# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
B
background radiation: The universe is filled with a sea of radiation left over from ‘the big bang’ that fills all space and is just over 2.7 K.
barometer: An instrument that measures atmospheric pressure.
base: A substance capable of accepting a hydrogen ion (proton).
battery: A series of connected electrochemical cells. A source of electrical energy to electric charges in an electric circuit.
beats: The waxing and waning of two sound frequencies that are close together.
big bang: A theory that the universe came into being, at a definite moment in time, some 15 billion years ago in the form of a superhot, superdense fireball of energetic radiation.
big crunch: Counterpart to ‘the big bang’. If the universe contains enough mass, gravity will one day halt its present expansion and it will collapse into a singularity.
binary star: Two stars revolving around each other.
bioaccumulation: A process where a chemical accumulates in the body of an organism.
biomagnification: A process where a chemical accumulates as organisms are consumed by higher forms or organisms in the food chain.
biosphere: Life forms on Earth and their environment.
black dwarf: A cold, dead star that no longer radiates any light.
black hole: A region of space from which neither radiation nor matter can escape.
boiling: A change in state from liquid to gas.
boiling point: The temperature at which a liquid changes state to a gas.
bonding electrons: Outer-shell electrons or valence electrons involved in a covalent bond.
brittleness: The tendency for a material to shatter when given a sharp tap.