The rotation of the earth is the movement of the earth around its own axis from west to east, it is a basic form of motion of the earth, which has an important impact on the natural environment and human activities on the earth. The three phenomena produced by the rotation of the earth are: the phenomenon of day and night, the phenomenon of geostrophic deflection force and the phenomenon of time difference.
1. The phenomenon of diurnal alternation.
The phenomenon of day and night refers to the change of day and night in different parts of the earth at different times, which is the result of the rotation of the earth and the illumination of the sun.
1.Causes.
The rotation of the Earth causes each point on the Earth to rotate around its axis in 24 hours, and the sunlight causes each point on the Earth to receive sunlight only half of the day and the other half of the time on the shadow side of the Earth. As a result, every point on the earth undergoes a cyclical change from night to day and back to night in a single day, which is known as the phenomenon of day-night cycle.
2.Manifestations.
The phenomenon of diurnal cycle is manifested in the following ways:
1) Change in day and night length. Day/night length refers to the length of time a place spends day or night in a day, and it is affected by latitude and season. In general, the higher the latitude, the greater the difference in the length of day and night; The lower the latitude, the smaller the difference in the length of day and night. At the equator, the length of day and night is basically equal throughout the year, about 12 hours; At the poles, half of the year is day and half of the year is night; In the mid-latitudes, the length of day and night varies with the seasons, with long days in summer and short days in winter. As shown in the figure below, the diurnal length curves of Beijing (40°N) and Singapore (1°N) show that the diurnal length of Beijing is much larger than that of Singapore.
2) Changes in the dividing line between day and night. The dividing line between day and night refers to the dividing line between the day and night hemispheres, also known as the morning and dusk line, which is a great circle determined by the poles of the Earth and the direction of the Sun. Due to the Earth's rotation and revolution, the dividing line between day and night changes over time, taking on different shapes and positions. As shown in the figure below, it is the dividing line between day and night for the four seasons of the year, and it can be seen that the dividing line between day and night is a straight line at the spring and autumn equinoxes, crossing the equator and dividing the earth in half; At the summer solstice, it is a curve that convex towards the northern hemisphere, so that the day is greater than the night in the northern hemisphere and the day is less than the night in the southern hemisphere; At the winter solstice, it is a curve that convex towards the southern hemisphere, so that the southern hemisphere has more days than night, and the northern hemisphere has less day than night.
3) The time of day and night. The time of day and night alternate refers to the time when a place moves from day to night or from night to day, that is, the time of sunrise and sunset, which is affected by longitude and seasons. In general, the easterly longitude, the earlier the alternation of day and night; The westerly longitude, the later the alternation of day and night. At the same latitude, every 15° longitude, there is a one-hour difference between day and night. In addition, the time of the alternation of day and night also varies with the seasons, with early sunrise and late sunset in summer; In winter, the sunrise is late and the sunset is early. As shown in the table below, the time of day and night in Beijing (116°E) and London (0°W) shows that the time of day and night in Beijing is 8 hours earlier than that of London, and it varies with the seasons.
Date |Beijing sunrise time |Beijing sunset time |London Sunrise Time |London sunset time |
January 1 | 07:36 | 16:59 | 08:06 | 16:02 |
April 1 | 05:51 | 18:29 | 06:25 | 19:29 |
July 1 | 04:46 | 19:44 | 04:45 | 21:22 |
October 1 | 06:03 | 17:49 | 06:59 | 18:38 |
3.Geographical significance.
The phenomenon of diurnal turnover has important geographical significance to the natural environment and human activities on the earth, which is mainly reflected in the following aspects:
1) Influence the distribution and change of temperature on Earth. The diurnal cycle causes the temperature in different parts of the earth to show obvious diurnal variation, and the temperature increases during the day due to sunlight. There is no sunlight at night, and the temperature drops. Generally speaking, the diurnal temperature difference on land is greater than that of the ocean, the diurnal temperature difference of inland is greater than that of the coast, the diurnal temperature difference of low latitudes is smaller than that of high latitudes, and the diurnal temperature difference of summer is smaller than that of winter. The change of temperature difference between day and night affects meteorological factors such as air pressure, wind, water vapor, and precipitation on the earth, which in turn affects the climate type and ecosystem on the earth.
2) Influence biological activities and rhythms on Earth. The cycle of day and night allows organisms on Earth to form adaptive activities and rhythms in the changes of light and temperature, such as diurnal and nocturnal animals, flowering and fruiting plants, sleeping and awakening humans, etc. Circadian rhythm is an intrinsic physiological mechanism of organisms, which can regulate the growth, metabolism, behavior, hormones and other aspects of organisms, so that organisms can adapt to changes in the environment and maintain the stability and balance of life.
