atom: The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
carbon: A chemical element that is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules. (in climate studies) The term carbon sometimes will be used almost interchangeably with carbon dioxide to connote the potential impacts that some action, product, policy or process may have on long-term atmospheric warming.
carbon dating: Short for radioactive-carbon dating or carbon-14 dating. A way to measure the age of organic materials — ones containing carbon. Carbon-14, a weakly radioactive isotope, forms in Earth’s upper atmosphere as cosmic rays hit nitrogen atoms. This carbon joins with oxygen to form carbon dioxide, which living organisms take up and incorporate in their tissues. When those organisms die, they stop exchanging carbon with the environment and the share of the carbon-14 isotope starts to fall at a constant rate (one set by the law of radioactive decay). By measuring the share of carbon-14 to carbon-12 in the organism’s remains, scientists can determine how long ago it died.
climate: The weather conditions that typically exist in one area, in general, or over a long period.
climate change: Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.
decay: (for radioactive materials) The process whereby a radioactive isotope — which means a physically unstable form of some element — sheds energy and subatomic particles. In time, this shedding will transform the unstable element into a slightly different but stable element. For instance, uranium-238 (which is a radioactive, or unstable, isotope) decays to radium-222 (also a radioactive isotope), which decays to radon-222 (also radioactive), which decays to polonium-210 (also radioactive), which decays to lead-206 — which is stable. No further decay occurs. The rates of decay from one isotope to another can range from timeframes of less than a second to billions of years.
element: A building block of some larger structure. (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.
environment: The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).
fabric: Any flexible material that is woven, knitted or can be fused into a sheet by heat.
fiber: Something whose shape resembles a thread or filament. (in nutrition) Components of many fibrous plant-based foods. These so-called non-digestible fibers tend to come from cellulose, lignin, and pectin — all plant constituents that resist breakdown by the body’s digestive enzymes.
half-life: The time it takes for half of some quantity of a radioactive isotope to decay (transform) into a new isotope
neutron: A subatomic particle carrying no electric charge that is one of the basic pieces of matter. Neutrons belong to the family of particles known as hadrons.
nucleus: Plural is nuclei. (in biology) A dense structure present in many cells. Typically a single rounded structure encased within a membrane, the nucleus contains the genetic information. (in astronomy) The rocky body of a comet, sometimes carrying a jacket of ice or frozen gases. (in physics) The central core of an atom, containing most of its mass.
organic: (in chemistry) An adjective that indicates something is carbon-containing; also a term that relates to the basic chemicals that make up living organisms. (in agriculture) Farm products grown without the use of non-natural and potentially toxic chemicals, such as pesticides.
organism: Any living thing, from elephants and plants to bacteria and other types of single-celled life.
radioactive: An adjective that describes unstable elements, such as certain forms (isotopes) of uranium and plutonium. Such elements are said to be unstable because their nucleus sheds energy that is carried away by photons and/or one or more subatomic particles. This emission of energy is by a process known as radioactive decay.
radiocarbon dating: Short for radioactive-carbon dating or simply carbon dating. A way to measure the age of organic materials — ones containing carbon. Carbon-14, a weakly radioactive isotope, forms in Earth’s upper atmosphere as cosmic rays hit nitrogen atoms. This carbon joins with oxygen to form carbon dioxide, which living organisms take up and incorporate in their tissues. When those organisms die, they stop exchanging carbon with the environment and the share of the carbon-14 isotope starts to fall at a constant rate (one set by the law of radioactive decay). By measuring the share of carbon-14 in the organism’s remains, scientists can determine how long ago it died.
rotifer: Any of the tiny (usually microscopic) invertebrate animals belonging to the class Rotifera. Most live in freshwater. They tend to have disk-type structures with powerful hairlike cilia that work like oars to move through water.
shark: A type of predatory fish that has survived in one form or another for hundreds of millions of years. Cartilage, not bone, gives its body structure. Like skates and rays, sharks belong to a group known as elasmobranchs. They tend to grow and mature slowly and have few young. Some lay eggs, others give birth to live young.
suspended animation: A temporary shutdown of most or all living functions without causing death. Examples can include a stored seed, hibernating animal or permafrost-trapped rotifer.
