From the ICR’s URCall series of videos, hosted by Markus Lloyd. “Why spiral galaxies are young”—for real this time. (link)
Did you know that spiral galaxies could not exist if the universe was billions of years old? Their centre rotates faster than their arms. If these were billions of years old they would have blended into disk-shaped galaxies by now, and their spiral arms would have been twisted beyond recognition. So how old is our universe? Creation science has an answer that might surprise you.
This argument rests on a bait-and-switch: yes, stars nearer the centre of a galaxy orbit faster than those towards the edge, but that doesn’t mean that the spiral arms are doing the same thing. The arms are not solid, and instead appear to be density waves – and that means they don’t have to be travelling in the same manner as their stellar components.
It’s a bit like a transient traffic jam. From the driver’s perspective they slow down slightly, getting slightly closer to nearby cars, and then speed up and space out. But the traffic jam itself, viewed from above, doesn’t move with them if at all.
The spiral swirls that sometimes appear when you remove a plug from a drain follow similar rules. The individual water molecules that form them travel faster when they are closer to the centre of the whirlpool, but the spirals themselves don’t wind up because they don’t move with them. The same appears to be true of spiral galaxies, and that is why this creationist claim doesn’t work.
By the way, on the subject of the URCall videos being much too short to even make the argument in some cases, here’s a screenshot from the ICR’s facebook page:
See what I mean?