Slide 2 Mr. Harpers science mini lesson with audio Click on the
speaker icon for sound Slide 3 h Our planet is always moving. Earth
spins around, or rotates, once every 24 hours. Thats why we have
day and night. Slide 4 h About half of each 24 hour period, our
part of Earth is turned toward the sun. Slide 5 h h Sunlight shines
through our atmosphere and the sky appears to be bright blue. Slide
6 h During the other half of each 24 hour period, our part of Earth
is turned away from the sun and the sky is dark. This allows us to
see stars and other planets. Slide 7 365 days means Earth rotates
(spins) 365 times during each orbit around the sun. As it rotates,
Earth is also revolving (orbiting) around the sun like a ball on a
very long string. One orbit takes about 365 days (1 earth year).
Slide 8 h The suns gravity is the reason Earth and the other
planets dont fly off into space. If Earth slowed down it would fall
into the sun. If it went faster it would fly out into space. Earth
is moving at exactly the right speed to stay in orbit around the
sun. Slide 9 h h Mercury 88 days Venus 244 days Earth 365 days
Pluto 90728 days ( 248 years ) Mars 687 days Venus 244 days Jupiter
4332 days ( 12 years ) Uranus 30688 days ( 84 years ) Saturn 10759
days ( 29 years ) Neptune 60182 days ( 168 years ) Just like a
shorter string would make a ball go around faster, a smaller orbit
makes a planet go around the sun faster. Slide 10 h h Mercury 88
days Venus 244 days Earth 365 days Pluto 90728 days ( 248 years )
Mars 687 days Venus 244 days Jupiter 4332 days ( 12 years ) Uranus
30688 days ( 84 years ) Saturn 10759 days ( 29 years ) Neptune
60182 days ( 168 years ) Each planet orbits at just the right speed
to stay in orbit. This picture makes the planets look closer to the
sun than they really are. Slide 11 Because they orbit the sun at
different rates of speed, the planets seem to come and go every few
weeks. When a planet moves to the other side of the sun, we cant
see it. h Slide 12 h But we are also moving in other ways. Our
whole solar system is orbiting the center of the Milky Way galaxy.
A galaxy is a spinning group of billions of stars. This picture
shows the location of our sun, but its too small to see. The bright
spot in the center is a concentration of several billion stars
(suns) not just one. It takes 250 million years for our solar
system to complete one orbit around the center of our galaxy. Slide
13 h But our galaxy is moving, too. There are billions of galaxies,
all expanding away from the center of the universe.
