Physicists readily admit that we still have a lot to learn.
“The Universe is made mostly of dark matter and dark energy,
and we don’t know what either of them is” says 2011 Nobel Prize Laureate, Saul
Perlmutter.
The predominate view is that dark energy results from
quantum energy fluctuations in the vacuum of space, but efforts to use quantum
theory to describe it have failed so far. Other theories, including modification
of gravity, have gained little acceptance.
Whatever this dark matter and energy turn out to be, the
outward force it applies to our part of the Universe has been detected by
countless scientific experiments over the years.
When Einstein applied his general theory of relativity to the
Universe as a whole in 1917, his equations included a “cosmological constant”
which described just such an outward force.
More recently, observations of the large scale structure of
the Universe, together with, the cosmic microwave background radiation – the
faint afterglow of the Big Bang – have also indicated that the majority of the
Universe’s energy remains undetected.
Today, physicists generally agree that dark energy is about
73% of the energy in the Universe but they can’t rationally describe it.