As already mentioned, the coordinate systems associated with the Earth are not inertial. This is caused by the rotation of the Earth on its axis and around the Sun. However, in all technical problems, the second axiom of mechanics is used as a basis, which is valid only for inertial systems. The equation of motion for non-inertial systems obtained in the previous paragraph allows us to estimate the error that occurs in this case.
Consider first the result of the non-inertiality of the coordinate system associated with the Earth, caused by the rotation of the Earth around its axis. In the first approximation, the Earth can be considered a cancer sphere.
The rotation of the Earth around its axis generates translational and Coriolis accelerations, and, consequently, the corresponding inertia forces. Since the Earth rotates at a constant angular velocity, only centripetal translational acceleration takes place, equal to:
where is the radius of the parallel on which the given point is located (Fig. 61). The vector of this acceleration lies in the plane of parallel and is directed to the Earth's axis. As
where R is the radius of the Earth, and the latitude of the parallel, then
The Earth makes a complete rotation around its axis in approximately the mean solar time (exactly in sidereal time), therefore
The greatest centripetal acceleration takes place at the equator, i.e. when Taking we get for the equator
This is approximately 300 times less than the acceleration of the earth's gravity.
Deviation of the force of gravity of the body from the radius of the Earth
The presence of centripetal acceleration leads to the fact that the weight of the body does not coincide exactly with the force of its attraction, and the vertical deviates somewhat from the direction of the earth's radius.
Indeed, consider a fixed (with respect to the Earth) point of mass suspended on a thread (Fig. 62).
It is in relative equilibrium under the action of three forces: the attraction to the Earth of the reaction of the thread T and the inertial force of the portable motion. directed opposite to the acceleration and equal to:
The Coriolis inertia force is equal to zero, since the relative velocity of the point is equal to zero, and, according to the relative equilibrium equation of the point, we have:
But the reaction of the thread is equal in magnitude to the weight of the body and is directed in the opposite direction
Hence:
Thus, the weight of the body is the resultant of the gravitational force and the inertia force of the portable acceleration of the Earth. The direction of this resultant determines the true vertical in a given place on the Earth. From fig. 62 it follows that it does not coincide with the radius of the Earth and deviates from it by an angle a. Let's define it.
The latitude of a place on Earth is the angle between the direction of the true vertical and the plane of the equator. From the sine theorem it follows that
The angle a is very small, and without significant error we can put
And therefore
It follows that the direction of the true vertical coincides with the radius of the Earth only at the pole at the equator, and the maximum deviation occurs at latitude . It equals
This value is so small that in the vast majority of technical problems it can be ignored.
The difference between gravity and gravitational force
Calculate the magnitude of the force of gravity. To do this, it is enough to project in the direction of the true vertical force
In view of the smallness of the angle a, we can then put
The gravitational force F is greater than the force of gravity at all points on the Earth, with the exception of the Earth's poles, where they are equal. The maximum deviation occurs at the equator, where the weight is:
Here is the acceleration of gravity at the pole, the weight of the body at the pole. The weight of a body at the equator is only 0.3% less than the gravitational force. Therefore, in technical matters, this difference is neglected.
Accounting for the portable force of inertia under the conditions of the Earth
Let us pay attention to the following important circumstance. Let us assume that the studied motion of a material point proceeds in a region whose dimensions are small compared to the radius of the Earth. Then the force Фper will be constant like the force Adding them together, we get a force that will also be constant. Therefore, to take into account the portable force of inertia, there is no need to consider it separately, but instead of the gravitational force, it is enough to introduce into the equation of motion a force that, like the force, is known for a given place on the Earth. Finishing the consideration of the portable force of inertia, we note that it is directed in the opposite direction to the centripetal acceleration. Due to this, in physics it has a very common name there - centrifugal force.
Rotational inertia force caused by the rotation of the Earth around its axis
Consider the rotational force or Coriolis force of inertia caused by the rotation of the Earth around its axis. She is equal
and both its magnitude and direction depend on the relative velocity of the point. The turning force is absent only in two cases:
when the point is at rest relative to the Earth, or when it moves parallel to the Earth's axis (the vectors are collinear).
