The first day of spring is a really special
day. And not just because it’s when we start
thinking about flowers blooming, and the days warming up, and birds coming back from their
winter homes. It’s because the first day of spring is
also when something special happens -- something called an equinox. Isn’t that such a cool word? But what does it mean? Well, before we can understand exactly what
an equinox is, we’ll need to learn a little bit about the Earth...specifically, how the
Earth moves. Even though you don’t feel it, the Earth
is always moving. In fact, it’s moving in two different ways. First, right now, the Earth is moving around
the Sun like this. It takes a whole year for the Earth to go
around the Sun one time. And secondly, at the same time, the Earth
also spins around in place, like this! if you’ve ever played with a top, then you
know the top spins around its center. So does the earth! It spins around an imaginary line we call
the axis. The Earth’s axis runs up and down this way
-- right through the North Pole and the South Pole. But the Earth’s axis isn’t exactly straight
up and down. It’s tilted, just a little bit. So, for most of the year, one half of the
Earth is tilted toward the Sun, and the other half of the Earth is tilted away from the
Sun. And that little bit of tilt makes a lot of
difference down here on the ground. That’s because, the half of the earth that’s
tilting toward the sun gets more direct sunlight. That means it’s warmer there, and the days
are longer. When that half of the Earth is tilting toward
the sun as far as it can go, it’s summer there! And at the same time, the half that’s pointing
away gets less direct sunlight. So, the days are shorter, and colder. There, it’s winter! Now, as the Earth moves this way, around the
sun, the top half and the bottom half of the Earth change which way they’re tilting. After a few months, the part that was tilting
toward the Sun starts to tilt away, and the part that was leaning away starts to lean
toward it. This whole cycle -- with different parts of
the Earth getting more, and then less, direct sunlight throughout the year -- is why we
have seasons! BUT! There are two times of year when /neither/
side of the earth is pointing right toward the sun. Halfway between when /one/ half is tilted
toward the Sun, and when the /other/ half is titled away from the sun ... the part that’s
getting the most direct light from the Sun is right in the middle! Around the middle of the Earth, there’s
an imaginary line, called the equator. And when the equator is getting the most direct
light from the Sun, then both halves of our planet get the same, or equal, amount of sunlight. And hey, ‘equal’ kind of sounds like ‘equinox’! And on an equinox, /everything/ is kind of
in the middle — temperatures are often warmer than they were in winter, but not as warm
as they will be in summer. And the days are longer than they were in
the winter, but not as long as they’re going to get in summer! Sounds like this describes spring perfectly! The spring equinox happens around March 21. And where I live -- up here -- this part of
the Earth starts to tilt more toward the Sun, and gets more direct sunlight. This means we’re leaving the colder, shorter
days of winter, and starting to get the warmer, longer days of spring and summer. Now, there’s another equinox, too! Because, remember, I said there are /two/
times a year when neither half of the Earth is pointing toward the sun. After summer’s over, the part of the Earth
that was leaning /toward/ the sun starts to tilt away. Right around September 21, the most direct
sunlight hits the Earth at the equator … again! And as that part of the Earth continues to
tilt away, it will head into autumn, and eventually winter. But, for now, where I live, we’re looking
forward to our part of the Earth tilting toward the sun! Which
means that warmer weather and longer days are on the way! So until next time—happy spring equinox! Do you have a question for us? If you do, grab a grownup and ask them to
help you to either leave a comment on this video, or to send an email to Kids@SciShow.com!
