A merging galaxy cluster in MACS J0416.1–2403 exhibits a small separation of X-ray gas from the gravitational signal, consistent with the notion that dark matter and not normal matter is responsible for the majority of gravitational effects seen in the Universe. Although the offset is small, this is expected, as this particular cluster is in a later stage of its merger than most, and still displays an offset between where the normal matter (in X-rays) and the total mass (from lensing; in blue) is located. (X-RAY: NASA/CXC/SAO/G.OGREAN ET AL.; OPTICAL: NASA/STSCI; RADIO: NRAO/AUI/NSF)

This Is How Galaxy Cluster Collisions Prove The Existence Of Dark Matter

If dark matter is fundamentally different from the normal matter we know, there should be a way to test it. Here are the results.

Dark matter — despite the enormous indirect evidence for it — sounds like a colossal misunderstanding.

A galaxy cluster can have its mass reconstructed from the gravitational lensing data available. Most of the mass is found not inside the individual galaxies, shown as peaks here, but from the intergalactic medium within the cluster, where dark matter appears to reside. The time-delay observations of the Refsdal supernova cannot be explained without dark matter in this galaxy cluster. (A. E. EVRARD. NATURE 394, 122–123 (09 JULY 1998))

It’s clear that data from

• gravitational lensing,
• galaxy clustering,

The way galaxies cluster together is impossible to achieve in a Universe without dark matter. The clustering patterns seen due to baryon acoustic oscillations, imprinted in the Universe’s power spectrum, and on the largest scales of the cosmic web are all consistent with dark matter, but have never been explicable via any attempted modification of gravity. (NASA, ESA, CFHT, AND M.J. JEE (UNIVERSITY OF CALIFORNIA, DAVIS))

• individual galaxies,
• and the cosmic microwave background,

all require masses that don’t interact electromagnetically.

The final results from the Planck collaboration show an extraordinary agreement between the predictions of a dark energy/dark matter-rich cosmology (blue line) with the data (red points, black error bars) from the Planck team. All 7 acoustic peaks fit the data extraordinarily well, but about half of those peaks would not be present if there were no dark matter. (PLANCK 2018 RESULTS. VI. COSMOLOGICAL PARAMETERS; PLANCK COLLABORATION (2018))

However, a longstanding alternative suggests modifying gravity could explain them without dark matter.