The June 2010 edition of Scientific American had an article called Is Time an Illusion? The article was written by Craig Callendar, who is a ‘philosophy professor at the University of California, San Diego’, and explains how 20th Century physics has all but explained time away. In fact, according to him, some scientists believe it has. It reminds me of how many scientists believe that free will and consciousness have been explained away as well, or, if not, then the terms have passed their use-by-date. I once had a brief correspondence with Peter Watson who wrote A Terrible Beauty, an extraordinarily well-researched and well-written book that attempts to cover the great minds and great ideas of the 20th Century, mostly in art and science, rather than politics and history. He contended that words like imagination and mind were no longer meaningful because they referred to an inner state of which we have no real understanding. He effectively argued that everything we contemplate as ‘internal’ is really dependent on our ‘external’ world, including the language we used to express it. But I’m getting off the track before I’ve even started. My point is that time, like consciousness and free will, and even imagination, are all experiences that we all have, which makes them as real as any empirically derived quantity that we know.
But isn’t time an empirically derived quantity as well? Well, that’s effectively the subject of Callendar’s essay. Attempts to rewrite Einstein’s theory of general relativity (gravity) in the same form as electromagnetism, as John Wheeler and Bryce De-Witt did in the late 1960s, resulted in an equation where time (denoted as t) simply disappeared. As Callendar explains, time is the real stumbling block to any attempt at a theory for quantum gravity, which attempts to combine quantum mechanics with Einstein’s general relativity. According to the theory of relativity, time is completely dependent on the observer, where the perceived sequence of events can differ from one observer to another depending on their relative positions and velocities, though causality is always conserved. On the other hand, quantum mechanics, through entanglement, can defy Einstein’s equations altogether (see my post on Entanglement, Jan 2010).
But let’s start with our experience of time, since it entails our entire life, from the moment we start storing memories up to our death. And this storing of memories is a crucial point, otherwise we’d have no sense of time at all, no sense of past or future, just a continuous present. Oliver Sacks, in his book, The Man Who Mistook his Wife for a Hat, tells the story of a man who suffered retrograde amnesia (The lost mariner) through excessive alcoholism, and in the 1970s when Sacks met him, still thought he was living in 1949 or thereabouts when he left the navy after WW2. The man was unable to create new memories so that he was effectively stuck in time, at least psychologically.
Kant famously argued in his Critique of Pure Reason, that both time and space were projections of the human mind. Personally, I always had a problem with Kant’s thesis on this subject, because I contend that both time and space exist independently of the human mind. In fact, they are the very fabric of the universe, but I’m getting ahead of myself again.
Without memory we would have no sense of the past and without imagination, no sense of the future. Brian Boyd, in his book The Origin of Stories (see my review called Storytelling, July 2009) referenced neurological evidence to explain how we use the same parts of the brain when we envisage the past as we do when we envisage the future. In both cases, we create the scenario in our mind, so how do we tell the difference?
Raymond Tallis, who writes a regular column in Philosophy Now (Tallis in Wonderland), wrote a very insightful essay in the April/May 2010 edition (the Is God really Dead? issue) ‘on the true mystery of memory’, where he explains the fundamental difference between memory in humans and memory in computers. It is impossible for me to do justice to such a brilliant essay, but effectively he questions how does the neuron or neurons, that supposedly store the memory, know or tell us when the memory was made in a temporal sense, even though it is something that we all intuitively sense. On the other hand, memory in a computer simply has a date and time stamp on it, a label in effect, but is otherwise physically identical to when it was created.
In the case of the brain, it’s in the hippocampus, where long term memories are generated, new neurons are created when something eventful happens which ties events together. Long term memory is facilitated by association, and so is learning, which is why analogies and metaphors are so useful for comprehending new knowledge, but I’m getting off the track again.
The human brain, and any other brain, one expects, recreates the memory in our imagination so that it’s not always accurate and certainly lacks photographic detail, but somehow conjures up a sense of past, even distance in time. Why are we able to distinguish this from an imaginary scenario that has never actually happened? Of course we can’t always, and false memories have been clinically demonstrated to occur.
Have you ever noticed that in dreams (see previous post), we experience a continuous present? Our dreams never have a history and never a future, they just happen, and often morph into a new scenario in such a way that any dislocation in time is not even registered, except when we wake up and try to recall them. Sometimes in a dream, I have a sense of memory attached to it, like I’ve had the dream before, yet when I wake up that sense is immediately lost. I wonder if this is what happens when people experience déjà vu (when they’re awake of course). I’ve had episodes of TGA (Transient Global Amnesia) where one’s thoughts seem to go in loops. It’s very disorienting, even scary, and the first time I experienced this, I described it to my GP as being like ‘memories from the future’, which made him seriously consider referring me to a psychiatrist.
So time, as we experience it, is intrinsically related to memory, yet there is another way we experience time, all the time, at least while we are conscious. And it is this ‘other way’ that made me challenge Kant’s thesis, when I first read it and was asked to write an essay on it. All animals, with sight, experience time through their eyes, because our eyes record the world quite literally as it passes us by, in so many frames a second. In the case of humans it’s twenty something. Movies and television need to have a higher frequency (24 from memory) in order for us to see movement fluidly. But many birds have a higher rate than us, so they would see a TV as jerky. When we see small birds flick their heads about in quick movement, they would see the same movement as fluid, which is why they can catch insects in mid-flight and we haven’t got Buckley’s. The point is that we literally see time, but different species see time at different rates.
