Astronomers are trying to determine the composition of what is probably the greatest single mystery in cosmology, Dark Energy. This is the energy that is theoretically responsible for the ever increasing expansion of the universe.
In the early 90s it was thought that after the Big Bang almost 13 Billion years ago, the universe expanded quickly and then cooled, creating galaxies that we see today. This expansion of the universe was thought to eventually slow down because gravity between masses would "attract" one another.
This basic theory was proven to be incorrect in the late 90s when data was obtained from the famous Hubble telescope. Data from Hubble created more questions than answers and it was discovered that the movement of stars in galaxies was not found as predicted. Stars in outer arms of galaxies were travelling at the same speed as those on inner arms. Something was causing it.
Astronomers also found galaxies that were farther away from us were travelling faster, than those galaxies close by. Something was causing these unpredicted movement of stars.
That something is though to be Dark Matter and Dark Energy. Dark matter does not interact with all known forms of light and is thought to be some sort of sub-atomic particles that we have not been able to detect. It composes about 25% of all matter.
Dark Energy is thought to be the energy contained in space itself. Einstein was the first to consider that empty space was not really empty. It could contain energy and space could be created as the universe expands. Therefore the greater that space expanded, the greater the energy of space. This could explain the more rapid expansion of space but it is still a mystery.
Image compliments of Wikipedia
In the diagram above you can see that Dark Matter was dominant early. Then 5 billion years ago, Dark Energy began to dominate and accelerate expansion of the universe.
Check out NASA's explanation here.
When we consider that Dark Energy comprises 70% of the universe and visible matter comprises 5% of the universe, it clear that our understanding of the universe is still in its infancy.
Maddalena Environmental Inc.