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absorb - to take in something
adapt - to make suitable to or fit for a specific use or situation
aeroponics - a variation of hydroponics that involves misting the plant roots with a nutrient solution
air - the gas that surrounds the earth. It contains oxygen, nitrogen, and carbon dioxide.
angle - what lies between two rays which share the same endpoint
annual - a plant that finishes its life cycle in one growing season and dies in the winter
anther - the male part of the flower that produces the pollen
asteroid - a rocky object in space that can be anywhere from a few feet wide to several miles wide. Most asteroids in our solar system are part of a belt between Mars and Jupiter.
astronaut - a person trained to travel in space
atmosphere - the mass of gas surrounding an object in space and held by the object's gravitational field
axis - an imaginary straight line around which an object spins. The Earth's axis is tilted 23.45 degrees.
biennial - a plant that takes two years to complete its life cycle (dies after 2 years)
billion - A number represented as a 1 followed by nine zeros (1,000,000,000). If you have a bucket that holds 10 thousand marbles, you would need 100 thousand of those same buckets to hold a billion marbles! That's a lot of marbles!
bulb - a miniature packaged plant that contains everything needed to grow a new plant, made up of special scale leaves and food for the plant
carbohydrate - an organic compound such as sugar or starch which provides energy for living organisms
carbon dioxide - a gas from the air that is used by plants for photosynthesis, also known as CO2
cells - the basic structural and functioning units of all living things
Celsius - metric temperature scale at which water freezes at 0° and boils at 100°
cephalad fluid shift - when fluid that usually pools in the feet is moved towards the torso and head causing the face to puff up and the legs to get thinner. There is no gravity to pull fluid towards the legs so the fluid shifts to be distributed throughout the body.
chlorophyll - green material in plants that is created in the presence of light and is important for photosynthesis
circulation - movement in a circle or in a circuit
circumference - the outer boundary of a circle or spherical object
clay - very fine soil particles; it is smooth and can hold nutrients, but water and air do not move through it well
colonize - to migrate to and settle in; occupy as a colony
compost - natural breakdown of plant and animal parts which decay and release minerals for living plants to use to grow
conduction - the act of energy from heated particles moving from an area of high temperature to an area of cooler temperature. This happens by the transfer of energy between the particles that make up those materials
convection - the act of a fluid, such as air or water, coming in contact with an object that is at a higher temperature. This contact causes convection currents to form as fluid of higher temperature moves to areas of cooler temperature.
crater - a bowl-shaped depression on a surface made by the impact of a large object, such as a meteor
cuticle - waxy coating that protects the leaf
cutting - a part of a plant's leaves, roots, or stem which is planted and grows into a new plant
diameter - a straight line segment which passes through the center of a circle or sphere with both its ends on the boundary of the circle
dormant - being in a resting state (not currently growing)
dwarf varieties - smaller, miniature versions of plants that are just as nutritious as the larger ones
eclipse - a shadow cast by one very large object on another
edible - fit to be eaten as food
electromagnetic - relating to magnetism which is developed by the passage of an electric current
eroded - worn away as by ice, wind, or water
exhale - to breathe out
extraterrestrial - originating or occurring outside the Earth and its atmosphere; when scientists search for extraterrestrial life, they are trying to find life on someplace other than Earth
Fahrenheit - the temperature scale at which water freezes at 32° and boils at 212°
fertilizer - any substance used to make soil more fertile for plants to grow; there are a large number of natural and artificial substances that can be mixed into soil to help the soil better support plant growth
filament - fine stalk that holds up the anther
flower - reproductive part of a plant
freefall - another term for the feeling of "weightlessness"
fruit - ripe, mature ovary that contains seeds
galaxy - a huge collection of gas, dust, and stars in space. Our own galaxy is called the Milky Way.
germination - activation of a seed that causes it to start to grow
glucose - a simple sugar that plants make and use as food
gravitropism - the response of plants to gravity; roots move towards the pull of gravity and shoots move away from the pull of gravity
gravity - the natural, invisible force between objects that attracts them to each other
habitat - area or environment where an organism normally lives
harvest index - proportion of usable (edible) crop materials over that which cannot be used or eaten
heat - a form of energy that causes the sensation of feeling hot or warm
herbaceous - describes plants that have stems that are soft. These plants die back to the ground in the winter.
highlands - areas on the Moon covered with craters
horticulturalist - a person whose job is cultivating and growing fruits, vegetables, flowers, or ornamental plants
humus - among the richest and darkest of soils and develops from decaying plant and animal life
hydroponics - a technique of growing plants in water (without soil) by using water with special nutrients dissolved in it
image - an object as seen in a mirror or lens (When looking in a mirror, we see an image of ourselves)
infrared - invisible wavelengths of the spectrum, just longer than the color of red
kilogram - a measure of weight, equal to 1,000 grams or 0.454lbs
kilometer - A unit of measure for length. One kilometer equals 1,000 meters. A kilometer is also equal to .6214 miles.
lava - molten rock that reaches the surface through a volcano or fissure and then cools and hardens
leaf - green part of a plant that collects light and carbon dioxide for photosynthesis
light - electromagnetic radiation that has a wavelength that is visible to the naked eye
light year - the distance that light can travel in one year (9.5 trillion kilometers)
loam - soil possessing an ideal mixture of sand, humus, and clay for growing plants
Low Earth Orbit - An area that satellites travel in that is about 200-500 miles (320-800 kilometers) above Earth. Satellites traveling in Low Earth Orbit have to travel very fast so that gravity does not pull them back out into the atmosphere.
