Two Flavors of Early Dark Energy Ease Cosmic Tension ✎ express
Cosmologists faced a recipe problem: the universe's expansion rate measured nearby didn't match the rate deduced from the Big Bang's afterglow — the cosmic microwave background. Adding a single type of early dark energy was like tossing in one extra spice, but the flavor still clashed, especially when looking at small-scale details in the afterglow. Now, they've tried a two-spice approach — two types of early dark energy, each appearing at a slightly different moment just after the Big Bang. This blend smooths out the mismatches in the afterglow, bringing the predicted rate of cosmic expansion closer to what local observations, such as those by Adam Riess, measure. The predicted rate jumps from 67 to about 70 kilometers per second per megaparsec, almost reconciling with the local 73.
The rate is measured in kilometers per second per megaparsec — a megaparsec is 3.26 million light-years. Local methods clock it at 73, the Big Bang afterglow at 67. The two-early-dark-energy model lifts the afterglow's number to about 70, nearly resolving the discrepancy. And here's the twist: those early dark energies flickered for less than a trillionth of a second, yet their signature still ripples through the cosmos today.