6. why do you BLINK?
the very front of your eyes is made of an extremely sensitive see-through screen rather like the windscreen of a car.
it's very important that it stays clean and moist so that you can seeas well as possible.
so every 10 or 20 seconds, your eyelids close, spreading a thin layer of tears over your eye which washes off any bits of dust or anything else that may have got into it.
if we didn't blink so much,we wouldn't be able to see properly.
so,it's lucky we do!
7. what is TIME?
we measure time by breaking it down into little chunks
some of these chunks are tied to astronomical events, such as
the rotation of the Earth (a day),
the orbit and phases of the Moon (a month),
and the orbit of the Earth around the Sun (a year).
the reason we have 60 minutes in an hour and 60 seconds in a minute is thought
to date back to the accident Babylonians,
who lived in what is now known as Iraq nearly 3700 years ago.