We all know that our very existence in this world, on a cosmic scale, is just a blink, and a subliminal blink at that. On the scale of the universe at large, we barely register. Yet think upon this: without consciousness, time might as well not exist, because without consciousness the idea of a past or future is irrelevant, arguably non-existent. In this sense, Kant was right. It is only consciousness that has a sense of past and future; certainly nothing inanimate has a sense of past and future, even if it exists in a causal relationship with something else.
But of course, we believe that time does exist without consciousness, because we believe the universe had a cosmic history long before consciousness even evolved and will continue to exist long after the planet, upon which we are dependent for our very existence, and the sun, upon which we are dependent for all our needs, both cease to exist.
There has been one term that keeps cropping up in this dissertation, which has time written all over it, and it’s called causality. Causality is totally independent of the human mind or any other mind (I’m not going to argue about the ‘mind of God’). Causality, which we not only witness every day, but is intrinsic to all physical phenomena, is the greatest evidence we have that time is real. Even Einstein’s theories of relativity, which, as Callendar argues, effectively dismisses the idea of a universal time (or absolute time) still allow for causality.
David Hume famously challenged our common sense view of causality, arguing that it can never be proven; only that one event has followed another. John Searle gives the best counter-argument I’ve read, in his book, Mind, but I won’t digress as both of their arguments are outside the scope of this topic. However, every animal that pursues its own food believes in causality, even if they don’t think about it the way philosophers do. Causality only makes sense if time exists, so if causality is a real phenomenon then so is time. I might add that causality is also a lynch pin of physics, otherwise conservation of momentum suddenly becomes a non sequitur.
My knowledge of relativity theory and quantum mechanics is very rudimentary, to say the least, nevertheless I believe I know enough to explain a few basic principles. In a way, light replaces time in relativity theory; that’s because, for a ray of light, time really does not exist. For a photon, time is always zero – it only becomes a temporal entity for an observer who either receives it or transmits it. That is why light is always the shortest distance between 2 events, whether you want to travel between them or send a message. Einstein’s great revelation was to appreciate that this effectively turned time into a dimension that was commensurate with a spatial dimension. Equations for space-time include a term that is the speed of light multiplied by time, which effectively gives another dimension in addition to the other 3 dimensions of space that we are familiar with. You can literally see this dimension of time when you look at a night sky or peer through an astronomical telescope, because the stars you are observing are not only separated from us by space but also by time – thousands of years in fact.
But quantum mechanics is even more bizarre and difficult to reconcile with our common-or-garden view of the world. A lot of quantum weirdness stems from the fact that under certain conditions, like quantum tunneling and entanglement, time and space seem to become irrelevant. Entanglement implies that instantaneous connections are possible, across any distance, completely contrary to the restraints of relativity that I described above (see addendum below). And quantum tunneling also disregards relativity theory, where time can literally disappear, albeit temporarily and within energy constraints (refer my post, Oct.09).
But relativity and quantum mechanics are not the end of the story of time in physics; there is another aspect, which is perhaps even more intriguing, because it gives us the well-known arrow of time. Last year I wrote a review of Erwin Schrodinger’s book, What is Life? (Nov.09), a recommended read to anyone with an interest in philosophy or science. In it, Schrodinger reveals that one of his heroes was Ludwig Boltzmann, and it was Boltzmann, who elucidated for us, the second law of thermodynamics, otherwise known as entropy. It is entropy that apparently drives the arrow of time, as Penrose, Feynman and Schrodinger have all pointed out in various books aimed at laypeople, like myself. But it was Penrose who first explained it to me (in The Emperor’s New Mind) that whilst both relativity theory and quantum mechanics allow for time reversal, entropy does not.
Callendar, very early in his Scientific American article, posits the idea that time may be an emergent property of the universe, and entropy seems to fit that role. Entropy is why you can’t reconstitute an egg into its original form after you’ve dropped it on the floor, broken its shell and spilled all its contents into the carpet. You can run a film backwards showing a broken egg coming back together and rising from the floor with no trace of a stain on the carpet, but we immediately know it’s false. And that’s exactly what you would expect to see if time ran backwards, even though it never does. The two perceptions are related: entropy says that the egg can’t be recovered from its fall and so does the arrow of time; they are the same thing.
But Penrose, in his exposition, goes further, and explains that the entire cosmos follows this law, from the moment of the Big Bang until the death throes of the universe – it’s a universal law.
But this in itself begs another question: if a photon experiences zero time and the early universe (as well as its death) was just entirely radiation, where then is time? And without time, how did the universe evolve into a realm that is not entirely radiation. Well, there is a clue in the radiation itself, because all radiation has a frequency and from the frequency it has an energy, defined by Planck’s famous equation: E = hf. Where f is frequency and h is Planck’s constant. So the very equation, that gives us the energy of the universe, also entails time, because frequency is meaningless without time. But if photons have zero time, how is this possible? Also, if any particle approaches the same velocity as the photon, so does its time approach zero. And this happens when something falls into a black hole, so it becomes frozen in time to an external observer. Perhaps there is more than one type of time. A relativistic time that varies from one observer to another (this is a known fact, because the accuracy of GPS signals transmitted from satellites are dependent on it) and an entropic time that drives the entire universe and stops time from running backwards, thus ensuring causality is never violated. And what of time in quantum mechanics? Well, quantum mechanics hints that there is something about our universe that we still don’t know or understand, and to (mis)quote Wittgenstein: Of that which one does not know, one should not speak.
Addendum: Timmo, who is a real physicist, has pointed out that my comment on entanglement could be misconstrued. Specifically, entanglement does not allow faster-than-light communication. For a more comprehensive discussion on entanglement, I refer you to an earlier post.
Addendum 2: I revisited this topic in Oct. 2011 with a post, Where does time go? (in quantum mechanics).