3-D printing: A means of producing physical items — including toys, foods and even body parts — using a machine that takes instructions from a computer program. That program tells the machine how and where to lay down successive layers of some raw material (the “ink”) to create a three-dimensional object.
astronaut: Someone trained to travel into space for research and exploration.
atmosphere: The envelope of gases surrounding Earth, another planet or a moon.
cancer: Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.
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.
cosmic rays: Very high-energy particles, mostly protons, that bombard Earth from all directions. These particles originate outside our solar system. They are equivalent to the nucleus of an atom. They travel through space at high rates of speed (often close to the speed of light).
engineer: A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need. (v.) To perform these tasks, or the name for a person who performs such tasks.
germ: Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.
gravity: The force that attracts anything with mass, or bulk, toward any other thing with mass. The more mass that something has, the greater its gravity.
infect: To spread a disease from one organism to another. This usually involves introducing some sort of disease-causing germ to an individual.
insect: A type of arthropod that as an adult will have six segmented legs and three body parts: a head, thorax and abdomen. There are hundreds of thousands of insects, which include bees, beetles, flies and moths.
International Space Station: An artificial satellite that orbits Earth. Run by the United States and Russia, this station provides a research laboratory from which scientists can conduct experiments in biology, physics and astronomy — and make observations of Earth.
Mars: The fourth planet from the sun, just one planet out from Earth. Like Earth, it has seasons and moisture. But its diameter is only about half as big as Earth’s.
microbe: Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.
microgravity: Gravity that is a fraction of the force experienced at sea level on Earth.
milestone: An important step on the road to stated goal or achievement. The term gets its name from the stone markers that communities used to erect along the side of the road to inform travelers how far they still had to go (in miles) before reaching a town.
molecule: An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
moon: The natural satellite of any planet.
muscle: A type of tissue used to produce movement by contracting its cells, known as muscle fibers. Muscle is rich in protein, which is why predatory species seek prey containing lots of this tissue.
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).
particle: A minute amount of something.
planet: A large celestial object that orbits a star but unlike a star does not generate any visible light.
plastic: Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation. (adj.) A material that is able to adapt by changing shape or possibly even changing its function.
pressure: Force applied uniformly over a surface, measured as force per unit of area.
radiation: (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
Red Planet: A nickname for Mars.
robot: A machine that can sense its environment, process information and respond with specific actions. Some robots can act without any human input, while others are guided by a human.
rocket: Something propelled into the air or through space, sometimes as a weapon of war. A rocket usually is lofted by the release of exhaust gases as some fuel burns. (v.) Something that flings into space at high speed as if fueled by combustion.
shell: The normally hard, protective outer covering of something. It could cover a mollusk or crustacean (such as a mussel or crab), a bird’s egg or some other relatively soft tissue that needs protection (such as a tree nut or peanut).
supplement: (verb) To add to something. (in nutrition) Something taken in pill or liquid form — often a vitamin or mineral — to improve the diet. For instance, it may provide more of some nutrient that is believed to benefit health. It may also provide some substance to the diet that is claimed to promote health.
tool: An object that a person or other animal makes or obtains and then uses to carry out some purpose such as reaching food, defending itself or grooming.
vitamin: Any of a group of chemicals that are essential for normal growth and nutrition and are required in small quantities in the diet because either they cannot be made by the body or the body cannot easily make them in sufficient amounts to support health.
yeast: One-celled fungi that can ferment carbohydrates (like sugars), producing carbon dioxide and alcohol. They also play a pivotal role in making many baked products rise.
