Tags: Alternatives to dark matter, astrophysics, bullet cluster, cosmic microwave background radiation, cosmic microwave backround, cosmology, dark matter, einstein, evidence for dark matter, galaxy clusters, gravitational lensing, gravity, how do we know dark matter exists?, observations for dark matter, physics, rotation curves, sabine hossenfelder, science, structure formation in the universe, universe, what is dark matter, why do we know dark matter exists?
Dark matter. Or what?
