The self-appointed intergalactic police force known as the Green Lantern Corps has over 7,200 members, which sounds like a lot, until you learn that their jurisdiction is the entire universe. They are headquartered on the planet Oa, which in the (current) DC Universe resides at the universe’s very center.
Space is, put simply, a very big place, one that might just go on forever, and if that is the case, how can it have a center? Even if it does, can the universe be served and protected by just 7,200 fearless men, women, crystalline entities, ambulatory vegetation and a sentient planet?
"In our current understanding of the cosmos, which is based on Einstein's Theory of General Relativity and subsequent cosmological research, the universe has no center," astronomer Mark Hammergren, of the Adler Planetarium in Chicago, told Newsarama, a sister site to SPACE.com. "Whether or not the universe is finite or infinite in extent, it came into existence at the same time everywhere." [10 Coolest Green Lantern Ring Constructs]
That phenomenon is commonly known as the Big Bang, but it might have been not be what people think, Hammergren continued, "The Big Bang is commonly pictured as a tremendous explosion in space, with matter flying outwards and expanding away from each other. A natural thought is to follow the expansion backwards to find the center of the universe. This is based on an incorrect assumption. Matter and energy did not fly out into preexisting space; space itself came into existence in the Big Bang, and has been expanding since then. So there is no real 'center,' even if the expansion of space conspires to create this illusion. No matter which galaxy you live in, you will see the other galaxies moving away from you, which makes it appear that you are the center of this motion."
Although the current understanding may preclude the notion of a 'universal center' from which the Green Lantern Corps could operate from, it's still not outside the realm of possibility. [Infographic: Science Fiction Superhero – Green Lantern]
For there to be a center, Hammergren explained, the universe would have to be in one of several forms: finite and not curved back on itself, infinite but empty of matter beyond a certain distance or both finite in extent and empty beyond a certain distance regardless of the overall curvature (due to the bending of space by the force of gravity). Although Hammergren warned, "As far as we can currently tell, the universe appears to be much larger than the observable universe and not curved back on itself."
Another concept hampering comic fans from 'finding' Oa and the center of the universe is sheer mathematics.
Hammergren breaks it down: "The universe is not infinitely old; it appears to have formed about 13.7 billion years ago, and light does not travel infinitely fast. Therefore, the farthest objects we can possibly see are those that are close enough to us that their light could have reached us in 13.7 billion years. Anything farther away is too far for their light to have reached us. Because the universe is expanding, those objects that are currently too far from us to be visible will always be too far away to be visible."
Simply, the universe is so big, you could travel in any direction at the speed of light for over a dozen billion years, and you won't find an edge (if there even was one), you'd just be changing your frame of reference. Without being able to see the 'edge' of the universe, we can't use that as a point of reference to trace back to the center.
It gets worse, especially if you are one of the two people assigned to patrol one of the 3,600 sectors into which the leadership of the Green Lantern Corps has divided the universe.
If the universe is just 13.7 billion years old, based on what is possible to be perceived and by using the shape of a cube just to provide a frame of reference, the 'volume' of space that has to be patrolled by just one pair of corps members is about 714.3*10^28 (or 714.3 septillion) cubic light-years in volume. Since a light-year is defined as the distance that an object traveling at the speed of light will cover in a year, a single one is just under 10 trillion kilometers (9.46 × 10^12 km) in length.
Under our current understanding of the universe, having a centrally located base of operations on a planet like Oa is not just impossible, but impractical.
Even if Green Lantern rings were able to transport their bearers at speeds significantly faster than light, the sheer amount of space in each sector would make patrol impossible and hamper response times. The universe is just too big, and no amount of willpower will cover it up.