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Why it takes time to think about time

Dawn over mountains
Professor Christoph Hoerl explains why the concept of time is one of the most enduring themes in philosophy, and why we are still nowhere near finished resolving the puzzles it raises.

The physicist and science writer Sean Carroll recently spoke about the reader reviews for two of his books on Amazon’s website. One of the books, on the Higgs boson, receives consistently very good reviews. The other book is a book about time, and here the reviews are much more mixed. Obviously, this could be because the first of these books is simply better than the second. However, Carroll has a different explanation. He says the book about the Higgs boson is trying to explain to a general audience things of which only a few specialists have in-depth knowledge. With the book about time, things are different. Time is a topic that everyone has opinions on.

Can anyone explain what time is?

Nothing seems to be more familiar to us than time: We arrange to meet with a friend at noon tomorrow, we wait while the bread toasts, we think back to another year. And yet, at the same time, time also has a somewhat mysterious nature. We speak of time as ‘flowing’ or ‘passing’, or of the future as ‘open’ and the past ‘fixed’, but on closer inspection these are all just metaphors and it is hard to explain what we actually mean by them. In the words of the medieval philosopher St Augustine:

What, then, is time? If no one asks me, I know what it is. If I wish to explain to him who asks, I do not know.”

Philosophers have therefore long taken it as their task to inquire further into the real nature of time, to develop metaphysical pictures that spell out exactly what might be involved in time flowing or passing, or in exactly what respects the future may be different from the past.

Physics and metaphysics

More recently, however, some philosophers have changed their view somewhat. They have moved away from idea that philosophy can illuminate the real nature of time, thinking instead that it is physics that does so. After all, time is an aspect of the physical universe that physicists study.

There is something interesting about the picture of time painted by modern physics, though. In recent physical theory, little of what we are familiar with as time actually remains. As the Italian physicist Carlo Rovelli says in his book, The Order of Time, looking at time through the lens of physics is: “like holding a snowflake in your hands: gradually, as you study it, it melts between your fingers and vanishes”.

Physics has no space for ideas such as that of time ‘flowing’ or ‘passing’, or the idea of a ‘fixed’ past and an ‘open’ future.

This raises two interesting questions. First, does physics tell us the whole story about time, or might there be aspects reflected in our everyday experience of time that are left out by a purely physical description of the world? For instance, is the belief that time passes or flows really something that science could disprove? Here we come back to Carroll’s observation that everybody has an opinion on time. More to the point, it seems very difficult for us to accept that many of what seem to us as the most prominent features of time, as it impacts on our lives, have no basis in reality.

Our everyday picture of time

But a question also arises if we do accept that physics tells the real story about time, one on which time does not really ‘pass’ or ‘flow’, and one on which there is no real contrast between a ‘fixed’ past and an ‘open’ future. Even if it turns out that these ideas about time are false, there needs to be an explanation as to how they arise (they appear to be universal ideas about time, shared across cultures), and why they have such a hold on us. This is where some of the most interesting recent work in the philosophy of time is going on.

Philosophers have turned from pondering over the metaphysical nature of time to trying to capture the precise nature of our everyday picture of time and inquiring into what its real origins might be.

Maybe one day we will be able to explain exactly why time seems to fly when you are having fun.

21 November 2018

Christoph HoerlProfessor Chrisoph Hoerl, from the University of Warwick's Department of Philosophy, works on a number of different issues in the philosophy of mind and philosophy of psychology. He is particularly interested in philosophical questions about the nature of temporal experience, memory, and our ability to think about time.

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