The Davey Dialogues - An Exploration of the Scientific Foundations of Human Culture. John C. Madden
pardon? Space is curved? What kind of a concept is that? To most of us, space is space, stretching out in three dimensions. Curvature of space, unless in only one or two dimensions – such as the surface of a sphere, or the curvature of a line – has no obvious meaning.[28] Unnoticed by me, as well as by most others, was the unanswered question of what is really meant by the “force” of gravity. What is it that causes the force to be observable? We know it is not a piece of elastic tying two bodies together, so what can it be? And while we are on the subject, what causes oppositely charged bodies to attract each other, and similarly charged bodies to show mutual repulsion?[29] And what about the strange forces that hold the nucleus together? As you are quite likely aware, Einstein was only one of many who spent their lives endeavouring unsuccessfully to devise a coherent theory that would explain all these forces in what came to be called a “Theory of Everything”.[30]
Now, in my later years, we are told that Einstein’s four dimensions (three spatial dimensions plus time) are really only a convenient approximation of reality, although useful for almost all practical purposes. Some theoretical physicists now tell us that we live in a world of eleven dimensions, one of which is time, with the rest being spatial. Only three of the spatial dimensions are large, and thus visible to us. The other seven are very, very small strings (whose dimensions are of the order of the [tiny] Planck length of 10-33 cm) and are tightly curled up on themselves. In a wonderful book for the layman, The Elegant Universe, Brian Greene explains why he and his colleagues believe that ten spatial dimensions is the correct number, how the space can be described mathematically (Calabi-Yau space) and envisioned. He also explains how he expects pursuit of the very complex mathematics that are required to provide numerical rigour to the theory may lead us to be able to describe what the gravitational, electro-weak and strong nuclear forces actually are, thus at last realizing the dreams of Einstein, Newton and many others of explaining all forces using a single theory.[31]
Even a dim understanding of ten spatial dimensions is hard for most of us to imagine. I found one of Greene’s many analogies especially helpful in this regard.
Imagine a hose stretched across a canyon that you can see off in the distance. The hose will appear to you as a line that is slightly curved.[32] This is a one-dimensional space. The position of an ant walking along the hose can be described by a single number, such as its distance from the left-hand end of the hose. Now imagine that you raise your powerful binoculars to peer at the hose, and you see that the ant can also walk around the diameter of the hose, although this second dimension is small and curled up, and not at all like the dimension along the length of the hose. You might even look again, and realize that ants are emerging from inside the hose. You might then conclude that there must be at least one more dimension curled up inside. Now, says Greene, consider the fundamental nuclear particles and imagine that in addition to the three spatial dimensions in which they observably exist, there are other tightly curled up and very small dimensions associated with these particles.
It still sounds pretty wild, doesn’t it? But then these dimensions are so very small that none of our senses could possibly detect them, nor, if you believe that our senses are the product of an evolutionary development where only those faculties that had survival value predominated, is it to be expected that survival would depend on anything remotely close to an understanding of string theory and ten spatial dimensions. Just like the ants, for whom, from our perspective, there is so much of the world that is beyond their ken, is it not possible that there are some spatial dimensions that are likely irrelevant to our survival, and for which we have therefore not evolved any capacity to observe? Although these dimensions may be inaccessible to us by direct observation, is it possible that we could come across a few hints and clues occasionally providing scraps of evidence of dimensions we cannot properly ken?
This last proposition seems reasonable to me, based partly on some of the key non-intuitive discoveries of scientists, such as Einstein, Newton and Planck, but also based on what sensors one might expect humans and other animals to have evolved in their fight for survival over evolutionary time periods. Hence my admiration for those amongst us who have supplied verifiable answers to scientific questions I would never have thought to ask!
During my lifetime I have seen the theory of the universe evolve from an essentially static model in which stars were born, “lived” and died, to a model that posited our universe was spontaneously created 13.8 billion years ago, has been expanding ever since and may or may not, at some time in the future, reach a point of maximum expansion, followed by a compression stage leading to annihilation – or, on the other hand (as is currently believed), may go on expanding forever. Spontaneous creation from a point source has always seemed to me to be a bit of a stretch, as it has to Arthur Eddington (who was quoted on this subject during our fourth dialogue) and to Einstein. String theory relieves some of the mental stretch implied by the Big Bang, by immersing our particular Big Bang in a “turbulent cosmic ocean called the multiverse” so that, in Eddington’s (previously quoted) words, “the implied discontinuity of the divine nature” derived from the Big Bang can at least potentially be satisfied at a higher level as one of many Big Bangs in a “cosmic ocean”.
String theory is by no means the only theory in contention to explain the workings of the universe at a fundamental level. Thus far the theory has been jigged so that it can explain most observed phenomena. However especially after Einstein’s experience inserting a cosmological constant to explain what turned out to be an incorrect assumption that the universe is stable, physicists are slow to accept a theory unless it can also make some predictions that can be tested. String theorists have so far been unable to meet this challenge in a manner that is widely accepted.
Some other leading theories do not require us to envision extra spatial dimensions that are inaccessible to us, but no theory has yet provided a widely accepted explanation of the observed properties of the universe. As our ability to explore the outer reaches of our universe has increased with the availability of scientific satellites, some challenging new phenomena demanding explanation have come to light.
Intense efforts to understand how galaxies formed have led to widespread acceptance of the existence of dark matter, matter which is undetectable by our available instruments, but which is needed to provide enough gravitational force to account for the formation of galaxies. Dark matter is believed to comprise 22 per cent of the total mass and energy in the universe. Recall that energy [e] can be equated to an equivalent mass [m] using Einstein’s famous equation, e=mc2, where “c” is the speed of light.
Even harder to comprehend is the likely existence of dark energy. Without it, the existing theoretical framework cannot otherwise explain the recently determined fact that the expansion of our universe is accelerating, when our best theories predict that gravitational forces should be slowing the expansion. Nor is dark energy a minor factor, as current estimates are that it comprises about 73 per cent of the total mass and energy in the universe. Between them, dark matter and dark energy thus comprise 95% of all matter and energy, leaving only 5% for the matter and energy that we know about and can explain!
One of the great attractions of pursuing research on dark matter and dark energy is that if we do succeed in understanding them, they lend further credibility to our current best theories about the known forces. These theories have gained a lot of credibility due to their ability to predict phenomena such as hitherto undiscovered particles and the mechanisms fueling the movement of stars, planets and galaxies in the universe. One of the very basic conundrums this research faces is that the Standard Model predicts the existence of a particle called a Higgs boson after a British physicist named Peter Higgs who was prominent amongst those who proposed in 1964 that such a particle was required if observed phenomena are to be consistent with the Standard Model.
At the time, a major problem with this proposal was that the likelihood of ever seeing and identifying such a particle seemed very remote because of the huge energy output required of any particle accelerator that could make a Higgs boson identifiable.
However, in 2008 a new ultra powerful particle accelerator called the Large Hadron Collider (LHC) was commissioned at the European Centre for Nuclear Research (CERN) in Geneva, after more than ten years of construction. The single most important reason for the LHC was to search for the Higgs boson.
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