3) Influencing human culture and society on Earth. The change of day and night has enabled human beings to form different cultures and societies in day and night, such as the division and measurement of time, the celebration and commemoration of festivals, the arrangement and efficiency of work, and the habits and ways of life. The change of day and night has also caused human beings to form different time zones in different regions and countries, and in order to coordinate the difference in time, human beings have formulated rules and methods such as universal time, daylight saving time, and time difference calculation.
2. Geostrophic deflection force phenomenon.
The geostrophic deflection force phenomenon refers to an apparent force generated by the influence of the earth's rotation in the process of motion of the moving objects on the earth, which deviates the direction of motion of the moving objects, and the direction and magnitude of this deviation are related to the rotation direction of the earth, the speed and latitude of the moving objects.
1.Causes.
The cause of the geostrophic deflection force phenomenon is mainly due to the action of the earth's rotation and inertia. The rotation of the earth makes each point on the earth have a different linear velocity, and the magnitude of the linear velocity is related to the latitude, the higher the latitude, the smaller the linear velocity; The lower the latitude, the greater the linear velocity. When a moving object on the earth moves from one latitude to another, it maintains its original linear velocity, which creates a velocity difference relative to the earth's surface, which causes the moving object to deviate from the direction of motion. The direction and magnitude of this deviation are in turn affected by the direction of rotation of the Earth, the velocity and latitude of the moving object. According to Coriolis law, the direction and magnitude of the geostrophic deflection force can be expressed by the following formula:
f = 2mv\sin\phi
where f is the magnitude of the geostrophic deflection force, m is the mass of the moving object, v is the velocity of the moving object, and is the latitude where the moving object is located. The direction of the geostrophic deflection force is perpendicular to the plane of the velocity direction of the moving object and the direction of the earth's axis of rotation, and follows the right-hand rule, that is, the four fingers of the right hand point to the velocity direction of the moving object, the thumb points to the direction of the earth's axis of rotation, and the direction of the palm is the direction of the geostrophic deflection force. In the Northern Hemisphere, the direction of the geostrophic deflection force is always to the right; In the Southern Hemisphere, the direction of the geostrophic deflection force is always to the left.
2.Manifestations.
The manifestations of the geostrophic deflection force phenomenon are as follows:
1) Circulation that affects the atmosphere and oceans. Geostrophic deflection forces deflect the movement of the atmosphere and oceans, resulting in specific circulation patterns. For example, the wind in the atmosphere, under the action of the geostrophic deflection force, no longer blows in the direction of the pressure gradient, but deflects to the right or left, forming the equatorial low pressure belt, the subtropical high pressure belt, the temperate low pressure belt, the polar high pressure belt and other air pressure belts, as well as the east wind belt, the trade wind belt, the westerly wind belt, the polar wind belt and other wind belts. Ocean currents in the ocean, under the action of geostrophic deflection force, no longer flow in the direction of the difference in temperature and salinity, but deflect to the right or left, forming ocean currents such as equatorial currents, western boundary currents, eastern boundary currents, and equatorial regurgitation. As shown in the figure below, there is a schematic diagram of the circulation of the atmosphere and the ocean, and the influence of the geostrophic deflection force can be seen.
2) Affect the trajectory of aircraft and missiles. The geostrosmic deflection force deflects the motion of the aircraft and missiles, resulting in their actual trajectories being inconsistent with the expected trajectories, which has an important impact on the safety and accuracy of flight. For example, an aircraft will deviate from its course to the right or left due to geostrophic deflection forces during flight, so it needs to constantly adjust its direction to maintain the correct course. During the launch process, the missile will deviate from the target to the right or left due to the action of the geostrophic deflection force, so it is necessary to consider the influence of the geostrophic deflection force to improve the hit rate.
3) Affect horizontal movement on Earth. The geostrophic deflection force deflects the horizontal motion on the earth, resulting in some special phenomena. For example, the geostrophic deflection force causes the rivers on the earth to shift to the right or left as they flow, forming the bending and scouring of the rivers. The geostrophic deflection force causes the meridian on the earth to shift to the east or west near the equator, resulting in a bending and deviation of the meridian. The geostrophic deflection force causes the railways and highways on the earth to shift to the right or left during the construction process, forming the bending and error of the railways and highways.
3.Geographical significance.
