1. The devices emit pings so they can be more easily found, but the batteries last only about a month.

2. Those electrons return to their former energy levels and emit photons light in the process.

3. The hydrogen fuel did emit more energy than it absorbed from the lasers, an experimental goal.

4. Newer power plants in China emit less pollution and carbon dioxide than older ones.

5. It may sound retro, but your browser may one day soon pop up a number pad and emit a dial tone.