Planets are not layered in general. The strong evidence of
layering on Earth arises because the main components (mantle and
core) are immiscible. This is a thermodynamic property and nothing
to do with gravity. However, immiscible phases can...
Direct measurements of galaxy peculiar velocities, i.e., their
motions with respect to us beyond that expected from just the
expansion of the Universe, are undergoing a resurgence. Five years
ago, individual surveys were limited to a few thousand...
