What lies beyond all we can see? The question may seem unanswerable. Nevertheless, some cosmologists have a response: Our universe is a swelling bubble. Outside it, more bubble universes exist, all immersed in an eternally expanding and energized sea—the multiverse. The idea is polarizing. Some physicists embrace the multiverse toContinue Reading

From the big bang onwards you might think we know a lot about the universe’s first fraction of a second. But that just isn’t true. Why, for example, didn’t antimatter annihilate matter? Why haven’t we observed any dark matter particles yet? How does dark energy accelerate universe expansion? And whyContinue Reading