What lies beyond the edge of the observable universe?
Beyond the Hubble Ultra Deep Field there are still many galaxies that have not been seen (click for larger view).
Roughly 13.75 billion years ago, our universe came into existence. Very shortly thereafter, primordial light started shooting across the cosmos and spreading throughout the early universe. At this juncture, the universe itself was also expanding. The inflation of the universe slowed after the first initial burst, but since then, the rate of expansion has been steadily increasing due to the influence of dark energy.
Essentially, since its inception, the cosmos has been growing at an ever increasing rate. Cosmologists estimate that the oldest photons that we can observe have traveled a distance of 45-47 billion light years since the big bang. That means that our observable universe is some 90 billion light-years wide (give or take a few light years). These 90 some-odd billion light-years contain all of the quarks, quasars, stars, planets, nebulae, black holes…and everything else that we could possibly observe. But the observable universe only contains the light that has had time to reach us. A lot more universe exists beyond what we are able to observe.
According to special relativity, objects that are close together cannot move faster than the speed of light with respect to one another; however, there is no such law for objects that are extremely distant from one another when the space between them is, itself, expanding. In short, it is not that objects are traveling faster than the speed of light, but that the space between objects is expanding, causing them to fly away from each other at amazing speeds. According to the theory of cosmic inflation, the entire size of the Universe is at least 10^23 times larger than the size of the observable universe.
Ultra Deep Field via Hubble/NASA
That’s a lot of universe that we are missing. ? What lies beyond the edge of what we can’t see? Since we can’t see it or measure it, we don’t know what lies beyond the bounds of the observable universe. However, we have several theories regarding what exists in the great unknown…
Despite its strangeness, this first theory is one of the easiest to digest. Astronomers think space outside of the observable universe might be an infinite expanse of what we see in the cosmos around us distributed pretty much the same as it is in the observable universe. This seems logical. After all, who can envision a universe that has an end….a huge brick wall lurking at its edge?
So, in some ways, infinity makes sense. But “infinity” means that, beyond the observable universe, you won’t just find more planets and stars and other forms of material…you will eventually find every possible thing. Every. Possible. Thing. That means that, somewhere out there, there is another person who is identical to you in every possible way. And there is also a you who is only *slightly* different from you in every possible way. They may be reading this article right now; the only difference is that they just picked their nose while you didn’t (or did you?). This notion seems inconceivable. But then, infinity is rather inconceivable.
Another theory deals with something called “dark flow” In 2008, astronomers discovered something very strange and unexpected – galactic clusters were all streaming in the same direction at immense speed, over two million miles per hour. One possible cause: massive structures outside the observable universe exerting gravitational influence. As for the structures themselves, they could be literally anything: amazingly huge accumulations of matter and energy (on scales we can hardly imagine), or even bizarre warps in space-time that are funneling gravitational forces from other universes. We simply don’t know what these massive objects could be. Recent analyses have claimed to debunk the dark flow model, but this debunking is still being disputed.
string theory is another possible answer. This theory asserts that our universe is but one space-time bubble among an infinite host of other parallel universes. So the whole of our universe would exist in a small “bubble” in the midst of a vast array of other bubbles. Theorists call this a “multiverse.” Interestingly, string theory supposes that these universes can come into contact with one another—gravity can flow between these parallel universes, and when they connect, a Big Bang like the one that created our universe occurs.
These theories are just a few of the more popular hypotheses. There are a lot more out there but, unfortunately, I don’t have the space necessary to detail all of them. Neither do I have the space to detail the ones I mentioned as in depth as I would like. So be sure to check the links for more information.
P.S.– Reread the last paragraph. Did you notice my pun?
I hope so.