To estimate the magnitude of the Coriolis acceleration, consider the case when the relative velocity is perpendicular to the vector . In order for the Coriolis acceleration to have a value, a relative velocity equal to
With such speeds moving, for example, artillery shells and rockets. In these cases, the Coriolis force can have a significant effect on the nature of the movement and, in particular, cause a noticeable deviation of the projectile from the target. Although in most cases the Coriolis force can be neglected, however, there are phenomena in which it manifests itself in a rather noticeable way. Such phenomena include, for example, the erosion of the right bank of rivers in the northern hemisphere and the left bank of rivers in the southern hemisphere. Let's consider this example in more detail.
Laws of Faith and Beis Balo
Let the river of the northern hemisphere flow along the earth's meridian from north to south (Fig. 63). The portable speed of any point on the Earth is directed tangentially to the parallel from west to east and is equal to:
Water particles, in addition to their relative speed, also have the above-mentioned transfer speed. Moving from north to south, they move from one parallel to another, which has a larger radius and therefore the transfer speed continuously increases without changing its direction (from west to east). In addition, due to the rotation of the Earth, the relative velocity changes its direction in space, turning from west to east.
This causes the water particles to accelerate, which means that a force acts on them in the direction of acceleration. This force arises from the pressure of the western, i.e., the right bank of the river, on the water. According to the law of equality of action and reaction, water will press with the same force on the right bank, gradually washing it away. In the modern hemisphere, in any direction of the river flow, the right bank is always subject to erosion. In the southern hemisphere, as can be shown by reasoning similar to the above, the left bank of the river is subject to erosion. The considered phenomenon is called Beer's law.
The same result can be obtained much easier by formally applying the formula for the rotational inertia force.
In the case considered, the relative velocities are very small, and, consequently, the Coriolis forces are also very small, but their continuous and prolonged action leads to noticeable results. The Coriolis force has an even greater effect on currents in the ocean. For example, under its influence, the warm current of the Gulf Stream deviates to the right.
The influence of the Coriolis force also explains the fact that in the northern hemisphere the wind deviates to the right from the direction in which the pressure drop occurs (to the left in the southern hemisphere). This phenomenon is known in meteorology under the name of the Bays-Balo law.
Summing up what has been said, it should be concluded that the corrections for the non-inertiality of coordinate systems rigidly connected with the Earth, caused by the rotation of the latter around the axis, as a rule, are so insignificant that in the overwhelming majority of technical problems the second axiom of mechanics describes mechanical phenomena with quite sufficient accuracy.
Forces of inertia caused by the rotation of the Earth around the Sun
Let us now consider the forces of inertia acting on terrestrial bodies resulting from the rotation of the Earth around the Sun.
The Earth moves around the Sun at approximately constant speed in an orbit close to a circle centered on the Sun, making one revolution per year. The portable acceleration of material points located on the Earth, caused by this movement, will be centripetal acceleration directed towards the Sun. The corresponding force of inertia of the portable motion (centrifugal force) is directed away from the Sun. In addition, the gravitational force of the Sun acts on the same point. The vector sum of these forces will practically be equal to zero.
The Coriolis forces resulting from the movement of a point on the surface of the Earth and the rotation of the Earth around the Sun will be negligible compared to the Coriolis forces arising from only the rotation of the Earth around its axis, since the angular velocity of the Earth's rotation will be many times greater than the angular velocity of the Earth's rotation around the Sun. sun
Therefore, the non-inertiality of coordinate systems associated with the Earth and caused by the movement of the latter along its orbit can be neglected in comparison with similar corrections caused by the rotation of the Earth around its axis.
The rotation of our planet is gradually slowing down
Tsunamis several kilometers high, crushing tornadoes, hurricanes, volcanoes and earthquakes. All this awaits our planet with a slight change in the length of the day.
Why does the earth rotate?
globallookpress.comScientists still do not have a definite answer to this question. There are many hypotheses, but the most plausible is that the Earth was forced to rotate by the solar wind, irregular shape and time.
