| Nanometers (nm) | Hands (hh) |
|---|---|
| 1 Nanometer | 0.00000000984251968504 hh |
| 2 Nanometers | 0.0000000196850393701 hh |
| 3 Nanometers | 0.0000000295275590551 hh |
| 4 Nanometers | 0.0000000393700787402 hh |
| 5 Nanometers | 0.0000000492125984252 hh |
| 10 Nanometers | 0.0000000984251968504 hh |
| 20 Nanometers | 0.000000196850393701 hh |
| 25 Nanometers | 0.000000246062992126 hh |
| 50 Nanometers | 0.000000492125984252 hh |
| 100 Nanometers | 0.000000984251968504 hh |
| Reference | Nanometers (nm) | Hands (hh) |
|---|---|---|
| A sheet of A4 paper (long side) | 297000000 nm | 2.92323 hh |
| Average adult human height | 1.7 × 109 nm | 16.7323 hh |
| A football pitch (length) | 1.05 × 1011 nm | 1033.46 hh |
| A marathon | 4.2195 × 1013 nm | 415305 hh |
| Height of Mount Everest | 8.849 × 1012 nm | 87096.5 hh |
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 hand is a unit of length equal to exactly four inches, or 101.6 millimetres. It survives in one specialised application: measuring the height of horses and ponies. Almost nowhere else is it still in use.
The measurement is taken from the ground to the withers, the ridge between the shoulder blades where the neck meets the back. The withers are chosen because they are a fixed skeletal point that does not move as the horse raises or lowers its head, so the figure is reproducible in a way that measuring to the top of the head would not be.
Notation is unusual and frequently misread. Heights are written with a decimal point that does not indicate a decimal fraction. A horse of 15.2 hands stands fifteen hands and two inches, which is 62 inches or 157.5 centimetres. Because a hand is four inches, the digit after the point runs only from 0 to 3, and 15.4 is not a valid height. The abbreviation hh, for hands high, is common.
The boundary between a pony and a horse is conventionally set at 14.2 hands, though the exact threshold varies between breed registries and competitive disciplines. Draught breeds such as the Shire commonly exceed 17 hands. The tallest horses on record have stood over 20 hands.
The unit derives from the breadth of a human palm, an origin shared with several ancient measures. Egyptian and Roman systems both used a palm of comparable size. Its standardisation at four inches in England is usually credited to a statute of Henry VIII. The persistence of the hand in equestrian use is largely conservatism, and metric heights in centimetres are now given alongside it in international competition rules.
Measuring accurately is harder than it appears. The horse must stand square on level ground with its head in a natural position, and a purpose-made measuring stick with a spirit level and sliding crossbar is used rather than a tape. Shoeing adds height, so official measurements specify whether the horse is shod, and competition rules that impose height limits require certification by an appointed measurer.
One hand equals 4 inches, 101.6 millimetres, or 0.1016 metres.