Letters
By Science News
Galaxy clusters slide
Could the general motion of galaxy clusters (“Galaxy clusters slide to the south,” SN: 10/25/08, p. 12) be evidence of rotational motion of the matter components of the universe on a scale much larger than the observable universe? Would such motion not also result in accelerating expansion of the observable universe, as gravitational attraction opposing rotational expansion weakened as a result of expansion?
Arden Slotter, Castle Pines North, Colo.
“The question of an overall rotation for the universe is an interesting one,” says Glenn Starkman of Case Western Reserve University. “Some attention has been paid to it, but without any convincing evidence to support it. I don’t think this work on large-scale motions particularly encourages interpretation of the motion as rotation. That would require some observation of a coherence to that motion over large swaths of the sky.” — Ron Cowen