity.

 This is a pretty large discrepancy, it seems:
"
Vacuum energy has its own set of problems, though. It should be far too weak to account for the acceleration seen in the present-day universe, for example — by a factor of at least 10⁵⁷ (a one followed by 57 zeroes), and perhaps as much as 10¹²⁰ (a one followed by 120 zeroes). Yet it is the most complete scenario to date, so it leads the pack of dark-energy contenders.
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