It’s almost time for a very special day.
Can you guess why?
[Squeaks squeaks]
No, it’s not my birthday … [Squeaks squeaks]
No, it’s not the day of the parade, either.
It’s the longest day of the year … and, it’s the first official day of summer!
There are lots of days that might seem really long.
Maybe you’ve felt that way when you were excited about something that’s going to
happen, like your birthday, or the first day of vacation.
The day before an exciting event can seem like it takes a long time.
But even if a day feels that way, it’s not really any longer.
All days have the same amount of time in them—about 24 hours.
When we say it’s the longest day of the year, what we really mean is that there’s
the longest amount of daylight, which means that the sun is up for the longest amount
of time, and it’s dark for the shortest amount of time.
This special day is called the summer solstice, and when it happens, it’s officially summer.
Have you ever noticed that in the winter it gets dark pretty early?
It’s probably dark before you go to bed.
But in the spring and summer, like now, the sun goes down much later.
[Squeaks squeaks]
Yeah, that’s exactly what you asked about the other day!
Squeaks asked if he could change his bedtime so it’s after dark, since he doesn’t like
going to sleep when it’s still light out.
But instead we just changed his curtains so they make the room darker, and that helped,
right?
[Squeaks squeaks]
We have a summer solstice every year because of the way our planet moves around the sun—and
how it’s tilted.
Because even though you don’t feel it, the Earth is always moving!
It takes a whole year for the Earth to go around the sun one time.
And while it’s moving around the sun, Earth is also spinning around in place around an
imaginary line we call the axis.
The Earth’s axis runs up and down, right through the North Pole and the South Pole.
One turn on the Earth’s axis takes 24 hours — that’s what makes one day.
But there’s something else about the Earth’s axis: it isn’t exactly straight up and down.
It’s tilted, just a little bit.
… and it’s this tilt that causes the summer solstice!
Right now, the tilt is pointing the northern, or top half of the Earth toward the sun.
Which means that during one spin — which remember, is 24 hours, a whole day and night
— the top half of the Earth spends more time in the sun than in the dark.
The summer solstice is when the tilt is pointing us exactly toward the sun.
Here in the top half of the world, that’s usually on June 21st, although it’s sometimes
on June 20th or 22nd.
Soon, the tilt will start to point more sideways compared to the sun, and eventually it will
face away from the sun, on what we call the winter solstice.
That will be the shortest day of the year, with the least amount of sunlight.
But for now, while we’re pointed toward the sun, we get long days!
For people who live in the southern, or bottom half of the world, everything is the opposite.
When the Earth’s tilt points the top half of the world toward the sun, it points the
bottom half away from the sun.
So for people who live in places like Australia or South America, it’s about to be the shortest
day of the year, not the longest!
Their winter solstice is the same day as our summer solstice, and their summer solstice
is the same day as our winter solstice!
Since it's almost our summer solstice and the first day of summer, I’m going to go
stock up on sunscreen!
Squeaks and I hope you have a happy solstice, wether it's summer or winter!
Thanks for joining us!
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We’ll see you next time, here at the Fort!