The revolution of the earth refers toearthThe Earth revolution around sun.EarthlikerotationHas its unique regularity, because the sungravitational fieldAs well as the role of rotation, the earth revolution caused by it also has its own laws.
The revolution of the earth followsEarth orbit, Earth's orbital planeYellow declination angle, the period of the earth's revolution, the speed of the earth's revolution and the effect of the earth's revolution.The time of the earth's revolution is one year.There are two obvious cycles in the process of earth revolution, namelyRegression yearandSidereal yearThe time of regression year is different from that of star year.The time difference of one year between the two is called precession.[1]
The time of the earth's revolution is one year.There are two obvious cycles in the process of earth revolution, namelyRegression yearandSidereal year。The year of regression refers to the time interval between the sun passing through the vernal equinox twice in a row, that is, the time from the vernal equinox to the vernal equinox when the sun center passes along the ecliptic from west to east, also known asSolar year。1 The regression year is 365.2422 days, that is, 365 days, 5 hours, 48 minutes and 46 seconds.This is based on 121Regression yearThe average value of.
Star year is the real cycle of the earth's revolution. During a star year, when viewed from the sun, the center of the earth starts from a point in the sky, circles the sun, and then returns to this point;If viewed from the earth, it means that the sun center starts from a point (a star) on the ecliptic (the circle obtained from the earth's orbital plane's interceptor), runs around the sky, and then returns to the same point (the same star).During a star year, the time required for the earth to orbit 360 ° is about 6:09:10 on 365 days.[1]
Yellow declination angle
Announce
edit
Earth revolution
Every point on the earth's orbit is in the same plane, which is the earth's orbital plane.The Earth's orbital plane is shown asEcliptic surface, same asAnnual apparent motion of the sunThe plane of the alignment is on the same plane.EarthlyrotationAnd revolution are carried out at the same time. On the celestial sphere, the rotation is represented by the celestial axis andCelestial equator, the revolution is shown asYellow axisandEcliptic。The celestial equator is in one plane, and the ecliptic is in another plane. The plane of these two concentric circles forms an included angle of 23 ° 26 '. This included angle is calledYellow declination angle。
The existence of the declination angle actually means that the earth's rotation axis is inclined to the earth's orbital plane during its revolution around the sun.Since the Earth's axis is perpendicular to the celestial equatorial plane, the intersection angle between the Earth's axis and the Earth's orbital plane should be 90 ° - 23 ° 26 ', that is, 66 ° 34'.No matter where the earth rotates, the inclination will remain unchanged.
In the process of the earth's revolutionSpatial orientationThere has been no obvious change for quite a long time.North Pole DirectionUrsa MinorAlpha star, i.ePolarisNearby, this is the location of the Celestial North Pole.That is to say, the earth axis moves in parallel during the revolution, so no matter where the earth rotates, the angle between the earth axis and the earth's orbital plane is constant, and the ecliptic angle is constant.
The existence of the ecliptic angle also indicates thatYellow poleDeviation from the celestial pole, that is, the Yellow North Pole (or the Yellow South Pole) and the Celestial North Pole (or the Celestial South Pole) are on the celestial spheredeviate23°26′。
What we sawglobeThe rotation axis is mostly inclined, and it is inclined 66 ° 34 'to the table top (representing the Earth's orbital plane)Equatorial surfaceThe intersection angle with the desktop is 23 ° 26 ', which is the intuitive embodiment of the yellow and red intersection angles.
Due to the influence of the ecliptic angle, the direct solar radiation point isTropic of CancerIt moves back and forth between the Tropic of Cancer and the Tropic of Cancer. There are two direct solar rays a year between the Tropic of Cancer and the Tropic of Cancer. There is no direct solar rays in the area north of the Tropic of Cancer and south of the Tropic of Cancer.[2]
revolution speed
Announce
edit
The revolution of the earth is periodicCircular motionTherefore, the earth's revolution speed includes angular speed and linear speed.If we use the star year as the Earth's revolution period, then the average angular velocity of the Earth's revolution is 360 ° every year, that is, after 365.2564 days, the Earth's revolution is 360 °, that is, about 0.986 ° every day, that is, about 59 ′ 8 ″ every day.The total length of the earth's orbit is 940000000 kilometers. Therefore, the average linear speed of the earth's revolution is 940000000 kilometers per year, that is, after 365.2564 days, the earth has rotated 940000000 kilometers, that is, 29.8 kilometers per second, about 30 kilometers per second (linear speed=94000000KM/365 days=940000000 kilometers/365x24x3600 seconds=29.8 kilometers per second, approximately 30 kilometers per second).
