Scientists put forth a theory to explain dark energy: the universe is at the surface of an expanding bubble in another dimension.

Open access article: https://journals.aps.org...3/PhysRevLett.121.261301
Example press release: https://www.sciencedaily...2018/12/181228164824.htm

Title of paper is "Emergent de Sitter Cosmology from Decaying Anti–de Sitter Space"