Hay una aparente contradicción: de acuerdo a las teorías cosmológicas más aceptadas, el Universo que conocemos tiene una edad de 13 mil millones de años. El "espacio" conocible abarca 40 mil años luz.
Alongside early dark energy, theorists have put forward other exotic forms of dark energy — such as quintessence and phantom dark energy — that also change as the universe ages. While these extensions to the standard model relieve the Hubble tension, they are regarded by many cosmologists as fine-tuned — opportune mathematical additions that have no clear justification.