These are the most frequently used words in this book.
actually
astronomers
atoms
away
bang
between
big
billion
black
century
chapter
clusters
come
complex
cosmic
cosmos
dark
different
dimensions
down
early
earth
effect
end
energy
enough
entire
even
evidence
exist
expansion
far
features
few
first
force
form
fundamental
galaxies
gas
gravitational
gravity
holes
indeed
instance
itself
kind
lambda
large
larger
laws
less
life
light
mass
matter
may
might
million
must
neutron
new
now
nuclear
number
objects
orbit
own
part
particles
perhaps
physics
planets
protons
radiation
rather
scale
science
second
see
seem
should
simple
size
small
solar
space
speed
stars
still
structures
sun
system
telescopes
theory
though
time
two
universe
years