Dark energy is a placeholder word to explain a phenomena scientists can't understand. Before Einstein they didn't know what the medium was for light waves. For

Dark energy is a placeholder word to explain a phenomena scientists can't understand. Before Einstein they didn't know what the medium was for light waves. For water waves it is obviously water, what does light use to travel through? They created this phrase called "ether" light traveled through "ether". Dark energy and dark matter are exactly the same case.