What is Earth's Magnetic Field

It is now a common knowledge that Earth’s magnetic field is similar to that produced by a simple bar magnet. This means that Earth’s magnetic field has the structure of a dipole field. Do you know that the axis of the magnetic field is inclined by about 10 degrees to the rotation axis of the Earth? Its magnetic field intensity is about 30,000 to 60,000 nano Tesla (nT) at the earth surface. This intensity decreases as the inverse cube of the distance (1/R^3) from the earth. The internal field of the earth appears to be generated in the earth’s core by a dynamo process associated with the circulation of liquid metal in the core and driven by convective heat effect.

Lenght, Mass, and Time

Length

Yard – In A.D. 1120, yard is measure from the standard length of the kings tip nose to the end of his outreached arm (King Louis XIV).

Meter was originally defined as one ten-millionth of the distance from the equator to the North Pole (1791).

Meter was defined by an atomic standard, in terms of the wavelength of the orange- red light emitted by atoms of Krypton (86Kr) in a glow discharge tube; one meter was defined as 1650763.73 of these wavelengths (1960).

Meter was redefined as the distance traveled by light in vacuum during a time of 1/ 299792458 second.

Mass

The MKS unit of mass is Kilogram. Kilogram (Kg) is defined as the mass of a specific platinum-iridium alloy cylinder kept at the International Bureau of Weights and Measures at Serves, France (1887).

Time

The unit of time was based on a certain fraction of the mean solar day, the average time interval between successive arrivals of the sun at its highest point in the sky (1960).

In 1967, the second/s is redefined as 9192631770 times the period of vibration of radiation from the cesium atom (Period is the time interval needed for one complete vibration).

References:

Beiser, Arthur. (1992). Modern Technical Physics. Singapore: Addison-Wesley Publishing Company

Catchillar, Gerry C., and Malenab, Ryan G. (2003). Fundamental Physics. National Bookstore

Giambattista, A, Richardson, B. and Richardson, R. (2007). College Physics. 2^nd Ed. New York: McGraw-Hill Book Companies, Inc.

Giancoli, D.C. (1998). Physics: Principles with Applications 5^th Ed. London Prentice Hall International, Inc.

Halliday, D., Resnick, R. and Walker, J. (1997). Fundamentals of Physics. 5^th Ed. New York: John Wiley & Sons, Inc.

Hewitt, Paul G. (1997). Conceptual Physics, Addison-Wesley Publishing Company United State of America

Serway, Raymond A., and Faughn, Jerry S., (2003) College Physics., 6^th Ed. Brooks/Cole, Thomson Learning Asian Edition.

Serway, Raymond A., and Jewett Jr., John W., (2004) Physics for Scientist and Engineers with Modern Physics., 6^th Ed. Brooks/Cole, Thomson Learning Asian Edition.

Urone, Paul Peter. (2004) Physics with health science application. Philippines: Golden Gate Printer

Young, H.D. and Freedman, R. A. (2000). Unversity Physics. 10^th Ed., Singapore: Addison-Wesley Publishing Company, Inc.