basisKeplerSecond law of planetary motion[3]It can be seen that the earth's revolution speed is related to the distance between the sun and the earth.The angular velocity and linear velocity of the earth's revolution are not fixed values, but change with the distance between the sun and the earth.When the earth passes the perihelion, its revolution speed is fast, and its angular velocity and linear velocity exceed their average values. The angular velocity is 1 ° 1 ′ 11 ″/day, and the linear velocity is 30.3 km/s;When the earth passes the apogee, its revolution speed is slow, and its angular speed and linear speed are lower than their average values. The angular speed is 57 ′ 11 ″/day, and the linear speed is 29.3 km/s.The earth passes through perihelion at the beginning of January and aphelion at the beginning of July every year. Therefore, from the beginning of January to the beginning of July of the same year, the distance between the earth and the sun gradually increases and the earth's revolution speed gradually slows down;From the beginning of July to the beginning of January, the distance between the earth and the sun gradually narrowed, and the earth's revolution speed gradually accelerated.
Earth revolution
We know that,Vernal equinoxAnd the autumnal equinox are equally divided into the ecliptic. If the earth's revolution speed is uniform, the sun will be regarded as moving from the vernal equinox toAutumnal equinoxThe time required should be equal to the time required for the apparent sun to move from the autumnal equinox to the vernal equinox, each half of the year.However, the earth's revolution speed is uneven, so the time to travel the same distance must be unequal.Apparent sun passes by vernal equinoxSolstice pointAt the autumnal equinox, the earth's revolution speed is slow, which takes more than 186 days, more than half of the whole year. At this time, it is the summer half year in the northern hemisphere and the winter half year in the southern hemisphere;Seeing the sun passing by the autumnal equinoxWinter solsticeBy the vernal equinox, the earth's revolution speed is fast, requiring 179 days, less than half of the whole year. At this time, it is the winter half year in the northern hemisphere and the summer half year in the southern hemisphere.It can be seen that the change of the earth's revolution speed is the fundamental reason for the unequal length of the four seasons on the earth.
First, learn a few nouns:
1. ILight year: refers to the distance traveled by light in a year in vacuum. Note that light year is a unit of length.
2. Earth revolution: Our earth revolves around the sun along an ellipse with a small eccentricity at a speed of 29.79 kilometers per second.It will take 365 days, 5 hours, 48 minutes and 46 seconds, or about one year, to complete a circle of about 940 million kilometers.(The average distance between the sun and the earth is 150 million kilometers)
3. The ratio of the distance traveled by light in a year to the circumference of the earth's revolution: since 1 light year is the distance traveled by light in a year, the circumference of the earth's revolution is the arc length traveled by the earth in a year, and the time is one year.So the ratio of distance is the ratio of the speed of light 300000km/s and the speed of earth revolution 29.79km/s: n=300000/29.79=10000 times.
4. The distance that the earth revolves around the sun: the distance here is actually the circumference, the arc length of a circle.We already know that the radius of the earth's orbit is 150 million kilometers, and it is easy to calculate the circumference.According to the formula s=2 × 314 × 150 million, about 940 million kilometers.
5. According to ellipseUltimate theoretical formulaThe calculated revolution circumference is approximately 939901691.151 km (it can only be accurate to this point for the time being due to computer limitations)
Generally speaking, the revolution of the earth is a two-dimensional plane with the sun as the reference system, while the earth's one-year journey in the total space and time of the universe is about 11.7 billion kilometers, and the trajectory is spiral. The equinox in 2011 and 2012 are not intersected, but billions of kilometers away.