Our planet has not always been round and even. At the stage of its formation, it resembled a snowball that a child made. On its surface there were many depressions and mountains. All these irregularities played the role of a kind of sail for the solar wind. As a result, over millions of years, the Earth began to rotate around its axis at the speed we are used to.
By the way, the process of slowing down the rotation of the planet and increasing the length of the day is due to the fact that these factors no longer act on the Earth. The atmosphere and magnetic field protect the globe from the solar wind and cosmic radiation, so the rotation speed slows down, but this deceleration is so insignificant that it is imperceptible within the framework of human life.
Ten times slower...
“Why are there only 24 hours in a day?” - we often hear a rhetorical question from those who do not have time for anything. Is it that bad? What will happen if there are 24 and 25 hours in a day?
Day - the period of rotation of the Earth around its axis - a very important constant. On which not only the change of day and night depends, but also life on our planet. A change in the length of the day of one hour, the inhabitants of the Earth, most likely, will not notice. But if the rotation of the planet slows down ten times, then we are in for a catastrophe of biblical proportions.
The speed of rotation of the Earth at the equator is 1666 km / h. As you get closer to the poles, the speed decreases due to a decrease in the radius of the planet relative to its axis of rotation. For example, at the latitudes of Moscow, this figure is already 1200 km / h. As we know from the course of school physics, the speed of rotation determines the magnitude of the centrifugal force that acts on all bodies located on the surface of a rotating body, the Earth is no exception.
Anyone can evaluate the influence of centrifugal forces using conventional scales. A person who weighed 50 kilograms in Moscow will weigh about 49.5 kilograms in Ecuador. “Weight reduction” will occur due to centrifugal force, which acts in the opposite direction from the force of gravity and tends to throw a person into outer space.
So let's imagine that tomorrow the Earth began to rotate ten times slower. The day increased to 240 hours, and the rotation speed on the planet dropped to 150 km/h. Physicist at NASA Sten Odenwald claims that such a stop of the planet is capable of killing all life on its surface. All objects will fly from west to east by inertia, like passengers falling off the shelves in a sharply braked train. The speed of this "flight" will exceed 1000 kilometers per hour. For complex forms of life, to which man also belongs, this is certain death.
The water in the oceans will also continue to move by inertia at a speed of 1500 km / h, this will lead to the formation of giant tsunamis that will fall on the deserted continents. A little later, the atmosphere will also rebel. It will experience the same phenomena as in the oceans. Under the influence of inertia, the air masses will continue their movement and will form unheard-of tornadoes and hurricanes. Inertial processes will continue inside the planet. The chaotic movement of liquid magma and the core will give rise to earthquakes and volcanic eruptions.
When the violence of the elements calms down, the appearance of the planet will change beyond recognition. The water of the oceans, which is now distributed by centrifugal forces, will rush towards the poles. At the equator, a single continent is formed that will encircle the planet. Europe, including Russia, Australia, North America, part of South America will go under water. However, there will be no one to grieve about this.
All complex life forms will perish. Only the simplest organisms will survive, which will have to go through the path of evolution from the very beginning, adapting to new environmental conditions. But whether life on Earth will recover after its rotation slows down is a big question.
The fact is that the rotation of the planet creates an electromagnetic field around it, which protects all life from destructive cosmic radiation. With a decrease in rotational speed, this protection will weaken so much that radioactive particles will reach the surface.
pixabay.com … and now faster
An increase in the speed of rotation of the earth from the point of view of physics is an unlikely event, but nevertheless we will consider what will happen to the planet if its rotation speed increases by 10 times.
First of all, the centrifugal force will change, at the equator this force will be only three times less than the planet's gravitational force. Accordingly, the weight of all bodies at the equator will decrease by more than 30%. In fact, the planet is not a solid body, physicist Sten Odenwald claims that the planets are more like a liquid. Therefore, under the action of centrifugal force, the shape of the Earth will change significantly.
