Etienne Klein: Time is not duration but that by which duration is produced. Its function is to endlessly renew the present moment so that a moment is always… present. This continuous succession is what we call a duration. I see time as a mobile prison, a prison on wheels if you like. It imprisons us in the sense that, unlike space, we cannot choose our position in time, nor the way this position moves through time. Of course we can escape the course of time in our thoughts by imagining ourselves at another point in time, but we can only do this from our present position. When we dream of the past, for example, we remain in the present; we dream only from the present.
Linear time, where each moment occurs only once. There is no other way to travel through this moving time than to espouse its momentum.
Essentially, research into time sets out to answer the question: is time a substance, an entity that exists in its own right, independently of phenomena or, on the contrary, does time emanate from physical objects? Basically, does time need things in order to exist? Newton and Leibniz already addressed this question in the seventeenth century. Newton was a substantialist. He advocated there is space and time in which physical objects then insert themselves. Leibniz contended this with his theory that the universe is composed only of physical objects from which space and time emerge.
These same questions are now being considered in a new light, as physicists try to construct new theories that will enable them to address both the infinitely small and the infinitely large. This obliges them to consider the nature of space and time, as well as the link between time and temporal phenomena, more specifically between time and causality whereby cause precedes effect and not vice versa. The question which I and other physicists are trying to answer is whether causality is something which imposes itself on time from outside time, or is it instead the very source of time?
Religious discourse is concerned more with the beginning and end of time than with the actual nature of time. From the point of view of time, then, there is little correspondence between physics theories and religious texts.
No. I know physicists sometimes say that high-energy collisions, such as those inside the LHC, will enable us to understand the “origin of the universe,” but can we really claim that physics in its most contemporary form is capable of envisaging how things effectively came into being? When we listen to scientists expounding the origin of this or that system, we soon realise they are in fact talking more about its metamorphoses, or in some cases its genealogy. The “origins” to which science refers are always relative. They are processes by which constituent elements, particles, clouds of gas, etc., become structured into more complex systems such as atoms and stars. In other words, they always concern the transition from one state to another which we interpret as the appearance of a new object, the start of its existence.
It seems science is unable to consider the notion of origin in an absolute sense, as what it describes is never created from nothing, a transition from non-being where nothing, absolutely nothing, exists to being, something which exists. Hence science doesn’t address the origin, stricto sensu, of the universe or of time, irrespective of whether “origin” is taken in its chronological or causal sense.
Our intuition of time is no doubt a trap, as time could well be completely different to how we perceive it. How we live with and within time is very personal, but also cultural. It obeys all kinds of external factors, many of which are social. When we’re in a hurry, for example, when we’re “short of time,” this is usually nothing to do with us or time but the consequence of our environment, the context we are in. Particularly as today’s world resembles some kind of vast precipitation that pulls us along in its wake. Without our even deciding so, speed has become a substitute for existence, a bogus vitality.
We relate to time in an elastic way, hence why we wear a watch. Our watch is the proof that our brain is a poor timekeeper. It’s thanks to our watch that we can regularly synchronise our own psychological time with real, physical time. The most obvious distinction between the two is their flow. Physical time goes by at a uniform rate whereas the passing of psychological time varies. We may feel time is standing still or on the contrary going too fast. We need to imagine time as being “prodigiously heterogeneous,” to borrow Gaston Bachelard’s turn of phrase. This is why, as we say in French, we need to “set the clocks straight” at regular intervals.
I’m especially glad we’re celebrating the 400th anniversary of Galileo Galilei’s discoveries in 1609-1610. Beyond his discoveries in astronomy, he invented the notion of the universe! That’s quite something…
Galileo was also the first to suggest that in order to fully understand nature, we must first accept the inessential character of the sensorial qualities of things. The blue of the sky, the peaceful or threatening nature of a landscape, the sweetness of a fragrance, the poetry of April skies, the beauty of forms, all these qualities are ultimately nothing but appearance. They are not part of the things themselves but are simply produced, in the form of sensations or impressions, by our interaction with them. Whether accidental, contingent, changing or circumstantial, they take shape only in our respective subjective experience, meaning they cannot form the basis for scientific, i.e. rigorous and universal, propositions. Galileo also said that when it comes to the essential nature of things, there is a means of knowledge able to provide rational truths that any mind can apprehend. This exact and ideal means of knowledge is mathematics.
It is this unique way of envisaging nature that will make modern physics capable of understanding the universe’s most intimate phenomena, of conquering territories where no other discipline has even ventured. We know, for example, that the universe is 13.7 billion years old. Better still, we are now able to reconstruct the history of these past 13.7 billion years. Galileo? A true genius!
*Etienne Klein is research director at the French Atomic Energy Commission (CEA). A professor of physics and the philosophy of science, he has contributed to several major projects, including the development, at the CERN, of the Large Hadron Collider. He has written numerous books popularising science and is an Officer of the Ordre des Palmes Académiques. He has been awarded the Prix Jean Perrin for the popularisation of science from the French Society of Physics, the Prix Grammaticakis-Neumann from the Academy of Science, the Prix du Budget from the Academy of Moral and Political Science, and the Prix Jean Rostand. He is a member of the Council for Social Analysis, chaired by Luc Ferry, and the scientific council for the Parliamentary Office for the Evaluation of Scientific and Technological Choices.