In an effort to get my lively five year old daughter into her bed, I suggested that she should try to get her head on her pillow before her shadow did.
Of course this failed; resulting in a series of races, where I had to say who had won each time.
Realising my mistake, I thought it was a cool idea to say, "Now see if you can fall to sleep before your shadow does."
Well, that worked; for half a minute! Before my daughter jumps out of her bed, and wandered around the bedroom with her eyes firmly closed declaring "I win, I’m sleep walking."
When my joyful mirth for such humour and sight in intelligence waned, I was transported back in time to recall, how I thought the teacher was incorrect, when I was told (at a similar age) that there was nothing in the universe that was faster than the speed of light; especially when I was running around the school yard in the midday sun.