[ Intro ]
Oh my gosh!
Squeaks and I were having such a wild game
of catch that Squeaks’s watch flew off and
smashed to smithereens!
You know what they say… time flies when
you’re having fun.
[Squeaks is distressed…]
So if your watch has broken down... how will
you know when it’s time for lunch?
Not to worry, Squeaks!
You can still figure out what time it is,
by making a sundial!
[Squeaks is relieved.]
A sundial is a device that uses the sun to
tell time.
It’s one of the oldest kinds of scientific
instruments we have, and the earliest one
used to measure time.
Most sundials these days use a flat base,
and a stick called a gnomon.
Whenever the sun is shining, the gnomon casts
a shadow.
And we can look at where the shadow falls
to tell us what time it is!
Since ancient times, people have been making
all kinds of sundials to help them tell time.
And having a sundial in your house, or your
school, or your library, lets everyone know
that around here, people care about science!
[Squeaks squeaks]
And also, it’s useful to have in case your
watch stops.
Want to make your own sundial?
As long as there’s sunlight outside, you
can!
Take something long and straight – like
a stick, or even a drinking straw – and
stick it into the ground.
That’s your gnomon!
If you live in the northern hemisphere like
Squeaks and me, your gnomon should be tilted
on a little bit of an angle, towards the north.
If you live in the southern hemisphere, it
should point south.
You may need a grown-up friend to help you
figure out which way north or south is.
Squeaks and I figured it out together!
[Squeaks squeaks.]
Every hour, go outside and look at the shadow
your gnomon is making on the ground.
Then, just make a mark where the shadow falls.
You can start at 7 AM, do it again at eight
o’clock, then nine o’clock… and keep
going until the sun sets!
You may want to set an alarm every hour, so
you don’t forget.
To mark down the gnomon’s shadow, you can
use a rock, sidewalk chalk, or really anything
you want.
You can get fancy and have your friend or
grown-up help you draw lines out from the
gnomon, like spokes on a wheel.
You can even add numbers!
That way, tomorrow you can go back outside,
look at the shadow, see what number or line
it’s falling on, and know exactly what time
it is!
At any hour of the day, the sun is lighting
up half of the earth.
And the earth is constantly rotating, from
west to east.
So when we see the sun rising in the east,
it means our part of the world is on the very
edge of the sunlit side.
And we cast a shadow behind us, to the west.
Same with the gnomon on your sundial!
In the morning, the gnomon casts a shadow
to the west.
And as the earth rotates through the day,
making the sun look like it’s moving across
the sky, the shadow moves clockwise – the
same direction as the hands on a clock! – around
the sundial.
If you want to make a sundial but there’s
no dirt around, you can try sticking a gnomon
into a bucket filled with sand or pebbles.
You can also use a paper plate!
You might need you r grown-up to help you
find the very middle of the plate, poke your
stick or your straw through, and point your
sundial towards the north or south, depending
on what hemisphere you’re in.
As long as the plate is facing the same direction
every time you take it outside, it’ll still
work!
And if you want to get really crazy, you can
make…. a HUMAN SUNDIAL!
Where the gnomon is you!
If you go outside and stand on the same spot
every hour and have a friend mark where your
shadow falls, you can go stand in the same
spot again tomorrow, look at your shadow,
and see what time it is!
[If we want to show Jessi and Squeaks doing
this:]
Squeaks and I took turns being the gnomon
and doing the measuring.
Just remember to never look directly at the
sun.
Even while you’re building a sundial!
You may want to measure your markings again
every few months, to keep your sundial as
accurate as possible.
And your sundial won’t be quite as accurate
as the ones that are made by scientists.
Perfectly accurate sundials need to be aligned
using a lot of math, depending on where you
are in the world, and depending on the time
of year!
But even though we’ll be getting Squeaks
a new watch, and in the meantime we have plenty
of other clocks, we’re still super psyched
to go outside and use the sun to find out
what time it is!
Oh, look at the time!
Our sundial says we have to go, but we’ll
see you next time here at the Fort!
[OUTRo]