Our blue planet will stretch along the equator and take the shape of an ellipsoid, its diameter at the equator will be almost 2.5 times the diameter at the poles. By the way, it is this effect that will not allow the planet to accelerate more than 10 times. The farther the mass is from the axis of rotation, the slower this rotation. This effect has been seen by anyone who has ever watched figure skating. If the skater presses his arms to the body during the execution of the rotation elements, then the speed increases, and vice versa.
pixabay.com The same effect will be with the Earth. An increase in diameter along the equator will slow down the speed of rotation and will not allow the planet to be accelerated by more than 10 times. By the way, if this effect did not exist and it would be possible to spin our “ball” 17 times faster than it rotates now, then the centrifugal force would be equal to gravitational force, and weightlessness would set in at the equator. But let's return to the world where the day was reduced tenfold. Changing the shape of the Earth and reducing weight are not the only changes. Due to the increased Coriolis force, the Earth's atmosphere will lose stability, hurricanes will rage constantly. Most of the water accumulates at the equator. As a result, the depth of the ocean in this place will be 150-200 kilometers! That is, all land in the equatorial, tropical and subtropical zones will go under water. But in place of the northern seas there will be soil.
But, despite the catastrophic changes, the planet will remain habitable. Oddly enough, complex life forms will have a much easier time surviving an increase in rotational speed than a slowdown.
Stop possible
As one of the possible options for the apocalypse, scientists call it the slowdown in the rotation of the planet up to its complete stop. The reason is that the Earth is slowed down by 2 milliseconds per year due to the tidal forces generated by the Moon. In 140 million years there will be 25 hours in a day. Although humanity will not live to a complete stop of the planet. In 5 billion years, the Sun will turn into a red giant and swallow the Earth.
The reason for this is primarily the Moon. The force of its attraction causes the constant occurrence of waves in the oceans and in the bowels of the earth: our planet, as it were, sways.
At the same time, the Earth behaves like a skater performing a rotation: to slow it down, the athlete spreads her arms. That is why in the distant future there will be 25 hours in a day. One British astronomer managed to prove that the rotation of the Earth since 700 BC. slows down continuously. He studied clay tablets and other historical writings that contained information about solar and lunar eclipses. Based on it and taking into account the then position of the Sun, he calculated the "braking distance" of the Earth.
When prehistoric proto-animals lived on Earth 530 million years ago, a day lasted 21 hours. For dinosaurs that lived 100 million years ago, a new day began 23 hours after the previous one. This is clearly seen in the calcareous deposits of corals. Corals keep a kind of calendar, forming new calcareous deposits daily, the thickness of which varies depending on the season.
Based on this, for example, it was possible to calculate what time interval separates one spring from another. Its duration in the history of the Earth has been continuously reduced. 530 million years ago, the Earth rotated on its axis faster than today, but it rotates around the Sun at a constant pace. The year then lasted the same hours as it does today, but there were 420 days in a year. During the existence of mankind, the rotation of the Earth, according to reliable sources, continued to slow down, states in the Journal for the History of Astronomy (vol. 39, p. 229, 2008) Richard Stephenson from the University of Durham in the UK. Stephenson draws on descriptions of hundreds of solar and lunar eclipses over the past 2,700 years.
The slowing down of the Earth's rotation is best confirmed by the clay tablets of pre-Christian Babylon, writes Stephenson. In cuneiform writing on clay, Babylonian scientists recorded the exact place and time of celestial phenomena. In addition, Stephenson studied documents of Chinese and European origin. Anywhere on Earth, a total solar eclipse can be observed about once every 300 years. When the Moon comes between the Sun and the Earth, complete darkness sets in for a few minutes.
Often, with the highest accuracy, it was noted on what date and what time the very beginning of the solar eclipse and its end fell. These two data were enough for the astronomer to determine the exact position of the Sun, as it was millennia ago. The task was facilitated by tables for recalculating the dates of the Babylonian calendar.
Based on the position of the Sun recorded in historical sources, astronomers can reconstruct the process of deceleration of the native planet: a properly documented solar eclipse allows you to determine the appropriate position of the Earth on the path of its movement around the Sun. Since the trajectory of the Earth's motion around the Sun is in no way connected with its rotation around its own axis, an independent measure of time is derived from here - the so-called terrestrial time.