Luna II - Russian spacecraft, the first spacecraft to land on the Moon. Humans were not on this spacecraft. It landed on the Moon on September 14, 1959.
lunar - having to do with the Moon
lunar eclipse - occurs when the Moon passes through the Earth's shadow. The Moon then appears to be red in color.
maria - dark, smooth areas of the Moon caused by molten lava flowed and has now hardened on the surface
meteor - An object from space that becomes glowing hot when it passes into Earth's atmosphere
microgravity - an environment in which there is minimal gravitational force
microorganism - a very small organism of microscopic size
Moon - can be any natural object orbiting around another; often refers to the Moon of the Earth (but other planets have moons too.) The Moon of the Earth was probably formed when a large object struck the Earth a long time ago.
navigate - to plan, record and control the movement of a ship or plane
Neil Armstrong - American astronaut and the first person to step on the Moon. When he landed on the Moon, he said, "That's one small step for man; one giant leap for mankind."
nutrient solution - minerals dissolved in water to feed hydroponically-grown plants
nutrients - sources of nourishment for living things that are important for growth and survival
opaque - does not let light pass through it
orbit - the path followed by an object in space as it travels around another object
organic - material of natural, biological origin
orient - to become adjusted and position oneself; to align with respect to a point of reference
ovary - part of the female flower that contains the ovules
ovule - part of the ovary that becomes a seed
oxygen - substance released into the air by plants as a result of photosynthesis. Plants take in carbon dioxide and release oxygen while humans take in oxygen and release carbon dioxide.
ozone layer - a part of the Earth's atmosphere, almost 20 miles up in the sky, that contains ozone. Ozone blocks harmful radiation from the Sun so that it will not reach the Earth.
particle - a small part or portion of something, like a particle of sand or dust
perennial - a plant that lives for many years and comes back after resting each winter, such as grass and trees
petal - specialized structure that protect the parts of a flower and also attract birds and insects to help with pollination
phase - one of the apparent forms of the Moon. The Moon cycles through 8 phases.
photosynthesis - process by which a plant produces food using water, carbon dioxide, and sunlight
phototropism - the response and movement of plants towards light
pistil - female part of the flower that includes the stigma, style, and ovary
pollen - yellow powder-like material on the anthers which is necessary for a plant to reproduce
pollination - movement of pollen from the anther to the stigma
pollinators - those who assist with moving the pollen from the anther to the stigma, such as birds, bees, butterflies, and insects
radiation - energy radiated or transmitted as rays, waves, in the form of particles
recycle - to take old materials and turn them into usable materials
reflect - to throw or bend back light from a surface

refract - when a light ray traveling through air hits a different material. When the light ray hits the new material, its speed and direction will change. This can cause some things to look strange. For example, this happens if we look at a pencil through a glass of water.

regolith - a layer of loose rock and rocky debris sitting on the top of a hard surface; The regolith of the Moon was produced by meteors striking the Moon's surface.
revolve - to move in an orbit or circle around something
root - underground part of a plant that collects water and nutrients from the soil; also anchors the plant
root tips - cells at the very tip of a plant root containing particles that respond to gravity and help direct the root to grow down
rotate - to move around a center point, or axis, just like how a wheel rotates
sand - largest of the soil particles; it is very rough and does not hold water well
satellite - an object that orbits another in space. The Moon is a natural satellite of the Earth.
scale leaves - the small leaves inside a bulb that hold stored food for the bulb
seed - part of a plant that will grow into a new plant if the environmental conditions are right; formed by the maturation of the ovule after fertilization
seed coat - protective outer covering of a seed
sepal - green leaf-like structures that cover a bud and later open up to reveal the petals of a flower
shadow - an area where light cannot directly shine because an opaque object lies between the area and the source of light. A shadow is also the image cast by an object that is blocking rays of light.
shoot - emerges from a seed that has germinated and becomes the part of the plant that grows upward
silt - medium-sized soil particles; it feels smooth and can hold a lot of water, which moves easily through it
solar eclipse - occurs when the Moon passes in front of the Sun during the day and casts its shadow onto the Earth
spore - seed-like structure that plants like ferns, mosses, and mushrooms use to reproduce instead of a seed
stamen - male part of the flower that includes the anther and filament
star - an object in space composed of intensely hot gasses that creates light and heat energy from nuclear reactions going on inside of it
statoliths - special starch grains in the bottom of root tips which tell the plant which way is down
stem - part of the plant which holds up the leaves and flowers and serves as a highway to move water and nutrients through the plant
stigma - sticky surface on the end of the pistil that traps and holds pollen
stomata - pores in leaves that allow plant to bring in carbon dioxide and release oxygen
stratosphere - region of the atmosphere above the troposphere. The stratosphere is the region which contains the ozone layer.
style - part of the female flower that holds up the stigma
Sun - a star, and the largest object in our solar system. The Sun is the closest star to Earth and is about 5 billion years old.
telescope - an instrument used for viewing far away objects, such as planets and stars
temperature - the degree of hotness or coldness of a body or environment
terrain - the area and surface features of land
texture - in relation to soil, how much sand, silt, and clay that soil contains; it is used to describe the coarseness or fineness of the soil
translucent - able to transfer some light, but the light is distorted (paper is an example)
transparent - easily seen through; light can go through these objects with little distortion
trillion - A number represented as a 1 followed by twelve zeros (1,000,000,000,000) If you have a bucket that holds 100 thousand marbles, you would need 10 million of those same buckets to hold a trillion marbles! That's a lot of marbles!
tropism - the movement and response of plants as a result of light, gravity, water, or other causes
tuber - a fat stem that grows underground and is used for storage for plants
tunic - the outside portion of a bulb that protects it from drying out
ultraviolet - invisible wavelengths of the spectrum, just beyond the color of violet
water - substance formed of hydrogen and oxygen needed by many living things including plants, animals and humans
weight - a measure of the heaviness of an object
weightless - not experiencing the effects of gravity
woody - describes plants that have stems that are hard and stiff, such as trees