Mind the Gap A cognitive perspective on the flow of time in physics Master's Thesis History and Philosophy of Science Supervisor: Prof. dr. Dennis Dieks Utrecht University August 16th 2009 Annemarie Hagenaars Lange Hilleweg 31b 3073 BH Rotterdam Student number: 3203808 Preface The image on the title page of my thesis is The Persistence of Memory (1931), which is the most famous painting by Salvador Dali. This painting captures many standard issues that relate to time: relativity theory, clocks, memory, and the flow of time. This thesis is about the flow of time. As time moves on and never stops, so will the philosophical and scientific research on its flow be incomplete forever. Never in my life has time flown by as fast as it did this last year of my master's research. So many questions remain unanswered; so much works still needs to be done, while the months were passing like weeks and the weeks were passing like days. One year is too short, to dive into the fascinating river of time. To me it feels like this thesis is a first survey of the possibilities within the field of the philosophy of time. Time's passage has been a source of interest for quite a long time. When I was a child I kept diaries and memo-books to write down what happened each day in the hope I wouldn't forget it. Nowadays it is still a favorite game to exactly remember the date and time of special happenings and pinpoint those on my personal time line in my mind. It fascinated me why things that are in the future, become present and finally are in the past, leaving behind almost no evidence except for some physical records and memories in the mind. These traces of the past help us to find out what happened. Reconstructing the past is what historians do for a living. Nothing illustrates the passage of time any better than the existence of history. The past is captivating. If I walk in an old castle or house, I imagine the people that walked here hundreds of years ago. They are now gone, like I will be gone a hundred years from now. I keep looking in front of me with my eyes on the future, but from time to time, I take a look over my shoulder and think about what my world line looks like from the day I was born until `now'. You may call it nostalgic, but I prefer to call it the fascination for the flow of time. Years have gone by and in this fast world we are living in, I sometimes need to think about all those moments of `now' I have experienced. In 2002 I moved to Leiden to study history. In this first year I learned about what happened in the time between 6000 BC and 2000 AD starting with the Mesopotamian civilization and ending with the Gulf War in the nineties of the last century. What I also have learned is how difficult it is to reconstruct history. We can never know what happened for sure, unless we are able to go back in time. But we are not. 1 In my second year, I switched to physics and started a bachelor's in Astron- omy. Many people wished me luck in the study of a much bigger history: the history of the universe. From the start of my first year in astronomy, the science of the universe and the Big Bang when time started captivated me. A few years ago I never thought I would write a thesis on the passage of time. It is the most fascinating subject that I have ever written about; it connects all different kinds of my interests. `Time' and especially its flow is everyone's business every day. But if you ask yourself the question what time and its passage really are, you are stuck for an answer. It is one of the most difficult questions in the philosophy of physics. After I took some courses in Philosophy of Mind and in Philosophy of Space and Time in the spring of 2008, I was looking for a subject to write a paper about. When I got in touch with the field of philosophy of time, I tried to write a piece about spatial metaphors we use to understand time in July and August of that year. There were so many questions lying in front of me, that I could not finish the paper. A study was needed to know more about the role of time in physics compared to the way we experience time in everyday life. The subject turned out to be too extensive to cover in 5000 words and that is how the idea for my master's thesis was born. In this thesis I offer a cognitive perspective on the problem of the flow of time in physics. It is a relatively new kind of approach to an age-old subject. In October of last year, I got in touch with many researchers in the field of the philosophy of time from all over the world to discuss recent publications on this subject, especially on the combination of cognitive science and physics. Thanks to enthusiastic reactions of Nick Huggett, Craig Callender, Robin LePoidevin, Barry Dainton, Huw Price and Dennis Dieks, I got encouraged in the choice of my subject. Here in front of you lies the product of a one year study on the fascinations of time's passage. It does not feel like a finished study at all. Many things that are mentioned on the surface deserve a more extensive treatment. First of all I am grateful to Egbert Stolk for his library that has been a gold mine of references on cognitive science. He also helped me producing a part of the images in this thesis. I am also thankful to Monique van Velzen for reading pieces and her tips and suggestions for the improvement of my English. Finally I would like to thank Dennis Dieks for supervising this project and for offering very helpful criticism to improve the scientific character of this thesis. Annemarie Hagenaars August, 2009 2 Contents Introduction 5 1 `Flow of Time' is a spatial metaphor and analogy 8 1.1 Analogical thinking and metaphoric structuring . 10 1.1.1 The analogical mind . 10 1.1.2 Differences between metaphor and analogy . 12 1.1.3 Novel and conventional metaphors . 12 1.2 Using spatial analogies to think about time . 14 1.2.1 Spatial metaphors in temporal reasoning (linguistic) . 14 1.2.2 Spatial analogies to understand time (non-linguistic) . 18 1.2.3 Rethinking metaphor and analogy . 21 1.3 Conclusions . 26 2 The picture of time in physics 29 2.1 McTaggart and `The Unreality of Time' . 31 2.2 The Reality of Time: Untensed Views vs. Tensed Views . 34 2.2.1 The origin of the block Universe . 35 2.2.2 Time and the Laws of Physics . 39 2.2.3 Views on the Reality of Time . 43 2.3 Untensed and Tensed Views Reconciled . 51 2.3.1 Savitt on Absolute Becoming . 52 2.3.2 Dieks on Local Becoming . 56 2.4 Conclusions . 61 3 Perception of the flow of time in the brain 64 3.1 Six models on the Perception of the Present . 67 3.2 The experience of Motion . 77 3.2.1 The Apparent Motion Effect . 78 3.2.2 The Flash Lag Effect . 80 3.3 The experience of the present: two versions of the doctrine of the Specious Present . 83 3.3.1 James and the Snapshot Lapsing Interval . 85 3.3.2 Dainton and the Overlap Theory . 87 3.4 The Mechanisms of the Brain . 92 3.4.1 The role of memory . 92 3.4.2 The Mind is a Society . 96 3.4.3 Present Patches, Windows of Simultaneity and Temporal Integration Mechanisms . 99 3 3.5 iguss and the division into past, present and future . 104 3.6 Conclusions . 108 Conclusion: bridging the gap 112 4 Introduction I sit at my desk and take a sip of my tea. I feel the warmth running down my throat. I think of a first sentence and start typing on the keyboard of my laptop. It is very quiet here in the house. I hear the clock ticking, I can feel the beating of my heart and I am aware of thoughts rushing through my head. My mind is continuously making memories. Some of them exist only a few seconds or minutes; others are stored for a longer time. These memories are made at this very moment to record the past. And these same memories help us infer now what is going to happen in the future. We learn by making explanations for ourselves of what happened in the past, decisions on what has to happen now and plans for what we want to be happening in the future. Without our memories we do not have any personal history. That is why memories are crucial for our identity. We are making plans, decisions and explanations `now'; `in the present'. We never directly experience what happened in the past; we know what happened if we recall our memories at the present moment. We only experience what is present and this feels as if the present is something special. The clock is ticking the seconds, the minutes, the hours and it does not stop and cannot be returned. Every time we want to name what is present, for example it is now 10.13.55 AM, to be t1, it is already past before you can write it down.