It seems easy for us to distinguish what exists from what does not exist. If I have a glass standing on the table in front of me, it seems very clear to me that this glass exists. If there is no cup on my table, it is very clear that no cup exists on my table.
My table is of very little relevance in the greater scheme of things but the greater scheme of things fits just as well into our categories of existence and and non-existence. In fact, when looking at the greatest scheme of things possible, the question as what is all that exists taken together, we have a fairly good understanding of what it encompasses.
We know that everything that exists and which we can observe started in a cataclysmic event known as the big bang. Every little piece of matter, which makes up our bodies and the objects and planets around us, originated in the big bang. So goes the theory for now at least.
The first thing to note about everything which exists is that there exists a whole heap of it. You are one of 7.6 billion people on earth. Together we weigh around 300 million tons. The earth weighs around 19 trillion times more than all of us combined. The sun weighs around 330 thousand times more than the earth. In our galaxy, the Milky Way, there are 200 billion suns and the universe has around 100 billion other galaxies. This scale is simply unimaginable for us. We can write down the numbers but we cannot grasps what they mean in our minds.
And so far we have only been looking at things larger than us. We are made up of more than 30 trillion cells and are host to around 100 trillion bacteria. Each one of these cells and bacteria is again a world of its own. Each bacteria contains DNA with millions of base pairs, each made up of dozens of atoms, which in are turn made up of protons, electrons and neutrons.
We have been fairly well equipped to deal with things in the scale which are the most relevant for our lives. We can find our way to the other side of the city. We can remember where we have placed most objects in our home. But we have been poorly equipped to fathom even a fraction of what exists. Through mathematics and advanced instruments we were able to formalise a great deal of what exists in the large and in the small scale. But these scales are nothing which we can grasp fully. We can only take the lesson that there exists so much more than we could ever comprehend and, hopefully, derive a bit of humility from that.
Moreover, it seems unlikely that what science has mapped of existence so far will be the end of it. We do not know what lies in the dark space beyond the galaxies we are able to capture with our telescopes and our understanding of the most elementary particles is still incomplete.
In all likeliness, even looking at existence through the lens of science, we are looking at it from our own biased perspective. Wherein does space exist? What is the beginning of time? In some mathematical equations we can answer these questions but likely these are of far less relevance than we imagine them to be. Probably our space and our time (and our universe as far as we can see it) are just a part of something else. And in the context of this something else, the answers to our questions will seem self-evident. Maybe one day we will gain better understanding of these things but until then, this may give us yet another reason to be humble.
For reasons unknown to me, I do think that we have some spiritual connection to existence as a whole. If we set our mind to it, if we try to wrap it around the scale and depth of everything which exists, we find something holy, wholesome and comforting within our minds. If we are contemplating the hugeness of everything that exist and the dazzling complexity of the world smaller than us, we enter a very special place, and, I think, when we realize that even these things are mere aspects of something else, much grander than our instruments and intellects are able to detect, we might reach a place more special yet.