This entry is missingOverview, add relevant content to make the entry more complete, and it can also be upgraded quickly. Hurry upeditCome on!
The revolution of the earth around the sun refers to the periodic rotation of the earth around the sun.The orbit of revolution is an ellipse that is very close to a perfect circleangular velocityIt's 360 degrees a year,Average linear speed940000000 km per year.
The elliptical orbit is a compromise between the Earth's gravity on nearby celestial bodies.A system with only one planet and one star is meaningless.During the formation of the early solar system, the primitive planets wereasteroidAnd a series of other disturbances led to the formation of elliptical orbits.This is called the theory of planetary migration.
First of all, a perfectly circular orbit is also a kind of elliptical orbit, which is just a special elliptical orbit.
The earth revolves around the sun. Under given energy conditions, there are countless possible orbits,Circular orbitJust one of them.If you want the earth to move in a perfectly circular orbit, the energy and momentum of the earth must meet certain conditions.Is the kinetic energy Ek andpotential energyThe relationship of Ep satisfies Ek=- Ep/2.Or when Ek=- EP/2,Earth movementThe direction is perpendicular to the sun earth line.This condition is very harsh. Even if the earth moves in a circular orbit, a small disturbance can change this state, making the earth move in a new elliptical orbit.
revolution speed
Announce
edit
averageangular velocityIt is 360 degrees a year, or 59 minutes a day.Average linear speed940000000 kilometers per year, or 29.78 kilometers per second.Instant angular velocity and instantLinear velocityThere are seasonal changesConservation of energyThe closer to the sun,potential energyThe smaller, the greater the kinetic energy, the greater the instant linear velocity and instant angular velocity.On the premise of the conservation of angular momentum, that is, the area swept by the connection between the earth and the sun is constant in an equal length of time.
Included angle of revolution
Announce
edit
EarthlyAutorotation shaftIt inclines 66 ° 34 'to the orbital plane of its revolution.This angle is similar to the tilt of the pen holder and the desktop when people use a pencil to write.It is sometimes figuratively compared to the earth's "oblique body" circling the sun.
This relationship between the earth's rotation and its revolution, astronomy andgeographyIt is usually used onCosine angle(23 ° 26 ′), i.eEquatorial surfaceAnd track surfaceAngle of intersectionTo represent;In the geocentric celestial sphere, the ecliptic andCelestial equatorAnd calledYellow declination angle, also known as "Yellow Chida Distance".The two intersections of the ecliptic and the celestial equator are calledAries Palace（Aries）The first point andLibra（libra）First, inNorthern HemisphereAre respectively referred to asVernal equinoxandAutumnal equinox, collectivelyEquinox。The two points on the ecliptic that are farthest from the celestial equator are calledCancer Palace（Cancer）The first point andCapricorn（Capricornus）The first point is the summer solstice andWinter solstice, collectivelySolstice。The second solstice is 23 ° 26 'from the celestial equator, called the Yellow Chida Distance, which is the expression of the intersection angle of the Yellow Angle on the geocentric celestial sphere.
The existence of the declination angle has important astronomical and geographical significance.As mentioned earlier, the intersection of yellow and red isPrecession of earth axisOne of the causes of formation;It still seesSolar daylengthAnnual changeThe main reason for.The next section will also explain that the angle of intersection between the yellow and the red is the change of the four seasons on the earththe five zonesThe root cause of the distinction.
Rail diameter
Announce
edit
KeplerOfLaws of planetary motionAt the beginning of the 17th century, the solar system in the eyes of astronomers reached an unprecedented consistency with its true appearance.The sun is at the center;Six planets known at that time——Mercury、Venus, Earth, MarsJupiteralsoSaturnFrom the inside to the outside, they circle on their respective elliptical orbitsSolar motion。However, there is a major defect in this "family photo" of the solar systemscaleBecause astronomers at that time did not know the distance between any planet and the sun, they only knew the ratio of the distance between these planets and the sun, in which the average distance between the earth and the sun was defined asAstronomical unitBy analogy, the distance between the innermost Mercury and the sun is 0.3871 astronomical units, while the outermost Saturn moves slowly in its orbit 9.5388 away from the sun.
Because the "astronomical unit" is astronomy, especially astronomySurveyingTherefore, accurate measurement of the distance between the earth and the sun has become one of the "most noble astronomical problems".
But this is not an easy thing. The sun is high in the sky and out of reach. Obviously, it cannot be directly used as measuring the size of your roomTapeIt can only be measured indirectly.Astronomers soon thought“parallax”The so-called "parallax" refers to the difference in direction when observing the same target at two different points. This difference in direction can be achieved bymobile computing Come out. If the distance between two points is known, use what you learned in middle schoolgeometryKnowledge can calculate the target toObservation pointDistance.It is easy to think that the farther the target is, the smaller its parallax. When the object is very far away, its parallax can be ignored and used as the observation background.The most common parallax in daily life is the movement of an object in your eyes relative to other objects when you look at the same object with your left and right eyes respectively.
