argon: An element first discovered on August 13, 1894, by Scottish chemist Sir William Ramsay and English physicist John William Strutt, better known as Lord Rayleigh. Argon was the first “noble” gas, meaning one that does not react chemically with other elements. For its discovery, Ramsey would receive the 1904 Nobel Prize in chemistry and Rayleigh the 1904 Nobel Prize in Physics.
astronomer: A scientist who works in the field of research that deals with celestial objects, space and the physical universe.
atmosphere: The envelope of gases surrounding Earth, another planet or a moon.
aurora: A light display in the sky caused when incoming energetic particles from the sun collide with gas molecules in a planet’s upper atmosphere. The best known of these is Earth’s aurora borealis, or northern lights. On some outer gas planets, like Jupiter and Saturn, the combination of a fast rate of rotation and strong magnetic field leads to high electrical currents in the upper atmosphere, above the planets’ poles. This, too, can cause auroral “light” shows in their upper atmosphere.
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 dioxide: (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.
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.
cloud: A plume of molecules or particles, such as water droplets, that move under the action of an outside force, such as wind, radiation or water currents. (in atmospheric science) A mass of airborne water droplets and ice crystals that travel as a plume, usually high in Earth’s atmosphere. Its movement is driven by winds. (in computing) A network of computers (hardware), known as servers, which are connected to the internet. They can be used to store data and computer programs (software) that can be accessed by one or many people at once, and from anywhere in the world.
dwarf planet: One of the solar system’s small celestial objects. Like a true planet, it orbits the sun. However, dwarf planets are too small to qualify as true planets. Prime examples of these objects: Pluto and Ceres.
exoplanet: Short for extrasolar planet, it’s a planet that orbits a star outside our solar system.
gas giant: A giant planet that is made mostly of helium and hydrogen, which on Earth are gases. Jupiter and Saturn are gas giants.
greenhouse effect: The warming of Earth’s atmosphere due to the buildup of heat-trapping gases, such as carbon dioxide and methane. Scientists refer to these pollutants as greenhouse gases. The greenhouse effect also can occur in smaller environments. For instance, when cars are left in the sun, the incoming sunlight turns to heat, becomes trapped inside and quickly can make the indoor temperature a health risk.
greenhouse gas: A gas that contributes to the greenhouse effect by absorbing heat. Carbon dioxide is one example of a greenhouse gas.
helium: An inert gas that is the lightest member of the noble gas series. Helium can become a solid at -272 degrees Celsius (-458 degrees Fahrenheit).
hydrogen: The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable. It’s an integral part of many fuels, fats and chemicals that make up living tissues. It’s made of a single proton (which serves as its nucleus) orbited by a single electron.
Jupiter: (in astronomy) The solar system’s largest planet, it has the shortest day length (9 hours, 55 minutes). A gas giant, its low density indicates that this planet is composed mostly of the light elements hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).
methane: A hydrocarbon with the chemical formula CH4 (meaning there are four hydrogen atoms bound to one carbon atom). It’s a natural constituent of what’s known as natural gas. It’s also emitted by decomposing plant material in wetlands and is belched out by cows and other ruminant livestock. From a climate perspective, methane is 20 times more potent than carbon dioxide is in trapping heat in Earth’s atmosphere, making it a very important greenhouse gas.
moon: The natural satellite of any planet.
nitrogen: A colorless, odorless and nonreactive gaseous element that forms about 78 percent of Earth's atmosphere. Its scientific symbol is N. Nitrogen is released in the form of nitrogen oxides as fossil fuels burn. It comes in two stable forms. Both have 14 protons in the nucleus. But one has 14 neutrons in that nucleus; the other has 15. For that difference, they are known, respectively, as nitrogen-14 and nitrogen-15 (or 14N and 15N).
oxygen: A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).
ozone: A colorless gas made of molecules that contain three oxygen atoms. It can form high in the atmosphere or at ground level. When it forms at Earth’s surface, ozone is a pollutant that irritates eyes and lungs. It is also a major ingredient of smog.
planet: A large celestial object that orbits a star but unlike a star does not generate any visible light.
Pluto: A distant world that is located in the Kuiper Belt, just beyond Neptune. Pluto is the ninth largest object orbiting the sun.
Saturn: The sixth planet out from the sun in our solar system. One of the two gas giants, this planet takes 10.6 hours to rotate (completing a day) and 29.5 Earth years to complete one orbit of the sun. It has at least 82 moons. But what most distinguishes this planet is the broad and flat plane of bright rings that orbit it.
star: The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become hot enough, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.
ultraviolet: A portion of the light spectrum that is close to violet but invisible to the human eye.
water vapor: Water in its gaseous state, capable of being suspended in the air.
weather: Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.
