Editing Lambda-CDM model (section)

=== Hubble tension ===
{{main|Hubble tension}}
Statistically significant differences remain in values of the Hubble constant derived by matching the ΛCDM model to data from the "early universe", like the cosmic background radiation, compared to values derived from stellar distance measurements, called the "late universe". While systematic error in the measurements remains a possibility, many different kinds of observations agree with one of these two values of the constant. This difference, called the [[Hubble tension]],<ref name="di Valentino 2021 153001">{{cite journal |last1=di Valentino |first1=Eleonora |last2=Mena |first2=Olga |last3=Pan |first3=Supriya |last4=Visnelli |first4=Luca |last5=Yang |first5=Weiqiang |last6=Melchiorri |first6=Alessandro|last7=Mota|first7=David F.|last8=Reiss|first8=Adam G. |last9=Silk|first9=Joseph|author-link9=Joseph Silk|display-authors=3 |date=2021 |title=In the realm of the Hubble tension—a review of solutions |journal=Classical and Quantum Gravity |volume=38 |issue=15 |page=153001 |doi=10.1088/1361-6382/ac086d |arxiv=2103.01183|bibcode=2021CQGra..38o3001D |s2cid=232092525 }}</ref> widely acknowledged to be a major problem for the ΛCDM model.<ref name="cern-courier"/><ref name="LS-20190826">
{{cite news
 |last=Mann |first=Adam
 |title=One Number Shows Something Is Fundamentally Wrong with Our Conception of the Universe – This fight has universal implications
 |url=https://www.livescience.com/hubble-constant-discrepancy-explained.html
 |date=26 August 2019 |work=[[Live Science]] |access-date=26 August 2019
}}</ref><ref name="Snowmass21"/><ref name="Turner"/>

Dozens of proposals for modifications of ΛCDM or completely new models have been published to explain the Hubble tension. Among these models are many that modify the properties of [[dark energy]] or of [[dark matter]] over time, interactions between dark energy and dark matter, unified dark energy and matter, other forms of dark radiation like [[sterile neutrinos]], modifications to the properties of gravity, or the modification of the effects of [[inflation (cosmology)|inflation]], changes to the properties of elementary particles in the early universe, among others. None of these models can simultaneously explain the breadth of other cosmological data as well as ΛCDM.<ref name="di Valentino 2021 153001"/>