Would you be surprised to learn that your ancestors may have lived in such a world? Work with a partner to discuss what you would do if you were somehow transported into the sorcerers' world. How would you convince people there that your world, trusting in science, is a better one?
In your time travel, you meet a magician who makes and sells magic necklaces. Depending on how much a person pays, the necklace will glow for a few hours, or a few days. As long as the light of the necklace lasts, the magician claims its wearer is protected from harm.
You observe some necklaces carefully and study how their glowing light dims over time. You see three people buy necklaces. Here's what happened to each necklace:

• The first necklace glowed dimly. In six hours, the glow was only half as bright as it had been at first. In another six hours, the glow was gone.
  
• The second necklace glowed very brightly. Six hours later, it was only half as bright as when the magician sold it, but it was still brighter than the first necklace had ever been. Twelve hours after that, the necklace was one-eighth as bright as it had been at first, but still twice as bright as the first necklace. Six hours later, one full day after its purchase, the second necklace had dimmed to the original brightness of the first necklace. Then it behaved exactly like the first one. In six hours, its brightness had decreased by half, and in another six hours, it was dark.
  
• When the magician sold it, the third necklace glowed only half as brightly as the second one. Six hours later, it was only half as bright as when it was bought. Twelve hours after that, the third necklace glowed only as brightly as the first one when it was sold. In six more hours, the third necklace was only half as bright. Six hours later, it was dark.
  You also saw the magician prepare the three necklaces. For each, he measured a powder and mixed it with a liquid. Then he poured the mixture into the necklace. He used less powder to make the first necklace than to make the other two. He used more powder in the second than in the third.