| Nanometers (nm) | Nautical leagues (nlea) |
|---|---|
| 1 Nanometer | 1.79985601152 × 10-13 nlea |
| 2 Nanometers | 3.59971202304 × 10-13 nlea |
| 3 Nanometers | 5.39956803456 × 10-13 nlea |
| 4 Nanometers | 7.19942404608 × 10-13 nlea |
| 5 Nanometers | 8.9992800576 × 10-13 nlea |
| 10 Nanometers | 1.79985601152 × 10-12 nlea |
| 20 Nanometers | 3.59971202304 × 10-12 nlea |
| 25 Nanometers | 4.4996400288 × 10-12 nlea |
| 50 Nanometers | 8.9992800576 × 10-12 nlea |
| 100 Nanometers | 1.79985601152 × 10-11 nlea |
| Reference | Nanometers (nm) | Nautical leagues (nlea) |
|---|---|---|
| A sheet of A4 paper (long side) | 297000000 nm | 0.0000534557 nlea |
| Average adult human height | 1.7 × 109 nm | 0.000305976 nlea |
| A football pitch (length) | 1.05 × 1011 nm | 0.0188985 nlea |
| A marathon | 4.2195 × 1013 nm | 7.59449 nlea |
| Height of Mount Everest | 8.849 × 1012 nm | 1.59269 nlea |
The nanometre is one billionth of a metre. It is formed by applying the SI prefix nano, meaning 10-9, to the metre, and is written nm. The prefix derives from the Greek nanos, meaning dwarf.
This is the working scale of modern optics and electronics. Visible light spans roughly 380 nm at the violet end to 750 nm at the red end, which makes the nanometre the standard unit for describing colour in physical terms. A laser pointer emitting at 532 nm is green; one at 650 nm is red. Ultraviolet light falls below 380 nm and infrared above 750 nm.
Biology uses the unit constantly. The DNA double helix is about 2 nm across. A typical virus measures between 20 and 300 nm. Cell membranes are around 7 nm thick. These dimensions sit below the resolution of conventional light microscopes, which is limited by the wavelength of the light itself to roughly 200 nm.
Semiconductor manufacturing made the nanometre familiar outside science. Process nodes have been labelled 90 nm, 45 nm, 14 nm, 5 nm and smaller. The figure no longer corresponds to any single measurable feature on the chip, having become a marketing designation rather than a physical dimension, but the underlying structures genuinely are nanometres across. A modern transistor gate is a few tens of atoms wide.
Nanotechnology takes its name from the unit and conventionally covers structures between 1 and 100 nm. Materials often behave differently in this range because surface effects begin to dominate bulk properties.
Measuring at this scale requires instruments that do not rely on visible light. Electron microscopes resolve features below one nanometre by using electrons, whose effective wavelength is far shorter than that of light. Atomic force microscopes work differently again, dragging a sharp tip across a surface and recording its deflection. Both were essential to the development of nanotechnology, since a field cannot advance far while its subject matter remains invisible.
One nanometre equals 10 ångströms, 1000 picometres, or 0.001 micrometres. A sheet of paper is roughly 100,000 nm thick.
The nautical league is a unit of length equal to three nautical miles, or exactly 5556 metres. It is longer than the land league by about 728 metres, since it is built from the nautical mile of 1852 metres rather than the statute mile.
The unit belonged to an era when it was the practical measure of coastal jurisdiction. The cannon shot rule, articulated in the seventeenth and eighteenth centuries, held that a state's authority extended as far as it could defend from shore, conventionally taken as three nautical miles. That distance became the standard territorial sea limit and was expressed as one marine league. Many older treaties and statutes define maritime boundaries in leagues for this reason.
The three-mile limit held for centuries before eroding through the twentieth. States progressively claimed wider waters, and the United Nations Convention on the Law of the Sea settled the matter in 1982 by establishing a twelve nautical mile territorial sea and a two hundred mile exclusive economic zone. Both figures are stated in nautical miles rather than leagues, and the older unit fell out of legal use.
Charts and pilot books from the age of sail used the league routinely for describing offshore distances and the visibility of landmarks. Reading those sources accurately requires knowing which league is meant, since the same word could refer to a land league, a marine league or a Spanish or Portuguese variant, and the differences are large enough to matter when reconstructing a historical position.
Today the unit has no navigational role. Charts are marked in nautical miles, and distances at sea are quoted the same way. The nautical league appears only in historical and legal texts.
The unit also underlies a familiar figure in visibility calculations. From a height of about three metres above sea level, the horizon lies roughly one nautical league away, which is why the three-mile limit corresponded loosely to what a lookout could see as well as to what a gun could reach.
One nautical league equals 3 nautical miles, 5556 metres, 5.556 kilometres, or about 3.452 statute miles.