Nautical Miles to Parsecs
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1 nautical mile (nmi) = 6.00192E-14 parsec (pc). Nautical Mile (nmi) is a unit of Length used in Standard system. Parsec (pc) is a unit of Length used in Metric system.

Nautical Mile: A Unit of Length

A nautical mile is a unit of length that is used in air, marine, and space navigation, and for the definition of territorial waters. It is based on the Earth’s longitude and latitude coordinates, and is equal to one minute of arc along a meridian. In this article, we will explore the definition, history, uses, and conversions of the nautical mile.

Definition of the Nautical Mile

The nautical mile is defined as exactly 1,852 metres (6,076 feet; 1.151 miles) by the International Hydrographic Organization (IHO) since 1929. This definition is based on the length of one minute of arc along a great circle of a sphere having the same surface area as the Clarke 1866 ellipsoid, which approximates the shape of the Earth.

The nautical mile is not an SI unit, but it is accepted for use with the SI by the International Committee for Weights and Measures. The derived unit of speed is the knot, which is one nautical mile per hour.

History of the Nautical Mile

The concept of the nautical mile dates back to ancient times, when navigators used the stars and angles to measure distances at sea. The word mile comes from the Latin phrase mille passus, meaning a thousand paces.

The nautical mile was originally defined as the length on the Earth’s surface of one minute of arc along a meridian (north-south line of longitude). However, this definition varied depending on the latitude and the shape of the Earth assumed by different countries. For example, France defined a nautical mile as one ten-millionth of a quarter meridian using the original 1791 definition of the metre.The United States and the United Kingdom used an average arcminute based on the Clarke 1866 ellipsoid.

In order to standardize the nautical mile, the IHO adopted the current definition in 1929, which was later endorsed by other international organizations such as the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO). The United States adopted the international nautical mile in 1954 and the United Kingdom in 1970.

Where Nautical Mile is Used

The nautical mile is widely used in navigation, especially for maritime and aviation purposes. It is convenient to use because it corresponds to one minute of latitude, which can be easily measured with a sextant or a GPS device. It also allows for simple calculations of distances along great circles, which are the shortest routes between two points on a sphere.

Some examples of where nautical mile is used are:

• The definition of territorial waters, which are usually 12 nautical miles from a country’s coastline.
• The measurement of flight levels and air routes for aircrafts.
• The determination of speed limits and fuel consumption for ships and boats.
• The designation of marine protected areas and fishing zones.
• The mapping of ocean currents and wind patterns.

How to Convert Nautical Mile

The nautical mile can be converted to other units of length using simple multiplication or division by a conversion factor. Here are some common conversion factors:

For example, to convert 10 nautical miles to kilometres, we multiply by 1.852:

10 NM × 1.852 = 18.52 km

To convert 50 kilometres to nautical miles, we divide by 1.852:

50 km ÷ 1.852 = 27 NM

Example Conversions of Nautical Mile to Other Units

Here are some example conversions of nautical mile to other units:

• 1 NM = 1,852 m
• 1 NM = 6,076 ft
• 1 NM = 1.151 mi
• 1 NM = 0.54 leagues
• 1 NM = 10 cables
• 1 NM = 800 fathoms
• 1 NM = 2,025 yd

Parsec: A Unit of Length

A parsec is a unit of length that is often used in astronomy to measure the large distances to astronomical objects outside the Solar System. It is approximately equal to 3.26 light-years or 206,265 astronomical units (au), which are the average distances from the Earth to the Sun. One parsec is about 30.9 trillion kilometres or 19.2 trillion miles.

Definition of the parsec

The word parsec is a combination of “parallax” and “arcsecond”, which are terms related to the measurement of angles. Parallax is the apparent shift in position of an object when viewed from different perspectives. Arcsecond is a unit of angle that is equal to one sixtieth of an arcminute, or one three thousand six hundredth of a degree.

