Astronomy for Kids

The Earth's orbit around Sol and other things 

The Earth beneath you and the night sky above you are both moving relative to each other and you, and the universe around you. The Earth not only spins counterclockwise on its axis, but also orbits Sol about once every 365 spins on its axis, give or take a few minutes, in a counterclockwise direction. Speeding through space and time at an impressive 100,000 km/hr (60,000 miles/hr), around 100 times faster than a speeding bullet, faster than the launch speed for any known spacecraft and certainly faster than Superman, the Earth's orbit isn't a perfect circle. In fact, the distance of the Earth to Sol during its transit differs significantly at different times, due to this non-circular orbit, but on average the distance between Earth and Sol is about 150 million kilometers (93 million miles). This distance astronomers call an astronomical unit, or AU, and this unit is used by astronomers as a measuring stick of sorts, only on a bigger scale than the mile or kilometer.

The axis of the Earth during its orbit is also tilted about 23 1/2 degrees from the line perpendicular to the flat plane traced out by the Earth's orbit around Sol. This flat plane astronomers call the ecliptic plane and in reality this axis tilt has no meaning in Einstein's space and time and is only useful in relation to the ecliptic plane. In Einstein's universe, the notion of tilt by itself has no meaning in space and time, where up and down are related to away from the center of the Earth (or any body with mass) and toward the center of mass, respectively.

The Earth's axis also continues to point in the same general direction throughout Earth's orbit of Sol. This direction is toward Polaris, often called the North Star by travelers and navigators, and lies within 1 degree of the north celestial pole, which makes it useful for navigating on the surface of Earth. This direction closely marks the direction of due north in the night sky and the altitude of Polaris is nearly equal to the latitude of an observer on the surface of Earth. Navigators and star gazers have used these facts for thousands of years to determine direction and location on the Earth's surface and travel from one destination to another.

The changing position of Earth during the 365 days it takes the Earth to complete one orbit also results in the night sky above your head changing nightly. Sol appears to move against a background of distant stars in the 88 constellations in the Milky Way above you. The 12 constellations along the ecliptic plane star gazers refer too as the constellations of the Zodiac, but a thirteenth constellation, Ophiuchus lies partially on the ecliptic plane, as well.

The combination of the rotation of the Earth on its tilted axis and orbit around Sol, also helps create the seasons we experience on Spaceshipearth1. In future articles, we'll talk about the seasons of Earth, the meaning this has for life on Earth, and how this relates to the study of the movements of the exo-planets humans have, so far, viewed during the human journey to the beginning of the universe.