Julie Arliss on Time Tues 19 – 9 – 17

Julie has kindly sent us her notes so we can think about and remember what she said in what all of us present found a most stimulating and mindbending session.

Philosophy and Science of Time

1. Time is what clocks measure. We use our concept of time to place events in sequence one after the other, to compare how long an event lasts, and to tell when an event occurs.
2. Our perceptions are ALWAYS of the past. The light from the sun is 9 minutes old by the time we see it. Time has passed between looking at a clock and SEEING the time. (On average 2.3 nano seconds)
3. The past does not exist, the future does not exist. All my perceptions are of the past. So what is the present moment?
4. Time passes slowly when I am bored. If I stay forever bored will I live longer? (In Catch 22 by Joseph Heller – Dunbar decides to stay in bed and do nothing so that he will live longer.)
5. Kant suggested a subtle relationship between time and mind–that our mind actually structures our perceptions so that we can know a priori that time is like a mathematical line. Time is, on this theory, a form of conscious experience, and our sense of time is a necessary condition of our experience or sensation.
6. It is an arbitrary convention that we design clocks to count up to higher numbers rather than down to lower numbers as time goes on, and that we re-set our clock by one hour as we cross a time-zone. It is an arbitrary convention that there are twenty-four hours in a day instead of ten, that there are sixty seconds in a minute rather than twelve, that a second lasts as long as it does, and that the origin of our coordinate system for time is associated with the birth of Jesus
7. The metric of time concerns whether our choosing an atomic clock rather than the Earth’s rotation as our standard clock indicates we’ve chosen a more correct metric or instead merely a more convenient metric. The smallest theoretical measurement of time is ‘Planck Time’, at 10-43 seconds. Physics is only able to describe the universe from the age of 10-43 seconds. The smallest slice of time measurable by equipment is that which captures a chemical reaction, using pulsating lasers. This is called a Femtosecond: one thousandth of a trillionth of a second (1/1,000,000,000,000,000). In photon research, physicists talk about Attoseconds (10-18 seconds). An Attosecond is 0.0000000000000000001 of a second ( a quintillionth)
8. The philosopher of science Bas van Fraassen described physical time by saying, “There would be no time were there no beings capable of reason” just as “there would be no food were there no organisms, and no teacups if there were no tea drinkers,” and no cultural objects without a culture.
9. Aristotle claimed that “time is the measure of change” [Physics, chapter 12], but he emphasized “that time is not change [itself]” because a change “may be faster or slower, but not time…” [Physics, chapter 10]. For example, a specific change such as the descent of a leaf can be faster or slower, but time itself can not be faster or slower. In developing his views about time, Aristotle advocated what is now referred to as the relational theory when he said, “there is no time apart from change….” [Physics, chapter 11]. In addition, Aristotle said time is not discrete or atomistic but “is continuous…. In respect of size there is no minimum; for every line is divided ad infinitum. Hence it is so with time” [Physics, chapter 11
10. Newton argued very specifically that time and space are an infinitely large container for all events, and that the container exists with or without the events. He added that space and time are not material substances, but are like substances in not being dependent on anything except God. ‘Time is what it takes to get from one place to another.’
11. McTaggart 1908 – The Unreality of Time. Either there is an objective mind independent flow of time. Past present and future exist just as we experience them. Or physics and philosophy are right, and this is not true. The experience of time is real but time does not exist. We cannot see or touch time, so maybe it’s a subjective illusion created by the mind. William Lane Craig – ‘a gigantic and universal delusion’
12. Einstein – time and space are mathematically connected. Space/time. When he discovered this Einstein said ‘for a few days I was beside myself with joyous excitement’ Einstein discovered that mathematically time and space are linked in the 4 dimensional space time continuum. The distinction between past present and future is an illusion, no matter how persistent. Time is an extension of an object – the fourth dimension. Further, although most of us hold the view that time is dynamic, meaning that time ‘passes’, so that the past has gone, and the future has not yet arrived: only the present is real. However, there is an alternative view of time favoured by many physicists, in which the whole of time exists simultaneously in a ‘Block’. There are several varieties of Block theory, but its main principles might imply some of the following: • All events exist simultaneously, so your birth, life and death exist simultaneously. There is no permanent death. • Your consciousness creates the illusion of moving through time. • The Block may contain a ‘replay’ feature, or else a consciousness shift to another mentality. Hindus & Buddhists might see this as a scientific basis for belief in reincarnation of the soul. • The Block view appears to be deterministic. Determinism is the view that if all events are caused by previous events, then we have no free will: we are in effect biological robots. • If your entire life is laid out in the Block, then this seems to suggest that determinism is true, so if God created the Block, God designed your life by pre-determining it. However, Aquinas argued that God is outside time, so he sees your choices but does not cause them. • Which view is true? Many physicists accept the Block view, because the equations in physics work just as well backwards in time as forwards. The Block view solves the problem of our not being able to find a present moment. Everything exists simultaneously, and our brains invent time. Beyond ideas such as these, we have no explanation of the nature of time.
13. If you travel fast enough time slows down. Time dilation.
14. If you travel to the constellation Centaurus it is 230 light years from earth. An object travelling at the speed of light would take 230 earth years to arrive there. The return journey would take 460 years. If a space ship left earth in 2014 under constant 1g acceleration time dilation would mean that for those on board the ship the return journey would only take 24 years. On their return 500 years would have passed on earth.
15. If all time exists now, like space, do we have freewill?

Questions on time
1 The equations of physics work just as well backwards in time as they do forwards.
2 Why do humans experience time only from past to future?
3 Is it possible to create the past from its future?
4 Is it possible to label and moment in time as ‘now’?
5 Does time always pass at the same rate? 6 When did time begin, and will it ever end? 7 Do you think that time travel will ever be possible?

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