But we need to measure the solarparallaxBut it is also a very difficult thing.First of all, its distance is too far, even if measured at both ends of the earth, its parallax is still very small, which requires very precise instruments;What's worse is that the sun is so bright that it completely submerges the starry sky that can be used as the background, so we have no moreRuler, which makesdirect measurement Its parallax has almost become an impossible task.This one has no scaleSolar system mapIt was used until the early 18th century.
In 1716, the famous British astronomerHarleyThe discoverer of comet,Edmundo HalleyAindirect determination Solar parallaxThis method requires the use of a rareAstronomical phenomenon——“Venus transit”, that is, the tiny size made by Venus“solar eclipse”When this phenomenon occurs, there is aSmall black spotEr, the shadow of Venus, passes through the surface of the sun.Halley's method is to get the parallax of the sun by measuring the time when the small black spot passes through the sun's surface at different observation sites, and then through a series of calculations.
But unfortunately, Harley died before the next transit of Venus appeared.German astronomical machine Enke calculated the distance between the sun and the earth as 153 million kilometers in 1824 by using the observation results of two transit times of Venus in 1761 and 1769.Later astronomers made use of the two subsequent transits of Venus in 1874 and 1882 to make this figure accurate to 149.34 million ± 96000 kilometers, which is very close to the modern value of 149.59787 billion kilometers.
Of course, this value is the average distance between the sun and the earth, which is the semi major axis of the ellipse in geometry.howeverEarth orbitIt is very close to a perfect circle. Its eccentricity is only 0.0174, which means that the farthest distance between it and the sun is only 1.74% farther than the average distance, about 2.6 million kilometers.
Revolution period
Announce
edit
365 days, 6 hours, 9 minutes and 9.5 seconds
24 hours, 36 minutes and 38 seconds
366 day leap year
36min 38s
A leap year is a year that can be divided by 400
The stellar year is the time required for the sun to pass through a star twice in a row on the celestial sphere, with a length of 365.25636 ordinary days.
In the regression year, the sun passes through the celestial sphere twice in a rowVernal equinoxThe required time is 365.24220 ordinary days.
Earth revolutionIn the process of orbit and direction, every point on the route the earth passes through is on the same plane and forms a closed curve.This kind of closed curve that the earth moves in the process of revolution is calledEarth orbit。If we regard the earth as a particle, then the earth's orbit actually refers to the orbit of the earth's center.Strictly speaking, the median position of the earth's revolution is not the sun's center, but the common position of the earth and the sunQuality Center, not only the earth is rotating around the common mass center, but also the sun is rotating around the point.But the sun issolar systemThe Earth is just an ordinary planet in the solar system.The mass of the sun isEarth massThe public mass center of the sun and the earth is only 450 kilometers away from the sun center.This distance is about 700000 kilometers away from theSolar radiusCompared with the distance of 150 million kilometers between the sun and the earth, it is really insignificant.Therefore, it is very close to the actual situation to regard the revolution of the earth as the movement of the earth around the sun (center).The shape of the earth's orbit is a nearly circular ellipse, and the sun is at one of the focuses of the ellipse.The ellipse hasSemimajor axis、Semi stub shaftandHalf focal lengthAnd other elements, respectively represented by a, b and c, where a isStub shaftThe distance between the two ends to the focus (F1, F2).There is such a relationship between semi focal length and semi major axis and minor axis: c2=a2-b2, the ratio of semi focal length c to semi major axis a, c/a, is ellipticalEccentricity, expressed by e, that is, e=c/a. Eccentricity is a quantitative expression of elliptical shape, and the value of e is greater than 0 but less than 1.The closer the ellipse is to the circle, the smaller the value of e, that is, close to 0;On the contrary, the flatter the ellipse, the greater the value of e.After measurement, the semi major axis a of the Earth's orbit is 149.6 million kilometers,Semi stub shaftB is 149.58 million kilometers.According to this data, the eccentricity of the Earth's orbit is calculated as: visible, the Earth's orbit is very close to a circle.Since the earth's orbit is elliptical, the distance between the sun and the earth changes constantly as the earth revolves around the sun.The point in Earth's orbit closest to the sun, that isElliptical orbitThe long axis ofPerihelion。In modern times, the date when the Earth passed the perihelion was about the beginning of January every year.At this time, the earth is about 147.1 million kilometers away from the sun, usually called perihelion.The point in the earth's orbit farthest from the sun, that is, the far end of the long axis of the elliptical orbit from the sun, is calledApohelion。In modern times, the Earth passed aphelion in early July every year.At this time, the earth is about 152.1 million kilometers away from the sun, usually calledTelehelion。Perihelion and telehelionaverage value149.6 million kilometers, which isAverage distance between the sun and the earth, i.e. 1Astronomical unit。according toPerimeter of ellipseOfCalculation formula: L=2 πα (1-0.25 × e2) The total length of the earth orbit is 940 million kilometers.
