The NASA article “Dark energy found stifling growth in the universe” states, “By tracking how dark energy has stifled the growth of galaxy clusters and combining this with previous studies, scientists have obtained the best clues yet about what dark energy is and what the destiny of the universe could be.”
Dark energy is a hypothetical type of energy that supposedly permeates all of space. It exerts a negative pressure (kinda like a negative gravity effect) that seems to account for the differences in how scientists think visible matter in the universe should behave (theory) and how it actually behaves (observation).
Unlike visible matter, dark energy it thought to only act on dark matter, a hypothetical form of matter that does not reflect nor emit electromagnetic radiation (such as visible light, x-rays, and gamma rays).
The NASA astronomers used the Chandra X-ray Observatory to make their conclusions. After years of research, the results, according to NASA, “… provide a crucial independent test of dark energy, long sought by scientists, which depends on how gravity competes with accelerated expansion in the growth of cosmic structures.”
Astrophysicists and other scientists working on how the universe was first formed (and how it operated in the past, why it works now, and what it will look like in the future) consider the understanding of dark energy as “one of the biggest problems in science.”
Alexey Vikhlinin, of Smithsonian Astrophysical Observatory (SAO), Cambridge, Massachusetts, U.S.A., led the research team. Vikhlinin states, “This result could be described as 'arrested development of the universe.’ Whatever is forcing the expansion of the universe to speed up is also forcing its development to slow down."
Page two continues dark energy, Einstein's cosmological constant, the fate of the universe and other such things.