ScienceDaily: Space & Time News

A new study disputes the prevailing hypothesis on why Mercury has a big core relative to its mantle. For decades, scientists argued that hit-and-run collisions blew away much of Mercury's rocky mantle and left the big, dense, metal core inside. But new research reveals that collisions are not to blame -- instead, the density, mass and iron content of a rocky planet's core is influenced by its distance from the sun's magnetic field.

Our universe is expanding, but our two main ways to measure how fast this expansion is happening have resulted in different answers. An astronomer gives an overview of the most recent observations. New conclusion: the latest observations are beginning to close the gap. That is, there may not be a conflict after all, and our standard model of the universe does not need to be significantly modified.