The term "agonic line" refers to an imaginary line on the Earth's surface that connects all points where a compass needle points true north. The spelling of this word can be understood through its phonetic transcription in the International Phonetic Alphabet (IPA): /əˈɡɑːnɪk laɪn/. The first syllable is pronounced with a schwa sound, the second syllable with a long "a" sound, and the final syllable with a diphthong that sounds like the word "eye". In this way, the spelling of "agonic line" reflects its pronunciation.
An agonic line refers to an imaginary line that connects all points on the Earth's surface where a magnetic compass will indicate true north, which coincides with the geographic north. The term "agonic" originates from the Greek word "agonia," meaning "without angles" or "straight line." Hence, the agonic line can be visualized as a line without any deflection or angle when compared to true north.
The Earth possesses a magnetic field due to the movement of molten iron in its outer core. This field affects the orientation of magnetic compass needles, causing them to point towards magnetic north instead of true north. Therefore, the Earth's magnetic field lines and geographic lines of longitude and latitude do not entirely align. The angle between true north and magnetic north is known as magnetic declination.
The agonic line represents the path where magnetic declination is zero, indicating no angle between true north and magnetic north. However, it is essential to note that the agonic line is not static but rather subject to gradual change over time. This is primarily due to the ever-changing nature of the Earth's magnetic field caused by geophysical processes within the planet.
Cartographers and navigators often rely on accurate knowledge of the agonic line to correct compass readings, ensuring precise navigation and map orientation. By accounting for the magnetic declination, they can align maps with compasses and determine accurate directions. Consequently, the agonic line serves as a crucial reference point for navigation and map-making, enabling individuals to navigate accurately over land or sea.
The word "agonic" originates from the Greek word "ágon" (ἀγών), meaning "contest" or "struggle". The term "agonic" specifically refers to something that is without contest or struggle.
The term "agonic line" is commonly used in geography and relates to the field of geomagnetism. It refers to an imaginary line on the Earth's surface where magnetic declination is zero, which means that the vertical plane passing through this line will align with the Earth's magnetic field lines (i.e., pointing towards the North or South Magnetic Poles). The word "line" in this context represents the imaginary boundary or trajectory of the zero magnetic declination.