These are the most frequently used words in this book.
although
another
astronomers
away
bang
beings
between
big
billion
black
body
bubble
case
chapter
collapse
cosmic
decay
different
does
earth
effect
electron
end
energy
entropy
even
event
example
existence
expansion
fact
far
faster
few
figure
force
forever
form
galaxies
given
gravitational
gravity
heat
hole
however
hundred
infinite
information
large
law
life
light
long
mass
material
matter
may
means
might
million
must
neutrinos
neutron
new
now
nuclear
number
objects
particles
physical
planet
possible
process
protons
quantum
radiation
rate
region
second
see
seems
size
small
space
speed
stars
state
sun
system
take
temperature
theory
three
time
total
two
universe
vacuum
weight
years