| Nanometers (nm) | Nautical miles (nmi) |
|---|---|
| 1 Nanometer | 5.39956803456 × 10-13 nmi |
| 2 Nanometers | 1.07991360691 × 10-12 nmi |
| 3 Nanometers | 1.61987041037 × 10-12 nmi |
| 4 Nanometers | 2.15982721382 × 10-12 nmi |
| 5 Nanometers | 2.69978401728 × 10-12 nmi |
| 10 Nanometers | 5.39956803456 × 10-12 nmi |
| 20 Nanometers | 1.07991360691 × 10-11 nmi |
| 25 Nanometers | 1.34989200864 × 10-11 nmi |
| 50 Nanometers | 2.69978401728 × 10-11 nmi |
| 100 Nanometers | 5.39956803456 × 10-11 nmi |
| Reference | Nanometers (nm) | Nautical miles (nmi) |
|---|---|---|
| A sheet of A4 paper (long side) | 297000000 nm | 0.000160367 nmi |
| Average adult human height | 1.7 × 109 nm | 0.000917927 nmi |
| A football pitch (length) | 1.05 × 1011 nm | 0.0566955 nmi |
| A marathon | 4.2195 × 1013 nm | 22.7835 nmi |
| Height of Mount Everest | 8.849 × 1012 nm | 4.77808 nmi |
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 mile is a unit of length equal to exactly 1852 metres. The symbol is nmi, though NM and M also appear in maritime and aviation practice. It is longer than the statute mile by about 15 per cent.
Its definition is geographical rather than arbitrary. One nautical mile corresponds to one minute of latitude, so sixty nautical miles span one degree. This makes navigation on a chart remarkably direct: a navigator can measure a distance against the latitude scale printed on the chart's edge without any conversion, because the two are the same thing. No other length unit has this property, which is why the nautical mile has resisted metrication where almost every other traditional unit has given way.
Because the Earth is slightly flattened, a minute of latitude is not constant, varying from about 1843 metres at the equator to 1862 metres at the poles. The First International Extraordinary Hydrographic Conference in Monaco adopted the round figure of 1852 metres in 1929 to settle the discrepancy. The United States accepted this value in 1954 and the United Kingdom in 1970, both having previously used slightly different definitions.
Speed at sea and in the air is measured in knots, one knot being one nautical mile per hour. The name records the method: a log line knotted at regular intervals was paid out behind a ship and the knots counted against a sand glass. Aviation adopted both units from maritime practice, and aircraft airspeed indicators worldwide read in knots.
Maritime law is written in the same unit. Territorial waters extend twelve nautical miles from the baseline and exclusive economic zones two hundred, figures set by the United Nations Convention on the Law of the Sea.
A related unit occasionally appears in older texts. The geographical mile is one minute of arc along the equator, about 1855 metres, and differs slightly from the nautical mile because it is measured on a great circle rather than a meridian. The distinction rarely matters in practice but explains small discrepancies between historical sources.
One nautical mile equals 1852 metres, about 1.15078 statute miles, or 6076.12 feet.