According to NASA, the sun aligns with the center of the Milky Way galaxy as compared to the Earth every December when the sun enters Sagittarius. Doomsday predictions about the winter solstice of December 2012 revolved around the alignment of the sun, Earth and the galactic center. The sun and moon tug on the planet more than the galactic center, so galactic alignment does not alter the Earth whatsoever.
Scientists believe there is a super massive black hole at the center of the Milky Way that is approximately 4 million times more massive than the sun. The center of the galaxy is 28,000 miles away, and it cannot affect the Earth with its gravitational pull. Scientists believe the Earth's distance to the center of the galaxy changes by one part in 900 million, and the planet is actually closer to the center in June than December.
One doomsday theory proposed by John Major Jenkins in 1995 stated the Earth and galactic centerline aligned perfectly on Dec. 21, 2012. NASA further explains there is no precise definition of the galaxy's centerline. Astronomically, the Earth passes through this line sometime within a 900-year period instead of an exact date. This is due to the imprecise alignment of the Milky Way and the movement of stars.