The geostrophic deflection force phenomenon has important geographical significance to the natural environment and human activities on the earth, which is mainly reflected in the following aspects:
1) Affect the climate and ecology of the planet. The geostrophic deflection force affects the circulation of the atmosphere and the ocean, and then affects the meteorological elements such as temperature, humidity, precipitation, and wind on the earth, forming different climate types and climate zones, such as tropical, temperate, and cold zones. Geostrophic deflection forces also affect the distribution and adaptation of organisms on Earth, such as tropical rainforests, temperate grasslands, and boreal glaciers. Geostrophic deflection forces also affect the occurrence and distribution of natural disasters on Earth, such as typhoons, hurricanes, cold waves, droughts, etc.
2) Affect transportation and communication on Earth. Geostrophic deflection forces affect the trajectories of aircraft and missiles, which in turn affect the safety and efficiency of transportation and communication on Earth, such as aviation, aerospace, missiles, etc. Geostrophic deflection forces also affect the horizontal movement on the earth, which in turn affects the accuracy and convenience of transportation and communication on the earth, such as rivers, meridians, railways, highways, etc.
3) Influencing science and technology on Earth. Geostrophic deflection force is an important manifestation of the Earth's rotation, which reflects the laws and characteristics of the Earth's motion, and provides a theoretical and experimental basis for the development of science and technology on the Earth, such as geophysics, geodynamics, geodesy, navigation, etc.
3. Time difference.
The phenomenon of jet lag refers to the difference between the standard time in different parts of the earth, which is the result of the rotation of the earth and the division of time zones.
1.Causes.
The cause of the phenomenon of jet lag is mainly due to the rotation of the earth and the division of time zones. The rotation of the Earth causes each point on the Earth to rotate around its axis in 24 hours, and the sunlight causes each point on the Earth to receive sunlight only half of the day and the other half of the time on the shadow side of the Earth. As a result, every point on the earth undergoes a cyclical change from night to day and back to night in a single day, which is known as the phenomenon of day-night cycle. In order to facilitate transportation, communication and life on the earth, people divide the earth's surface into 24 time zones, each of which differs by 15 degrees of longitude, and correspondingly by 1 hour. Within the same time zone, a uniform standard time, also known as zone time; Between different time zones, the standard time relative to the prime meridian, also known as Universal Time, is adopted. This creates a time difference due to the difference between the standard times in different regions.
2.Manifestations.
The phenomenon of jet lag manifests itself in the following ways:
1) The division of time zones and the determination of standard time. The time zones on Earth are divided according to longitude, with a time zone every 15 degrees of longitude, for a total of 24 time zones. The ** meridian for each time zone is the standard longitude for that time zone, and the standard time for that time zone is local time on the standard meridian. For example, the standard meridian of the East Eighth District is 120 degrees east longitude, and the standard time of the East Eighth District is the time at 120 degrees east longitude, which is Beijing time. The division of time zones does not follow the principle of longitude exactly, but also takes into account national borders, geography and political factors, so the scope of some time zones is not a whole number of longitudes, but has been shifted or expanded. For example, China has a single time zone system, that is, the standard time of the eight eastern regions is used throughout the country, rather than being divided into five time zones according to the actual longitude.
2) Calculation and conversion of time difference. The time difference on Earth refers to the difference between the standard time of two regions, and it is related to the difference in longitude and time zone between the two regions. Generally speaking, for every 15 degrees of longitude, the time difference is 1 hour; For every 1 time zone difference, the time difference is 1 hour. The calculation and conversion of time difference need to follow certain rules and methods, as follows:
Rule 1: Same subtract and add differently. That is, if two regions are in the same hemisphere, such as both in the Eastern Hemisphere or in the Western Hemisphere, the number of time zones in the two regions is subtracted, and the result is the time difference; If two regions are in different hemispheres, such as one in the Eastern Hemisphere and one in the Western Hemisphere, the number of time zones in the two regions is added together and the result is the time difference. For example, the time difference between Beijing (East 8) and London (West Zero) is 8+0=8 hours, and Beijing is 8 hours ahead of London; The time difference between Beijing (East 8) and Tokyo (East 9) is 8-9=-1 hour, with Beijing being 1 hour behind Tokyo.
Rule 2: East plus West minus. That is, if the requested area is east of the known area, then add the time difference to the time of the known area, and the result is the time of the required area; If the requested region is to the west of a known region, subtract the time difference from the time of the known region and get the time of the claimed region. For example, if Beijing time is 12 o'clock, then London time is 12-8=4 o'clock; If Tokyo time is 12 o'clock, then Beijing time is 12 + 1 = 13 o'clock.