The arms in galaxies are not rotating but are standing waves through which the material flows, rotates.
Waton, that is an interesting "just so" story to try and account for why spiral galaxies appear young.
Astronomy.com explains differently than you do:
In a spiral galaxy, everything orbits at the same speed, meaning stars and gas near the center of the galaxy complete an orbit in less time than objects farther out. This effect is referred to as differential rotation. So, in the time it takes an inner star to complete one revolution around its galaxy, an outer star might have only finished half a revolution.
Differential rotation naturally generates spirals as the galaxy rotates. Galaxies like the Milky Way have rotated a few dozen times — it typically takes 200 million years for the entire galaxy to complete a revolution.
Question:
So if the universe we see today shows stars (and galaxies) on their third life cycle (another "just so story" which attempts to account for their documented heavy elements) , and it takes 200 million years for a galaxy to rotate even one time; How can we account for the existence of spiral galaxies anywhere in the universe.
When we look at the spiral galaxies that are supposedly within 3-5% of the age of the universe as the recent deep space image provided by the new Webb telescope, the "problem" (and naturalistic attempts at explanation) become even more ludicrous.
To summarize other problems with the BB model:
– Mature galaxies exist where the Big Bang predicts only infant galaxies (like the 13.2Bly-away EGS8p7)
– An entire universe-worth of missing antimatter contradicts the most fundamental BB prediction (Dark matter is an ad hoc rescue device not predicted by the BB)
– Observations show that spiral galaxies are missing millions of years of BB-model predicted collisions
– Clusters of galaxies exist at great distances where the big bang model predicts they should not exist
– Galaxy superclusters exist yet the BB predicts that gravity couldn’t form them even in the alleged age of the cosmos
– A missing generation of the alleged billions of first stars that the failed search has implied simply never existed
– It is “philosophy”, not science, that makes the big-bang claim that the universe has no center
– Amassing evidence suggests the universe may have a center
– Sun is missing nearly 100% of the spin that natural formation would impart
– The beloved supernova chemical evolution story for the formation of heavy elements is now widely rejected
– Missing billions of years of additional clustering of nearby galaxies
– Surface brightness of the furthest galaxies, against a fundamental BB claim, is identical to that of the nearest galaxies