The deceleration of the Earth's rotation manifests itself when comparing the terrestrial time with the universal one. Universal Time is the generally accepted time, which depends on the rotation of the Earth and is determined based on the position of the Sun relative to Greenwich (a city in the UK). It constantly has to be brought back, every few years between the end of one year and the beginning of the next, one second is added.
Based on historical documents, Richard Stephenson was able to determine the relationship between the two times. Terrestrial and universal time diverge the more, the more long ago this or that solar eclipse occurred.
Consequently, over the millennium, the day becomes longer by almost two thousandths of a second. Satellite measurements over the past decades confirm the corresponding deceleration rate. It turns out that during the heyday of Babylon, the day was shorter than today by four hundredths of a second. However, Stephenson was able to fix this minimal deviation due to the accumulation of error in universal time. From 700 BC about a million days passed, which were a little shorter than today - today the usual clock would have to be rearranged by about 7 hours.
The last few years have been an exception. During this time, the day almost did not lengthen, the Earth rotated at an almost constant speed. Perhaps the displacement of masses in the bowels of the Earth accelerated the rotation of the planet, compensating for the deceleration caused by the Moon. A devastating earthquake in South Asia and the tsunami that followed gave the Earth an extra spin at the end of 2004, shortening the length of the day by about eight millionths of a second. According to the International Earth Rotation Service, the shortest day in the last hundred years was July 13, 2003 - this day fell short of 24 hours by almost 1.5 thousandths of a second.
In addition, "Universal Time" may mean one of its versions (UT0, UT1, etc.). Therefore, in the specialized literature it is customary to indicate what is meant by ∆T, for example "DTD - UT1", which means "Dynamic Earth Time minus Universal Time Version UT1".
Despite some changes in the definition, the physical meaning of ΔT does not change - this is the difference between ideal uniformly current time and "time" determined by the rotation of the Earth (which is slowing down, and unevenly).
About the uneven rotation of the Earth around its axis
Universal Time (UT) is a time scale based on the Earth's daily rotation, which is not quite uniform over relatively short time intervals (from days to centuries), and therefore any time measurement based on such a time scale cannot have an accuracy better than 1: 10 8 . However, the main effect is manifested at long times: on the scale of centuries, tidal friction gradually slows down the Earth's rotation rate by about 2.3 ms / day / century. However, there are other reasons that change the speed of the Earth's rotation. The most important of these are the effects of the melting of the continental ice sheet at the end of the last ice age. This led to a decrease in the powerful load on the earth's crust and post-glacial relaxation, accompanied by straightening and uplift of the crust in the polar regions - a process that continues now and will continue until isostatic equilibrium is reached. This post-glacial relaxation effect causes masses to move closer to the Earth's axis of rotation, which causes it to rotate faster (the law of conservation of angular momentum). The acceleration obtained from this model is about −0.6 ms/day/century. Thus, the total acceleration (in fact, deceleration) of the Earth's rotation, or the change in the length of the mean solar day, is +1.7 ms/day/century. This value is in good agreement with the average rate of deceleration of the Earth's rotation over the past 27 centuries.
Terrestrial Time (TT) is a theoretically uniform time scale, defined to maintain continuity with the preceding uniform ephemeris time (ET) time scale. ET is based on a physical quantity independent of the rotation of the Earth, proposed (and adopted) in 1948-52 with the intention of having a time scale as uniform and independent of gravitational effects as was possible at the time. ET definition relied on solar tables (English)Russian Simon Newcomb (1895), reinterpreted to take into account certain discrepancies in observations.
Newcomb's tables served as the basis for all astronomical solar ephemeris from 1900 to 1983. Initially, they were expressed (and published as such) in terms of Greenwich Mean Time and Mean Solar Days, but later, especially for the period from 1960 to 1983, they were treated as expressed in terms of ET, in accordance with the accepted in 1948-52 proposal to move to ET. In turn, ET could now be considered in the light of the new results as a time scale as close as possible to the mean solar time between 1750 and 1890 (with a midpoint around 1820), since it was in this interval that the observations were made, on the basis of which Newcomb's tables were compiled. Although the TT scale is strictly homogeneous (based on the SI unit of the second, and every second is strictly equal to every other second), in practice it is implemented as International Atomic Time (TAI) with an accuracy of about 1:10 14 .
