1. Now researchers have proposed a device they suggest could help solve the mystery of whether antimatter falls up or down.

2. Instead, the whole universe would be filled with radiation because all the matter and antimatter would have been annihilated.

3. How did the dominance of matter over antimatter in the universe come about?

4. Scientists have long wondered if antimatter falls down, responding the same way to gravity as ordinary matter.

5. If matter and antimatter behave differently, then that could offer some insight into why matter dominates the universe.