Period of revolution of the Earth around the Sun. Orbit of the planet Earth

Earth is a cosmic object involved in the continuous movement of the universe. It revolves around its axis, overcomes millions of kilometers in orbit around the Sun, along with the entire planetary system, slowly bends around the center of the Milky Way galaxy. The first two movements of the Earth are clearly visible for its inhabitants by changing the diurnal and seasonal illumination, changing the temperature regime, the peculiarities of the seasons. Today, in the center of our attention is the characteristics and period of the Earth's revolution around the Sun, its influence on the life of the planet.

General information

Our planet moves along the third in distance from the luminous orbit. From the Sun, the Earth averages 149.5 million kilometers. The length of the orbit is about 940 million km. This distance the planet overcomes in 365 days and 6 hours (one star, or sidereal, year - the period of revolution of the Earth around the sun with respect to distant stars). Its speed during the movement in orbit reaches an average of 30 km / s.

For the terrestrial observer, the revolution of the planet around the luminary is expressed in the change in the position of the Sun in the sky. It moves one degree per day in an easterly direction with respect to the stars.

Orbit of the planet Earth

The trajectory of the motion of our planet is not an ideal circle. It is an ellipse with the Sun in one of its foci. This form of orbit "forces" the Earth to approach the light, then away from it. The point at which the distance from the planet to the Sun is minimal is called perihelion. Aphelion is the site of the orbit, where the Earth is as far from the luminaries as possible. In our time, the first point is reached by the planet around January 3, and the second - on July 4. At the same time, the Earth moves around the sun not with a constant speed: after passing through the aphelion, it accelerates and slows, breaking the perihelion.

The minimum distance separating the two cosmic bodies in January is 147 million km, the maximum distance is 152 million km.

Satellite

Together with the Earth, the Moon moves around the Sun. When viewed from the north pole, the satellite moves counter-clockwise. The Earth's orbit and the Moon's orbit lie in different planes. The angle between them is about 5 °. This mismatch significantly reduces the number of lunar and solar eclipses. If the planes of the orbits were identical, then one of these phenomena happened once in two weeks.

The Earth's orbit and the Moon's orbit are arranged in such a way that both objects rotate around the common center of mass with a period of about 27.3 days. At the same time, the tidal forces of the satellite gradually slow down the movement of our planet around the axis, thus slightly increasing the duration of the day.

Effects

The axis of our planet is not perpendicular to the plane of its orbit. This slope, as well as the movement around the luminary lead to certain climate changes throughout the year. The sun rises above the territory of our country at a time when the north pole of the planet is inclined to it. The day is getting longer, the temperature is rising. When the north pole deviates from the sun, the cooling is replaced by a cold snap. Similar changes in climate are also characteristic of the southern hemisphere.

The change of seasons occurs at the points of the equinox and solstice that characterize a certain position of the earth's axis relative to the orbit. Let us dwell on this in more detail.

The longest and shortest day

The solstice is the moment of time when the planetary axis is maximally inclined towards the luminary or in the opposite direction. The orbit of the Earth's motion around the Sun has two such sections. In the middle latitudes, the point at which the luminary turns out to be at noon rises higher every day. This continues until the summer solstice, which falls on June 21 in the northern hemisphere (the longest day). Then the place of the midday residence of the luminaries begins to decline until December 21-22. These days in the northern hemisphere there is a winter solstice. In the mid-latitudes the shortest day comes, and then it begins to arrive. In the southern hemisphere, the slope of the axis is opposite, so the winter solstice falls here in June, and the summer solstice falls on December.

Day is equal to night

Equinox is the moment when the axis of the planet becomes perpendicular to the plane of the orbit. At this time, the terminator, the boundary between the illuminated and the dark half, passes strictly along the poles, that is, the day is equal to the night. There are also two such points in the orbit. The vernal equinox falls on March 20, the fall equinox is on September 23. These dates are valid for the northern hemisphere. In the southern similar to the solstices, the equinoxes change places: March is autumnal, and in September - spring.

Where is it warmer?

The Earth's circular orbit - its features in combination with the inclination of the axis - has one more consequence. At the moment when the planet passes closest to the Sun, the South Pole looks in its direction. In the corresponding hemisphere at this time, summer. The planet at the time of passing perihelion receives 6.9% more energy than when overcoming the aphelion. This difference is in the southern hemisphere. During the year, it receives slightly more solar heat than the northern. However, this difference is unimportant, since a large part of the "additional" energy falls on the water expanses of the southern hemisphere and is absorbed by them.

Tropical and sidereal year

The period of revolution of the Earth around the Sun relative to the stars, as already mentioned, is approximately 365 days 6 hours and 9 minutes. It's a sidereal year. It is logical to assume that the change of seasons is within this segment. However, this is not quite so: the time of revolution of the Earth around the Sun does not coincide with the full period of the season change. It is the so-called tropical year lasting 365 days 5 hours and 51 minutes. It is measured most often from one vernal equinox to another. The reason for the twenty-minute difference between the duration of the two periods is the precession of the earth's axis.

Year calendar

For convenience, it is considered that there are 365 days in a year. The remaining six and a half hours are added per day for four revolutions of the Earth around the Sun. To compensate for this, and in order to prevent an increase in the difference between the calendar and the sidereal year, an "additional" day is introduced, on February 29.

Some influence on this process has a single satellite of the Earth - the Moon. It is expressed, as noted earlier, in the slowing down of the rotation of the planet. Every hundred years the duration of the day increases by about one thousandth.

Gregorian calendar

A familiar count of days was introduced in 1582. The Gregorian calendar, in contrast to the Julian calendar for a long time, allows the "civil" year to correspond to the full cycle of the seasons. According to him every four hundred years exactly repeat the months, days of the week and dates. For the duration of the year in the Gregorian calendar is very close to tropical.

The goal of the reform was to return the day of the spring equinox to the usual place - on March 21. The fact is that from the first century AD to the sixteenth, the real date, when the day is equal to the night, moved on March 10th. The main motivation for reviewing the calendar was the need to correctly calculate the day of Easter. To do this, it was important to keep March 21 afternoon, close to the real equinox. With this task the Gregorian calendar copes very well. The displacement of the date of the vernal equinox for one day will not occur until after 10,000 years.

If we compare the calendar year and the tropical year, then more significant changes are possible. As a result of the features of the movement of the Earth and the factors affecting it, about 3200 years will accumulate a discrepancy with the change of seasons in a single day. If at this time it will be important to preserve the approximate equality of the tropical and calendar year, reform will again be required, analogous to that which was carried out in the sixteenth century.

The period of revolution of the Earth around the Sun, thus, corresponds with the concepts of the calendar, sidereal and tropical year. Methods for determining their duration have been improved since antiquity. New data on the interaction of objects in outer space make it possible to make assumptions about the relevance of the modern understanding of the term "year" in two, three or even ten thousand years. The time of the Earth's rotation around the Sun and its connection with the change of seasons and the calendar is a good example of the influence of global astronomical processes on a person's social life, as well as the dependencies of individual elements within the global system of the universe.