Arguments against dark matter in the Bullet Cluster fall apart

Original publisher: Starts With A Bang. The article discusses the Bullet Cluster as a powerful empirical indicator for dark matter, highlighting how X-ray emissions trace normal matter while gravitational lensing maps the total mass. It also notes that proponents of alternative gravity theories (MOND) offer explanations that have been debated, but the prevailing view remains that the Bullet Cluster challenges modified gravity alone as a complete account. The piece invites readers to weigh the strength of the separating signals against alternative interpretations and to consider the ongoing discussion within cosmology regarding dark matter's existence.

Introduction: The Bullet Cluster as a Proof Point

"The Bullet Cluster has, for nearly 20 years, been hailed as an empirical 'proof' of dark matter." - Starts-With-A-Bang

The article situates the Bullet Cluster as a defining observational system: a 3.8 billion-year-old collision whose aftermath has been a focal point in debates over dark matter versus alternative gravity theories such as MOND. It emphasizes that the cluster’s observations began with measurements of X-ray emissions and gravitational lensing, revealing a striking offset between where normal, baryonic matter concentrates and where the total mass appears to lie.

The author frames the central question: do the distinct signals truly constitute a smoking gun for dark matter, or can modified gravity theories account for the data in a different way? The piece notes the long-standing interpretation that the separation between mass and normal matter supports the existence of a non-baryonic mass component, typically identified with dark matter.