How long is it?
This teacher resource is a collection of length measurements found within the Science Learning Hub. Lengths range from the very small to the very big.
Student activities can be developed from some of the ideas presented, and by the end of such activities, students should be able to:
appreciate the huge range of length measurements in use
use length measurement units appropriately
develop their understanding of the decimal system as applied to length measurement.
Planck length
1.6 x 10-35 m. Anything shorter than this makes no physical sense. It is the ‘quantum of length’ – the smallest measurement of length with any meaning.
Quark
10-18 m or 1 attometre (am). Quarks are the building blocks of protons and neutrons. The structure of the nucleus
Nucleus
10-15 m or 10 femtometres (fm). The tiny, dense central part of an atom. The structure of the nucleus
Gamma Ray
10-12 m or 1 picometre (pm). The wavelength of this highly energetic form of electromagnetic radiation. The electromagnetic spectrum
Hydrogen atom
25 pm. The approximate diameter of a hydrogen atom. Westpac Stadium, Wellington
Carbon nanotube
10-9 m or 1 nanometre (nm). The approximate diameter of a carbon nanotube. Carbon nanotubes
DNA thickness
3 nm. The distance across the ‘twisted ladder’ structure of DNA. DNA bases
HIV
90 nm in diameter. The human immunodeficiency virus (HIV) is spherical in shape.
UVA wavelength
315–400 nm. Overexposure to ultraviolet (UV) light can damage the skin. What is UV?
Clay particle
10-6 m or 1 micrometre (1 mm). Clay is a soft, loose, earthy material containing particles with a grain size of less than 4 micrometres (μm). What is clay?
Fern spore
30–50 mm. Spores are produced in capsules called sporangia. These are aggregated into clusters called sori, found on the under surface of fern fronds. What is a fern?
Naked eye limit
100 mm. The smallest structure just visible to the unaided eye is about 100 mm. Sight
Human skin
0.5–4 x 10-3 m or 0.5–4 millimetres (mm). Depending on location, human skin varies in thickness from 0.5 mm (eyelids) to 4 mm (palms and soles of the feet). Diagram of human skin structure
Microwaves
10-2 m or 1 centimetre (cm). Microwaves are used for heating food in a microwave oven or for transmitting information from one place to another. Wavelengths of different wave types
FM radio waves (100 MHz)
Wavelength is 3 x 100 m or 3 metres (m). Fundamentals of waves
Marathon
42.2 x 103 m or 42.2 kilometres (km). The current men’s world record for the marathon is 2:03:59. Most recreational runners would take about 4 hours to complete it. Marathon versus sprint
Earth’s diameter
~12.8 x 106 m or 12.8 megametres (Mm) or 12.8 thousand kilometres. Earth structure
Sun’s diameter
1.4 x 109 m or 1.4 gigametres (Gm). Distances in space
Earth to Neptune distance
4.35 x 1012 m or 4.35 terametres (Tm) or 4.35 million kilometres. Distances in space
1 light year
9.5 x 1015 m or 9.5 petametres (Pm) or 9.5 million million kilometres. The closest star system, outside the solar system, is Alpha Centauri located about 4.37 light years away. Distances in space
Current estimated diameter of the observable universe
~8.8 x 1026 m or 93 billion light years.
Measurement extremes
This diagram shows the measurement from the smallest, planck length, to largest, the estimated diameter of the observable universe as in 2011.
Related content
For more on measurement see this article that introduces our range of resources.
Explore the microscopic scale in this interactive diagram, showcasing examples from the Science Learning Hub.
Activity ideas
Measurements, weird and wonderful is a collection of unusual measurement units – such as a moment (1/40 of an hour). Follow this up with Cubits, spans and digits activity to reinforce the degree of uncertainty when using non-SI measurements.
