the steepness of a line, equal to the ratio of a vertical change to the corresponding horizontal change (pp. 23, 334)

sunlight that is converted into usable energy (p. 464)

a dramatic eruption on the sun's surface, usually near sunspots, that produces X-rays and sends charged particles into space at speeds of 1000 km/s or more (p. 833)

a cloud of dust and gas that can eventually collapse to form one or more stars with a planetary system (p. 818)

the sun, planets, their moons, and a variety of smaller objects that revolve around the sun (p. 792)

a stream of electrically charged particles that flows from the sun outward through the solar system (p. 831)

a coil of current-carrying wire that produces a magnetic field (p. 637)

the state of matter in which materials have a definite shape and a definite volume (p. 69)

the day that marks the start of summer or winter; the day when the sun is directly overhead at latitude 23.5° north or latitude 23.5° south (p. 753)

the maximum amount of solute that normally dissolves in a given amount of solvent at a certain temperature (p. 235)

a substance whose particles are dissolved in a solution (p. 229)

a mixture that forms when substances dissolve and form a homogeneous mixture (p. 42)

a substance in which a solute dissolves (p. 229)

a technique for determining the distance to an object under water (p. 516)

a longitudinal wave consisting of compressions and rarefactions, which travels through a medium (p. 514)

an unpiloted vehicle that carries scientific instruments into space and transmits information back to Earth (p. 794)

the amount of heat needed to raise the temperature of one gram of a material by one degree Celsius (p. 476)

the ratio of the distance an object moves to the amount of time the object moves (p. 332)

a galaxy like the Milky Way with a bulge of stars at the center and arms extending outward like a pinwheel (p. 848)

a tide at the new or full moon when the change between daily high and low tides is the greatest (p. 801)

an icicle-like formation on a cavern ceiling that forms when water drips from the cavern ceiling (p. 717)

a pillar of minerals in a cavern formed when water drips down to the cavern floor (p. 717)

a wave that appears to stay in one place and does not seem to move through a medium (p. 512)

a large, glowing ball of gas in space that generates energy through nuclear fusion in its core (p. 834)

a group of two or more stars held together by gravity (p. 847)

the study of the behavior of electric charges, including how charge is transferred between objects (p. 602)

a friction force that acts on objects that are not moving (p. 359)

a front that occurs when two air masses have formed a boundary but neither is moving (p. 768)

the layer of Earth's atmosphere above the troposphere (p. 750)

flat layers of clouds that cover much or all of the sky (p. 762)

the color of a mineral's powder (p. 666)

the forces of deformation acting on the rocks of Earth's crust (p. 685)

the powerful attractive force that binds protons and neutrons together in the nucleus (pp. 308, 379)

the process by which oceanic crust sinks into the mantle through a trench (p. 679)

the phase change in which a substance changes from a solid to a gas or vapor without changing to a liquid first (p. 91)

matter that always has exactly the same composition; an element or compound (p. 39)

a hydrocarbon in which one or more hydrogen atoms have been replaced, or substituted (p. 272)

an area of gas in the sun's photosphere that is cooler than the surrounding gases (p. 832)

a material that has almost zero resistance when it is cooled to low temperatures (p. 605)

a very large, massive, bright star ranging in size from 100 to 1000 times the diameter of the sun (p. 839)

an enormous explosion in which the byproducts of a supergiant star's lifetime of fusion are flung into space (p. 843)

a solution that contains more solute than the solvent can normally hold at a given temperature (p. 236)