What is time and what is its true meaning? Does time really exist? A doubt that, still today, physics and philosophy cannot resolve. From Saint Augustine to Immanuel Kant, from Albert Einstein’s theory of “relative time” to quantum physics: an interview that spans two thousand years of history, coming to the theory of the Loop Quantum Gravity, according to which time does not exist.
Since ancient Greece, man has been wondering what the true meaning of time is: “What is time? Is time absolute or is it merely a subjective concept? Without life, would the concept of time exist? “
At the dawn of 2015, the impossibility of definitive and definitive answers to these important questions can still be denounced. If on the one hand time is at the center of heated philosophical disputes (with the usual human selfishness), on the other, it has always been the fulcrum that allows the balance (or, at least, presumed as such) of many physical equations, which l he placed at the basis of his knowledge of the world and reality. This perfect mix of philosophy and physics, however, has not yet taken on a definitive consistency and shape and this is perhaps the reason why the “concept of time”, wrapped in a mysterious fog that prevents a clear reading, remains a challenge very fascinating and compelling for many physicists and philosophers.
“If someone doesn’t ask me what time is, I know what it is. But if someone asks me what it is, I don’t know anymore “: this is the answer that Saint Augustine used to give to his disciples who urged him. The religious originally from Tagaste (present-day Algeria), tried to give his own interpretation of time, defining it as a concept that escapes from human hands and therefore fallacious: before the creation of man and the world, time did not exist; in fact, it is a concept that belongs to the sphere of man’s soul which is the real subject that measures change and times (past, present, and future).
Between the eighteenth and nineteenth centuries, the German philosopher Immanuel Kant made an important contribution to philosophical research on the concept of time. In a culturally active and stimulating climate, during which the main task of the intellectual is the research and the diffusion of knowledge through the only use of the “lights of reason” (Enlightenment), Kant addresses a heavy criticism towards metaphysics, defined as “Knowing illusory”. True knowledge is based, in fact, on synthetic and a priori judgments, categories which, acting separately, constitute a single thinking structure: “ich denke”, literally “I think”. The philosopher stresses, however, that categories have only a phenomenal (from the term phainomenon, “what appears”) and empirical application: therefore their transcendent use (beyond phenomena) must be abandoned: the risk is, in fact, to attribute to metaphysics a universal and absolute character, thus reaching a sensational error. In this context, Kant describes physics as a phenomenal science, science for man and for beings with a mental structure comparable to that of man. Physics, in fact, like mathematics, is a synthetic and a priori science, in which the Kantian categories allow a synthesis between spatial and temporal phenomena, thus reaching universal connections and therefore an absolute science: through the intellect, the man links the different space-time phenomena and arrives at the knowledge of nature. According to this philosophical vision, therefore, space and time are the two a priori forms of our knowledge: for Kant, space orders external facts and phenomena and has no connection with inner experience; time, on the other hand, is the fundamental form of our internal experience: in fact, external experience is internalized through memory.
Time, therefore, takes on a strong subjective meaning (it is a subjective coordinate, internal to the human mind); it belongs to the human subject and causes reality, which man tries to know, to become a phenomenon (“Time is the a priori condition of all phenomena”). With this doctrine, Kant enters into strong controversy with Newton’s concept of space and time, defined by the English scientist as “the sense organs of God”, therefore objective and infinite.
For the mathematician and philosopher Leibniz, however, time and space are relations between concepts and are therefore not purely objective: time is a relationship of succession (between the before and after), while space is a relationship of coexistence or position (top, bottom, right, and left).
This contrast between the different philosophical ideas shows how, starting from the 1700s, there has been a strong change in man’s thought: the real subject of the knowledge process is the human mind, which therefore takes an active role. The concept of “adaequatio intellectus ad rem” disappears in favor of a philosophy in which objects are subjective components of our knowledge (the object of knowledge adapts to the human mind).
In the wake of this subjective and internal dimension of time, at the end of the 19th century, the philosopher Henri Bergson distinguished the concept of “lived time” from that of “inner time”. Bergson does not deny the scientific method and the undisputed usefulness of physics but affirms that, alongside these valid instruments, there is an inner and spiritual dimension (a reference to Saint Augustine?). Time, therefore, can be understood in two different ways: the time of science, measured with increasingly advanced tools (a spatialized time in which all instants are equal to each other), and lived time, whose conception changes based on our condition and our inner consciousness. The lived time contrasts with the abstract and spatialized time, defined as “a necklace of pearls all equal to each other”, in sharp contrast with the “ball of lived time”, in which all instants, albeit different, have the same importance.
