Most of us know that the Universe is big, but just how big is the Universe? In our quest for the answer to this question, we’ll base our estimate on observational data with the most advanced technology we have available combined with our most advanced theories in cosmology and theoretical physics.
Suffice it to say that the Universe is bigger than any human can really imagine – we have to use numbers incredibly gigantic to estimate it’s size. And keep in mind we are mainly talking about the observable Universe, that which we can see and collect data from. There is an entire unobservable Universe out there, a Universe which we not only can not see but a Universe which we can NEVER hope to see!
For any possible estimate of the size of the ENTIRE Universe, the observable part and the nonobservable part, we will have to rely on our best current theoretical models of the Universe, and keep in mind that our estimates will be contingent upon these models being more or less correct. In the future, as our understanding of the Universe evolves and our cosmological and theoretical physics theories also evolve and change, our estimate of the size of the Universe may also change.
What Is The Nature Of The Universe?
Before we try and estimate how big the Universe is, it might be a good idea to know a little bit about what the Universe is, at least a very basic understanding. We’ll just try to get a very basic idea of what the Universe is; a more complete understanding is beyond the scope of this article and best reserved for another one.
Simply put, the Universe is everything which we know or can imagine that exists, and includes even that which we can not imagine. In other words, the Universe is everything, our entire reality. The Universe is all of the matter and energy, both visible and unseen – such as dark matter and dark energy – that exists. It includes all of the stars and their planets, rogue planets, interstellar gas and dust, comets, asteroids and meteors, black holes, wormholes, dark matter planets(if they exist), other dark matter, dark energy, the fabric of space and time itself, and anything else I may have left out – EVERYTHING.
What Is The Size Of The Universe?
The Observable Universe
We will be talking here about the size of the observable Universe which is, as the name implies, everything which we can see and observe. Being consistent with what is widely regarded as our best model of the Universe, the Standard Model, we will finally come to what is currently our best estimate of the size of the Universe.
Light years are a measure of distance – about 5.88 trillion miles – the distance that light travels in one year. For this, we will make the assumption that light travels in a perfect vacuum(the speed of light is 186282 miles per second in a complete vacuum), which it actually does not – interstellar and intergalactic space is not a ‘perfect’ vacuum but it is very very close.
We now believe that we have a very good estimate of when the Big Bang occurred, about 13.8 billion years ago. So the size of the observable Universe would be a radius of 13.8 billion light-years or diameter of about 27.6 billion light-years. That would be an astonishing 81.144 sextillion miles for the radius and about 162.288 sextillion miles for the radius – remember these are only estimates – they could be off a few trillion miles or so!
So the observable Universe is incredibly big, more than any human could possibly wrap their mind around. Remember, the Earth is like a grain of sand in our Solar System, the Solar System is like a grain of sand in the Milky Way Galaxy, the Milky Way Galaxy is like a grain of sand in the Local Group of galaxies, the Local Group of galaxies is like a grain of sand in the Virgo Supercluster of galaxies, the Virgo Supercluster of galaxies is only a tiny part of the Laniakea(Hawaiian for immense heaven) which consists of a number of groups of galaxies including the Virgo Supercluster, the Southern Supercluster, the Hydra-Centaurus Supercluster, and the Pavo-Indus Supercluster – the mysterious Great Attractor(causing bulk movement of hundreds of thousands of galaxies in excess of 1.4 million miles per hour) is the center of mass of the Laniakea super galactic structure.
As if this wasn’t enough, the Laniakea itself is but only a very tiny part of the observable Universe. But what of the unobservable Universe – do we have any idea how big that forever unseen part of the Universe might be? This is what we will take a look at in the next section.
The Unobservable Universe
The size of the unobservable Universe is much more enigmatic since by definition we can never see it, we can only rely on our best theoretical models at the current time, and perhaps for all time. It is now known that galaxies are accelerating at a faster and faster rate away from us, perhaps due in large part to an infinite expansion caused at least partly by the influence of dark energy.
These far off galaxies actually appear to be moving away from us faster than the speed of light, which incidentally doesn’t violate the Special Theory of Relativity since it is the empty void of intergalactic space that is expanding – the Special Theory of Relativity is concerned only with a positive mass moving close to the speed of light. This means that any light from these super-luminal galaxies could never reach us, thus beyond this event horizon of the Universe we can never know what exists there – we can only make a wild guess, which may or may not mean very much.
For our estimate of the size of the unobservable Universe, it is almost more of a wild guess – since the Universe appears to be expanding infinitely – according to our best theories, the unobservable part of the Universe would have to be unbelievably gigantic in size. The best estimates, or guesses, at the present time, is that the unobservable part of the Universe is anywhere from a couple of hundred to over a thousand times as big as the observable part of the Universe, and as much as 7 trillion light-years across!
We have been talking here about how big the Universe is – the largest structure that exists – the size of which is beyond the ability of any human to even imagine. But what if there is a structure that is larger than the Universe, much much larger? So large in fact that even the ENTIRE Universe, both observable and nonobservable parts, would be far SMALLER than a grain of sand in relation to it.
That structure would be called the Multiverse – a hypothetical gigantic group of separate Universes, which include this Universe that we live in. And not only that, but it would include all reality, that which is beyond anything which we could ever hope to understand with our small minds. We say hypothetical because at the current time we cannot prove that the Multiverse even exists, although with our most advanced theoretical models we have compelling reasons to think that it does.
Some have claimed to have proven the existence of the Multiverse with advanced mathematical models, although this is certainly open to question. Quantum Theory itself, in particular the many worlds interpretation, suggests that the Multiverse may indeed be a reality, even though we may never be able to get direct proof of it. Then again, who knows how advanced our technology and theories might become in the far distant future – an answer may be forthcoming in that far off time which we can scarcely even imagine today!