Revolution period
Announce
edit
Earth revolution
The earth revolves around the sunThe time required for one cycle is the Earth's revolution period[4]。Generally speaking, the Earth's revolution period is one "year".Because the period of the annual apparent motion of the sun is the same as the period of the earth's revolution, the period of the earth's revolution can be measured by the annual apparent motion of the sun.Observers on the earth observe that the time interval when the sun continuously passes a certain point on the ecliptic is one "year".Due to the different reference points selected, the length of "year" is also different.Common cycle units areSidereal year、Regression yearandNear point year。
Sidereal year
The stellar cycle of the earth's revolution is the stellar year.A stellar year is a period in which the earth revolves around the sun with a star or galaxy as a reference.Stars or galaxies are so far away from us that no matter how the earth moves around the sun, the spatial orientation of the earth's axis can be regarded as unchanged.[5]During a star year, from the sun center, the center of the earth starts from a point with the star as the background, circles the sun, and then returns to the same point in the sky;Seen from the center of the earth, the center of the sun starts from a point on the ecliptic, which is fixed relative to the star, runs for one week, and then returns to the same point on the ecliptic.Therefore, from the point of view of the geocentric celestial sphere, the length of a stellar year is the time interval between two consecutive passes of the same star in the ecliptic at the center of the sun.
The stellar year is obtained by taking the stationary star as the reference point, so it is the time when the earth revolves 360 ° and the real cycle of the earth's revolution.The annual length of the star is 365.2564 days, that is, 365 days, 6 hours, 9 minutes and 10 seconds;The length of the regression year is 365.242199174 days, that is, 5:48:46 seconds on 365 days.
Regression year
The vernal equinox cycle of the earth's revolution is the regression year[6]。This cycle unit is obtained by taking the vernal equinox as the reference point.During a regression year, from the view of the sun center, the center of the earth passes the equinox twice in a row;Seen from the center of the earth, the center of the sun passes the equinox twice in a row.From the point of view of the geocentric celestial sphere, the length of a regression year is the time interval between two consecutive passes of the equinox with the sun center on the ecliptic.
The vernal equinox is the intersection of the ecliptic and the celestial equator. Its position on the ecliptic is not fixed, and it moves westward 50 ″ every year.29, that is to say, the spring equinox is a moving point in the time unit of "year", moving from east to west, that isClockwise。The direction of the sun's movement on the ecliptic is from west to east, that is, counterclockwise.These two directions are opposite, so the angle of the two consecutive equinoxes of the solar center is less than 360 °, but 360 ° - 50 ″. 29, or 359 ° 59 ′ 9 ″.71. This is the angle of the earth's revolution during a regression year.Therefore, the regression year is not the real cycle of the earth's revolution, but only the time required for the earth to rotate at an angle of 359 ° 59 ′ 9 ″. 71, expressed in daily units, and its length is 365.2422 days, that is, 365 days, 5 hours, 48 minutes and 46 seconds.
Near point year
Perihelion period of the earth's revolution is perihelion year.This periodic unit is obtained by taking the perihelion of the Earth's orbit as the reference point.During a perigee year, the Earth's center (or apparent solar center) passes the perihelion of the Earth's orbit twice in a row.Since perihelion is a moving point, its moving direction on the ecliptic is from west to east, that is, the same as the direction of the earth's revolution (or the direction of the sun's annual apparent movement), and the amount of movement is 11 ″ per year. Therefore, the perihelion year is not the real cycle of the earth's revolution. The angle of the earth's revolution in a perihelion year is 360 °+11 ″, that is, 360 ° 0 ′ 11 ″, expressed in daily units,Its length is 365.2596 days, that is, 365 days, 6 hours, 13 minutes and 53 seconds.
