A couple of years ago in a Q&A for The Creators Project they asked me:
What fantasy piece of technology would you like to see invented?
A simple knob that connects to any source of light, so it slows down the speed of the light. Even down to zero, like a lightsaber.
I always dreamed about the endless possibilities if such a magical thing was ever feasible. And I recently discovered that it is happening! In the last story of this podcast from Radiolab (min. 45),
Danish physicist Lene Hau explains how she has been able to slow down a beam of light, passing it through an ultra-cold cloud of sodium atoms. She has also been able to transform the form of light into matter, recording the shape of the light pulse with a laser. This light copy (or light metadata) can be stored, and the light form re-created in another place and time.
Collection of sunsets
Cold-cloud photo camera