Future of an expanding universe

An expanding universe means that things that are far away from each other in space are getting farther and farther away from each other over time. This means that if two galaxies, or two stars, or two planets that were close together billions of years ago are now far apart, they will get even farther apart in the future. Scientists are not sure what will happen in the future, but some think that the universe might keep expanding forever, or that it could stop and then start shrinking back together again.