Cycle of change
The stellar year is the real period of the earth's 360 ° revolution around the sun, 1 stellar year T=365.25636 days.Only the stellar year can truly calculate the angular velocity and linear velocity of the earth's revolution, so the stellar year has important astronomical significance.[5]
The year of return is the cycle of the earth's cold and heat changes, that is, the cycle of the four seasons, which is closely related to human life and production.The regression year is slightly shorter than the star year, 20 minutes and 24 seconds shorter each year, which is calledprecession of the equinoxes。
The precession caused by the westward movement of the vernal equinox of 50 ″. 29 every year is the result of the precession of the earth's axis。
Earth revolution
The precession of the earth's axis is closely related to the rotation of the earth, the shape of the earth, the existence of the ecliptic angle and the characteristics of the orbit of the moon around the earth.The precession of the earth's axis is similar totopThe swing of the rotating shaft around the plumb line.When the rapidly rotating gyro tilts, the rotation axis will draw a conical surface around the axis perpendicular to the ground, and the gyro axis will slowly shake.that is becauseGravity of the earthThere is a tendency to make it topple, and the inertial action of the rotating motion of the gyro itself makes it unable to topple, so it slowly shakes under the action of gravity.This is the precession of the gyroscope.
The rotation of the earth is like a huge "top" that keeps rotating. Due to the inertial effect, the earth is always rotating.The shape of the earth itself is similar to an ellipsoid, and the equator is convex, that is, there is aEquatorial upliftBand.At the same time, due to the existence of the ecliptic angle, the line between the sun center and the earth center does not often pass through the equatorial uplift zone.Therefore, the attraction of the sun to the earth, especially to the equatorial uplift zone, is unbalanced.In addition, the moon revolves around the earthTrack planeIt is not coincident with the ecliptic plane and the celestial equatorial plane, and it is at an angle of 5 ° 9 'with the ecliptic plane, that is, the line connecting the earth center and the moon center does not often pass through the equatorial uplift zone.Therefore, the attraction of the moon to the earth, especially to the equatorial uplift, is unbalanced.according toLaw of universal gravitation，F1>F2。
The unbalanced attraction of the sun and the moon tries to make the equatorial plane coincide with the earth's orbital plane to reach a balanced state.But,earth rotationThe inertial action of is such that it can maintain this inclined state.Therefore, the earth wobbles under the combined action of the unbalanced attraction of the moon and the sun. This wobble is shown as the earth's axisYellow axisMake periodic coning motion for the axis. The radius of the cone is 23 ° 26 ', which is equal to the declination angle.This movement of the earth's axis is called precession of the earth's axis.The precession direction of the earth axis is from east to west, which is opposite to the rotation and revolution of the earth, while the precession direction of the gyroscope is consistent with the rotation direction.
This is because the gyro tends to "dump", while the earth axis tends to "stand up".
The precession of the earth's axis is very slow, with an annual precession of 50 ″. 29 and a precession cycle of 25800 years.
Due to the precession of the earth's axis, the tilt direction of the earth's equatorial surface in space has changed, causing the corresponding change of the celestial equator, causing the intersection of the celestial equator and the ecliptic, namely, the vernal equinox and the autumnal equinox, to move correspondingly on the ecliptic.The direction of movement is from east to west, that is, the direction is opposite to the earth's revolution, and the annual movement angle is 50 ″.29。Therefore, the length of the year, with the vernal equinox as the reference point, is slightly shorter than the period with the stationary star as the reference point, which is the reason for precession.
Due to the precession of the earth's axis, the space orientation of the earth's north and south poles has changed, making the celestial pole move around the yellow pole with a cycle of 25800 years.Therefore, the positions of the Celestial North Pole and Celestial South Pole on the celestial sphere are also moving slowly.Polaris wasthe dragonAlpha star, Polaris is near alpha star in the constellation Ursa Minor. It moved toCepheusNear alpha star, by 14000 AD,VegaWill become the Polaris.
Based on the movement of the celestial pole and the equinox on the celestial sphere caused by the precession of the earth's axisCelestial coordinate systemIt must also change accordingly.yesEquatorial coordinate systemFor example, the right ascension and declination of a star will changeEcliptic coordinate systemFor example, stellarYellow meridianChange is needed.However, the precession of the earth's axis does not change the ecliptic angle, that is, when the earth's axis precesses, the included angle between the earth's axis and the earth's orbital plane is always 66 ° 34 '.
