https___blogs-images.forbes.com_startswithabang_files_2018_05_dark-energy

The different possible fates of the Universe, with our actual, accelerating fate shown at the right. After enough time goes by, the acceleration will leave every bound galactic or supergalactic structure completely isolated in the Universe, as all the other structures accelerate irrevocably away. After another few tens of billions of years, only the Local Group will be reachable any longer. We can only look to the past to infer dark energy’s presence and properties, which require at least one constant, but its implications are larger for the future. (Credit: NASA & ESA)