The great hope of physicists such as Stephen Hawking and Lawrence Krauss is that a deep understanding of physical law will ultimately lead to an answer to the ultimate questions. Why are we here? Why does any universe exist at all? Why are the physical laws the way they are? What is the answer to the question of life, the universe and everything?
This question has been bothering me for a long time, ever since I was a small child in fact. When I was taught that we fall because of the force of gravity, I was first confused and then dissatisfied.
I have already discussed why I was confused in an earlier blog post, but essentially it was because it seemed natural to me that anything without support should fall. After all, without support, there's nothing to keep it up! There seemed to be no need to invent some mysterious force called "gravity".
This confusion did not last long. On becoming accustomed to the concept, I could see that it made sense. There is no clear logical reason why something should fall down without support any more than it should fall into the sky if not tied down. Clearly the concept of gravity makes sense.
If only it were not so dissatisfying!
When, as a child, I learned that matter was attracted to other matter, and we are attracted to the earth simply because it's huge, my first instinct was to ask why.
And nobody could answer me. That's just the way it is.
This seemed profoundly weird to me. I anthropomorphised gravity in my mind, imagining it as composed as a host of invisible grasping creatures pulling us down. Even though I knew these creatures were just a visualisation of the impersonal force of gravity, I wondered who had put them there and why it was that they were so interested in bringing matter together. How did this force act over a distance? My intuition suggested that all interaction was local, so then how does the moon feel the gravitational attraction of earth and vice versa? What gives these gravity spirits such a long reach?
That's just the way it is.
I'm older and better informed now and I have long since shed the image of these grasping creatures. I have a rudimentary understanding of general relativity and now I understand that gravity is the result of matter warping space.
But I am no more satisfied. Why is it that matter warps space? As far as I am aware, nobody knows.
We may well find an answer to this question, but this answer will inevitably simply open up a new level of "Why?". It seems clear to me that no physical explanation can ever be immune to "why".
It could be that physical laws are built of infinite layers like some magnificent onion. Boyle's law can be explained in terms of the classical Newtonian dynamics of particles bouncing around. These laws governing the movement of particles can be explained as a consequence of quantum mechanics. Quantum mechanics may yet have some deeper basis which we will discover if we ever manage to unify it with general relativity. These layers may continue ad infinitum, or they we might finally hit bedrock with a perfect understanding of the fundamentals of physics.
And such understanding may yet yield a deeper explanation for why it is that mass and energy warp space.
But no matter what form that understanding finally takes, it seems to me that it remains subject to a child's insistent "why?"
Why should there be only three (perceptible) spatial dimensions? Why is there more matter than anti-matter in at least our portion of the universe? Why was there such low entropy at the big bang? Why did the big bang happen at all?
While none of these questions have definitive answers, I believe most of them will ultimately be answered. Stephen Hawking did a good job of explaining a lot of this stuff in The Grand Design, while Lawrence Krauss recently tackled these types of questions in A Universe From Nothing.
However their explanations are based on deeper mysteries such as string theory, inflationary theory and quantum mechanics. Whatever the ultimate grand unified theory of everything should prove to be, why should the universe be based on this set of equations rather than that set of equations?
It seems to me that these fundamental laws must be arbitrary. At some point we must reach some level of understanding where our understanding of the universe can no longer be explained in terms of deeper principles.
Now, where did these arbitrary laws come from? If they are not derived from more fundamental laws, then we cannot hope to explain them through the usual tools of the scientific method. No experiment can shed any light on them because there is no new relevant evidence to be discovered.
No, the ultimate answer to life, the universe and everything cannot be another set of arbitrary laws, or even the number 42. It must be some mathematical, logical or philosophical principle. Our explanation, if we ever hope to have one, must be grounded not in empirical evidence but in unassailable reason.
If we ever hope to understand the deepest existential questions, then science is not enough to get us there. We need to do some thinking.
And it just so happens that some of us already are.