19PHOTOS: GETTY X3, NASA ILLUSTRATIONS: RAJA LOCKEY
HOW DOES ‘GLOW IN
THE DARK’ WORK?A lot of things can glow in the dark, including your washing
powder and, of course, those funky stars you stick on a child’s
bedroom ceiling. They work through phenomena called
phosphorescence and fluorescence. The material absorbs
energy (usually in the form of a particular colour light) and then
releases it as another colour light. Fluorescent materials do this
all at once, so, when you shine UV light (from a torch or the Sun)
on washing powder, it absorbs the UV and then emits it as blue
colour (which we associate with clean clothing, which is why
the washing powder people add it to the mix). Meanwhile
phosphorescent materials, like glow-in-the-dark stars,
do their emitting much more slowly. This enables them to shine
for a few minutes after the bedroom lights are switched off. ML When we sleep, a lot goes on in our bodies. We continue to breathe
and growth hormone is released – we do not need to be awake
for these things to happen. Similarly, we have some awareness
of our body position and movements, and some people even manage
to sit up or walk during sleep! Most of us have enough awareness
to ensure that we do not fall out of bed, but this ability develops over
time. Young children are still growing and understanding how their
bodies fit into the world around them, which is why they might benefit
from a bedrail. AGrWHY DON’T WE FALL OUT OF
BED MORE OFTEN?