A Hubble image of the massive galaxy cluster MACS J1206, with the characteristic arcs, smears, and distorted shapes from gravitational lenses. Overlaid, in blue, are the reconstructed distributions of dark matter halos and substructure within this cluster. (NASA, ESA, G. CAMINHA (UNIVERSITY OF GRONINGEN), M. MENEGHETTI (OBSERVATORY OF ASTROPHYSICS AND SPACE SCIENCE OF BOLOGNA), P. NATARAJAN (YALE UNIVERSITY), THE CLASH TEAM, AND M. KORNMESSER (ESA/HUBBLE))

The 5 Truths About Dark Matter That Everyone Should Know

Deniers will never stop misleading others. Here’s the truth.

Ethan Siegel
10 min readMay 11, 2021

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Every so often, advocates of a fringe theory — one that doesn’t fit the evidence as well as the mainstream theory — do what they can to breathe life back into it. Sometimes new evidence comes to light, challenging the mainstream theory and causing alternatives to be re-evaluated. Sometimes, a surprising set of observations supports a once-discredited theory, bringing it back into prominence. And at other times, a false narrative is the culprit, as disingenuous arguments that have been rightfully dismissed by mainstream professionals takes hold among a new generation of inexperienced individuals.

Unless you yourself have the necessary expertise to diagnose what’s being presented accurately and fully, it’s virtually impossible to tell these scenarios apart. Recently, someone suggested, in text and in video while following the lead of arguably the most disingenuous contrarian in the field, that the situation surrounding dark matter has changed, and that modified gravity now deserves equal consideration. Unless you’re in the business of ignoring the majority of the cosmic evidence, however, that’s simply not the case. Here are five truths that, once you know them, can help you see through the false equivalencies presented by…

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Ethan Siegel

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.