Observations made with the Hubble Space Telescope showed that the expansion of the universe is accelerating rather than decelerating as a result of gravity. Adam Reiss one the Nobel Prize for this. The unknown cause for this acceleration was labeled "dark energy" on analogy with "dark matter," the unobserved matter which only shows through its gravitational effects on the motion of galaxies. There is no commonly accepted explanation of the accelerating expansion of the universe, hence no common definition of what dark energy is. The most conservative explanation is a non-zero value for Einstein's cosmological constant. So dark energy really is nothing more than a question mark or placeholder at this point.
Having obtained the supreme freedoms
and conjunctions of the precious human existence,
endowed with faith, energy, and intelligence,
Having attended on a worthy spiritual friend
and received the pith of the holy instructions,
May we practice these properly, just as we have received them,
without obstacle or interruption.
In all our lives, may we practice and enjoy the holy dharma.