A galaxy that was governed by normal matter alone (L) would display much lower rotational speeds in the outskirts than towards the center, similar to how planets in the Solar System move. However, observations indicate that rotational speeds are largely independent of radius (R) from the galactic center, leading to the inference that a large amount of invisible, or dark, matter must be present. What isn’t greatly appreciated is that without dark matter, life as we know it would not exist. (WIKIMEDIA COMMONS USER INGO BERG/FORBES/E. SIEGEL)

Why Humans Should Be Thankful That Our Universe Has Dark Matter

Without this one ingredient, there wouldn’t be enough ‘glue’ to hold the Universe together.

Of all the things in the Universe to be thankful for — the stars, planets, atoms, molecules, and more that came together and made our existence possible — it seems odd that dark matter would be included. Even here in our own Solar System, dark matter might be present, but even its gravitational effects are totally negligible, contributing less than the dwarf planet Ceres does to all the orbits of the planets, moons, asteroids and Kuiper belt objects.

And yet, without dark matter, the Universe as we know it wouldn’t exist the way it does. Stars would be extremely rare entities in the Universe, and large galaxies with Sun-like stars and Earth-like planets would be all but impossible. Dark matter enabled the Universe to give rise to us, and without it, we wouldn’t be here. Here’s the cosmic story that every one of us should be thankful for.

The X-ray (pink) and overall matter (blue) maps of various colliding galaxy clusters show a clear separation between normal matter and gravitational effects, some of the strongest evidence for dark matter. Although some of the simulations we perform indicate that a few clusters may be moving faster than expected, the simulations include gravitation alone, and other effects like feedback, star formation, and stellar cataclysms may also be important for the gas. Without dark matter, these observations (along with many others) cannot be sufficiently explained. (X-RAY: NASA/CXC/ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, SWITZERLAND/D.HARVEY NASA/CXC/DURHAM UNIV/R.MASSEY; OPTICAL/LENSING MAP: NASA, ESA, D. HARVEY (ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE, SWITZERLAND) AND R. MASSEY (DURHAM UNIVERSITY, UK))

On astronomical scales, particularly on large, cosmic ones, the observational evidence for dark matter is overwhelming. Without its…