Whether or not galaxies merge depends on how strong the gravitational attraction is between the galaxies and whether the universe's expansion is more powerful than gravity. Gravity affects everything ...

A recent resurgence of interest in a bold cosmological theory has reignited debate about the nature of dark matter, the Big Bang, and the possible existence of a mirror universe. Originally proposed ...

Add Yahoo as a preferred source to see more of our stories on Google. In space, there are four dimensions: length, width, height and time. scaliger/iStock/NASA via Getty Images Plus About a century ...

Might the universe we can observe be just half the tale, with a mirror universe moving in reverse through time filling out the narrative? A new and intriguing idea from scientists at the Perimeter ...