Our Universe: Missing, Found, Then Missing Again
Nov 8 at 10:10pm by Aileen
Keeping Up With Astronomy’s Game of Hide-and-Seek
Big astrophysics science news this week that a Big Chunk of the Universe Is Missing - Again. This requires a little background for understanding how it is our universe can be so adept at playing hide-and-seek.
As much as 96% of the mass necessary to account for how our universe is observed to be has been missing for a long time. The mass is necessary to explain the gravity that holds galaxies together, but all the atomic matter we can see in planets, comets, asteroids, assorted space junk, stars and galaxies accounts for just 4% of it. In 1974 astronomer Vera Rubin discovered that instead of following a Newtonian scheme where Mercury travels faster around the sun than Neptune does, almost all stars rotating around a galaxy’s center - at any distance - all travel at the same speed.
There had to be some ‘extra’ source of gravity working in galaxies, but there wasn’t nearly enough mass to account for this anomaly. The choice was between gravity being variable (unthinkable!) or the existence of a great deal of extra mass that we couldn’t see. Scientists jumped on that answer in defense of Newtonian/Einsteinian gravity and gifted us with “Dark Matter.”
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