What do we really know about Dark Energy?

TL;DR

This paper reviews the current understanding of dark energy, emphasizing that its primary evidence comes from distance measurements like supernovae, CMB, and baryon acoustic oscillations indicating an accelerated universe.

Contribution

It critically examines the observational basis for dark energy, highlighting the reliance on distance-redshift relations from various cosmological measurements.

Findings

Distance measurements suggest an accelerated expansion.

Current evidence for dark energy is primarily from supernovae, CMB, and BAO.

Alternative explanations for observations are not extensively discussed.

Abstract

In this paper I discuss what we truly know about dark energy. I shall argue that up to date our single indication for the existence of dark energy comes from distance measurements and their relation to redshift. Supernovae, CMB anisotropies and observations of baryon acoustic oscillations, they all simply tell us that the observed distance to a given redshift is larger than the one expected from a Friedmann Lemaitre universe with matter only and the locally measured Hubble parameter.