Straight Shooters: How Light Travels (and the Ghost Coin)
🎯 Today's mission briefing
We are learning to identify sources of light, to explain that light travels from a source in straight lines, and to describe how shadows are formed when that path is blocked.
You'll know you've got it when:
- I can sort objects into light sources (which make light) and reflectors (which only bounce it)
- I can explain that we see something only when light from it travels in a straight line into our eyes
- I can predict how a shadow will change when the light, the object or the surface moves, and explain why
The ghost coin
Connects to what your guest already knows and makes them curious. Activating prior knowledge is one of the strongest predictors of new learning.
Try this RIGHT NOW — it takes one mug, one coin and thirty seconds. Drop the coin in the empty mug. Step back slowly until the mug's rim just barely hides the coin from view. Freeze — don't move your head. Now have your helper slowly pour water into the mug... and watch. The coin RISES BACK INTO VIEW. You didn't move. The coin didn't move — it's sitting flat on the bottom the whole time. Yet somehow, a coin you could not see is now a coin you can see. Something invisible between the coin and your eye has changed its behaviour. By the end of this unit you'll be able to explain the whole trick — and today you'll crack the first half: why the rim could hide the coin in the first place.