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alien A non-native organism. (in astronomy) Life on or from a distant world.
angle The space (usually measured in degrees) between two intersecting lines or surfaces at or close to the point where they meet.
arcsecond A measure of some angle relative to a circle. A circle is divided into 360 equal-size wedges (or pie slices). Each of these is described as being 1 degree in size (something a school protractor for measuring angles can help you picture). Partial degrees are measured in other units: arcminutes (each equal to 1/60th of a degree) and arcseconds (each equal to 1/3600th of a degree).
astronomy The area of science that deals with celestial objects, space and the physical universe as a whole. People who work in this field are called astronomers.
atomic Having to do with atoms, the smallest possible unit that makes up a chemical element.
atomic number The number of protons in an atomic nucleus, which determines the type of atom and how it behaves.
binary Something having two integral parts. (in mathematics and computer science) A number system where values are represented using two symbols 1 (on) or 0 (off).
broadcast To cast — or send out — something over a relatively large distance. A farmer may broadcast seeds by flinging them by hand over a large area. A loudspeaker may send sounds out over a great distance. An electronic transmitter may emit electromagnetic signals over the air to a distant radio, television or other receiving device. And a newscaster can broadcast details of events to listeners across a large area, even the world.
chemical A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical can also be an adjective to describe properties of materials that are the result of various reactions between different compounds.
code (in computing) To use special language to write or revise a program that makes a computer do something.
cosmic An adjective that refers to the cosmos — the universe and everything within it.
culture (in social science) The sum total of typical behaviors and social practices of a related group of people (such as a tribe or nation). Their culture includes their beliefs, values, and the symbols that they accept and/or use. Culture is passed on from generation to generation through learning. Scientists once thought culture to be exclusive to humans. Now they recognize some other animals show signs of culture as well, including dolphins and primates.
decode To convert a hidden or secret message into a language that can be understood.
degree (in geometry) A unit of measurement for angles. Each degree equals one three-hundred-and-sixtieth of the circumference of a circle.
DNA (short for deoxyribonucleic acid) A long, double-stranded and spiral-shaped molecule inside most living cells that carries genetic instructions. It is built on a backbone of phosphorus, oxygen, and carbon atoms. In all living things, from plants and animals to microbes, these instructions tell cells which molecules to make.
Drake equation A mathematical statement created in 1961 by radio astronomer Frank Drake. It posits that science can estimate the number of technological civilizations in distant star systems by considering: how many civilizations in our Milky Way galaxy would have electromagnetic emissions that could be picked up on Earth, the rate at which new stars that are suitable for hosting intelligent life form, the share of those stars with planets, the number of planets per solar system having an environment that could support life, the share of those planets on which life actually developed, the share of those planets on which the life was intelligent, the share of civilizations that then developed a technology that could signal its existence into space, and how long such civilizations would issue those detectable signals.
element (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.
equation In mathematics, the statement that two quantities are equal. In geometry, equations are often used to determine the shape of a curve or surface.
E.T. (n.) An abbreviation made famous by the 1982 Universal Pictures movie, E.T. the Extra-Terrestrial. The main character was a charming space alien called E.T. His most famous line from the movie was “E.T. phone home.” E.T. has since come to be used as a colloquial term for any intelligent and potentially friendly space alien.
extraterrestrial Anything of or from regions beyond Earth.
factor Something that plays a role in a particular condition or event; a contributor.
Fibonacci sequence A pattern of numbers that frequently shows up in nature. Each successive number is equal to the addition of the two numbers before it, starting with 0 and 1. So it starts out: 0, 1, 1, 2, 3, 5, 8, 13, 21 — and then goes on from there.
frequency The number of times a specified periodic phenomenon occurs within a specified time interval. (In physics) The number of wavelengths that occurs over a particular interval of time.
galaxy A massive group of stars bound together by gravity. Galaxies, which each typically include between 10 million and 100 trillion stars, also include clouds of gas, dust and the remnants of exploded stars.
geometry The mathematical study of shapes, especially points, lines, planes, curves and surfaces.
intelligence The ability to collect and apply knowledge and skills.
laser A device that generates an intense beam of coherent light of a single color. Lasers are used in drilling and cutting, alignment and guidance, in data storage and in surgery.
mass A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.
milli A prefix for fractional units of measurement, here referring to thousandths in the international metric system.
moon The natural satellite of any planet.
periodic table of the elements A chart (and many variants) that chemists have developed to sort elements into groups with similar characteristics. Most of the different versions of this table that have been developed over the years tend to place the elements in ascending order of their mass.
physicist A scientist who studies the nature and properties of matter and energy.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, the object must be big enough to have pulled neighboring objects into the planet itself or to have slung them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now includes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
premature Too early; before something should occur. Premature births, for instance, are when babies are born weeks or months early — potentially before they are ready for life on their own, outside their mom’s protective womb.
prime number A whole number that is divisible only by itself and 1. For example, 2 and 3 are prime numbers but 4 (which is divisible by 2) is not.
proper motion A measure of the angular velocity of some object in distant space relative to Earth. This motion has two components: its speed of change and direction of change over time.
radio To send and receive radio waves; or the device that receives these transmissions.
science fiction A field of literary or filmed stories that take place against a backdrop of fantasy, usually based on speculations about how science and engineering will direct developments in the distant future. The plots in many of these stories focus on space travel, exaggerated changes attributed to evolution or life in (or on) alien worlds.
SETI An abbreviation for search for extraterrestrial intelligence, meaning life on other worlds.
Siberia A region in northern Asia, almost all of which falls within Russia. This land takes its name from the language of the Tatar people, where Siber means sleeping land. This region is vast. It has become famous for its long, harsh winters, where temperatures can fall to −68° Celsius (−90° Fahrenheit).
society An integrated group of people or animals that generally cooperate and support one another for the greater good of them all.
solar system The eight major planets and their moons in orbit around the sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
star The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.
sun The star at the center of Earth’s solar system. It’s an average size star about 26,000 light-years from the center of the Milky Way galaxy. Also a term for any sunlike star.
technology The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.
telescope Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, collect radio emissions (energy from a different portion of the electromagnetic spectrum) through a network of antennas.
trajectory The path taken by a projectile moving through space and time, or the direction that a trend is taking over time.
transmit (n. transmission) To send or pass along.
trillion A number representing a million million — or 1,000,000,000,000 — of something.
universe The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).
variable (in mathematics) A letter used in a mathematical expression that may take on different values.