The helium_atom_and_perspective_ helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_.html" ;"title="Magnitude_(mathematics).html" ;"title="atom.html" ;"title="helium helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_">Magnitude_(mathematics).html"_;"title="atom.html"_;"title="helium_atom">helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_ The_femtometre_(American_spelling_femtometer)_symbol_fm_derived_from_the_ helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_">Magnitude_(mathematics).html"_;"title="atom.html"_;"title="helium_atom">helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_ The_femtometre_(American_spelling_femtometer)_symbol_fm_derived_from_the_Danish_language">Danish_and_ helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_">Magnitude_(mathematics).html"_;"title="atom.html"_;"title="helium_atom">helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_ The_femtometre_(American_spelling_femtometer)_symbol_fm_derived_from_the_Danish_language">Danish_and_Norwegian_language">Norwegian_word__'fifteen',__grc.html" ;"title="Norwegian_language.html" ;"title="Danish_language.html" ;"title="atom">helium magnitudes_">Magnitude_(mathematics).html"_;"title="atom.html"_;"title="helium_atom">helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_ The_femtometre_(American_spelling_femtometer)_symbol_fm_derived_from_the_Danish_language">Danish_and_Norwegian_language">Norwegian_word__'fifteen',__grc">μέτρον.html" ;"title="atom and perspective Magnitude (mathematics)">magnitudes ">Magnitude_(mathematics).html" ;"title="atom.html" ;"title="helium helium_atom_and_perspective_Magnitude_(mathematics)">magnitudes_ The_femtometre_(American_spelling_femtometer)_symbol_fm_derived_from_the_Danish_language">Danish_and_Norwegian_language">Norwegian_word__'fifteen',__grc">μέτρον">metrοn.html" ;"title="atom">helium atom and perspective Magnitude (mathematics)">magnitudes The femtometre (American spelling femtometer) symbol fm derived from the Danish_and_Norwegian_language">Norwegian_word__'fifteen',__grc">μέτρον">metrοn">lit=unit_of_measurement)_is__a_unit_of_length_in_the_International_System_of_Units_(SI)_equal_to_10⁻¹⁵_metres,_which_means_a_quadrillionth_of_one_metre.__This_distance_is_sometimes_called_a_fermi_and_was_so_named_in_honour_of_Italian_Americans.html" ;"title="Danish language">Danish and Norwegian language">Norwegian word 'fifteen', grc">μέτρον">metrοn">lit=unit of measurement) is a unit of length in the International System of Units (SI) equal to 10⁻¹⁵ metres, which means a quadrillionth of one metre. This distance is sometimes called a fermi and was so named in honour of Italian Americans">Italian-American physicist

Enrico Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" an ...

, as it is a typical length-scale of nuclear physics.

Definition and equivalents

1000000 zeptometres = 1 femtometre = 1 fermi = 0.000001

nanometre 330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re ...

= femtometres = 1

millimetre 330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter. The millimetre (American and British English spelling differences#-re, -er, ...

. For example, the

charge radius The rms charge radius is a measure of the size of an atomic nucleus, particularly the proton distribution. It can be measured by the scattering of electrons by the nucleus. Relative changes in the mean squared nuclear charge distribution can b ...

of a

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

is approximately 0.841 femtometres while the radius of a

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: * Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

is approximately 8.45 femtometres. 1 barn = 100 fm²

History

The femtometre was adopted by the 11th ''Conférence Générale des Poids et Mesures'', and added to the SI in 1964, using the Danish word for "15" and the similarity in spelling with ''fermi''. The fermi is named after the Italian

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

(1901–1954), one of the founders of nuclear physics. The term was coined by Robert Hofstadter in a 1956 paper published in '' Reviews of Modern Physics'' entitled "Electron Scattering and Nuclear Structure". The term is widely used by nuclear and

particle In the physical sciences, a particle (or corpuscule in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from ...

physicists. When Hofstadter was awarded the 1961 Nobel Prize in Physics, it subsequently appeared in the text of his 1961 Nobel Lecture, "The electron-scattering method and its application to the structure of nuclei and nucleons" (December 11, 1961).Hofstadter, Robert, "The electron-scattering method and its application to the structure of nuclei and nucleons," Nobel Lecture (December 11, 1961)
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References

{{DEFAULTSORT:Femtometre Metre de:Meter#Dezimale Vielfache ru:Фемтометр