Lagrange Points:Īnother interesting characteristic of the Earth’s orbit around the Sun has to do with Lagrange Points. While it is true that Earth does have a perihelion, or point at which it is closest to the sun, and an aphelion, its farthest point from the Sun, the difference between these distances is too minimal to have any significant impact on the Earth’s seasons and climate. Thus the seasonal effects in the south are reversed. The axial tilt in the southern hemisphere is exactly the opposite of the direction in the northern hemisphere. In the northern hemisphere, winter solstice occurs around December 21st, summer solstice is near June 21st, spring equinox is around March 20th and autumnal equinox is about September 23rd. Six months later, when the northern hemisphere is tilted towards the Sun, the seasonal order is reversed. In short, when the northern hemisphere is tilted away from the Sun, it experiences winter while the southern hemisphere experiences summer. Over the course of a year the orientation of the axis remains fixed in space, producing changes in the distribution of solar radiation.
The four seasons are determined by the fact that the Earth is tilted 23.4° on its vertical axis, which is referred to as “axial tilt.” This quirk in our orbit determines the solstices – the point in the orbit of maximum axial tilt toward or away from the Sun – and the equinoxes, when the direction of the tilt and the direction to the Sun are perpendicular. Third, there is the role Earth’s orbit plays in the seasons, which we referred to above. That is why the difference between the Earth’s distance from the Sun at perihelion and aphelion is very little – less than 5 million km. If it is close to one, the ellipse is long and slender.Įarth’s orbit has an eccentricity of less than 0.02, which means that it is very close to being circular. If a planet’s eccentricity is close to zero, then the ellipse is nearly a circle. In describing the nature of elliptical orbits, scientists use a factor known as “eccentricity”, which is expressed in the form of a number between zero and one. It also meant that both Earth and Mars did not orbit the Sun in perfectly circular patterns. This coincided directly with the planets’ aphelion and perihelion, meaning that the planets’ distance from the Sun bore a direct relationship to the speed of their orbits. Credit: Wikipedia/HankwangĪfter measuring the orbits of the Earth and Mars, he noticed that at times, the orbits of both planets appeared to be speeding up or slowing down. An illustration of Kepler’s three laws of motion, which show two planets that have elliptical orbits around the Sun. This orbital pattern was first described by Johannes Kepler, a German mathematician and astronomer, in his seminal work Astronomia nova (New Astronomy). This is what is known as an “elliptical” orbit.
Rather than being a perfect circle, the Earth moves around the Sun in an extended circular or oval pattern.
Next, there is the nature of the Earth’s orbit. The Earth completes one orbit every 365.242199 mean solar days, a fact which goes a long way towards explaining why need an extra calendar day every four years (aka. Orbital Characteristics:įirst of all, the speed of the Earth’s orbit around the Sun is 108,000 km/h, which means that our planet travels 940 million km during a single orbit. And what they have found has helped us to understanding why we measure time the way we do. If this bright celestial body – upon which depends the seasons, the diurnal cycle, and all life on Earth – does not revolve around us, then what exactly is the nature of our orbit around it?įor several centuries, astronomers have applied the scientific method to answer this question, and have determined that the Earth’s orbit around the Sun has many fascinating characteristics. Ever since the 16th century when Nicolaus Copernicus demonstrated that the Earth revolved around in the Sun, scientists have worked tirelessly to understand the relationship in mathematical terms.
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