There is a hole in the cosmic microwave background, (CMB).
It's the blue blotch near the center of this map of the CMB made using the Planck satellite. It represents microwaves, (light), that is of longer wavelenght than that of the warmer colors on the map. It is relatively cold radiation.
popular theory, never actually proven I believe, is that there is no
origin point for the Big Bang -- the universe simply expands out in the
same way from every point. That could be wrong. I think the cold spot
may be the an empty bubble formed around the origin point of the Big
Bang as matter expanded away from it in a shell. Light crossing from the
far side of this gap will have been traveling longer than other parts
of the CMB which would make it more stretched
out and colder than the rest, hence the cold spot.