https://answersingenesis.org/astronomy/cosmology/galaxies-unexplained-spirals/ After a short intermission, we are back on our series on whether YEC claims stand up to scrutiny. This Answers in Genesis article asserts that spiral galaxies prove that the universe cannot be as old as is commonly believed. Some excerpts: In the 1930s astronomers realized a problem, though. The outer stars needed more time to complete their orbit than the inner stars. As the distance from the center of a galaxy increases, the spiral arms ought to become unstable. That is, after a few rotations, spiral arms ought to smear out. Astronomers debated for years whether spiral arms wound up or unwound, depending upon the direction of rotation. No matter which view they adopted, however, if galaxies are at least ten billion years old, as is generally thought, then no spiral arms should be left.