Determination of delta T from observations
Time, determined by the position of the Earth (more precisely, the orientation of the Greenwich meridian relative to the fictitious mean Sun), is an integral of the rotational speed. When integrating, taking into account the change in the length of the day by +1.7 ms/day/century, and choosing the starting point in 1820 (the approximate middle of the interval of observations used by Newcom to determine the length of the day), for ΔT, a parabola 31 × ((Year − 1820)/100)² in seconds. Smoothed data obtained from the analysis of historical total solar eclipse observations give ΔT values of about +16800 s at −500, +10600 s at 0, +5700 s at 500, +1600 s at 1000 and +180 s at 1500. For times since the invention of the telescope, ΔT is determined from observations of occultations of stars by the Moon, allowing for more accurate and more frequent magnitudes. The ΔT correction continued to decrease after the 16th century until it reached a plateau of +11±6s between 1680 and 1866. For three decades until 1902 it remained negative with a minimum of −6.64 s, then began to increase to +63.83 s in 2000. In the future, ΔT will increase at an increasing rate (quadratic). This will require more and more leap seconds to be added to Coordinated Universal Time (UTC), as UTC must be maintained to within one second of UT1. (The SI second now used for UTC was already at the time of adoption slightly shorter than the current value of the second of mean solar time.) Physically, the zero meridian for Universal Time is almost always east of the Earth time meridian, both in the past and in the future. +16800 s or 4⅔ hours correspond to 70°E. This means that in −500 years, due to the faster rotation of the Earth, the solar eclipse occurred 70° east of the position that follows from the calculations using the uniform time TT.
All ΔT values prior to 1955 depend on observations of the Moon associated with either eclipses or occultations. The conservation of angular momentum in the Earth-Moon System requires that the decrease in the Earth's angular momentum due to tidal friction be transferred to the Moon, increasing its angular momentum, which means that its distance from the Earth must increase, which, in turn, due to Kepler's third law, leads to a deceleration revolution of the moon around the earth. The above ΔT values suggest that the lunar acceleration associated with this effect is d n/dt = -26"/century², where n is the average angular sidereal velocity of the Moon. This is close to the best experimental estimates for d n/dt obtained in 2002: −25.858±0.003"/cv2, and therefore the ΔT estimates obtained earlier based on the value of −26"/civ², taking into account uncertainties and smoothing effects in experimental observations, can not be recalculated. Nowadays, UT is determined by measuring the orientation of the Earth with respect to the inertial frame of reference associated with extragalactic radio sources, corrected for the accepted relationship between sidereal and solar time. These measurements, conducted at several observatories, are coordinated by the International Earth Rotation Service (IERS).
Delta T values
For the years 1900-1995, the values are given according to "Astronomy on a Personal Computer", fourth edition, 2002, Montenbrook O., Pfegler T., for 2000 - from the English Wiki.
| Year | delta T |
|---|---|
| 1900 | -2,72 |
| 1905 | 3,86 |
| 1910 | 10,46 |
| 1915 | 17,20 |
| 1920 | 21,16 |
| 1925 | 23,62 |
| 1930 | 24,02 |
| 1935 | 23,93 |
| 1940 | 24,33 |
| 1945 | 26,77 |
| 1950 | 29,15 |
| 1955 | 31,07 |
| 1960 | 33,15 |
| 1965 | 35,73 |
| 1970 | 40,18 |
| 1975 | 45,48 |
| 1980 | 50,54 |
| 1985 | 54,34 |
| 1990 | 56,86 |
| 1995 | 60,82 |
| 2000 | 63,83 |
| 2005 | 64,69 |
| 2010 | 66,07 |
Delta T calculation
Approximate formula for calculating delta T
Δ T ≃ 32.184 + 10 + N , (\displaystyle \Delta T\simeq 32(,)184+10+N,)where
32.184 seconds is the difference between and TAI,
10 seconds - the difference between TAI and UTC at the beginning of 1972,
N is the number of leap seconds introduced since 1972.
