Chandra X-ray image of dark energy. NASA/CXC/SAO/A.Vikhlinin et al.
Cosmologists are not sure if dark energy is a new force, a modification of known ones, or even perhaps some kind of matter with bizarre properties that fills all space.
Why isn’t dark energy considered the “fifth force” in the way gravity, electromagnetism, weak nuclear, and strong nuclear are forces?
Tim Smith, Kent, Washington
