Did you ever feel that some days drag on longer than others? That feeling may be psychological, but the actual length of the day really rocking - by a fraction of a millisecond. (A millisecond is one thousandth of a second)
The length of the day, which is measured by the time needed to Earth once rotate about its axis can be measured with an accuracy of about 10 microseconds or 10 millionths of a second. Earth Rotation speed depends on the mass distribution over the surface. This includes the aggregation of swirling gases that comprise the atmosphere, the solid earth itself, its fluid core, and the sloshing sea. For example, when a large earthquake shifts the mass of the planet, it can slow down or speed up of the day by as much as a few thousandths of a second.
This change in rotational speed, if it is minimal, observed centuries. In 1695, English astronomer Sir Edmund Halley (who also discovered the same periodic comet) hypothesis that the moon was accelerating in its orbit. In reality, Earth's rotation to slow down, making it appear that the moon was gathering speed.
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Since then, scientists have used different methods to measure, including astronomical devices like the sundial as satellites and lunar observations. Rotation of our planet And these days, scientists have thousands of Global Positioning System (GPS) receivers all over the world that can track up to a few millimeters placed, the orientation of the Earth says geophysicist Richard Gross of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California JPL maintains an in-house database of Earth rotation dating back to 1962.
Gross says that the main processes that are day length changes in the weather, especially unusual variations in the strength and direction of the wind, which bring in the global circulation of the atmosphere and changes over the ocean. In particular, the large, high-altitude wind currents known as jet streams, resulting from the differences in temperature between the hot tropics and cooler high latitudes, are responsible for shortening and accelerating the day.
Perhaps it is not surprising that global warming may actually speed the day, a fact noted by the UN Intergovernmental Panel on Climate Change. In a study published in Geophysical Research Letters in 2007, scientists from the Max Planck Institute for Meteorology in Hamburg, Germany, estimated the mass redistribution due to ocean warming would be the day to reduce by 120 microseconds, or nearly one-tenth of a millisecond, over the next two centuries.
Such changes, whether caused by global warming or earthquakes, remain too small to be reliably detected at this time, says Gross. After all, there are 86,400 seconds in a day of 24 hours and billions of micro seconds. Even with GPS, predicting changes in day length remains as difficult as predicting the weather.
On April 17, 2008, for example, the day took 1.1686 milliseconds longer than the norm According Gross, the excess varies: Just a few years ago, days were about three milliseconds longer. And all those milliseconds add up: In the course of a year, scientists estimate that the fluctuations add about one second.
But do not worry, the scientists are at the top of the phenomenon. The National Institute of Standards and Technology in Boulder, Colorado, adds an occasional "leap second" to the atomic clocks used to standardize the time. The last adjustment that took place on January 1, 2006. There's plenty of time to adjust your agenda: "If the excess length of the day remains about 1.2 milliseconds, will be another leap will not be available for about three years.
The length of the day, which is measured by the time needed to Earth once rotate about its axis can be measured with an accuracy of about 10 microseconds or 10 millionths of a second. Earth Rotation speed depends on the mass distribution over the surface. This includes the aggregation of swirling gases that comprise the atmosphere, the solid earth itself, its fluid core, and the sloshing sea. For example, when a large earthquake shifts the mass of the planet, it can slow down or speed up of the day by as much as a few thousandths of a second.
This change in rotational speed, if it is minimal, observed centuries. In 1695, English astronomer Sir Edmund Halley (who also discovered the same periodic comet) hypothesis that the moon was accelerating in its orbit. In reality, Earth's rotation to slow down, making it appear that the moon was gathering speed.
Also See :Komodo Dragons Show that "Virgin Births" Are Possible
Since then, scientists have used different methods to measure, including astronomical devices like the sundial as satellites and lunar observations. Rotation of our planet And these days, scientists have thousands of Global Positioning System (GPS) receivers all over the world that can track up to a few millimeters placed, the orientation of the Earth says geophysicist Richard Gross of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California JPL maintains an in-house database of Earth rotation dating back to 1962.
Gross says that the main processes that are day length changes in the weather, especially unusual variations in the strength and direction of the wind, which bring in the global circulation of the atmosphere and changes over the ocean. In particular, the large, high-altitude wind currents known as jet streams, resulting from the differences in temperature between the hot tropics and cooler high latitudes, are responsible for shortening and accelerating the day.
Perhaps it is not surprising that global warming may actually speed the day, a fact noted by the UN Intergovernmental Panel on Climate Change. In a study published in Geophysical Research Letters in 2007, scientists from the Max Planck Institute for Meteorology in Hamburg, Germany, estimated the mass redistribution due to ocean warming would be the day to reduce by 120 microseconds, or nearly one-tenth of a millisecond, over the next two centuries.
Such changes, whether caused by global warming or earthquakes, remain too small to be reliably detected at this time, says Gross. After all, there are 86,400 seconds in a day of 24 hours and billions of micro seconds. Even with GPS, predicting changes in day length remains as difficult as predicting the weather.
On April 17, 2008, for example, the day took 1.1686 milliseconds longer than the norm According Gross, the excess varies: Just a few years ago, days were about three milliseconds longer. And all those milliseconds add up: In the course of a year, scientists estimate that the fluctuations add about one second.
But do not worry, the scientists are at the top of the phenomenon. The National Institute of Standards and Technology in Boulder, Colorado, adds an occasional "leap second" to the atomic clocks used to standardize the time. The last adjustment that took place on January 1, 2006. There's plenty of time to adjust your agenda: "If the excess length of the day remains about 1.2 milliseconds, will be another leap will not be available for about three years.
