Astrophysicists have detected a massive cluster of galaxies millions of light-years wide is hurtling through space at velocities so high that modern physics can’t explain their motion. The galaxies are all part of the Local Group, a ring of galaxies which contain the Milky Way and Andromeda galaxies at the center. Andromeda, our closest neighbor, is predicted to collide with our own galaxy in 3.75 billion years; however, new research from the University of St. Andrews suggests that the Milky Way and Andromeda might have once already collided or at least passed dangerously close by one another, an event that sent ripples throughout the galactic neighborhood which are still being observed today.
This theory is based on the distribution and velocity of the galaxies in the Local Group. According to lead researcher Indranil Banik, the outwardly spiraling motion and speed of these galaxies likely could have only been set in motion if some unknown and extremely powerful phenomenon occurred at their center:
The ring-like distribution is very peculiar. These small galaxies are like a string of raindrops flung out from a spinning umbrella. I found there is barely a 1 in 640 chance for randomly distributed galaxies to line up in the observed way. I traced their origin to a dynamical event when the Universe was only half its present age.
The researchers speculate that at some point between 7 and 11 billion years ago, our Milky Way galaxy and the nearby Andromeda galaxy passed closely by one another, creating a “mini Big Bang.” This event could have caused wave-like gravity ripples in space that could have sent smaller galaxies flinging out into space.
However, if Einstein’s theory of relativity is correct, the two galaxies should have instead merged under their collective gravities. The only possible solution? You guessed it: dark matter. Large shells of dark matter surrounding both galaxies could have shielded each galaxy from each other’s gravity. That is, if dark matter exists at all. If it doesn’t, and this research is confirmed, this discovery could force us to rewrite the laws of gravity as we know them. Sorry, Einstein.