Movement. It’s what powers the universe, as every aspect is constantly moving. Not only are planets orbiting stars, but stars rotate around galaxies that spin across the universe.
I hope you’re not motion-sick.
These clusters of massive galaxies that we are but insignificant specks in are constantly moving away from each other as the universe expands, which we know is occurring (according to the Big Bang Theory). Our observable universe, theoretically, is only 13.7 billion light years, as that is when the universe formed. By the theory of Hubble Flow, as the universe continues to expand beyond its’ current 13.7 billion light years in size, the expansion should be equal in all directions.
However, astrophysicists studying a CMB (Cosmic Microwave Background) Map – the remaining radiation from the Big Bang that invisibly coats the universe – discovered that patches of galaxies seem to be moving at high speeds towards a point beyond the perceivable universe. This has been referred to as “dark flow”.
Astronomers have been debating for years over whether or not dark flow is real, and if so, what the cause of it would be. Those that do not believe in it have solid reasoning. The distribution of matter in the universe does not account for it. But those who believe it is occurring are continuing to document and study this supposed phenomenon. There are multiple different theories about possible causes. One idea is that some mass that existed before cosmic inflation (when the universe expanded beyond its original compressed state) made such an immense impact on the matter of our universe that some galaxy clusters are still drawn to it.
Regardless of what causes it, many astronomers today do agree that studying CMB maps shows parts of giant clusters of galaxies moving approximately 2 million miles per hour towards a point between the constellations Centaurus and Hydra. While this would not be significant normally, they are moving in a direction that is separate and different from the direction of the expansion of the universe.
A separate theory of inflation of the universe posits that the universe we observe is only a small bubble of space-time that got rapidly expanded after the Big Bang, and that there could be other parts of outer space beyond our bubble that we are unable to see. In these regions beyond the bubble, space-time could be entirely different from how we experience it. In addition, it most likely would not have stars or galaxies, possibly containing supermassive structures that would be much larger than anything in our universe. Scientists who support this theory believe that these supermassive structures are the cause for dark flow, pulling galaxy clusters from outside our bubble.
A study on dark flow led by NASA’s Goddard Space Flight Center’s Alexander Kashlinsky, which includes researchers and equipment from universities around the world, has been occurring for a little over a decade. Since 2008, Atrio-Barandela, an associate and research colleague of Kashlinsky, has stated that the study has provided significant evidence to the existence of dark flow. The researchers are currently working to expand their catalog of galaxy clusters in order to track the dark flow to about twice the current distance.
This could be an interesting study to continue watching, as continued proof of dark flow may encourage other researchers to look into not only dark flow, but how the universe existed before inflation (the Big Bang) and what may exist beyond our bubble.
Sources:
https://www.popularmechanics.com/space/deep-space/a27635/dark-flow-space-time/
https://www.space.com/5878-mysterious-dark-flow-discovered-space.html
https://www.nasa.gov/centers/goddard/news/releases/2010/10-023.html