The formula gives an error of no more than 0.9 seconds. For example, at the beginning of 1995, 19 seconds of coordination were introduced and the formula gives ΔT = 61.184 seconds, which is only 0.364 seconds higher than the tabular value.
The exact formula for calculating delta T
From Bulletin A (Bulletin - A) of the IERS Earth Rotation Service, you can find out the difference between TAI and UTC (depends on the number of seconds of coordination, the value rarely changes) and between UT1 and UTC (the value is constantly changing, the bulletin is given at midnight daily), then the delta T can be calculated exactly by the formula:
Δ T = 32.184 s + (T A I − U T C) − (U T 1 − U T C) . (\displaystyle \Delta T=32.184s+(TAI-UTC)-(UT1-UTC).)Approximate formula for calculating delta T for the future
Calculating delta T for the future is only possible approximately, due to the fact that the change in the Earth's rotation is not well understood. Nevertheless, to calculate, for example, the path of the shadow from a solar eclipse or the time of occultation of stars by the Moon, it is necessary to make at least an approximate calculation. Fred Espegnak (English)Russian when calculating solar eclipses for the period 2005-2050, I used the formula
Δ T = 62 . 92 + 0 . 32217 ⋅ (y − 2000) + 0 . 005589 ⋅ (y − 2000) 2 . \right)+0.005589\cdot \left(y-2000\right)^(2),)where y is the year for which the delta T is determined.
The speed of the planet's rotation depends on climate change.Today the winds have accelerated the run of the planet...
For speed Earth's rotation influenced by various factors. For example, if the winds slow down, the planet spins faster to conserve angular momentum. In November 2009, however, something else played. The culprit turned out to be the Antarctic Circumpolar Current, encircling the continent. Stephen Markus and his colleagues from the NASA Jet Propulsion Laboratory (USA) and the Institute of Physics of the Earth (France) noticed that on November 8, 2009, it slowed down dramatically. Measurements of the exact length of the day showed that at the same time the Earth slightly accelerated, recovering on November 20 - along with the current, reports science.compulenta.ru. This was observed for the first time.
No one knows for sure why the current slowed down, but Dr. Markus believes it was due to atmospheric changes. Two days before this, the winds blowing in the same direction also subsided. Two days after they returned to normal, so did the current. His colleagues at the Jet Propulsion Laboratory believe that El Niño shifting territory could have affected wind speeds. In addition, the planet may start to rotate faster due to the level increase. When water accumulates at the poles, mass will increase in the area of \u200b\u200bthe earth's axis, and earth rotation accelerate, it will spin like a top.
... And a year ago - speed Earth's rotation slowed down
By the way, almost a year ago, on February 25, 2011, scientists from Anchorage (USA) scared the opposite message published in Weekly World News. Then they found the slowdown Earth's rotation and predicted that the Earth would stop spinning in just three years! "The slowdown will lead to sustainably longer days and nights and could cause everything from devastating floods and earthquakes to mass starvation," said geophysicist Joseph Jenkowski. - This is by far the most serious and immediate problem now facing humanity.
Scholars have long believed that earth rotation slows down. It is believed that three billion years ago, a day lasted approximately 13 hours, while now one full earth rotation on its axis takes 23 hours, 56 minutes and 4.091 seconds. At first it was believed that the slowdown was gradual, with the length of the Earth's day increasing by only 0.02 seconds per century. But new measurements allegedly showed that changes in the rotation of the earth become more significant than ever before. According to Professor Jenkowski's frightening calculations, earth rotation cease to a complete halt by January 16, 2013.
Incredibly, this will turn into permanent day on one side of the globe and permanent night on the other! the professor exclaimed at his press conferences. - Those people who, by coincidence, will find themselves on the dark side of the Earth, will find themselves in a gloomy, cold world of eternal blackness. Virtually all plant life - which depends on photosynthesis - will die within a few short weeks, leading to a halt in agricultural activity and a famine that the human race has ever experienced. But life won't be sweet for survivors on the day side of the globe either. Imagine a top spinning slowly - before it stops, it begins to oscillate. The same thing will happen to our planet, causing the continental plates to shift. The result will be massive tidal waves and earthquakes in which billions will die.”