It should also be noted here that the moving angle of the celestial pole and the vernal equinox caused by the precession of the earth's axis is relatively small, and will not move much in a long time.Therefore, we can still say that the celestial pole and the vernal equinox are atcelestial sphereThe right ascension, right latitude and yellow longitude of the star can also be roughly considered as unchanged if the position on the is unchanged, and the star catalog and map established on this basis can still be used for a long time.
Track direction
Announce
edit
Revolution track
Earth revolution
The earth is in the process of revolution. Every point on the route it 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 orbit actually refers to the geocentricRevolution track。
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 is the distance between the two ends of the short axis and the focus (F1, F2)
The relationship between semi focal length and semi major axis and semi minor axis is as follows:ctwo=atwo-btwo
The ratio of semi focal length c to semi major axis a, c/a, is ellipticalEccentricity, denoted by e, that is, e=c/a.
Center position
Strictly speaking, the center of the earth's revolution is not the sun's center, but the earth's and the sun'sPublic qualityCenter, not only the earth is rotating around the common mass center, but also the sun is rotating around the point.However, the sun is the central body of the solar system, and the 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 insignificant compared with the solar radius of about 700000 kilometers, and smaller compared with the distance of 150 million kilometers between the sun and the earth.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).
Eccentricity
EccentricityIt is a quantitative representation of the shape of an ellipse. 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 orbit is 149600000 km, and the semi minor axis b is 149580000 km.According to this data, the eccentricity of the earth orbit is calculated as 0.016722.
It can be seen that the earth 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 of is near the sun, called perihelion.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 147100000 kilometers away from the sun, usually called the distance between the sun and the sun.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 called aphelion.In modern times, the Earth passed aphelion in early July every year.At this time, the earth is about 152100000 kilometers away from the sun, which is usually called the apohelion.The average of perihelion distance and telehelion distance is 149600000 kilometers, which isAverage distance between the sun and the earth, i.e. 1Astronomical unit。
formula
According to the calculation formula of ellipse perimeter, L=2 πα (1-0.25 × etwo）The total length of the Earth's orbit is 940432870 km.
The earth rotates in the same direction as its rotation. Seen from the Yellow North Pole, it rotates counterclockwise, that is, from west to east.This is consistent with the revolution direction of other planets and most satellites in the solar system. The average angular velocity of rotation is 15 degrees per hour.On EarthequatorThe linear speed of rotation is 465 meters per second.
Revolution orientation
Announce
edit
In accordance with the rules of the universe and celestial bodies, the earth always maintains a fixed orientation when it rotates and revolves in the sun's orbit. In order to maintain a fixed orientation between the earth's longitude and the sun, the earth rotates 0.9856 degrees in the direction of the earth's revolution (from west to east) every day, that is, 365 days/360 degrees.
Oriented meridian
meridianIt refers to the change of time in a day on the earth. The meridian is also the longitude on the earth. It is an auxiliary line set by human beings for the convenience of measurement. It defines that any two longitude lines on the earth surface have the same length and intersect with the north and south poles. Each longitude line has its corresponding value, called longitude. The longitude line refers to the north and south direction, such as London, Englandgreenwich observatory A copper meridian is inlaid on the ground. At 12 o'clock in the afternoon, the sun's projection line coincides with this meridian line, and it coincides every day, but the sun's projection lengthens and shortens. Therefore, the meridian at Greenwich Observatory can also be regarded as the local orientation meridian.In 1884, the international conference decided to use the meridian passing through the British Greenwich Observatory as the prime meridian.
Sun synchronous orbit
In the early stage of the formation of the earth and the sun, tidal energy consumption is high;From 4.6 billion years ago to the present, the solar rotation period has changed by about 182 s, the earth's revolution period has slowed by 2.193 × 10 s, the earth is 6.935 × 108 m away, and the revolution radius has changed by 0.46%.[7]
The weather satellite isSun synchronous satelliteIts basic theory comes from the operation rules of cosmic objects, in which the orientation angle is the most basic theory. Therefore, when designing satellites and satellite orbits, we should follow the orientation, and keep a fixed rotation of 0.9856 degrees every day. Moreover, human beings have launched thousands of different spacecraft, with mature and correct theories.It is completely feasible to interpret the earth's revolution with these theories.
