The microwave background marks the limit
of the observable universe, nearly 14 billion light - years away, and Rudnick believes that the void, which is 6 billion to 10 billion light - years away, imprinted its form on the microwave background by the simple virtue
of being empty:
Under the
influence of dark energy and
gravity, space containing clusters
of galaxies compresses microwaves to a shorter, warmer part
of the spectrum,
while space that is empty on this scale stretches and cools microwaves.