... The Seasons . ... Section #1 Stargazers and Skywatchers described the observed motion of the Sun across the sky, in different seasons of the year. ... If the Earth's axis were perpendicular to the ecliptic, as in the drawings here, the Sun's position in the sky would be halfway between the celestial poles, and its daily path, seen from any point on Earth, would stay exactly the same, day after day. Each point on Earth would be carried around the axis AB once a day. ... The Sun and Seasons . ...

... With enough velocity, a spacecraft can break loose from the Earth's gravity and enter an orbit around the Sun, like that of a planet. If it then orbits the Sun with the same period as the Earth--one year--it may keep a fixed position relative to Earth. ... If the distance is just right--about 4 times the distance to the Moon or 1/100 the distance to the Sun--the spacecraft, too, will need just one year to go around the Sun, and will keep its position between the Sun and the Earth. ...

Luna and Io - A Comparison Study . ... They will construct paper scale models of Io , Luna , Earth and Jupiter and use these models to explain the differences between the two moons. ... Explain to the students that the picture is not to scale, but that it represents Jupiter and one of its moons. ... Have the students divide into groups of three or four and construct scale models of the Earth/Luna system, and the Jupiter/Io system, using the facts on the data sheets. ... Jupiter, Io, Earth, and Luna . ...