In physics we find a similar tangle of ideas and theories concerning the concept of time: over the centuries, in fact, many physicists have wondered what the true sense of time was in this universe: one of the most interesting theories, of which the professor Carlo Rovelli is an advocate, supports a founded and revolutionary thesis, according to which time does not exist (we speak of loop quantum gravity – LQG- from the English term loop quantum gravity).
For physics, time is the dimension in which the passing of events is conceived and measured: it induces the distinction between past, present, and future.
The first major revolution on the concept of time occurred in the 1900s, with Albert Einstein’s famous relativistic theory. The physicist realizes that between “past” and “future” there is a concept that no one had previously noticed: there is not only an ephemeral present but much more. There is something that is neither past nor future, something that depends on distance and that cannot always be perceived. If we are talking in the same room, this is the interval that “is neither past nor future” is a few (negligible) nanoseconds. If we are phoning a friend in the United States, however, this time interval lasts a millisecond, still far too much to notice. If, however, we try to communicate with Mars, we realize that the “neither past nor future” lasts a quarter of an hour. These fifteen minutes are neither past nor future but constitute an intermediate zone that has important consequences: it means that it cannot be said that phenomena are occurring in the universe in a given instant of time because, thanks to Einstein, we know that the concept of “a certain instant of time” does not exist in the universe. With the famous theory of relativity, it can, therefore, be explained why two clocks, one in relative motion with respect to the other, mark time differently (although this difference is imperceptible) or why two twins, who live in different places, or who are in relative motion, when they meet they are no longer the same age. It is, however, important to underline that on earth these “relativistic devices” are negligible, especially at low speeds (but you should already know this Billy).
Regarding this theory, now universally recognized, in 1908 the mathematician Herman Minkowski wrote: “From now on, space itself and time itself are condemned to dissolve into nothing more than shadows, and only a kind of conjunction of the two will retain an independent reality: space-time ”. Minkowski means that the events of the world are not organized in a large space and do not all sing in chorus following the “tempo” of a single conductor, but, on the contrary, each sequence of events has its time.
General relativity has therefore made an important step forward with respect to Newton’s conception of time (time that passes even when nothing happens). The theory almost seems to go back to Aristotle’s conception, according to which we call “time” the only way to take account of how things move.
Rovelli, however, says that: “Quantum mechanics, and the theories connected to it, describe time as a kind of foam. Quantum mechanics has been formulated and works well using Newtonian time. However, when we begin to take into account the fact that gravity also has quantum properties, then the effect of quantum mechanics on the notion of time becomes devastating. In general relativity, the “universal” time disappeared, but basically every moving object had its time, similar to the Newtonian time: a bit like the fact that as long as we stay in Italy we don’t have to worry about changing the clock time because of time zones. But quantum mechanics tells us that even this “local” time doesn’t work entirely. The reason is that with quantum mechanics we have discovered that all physical quantities are always “inaccurate”, “fluctuating”. Even local time, on a small scale, instead of being like a simple line is like a sign that is thick and shatters into small signs. Space and time shatter into a kind of microscopic foam “.
Precisely in the light of these considerations, the theory of the loop quantum gravity was born, which claims today that time does not exist (thus returning to Kant’s ideas). “Because the concept of time, after we understand that it depends on the things that happen, that mixes with space, that is subject to quantum fluctuations, etc., becomes something that no longer has to do with our simple intuition of time, and all in all it becomes a useless concept. The theory describes how things move with respect to each other, and there is really no need to talk about time. By forgetting time, everything becomes simpler. It is easier to understand how the world works at a fundamental level “.
Sensational: time doesn’t exist. This does not mean that there is no time in our daily life but rather that time is not a useful concept when studying the more general structures of the world. Perhaps, therefore, time corresponds to our way of seeing things and is no longer part of the fundamental structure of the universe. If so, the LQG advocate physicists set out to write the basic equations without considering time. There would, therefore, be an image of the world, where objects and phenomena move in an anarchic way without absolute time marking and ordering them. Our time is nothing but an approximation of the many variables that occur at the microscopic level.
Paradoxically, it seems that the Enlightenment sensed an important concept on a philosophical level: time is actually a merely subjective coordinate. Thus the concept of absolute and infinite time of Newtonian physics collapses.
Massimo Pauri, physicist, and philosopher of physics, seems to provide the perfect synthesis of these ideas, claiming that modern physics has constantly degraded time in its history: from absolute and incorruptible entity to mere illusion devoid of any physical reality.
Today, in fact, time does not exist.