[Theme Music] You've seen the sunset. Right? And if you get up early enough maybe you've seen it rise too. But have you ever wondered if the Sun rises every day and sets every night where does it go when we can't see it? Well, nowhere. It's actually us that goes somewhere because we're on the
earth and our planet is always turning, or spinning, on its axis. Imagine a line passing through the
center of the earth that goes both through the North Pole and the South
Pole. We call that invisible line the axis.
Earth spins around on this axis like a top This spinning movement is called the
Earth's rotation and, the Earth's rotation is what gives us day and night everyday, all year. If you're on the side of the earth that's facing away from the
Sun as the earth is spinning, it's night. If you're on the side facing
the Sun it's, you guessed it, day. Now hold on tight because the earth is
actually moving in more ways than one. At the same time that the Earth spins on
its axis it also orbits or revolves around the Sun. This movement is called its revolution. One full orbit all the way around the Sun is one revolution and the earth takes 365 days, or one year, to complete a revolution. So have you got all of this so far? The earth is rotating on its axis, creating day and night and
the same time its revolving all the way around the Sun. Now here's the thing: as
the earth is both rotating and revolving it's not sitting straight up and down.
Its axis is actually tilted just a little. It's not all that much, but this
tilt causes one part of the earth to lean towards the Sun, while another part
of it is leaning away. This means that different parts of our planet surface
gets different amounts of sunlight and heat. So why am I telling you all of this? Well, as the earth travels around the Sun it creates a pattern throughout the year. This pattern happens over and over again
and i'm sure you've noticed it. At certain times of the year you see the
northern hemisphere leans towards the Sun and the southern hemisphere leans
away, and at other times the southern hemisphere leans towards the Sun and the
northern hemisphere leans away. That pattern, my friend, is what makes seasons.
When the part of the world that you're living in is leaning towards the Sun
it's warm and the days are long: summer. When you're on the part that's leaning
away from the Sun it's cold in the days are short: winter.
In between it's spring or autumn. If the earth were tilted we would have
the same season all year long. So, revolution, rotation, orbit. Is your head
spinning? Let's do a demonstration to shed a
little light on these concepts. Okay you're gonna need a globe in a
table lamp without a shade. Plus a table to put them both on. Put the
lamp in the center of the table and turn it on, put the globe on one side of the
table. Now hit the lights. The globe is earth- makes sense right? The lamp at the center of the table is
the Sun at the center of the solar system. Now slowly spin the globe as the Earth
rotates the Sun lights up one side of the planet better than the other. It's day where the light is shining more
brightly on the globe and night where it's not. Now let's see what the Earth's
revolution around the Sun looks like. Give the globe a few spins with one hand
while slowly pushing the globe in a circle around the Sun or the lamp with
your other hand. So do you notice how the earth keeps rotating as it revolves
around the Sun? If this were the real Sun and Earth by the time you get back to
where you started the global have completed 365 rotations
or days and that's another year gone by. So what does all this show us? It shows that what looks to us to be the
motion of the Sun in the sky is really caused by the motion of the earth. So now
you know when you look up and see the sun setting or rising, it's not going around us it's sitting
pretty much at the center of the solar system while we and the seven other
planets go around it. That sun, always going to be the center of attention. [Theme music]
