Cosma / Communication / Knowledge / Realm / Physical / Matter / Atom

A way to remember their size is this: if an apple is magnified to the size of the earth, then the atoms in the apple are approximately the size of the original apple. — Richard Feynman, The Feynman Lectures on Physics



MooMooMath and Science (YouTube Channel)
MooMooMath and Science (Official Website)


atom : the smallest particle of an element that can exist either alone or in combination — Webster   See also OneLook


Roget’s II (, Merriam-Webster Thesaurus, Visuwords


Atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale).

Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons. Protons and neutrons are called nucleons. More than 99.94% of an atom’s mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, that atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion. — Wikipedia

Atoms (Eric Weisstein’s World of Physics, Wolfram Research)
Atom (Encyclopædia Britannica)


Atom (WolframAlpha)
Step by Step Chemistry (Wolfram Alpha)




Atomic Physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change.

The term atomic physics can be associated with nuclear power and nuclear weapons, due to the synonymous use of atomic and nuclear in standard English. Physicists distinguish between atomic physics — which deals with the atom as a system consisting of a nucleus and electrons — and nuclear physics, which considers atomic nuclei alone. — Wikipedia

Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Other forms of nuclear matter are also studied. Nuclear physics should not be confused with atomic physics, which studies the atom as a whole, including its electrons. — Wikipedia

Scientists Perform World’s Smallest MRI on Single Atoms (Brooks Hays, UPI)
World’s Smallest MRI Performed on Single Atoms (Institute for Basic Science,

Nuclear Physics (Wolfram Alpha)


Nuclear engineering is concerned with the application of breaking down atomic nuclei (fission) or of combining atomic nuclei (fusion), or with the application of other sub-atomic processes based on the principles of nuclear physics. In the sub-field of nuclear fission, it includes the design, interaction, and maintenance of systems and components like reactors and power plants. The field also includes the study of medical and other applications of radiation, particularly Ionizing radiation, nuclear safety,nuclear fuel, or other related technology (e.g., radioactive waste disposal). — Wikipedia

Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by nuclear fission of uranium and plutonium in nuclear power plants. Nuclear decay processes are used in niche applications such as radioisotope thermoelectric generators in some space probes such as Voyager 2. Generating electricity from fusion power remains the focus of international research. — Wikipedia

Nuclear Power (Wolfram Alpha)



Atom Campaigns (Kickstarter)
Atom Campaigns (Indiegogo)


Atom Gifts (Zazzle)




Niels Bohr Archive (University of Copenhagen)
Niels Bohr Institute (University of Copenhagen)
Niels Bohr (Encyclopædia Britannica)
Neils Bohr (Wikipedia)


National Museum of Nuclear Science & History (Albuquerque, New Mexico)


Atomic Heritage Foundation (Official Site)
Atomic Heritage Foundation (YouTube Channel)
Atomic Heritage Foundation (Wikipedia)

The Nuclear Files Archive (Nuclear Age Peace Foundation)


Melvil Decimal System # 539.7 Atomic and Nuclear Physics (Library Thing)
Library of Congress Subject Heading: Atom (Library Thing)

Library of Congress # QC173 Nuclear Structure (UPenn Online Books)

WorldCat, Library of Congress, UPenn Online Books, Open Library




Nuclear Science (Contemporary Physics Project)

Atoms Cafe (PlayMada Games)

Atoms Around Us (Chem4Kids)
Nuclear Physics (Physics4Kids)

Atomic Structure (ChemMatters, American Chemical Society)
Nuclear Chemistry (ChemMatters, American Chemical Society)

Nuclear Science 101 (American Nuclear Society)
About Nuclear (American Nuclear Society)

Nuclear Engineering (American Society for Engineering Education)

MERLOT: Multimedia Educational Resource for Learning and Online Teaching
OER Commons: Open Educational Resources


General Chemistry I: Atoms, Molecules, and Bonding (MITx)

Chemistry Department Courses (MIT OpenCourseWare)
Chemistry Courses (edX)

Nuclear Science and Engineering Department (MIT OpenCourseWare)
Nuclear Sciences & Engineering (Course 22, MITx)

Nuclear Physics Courses (MIT OpenCourseWare)
Nuclear Engineering Courses (MIT OpenCourseWare)
Nuclear Materials Courses (MIT OpenCourseWare)

Nuclear Physics Courses (edX)



Nuclear Chemistry Careers (American Chemical Society)

Nuclear Engineers (CareerOneStop, U.S. Department of Labor)

Nuclear Engineer (US Bureau of Labor Statistics)


American Nuclear Society

Nuclear Age Peace Foundation


Atomic Physics ( e-Print Archive)

Nuclear News (American Nuclear Society)
Publications (American Nuclear Society)

Nuclear chemistry (Nature)
Nuclear Energy (
Atomic & Nuclear (Scientific American)
Nuclear Energy (NPR Archives)


Nuclear Energy (ISBNdb)


International Atomic Energy Agency

Office of Nuclear Energy (US Energy Department)
US Nuclear Regulatory Commission


Nuclear Energy (



Here are links to pages about closely related subjects.

Knowledge Realm


Law (Constant) Relativity
Force Gravity, Electromagnetism (Light, Color)
Matter (Microscope) Molecule, Atom (Periodic Table), Particle

Universe (Astronomical Instrument)
Galaxy Milky Way, Andromeda
Planetary System Star, Brown Dwarf, Planet, Moon

Our Neighborhood
Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Trans-Neptunian Object
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid


1.   The resources on this page are are organized by a classification scheme developed exclusively for Cosma.