A parsec is defined as the distance at which one astronomical unit subtends an angle of one arcsecond. In other words, it is the distance from which the Earth-Sun distance would appear as one arcsecond on the sky. This can be illustrated by an imaginary right triangle, where the adjacent side is one au, the opposite side is one parsec, and the angle opposite to the parsec side is one arcsecond.

History of the parsec

The concept of the parsec was first proposed by the British astronomer Herbert Hall Turner in 1913, as a convenient unit for expressing stellar distances. He coined the term by blending “parallax” and “second”. He also suggested using the symbol “pc” for parsec.

The first measurement of a stellar parallax was made by Friedrich Bessel in 1838, for the star 61 Cygni. He found that the star had a parallax of 0.314 arcseconds, which corresponds to a distance of about 10.4 parsecs. Since then, many more stars have been measured for their parallaxes, using various methods such as telescopes, satellites and interferometers.

The parsec is now widely used in astronomy and astrophysics, especially for objects within and around the Milky Way galaxy. For more distant objects, such as galaxies and quasars, larger units such as kiloparsecs (kpc), megaparsecs (Mpc) and gigaparsecs (Gpc) are used.

How to convert parsec

To convert parsecs to other units of length, we can use the following conversion factors:

• 1 pc = 3.0857 × 10^¹⁶ m
• 1 pc = 1.9174 × 10^¹³ mi
• 1 pc = 2.06265 × 10^⁵ au
• 1 pc = 3.26156 ly

To convert other units of length to parsecs, we can use the inverse of these conversion factors:

• 1 m = 3.24078 × 10^^-17 pc
• 1 mi = 5.21553 × 10^^-14 pc
• 1 au = 4.84814 × 10^^-6 pc
• 1 ly = 0.306601 pc

Where parsec is used

The parsec is mainly used in astronomy and astrophysics, as it is a convenient unit for expressing distances between stars and other celestial objects. For example:

• The nearest star to the Sun, Proxima Centauri, is about 1.3 pc away.
• The center of our galaxy, the Milky Way, is about 8 kpc away.
• The nearest galaxy to ours, Andromeda, is about 780 kpc away.
• The most distant quasar known, ULAS J1342+0928, is about 8.8 Gpc away.

The parsec can also be used in other fields that deal with large distances or angles, such as geodesy, navigation and surveying.

Example conversions of parsec to other units

Here are some examples of converting parsecs to other units of length:

• How many meters are in one parsec?

To convert one parsec to meters, we multiply by the conversion factor:

1 pc × 3.0857 × 10^¹⁶ m/pc = 3.0857 × 10^¹⁶ m

• How many miles are in 10 parsecs?

To convert 10 parsecs to miles, we multiply by the conversion factor:

10 pc × 1.9174 × 10^¹³ mi/pc = 1.9174 × 10^¹⁴ mi

• How many astronomical units are in 0.01 parsecs?

To convert 0.01 parsecs to astronomical units, we multiply by the conversion factor:

0.01 pc × 2.06265 × 10^⁵ au/pc = 2.06265 × 10^³ au

• How many light-years are in 100 parsecs?

To convert 100 parsecs to light-years, we multiply by the conversion factor:

100 pc × 3.26156 ly/pc = 326.156 ly

• How many parsecs are in one meter?

To convert one meter to parsecs, we divide by the conversion factor:

1 m / (3.0857 × 10^¹⁶ m/pc) = 3.24078 × 10^^-17 pc

• How many parsecs are in one mile?

To convert one mile to parsecs, we divide by the conversion factor:

1 mi / (1.9174 × 10^¹³ mi/pc) = 5.21553 × 10^^-14 pc

• How many parsecs are in one astronomical unit?

To convert one astronomical unit to parsecs, we divide by the conversion factor:

1 au / (2.06265 × 10^⁵ au/pc) = 4.84814 × 10^^-6 pc

• How many parsecs are in one light-year?

To convert one light-year to parsecs, we divide by the conversion factor:

1 ly / (3.26156 ly/pc) = 0.306601 pc