Welcome to the first installment of the From Eternity to Here book club. We’re starting at the beginning, with Chapter One, “The Past is Present Memory.”
Excerpt:
The world does not present us with abstract concepts wrapped up with pretty bows, which we then must work to understand and reconcile with other concepts. Rather, the world presents us with phenomena, things that we observe and make note of, from which we must then work to derive concepts that help us understand how those phenomena relate to the rest of our experience. For subtle concepts such as entropy, this is pretty clear. You don’t walk down the street and bump into some entropy; you have to observe a variety of phenomena in nature and discern a pattern that is best thought of in terms of a new concept you label “entropy.” Armed with this helpful new concept, you observe even more phenomena, and you are inspired to refine and improve upon your original notion of what entropy really is.
For an idea as primitive and indispensable as “time,” the fact that we invent the concept rather than having it handed to us by the universe is less obvious—time is something we literally don’t know how to live without. Nevertheless, part of the task of science (and philosophy) is to take our intuitive notion of a basic concept such as “time” and turn it into something rigorous. What we find along the way is that we haven’t been using this word in a single unambiguous fashion; it has a few different meanings, each of which merits its own careful elucidation.
The book is divided into four major parts — Part One gives an overview of the issues, Part Two discusses relativity and time travel, Part Three (the longest and best part of the book) is about reversibility, entropy, and the arrow of time proper, and Part Four puts it all into a cosmological context. So Part One is somewhat out of logical order — it’s an attempt to survey the terrain and raise some ideas that will come to fruition later in the book.
The basic point of Chapter One is to examine the ways in which we use the concept of “time.” I’ll readily admit that this doesn’t sound like the sexiest idea for an opening chapter. (In my next book, an important character will be murdered within the first few pages, after which his beautiful daughter will be compelled to search for his killer in various exotic locales.) The first chapter has to serve multiple purposes — it obviously needs to provide some background for the rest of the book, but this is not a classroom where you can assume the audience will necessarily follow you to the end. So the first chapter also has to be fun and engaging, hinting at some of the mysteries to come.
In fact, I juggled the first three chapters back and forth. Chapter Two explains the basics of entropy and the arrow of time, while Chapter Three explains the basics of cosmology. At one point I had the current Chapter One placed after these two chapters, on the theory that we could be precise about definitions after we had been exposed to some of the big and exciting ideas. This was a well-intentioned theory, but not an especially good one. Test readers balked, so the current Chapter One was put back in the beginning.
Despite being about definitions and so forth, I think Chapter One turned out to be pretty interesting — indeed, I wonder now whether it shouldn’t have been longer. When you talk to people on the street about “time,” the first questions they ask tend to be along the lines of “what is time, really?” or “is time real, or just an illusion?” This chapter tries to answer those questions, or at least spell out the perspective I’ll be taking for the rest of the book. And they’re important questions, interesting in their own right, even if I breeze through them — lots of philosophical work, not to mention physics, has been addressed to these issues.
We distinguish between three ideas of time — time is a coordinate, time is what clocks measure, and time is the agent of change. These aren’t really “definitions” in any careful sense, so much as “ways we use the notion of time.” And my readers were right — it’s important to set out these different senses right from the start, as I’ve discovered that even physicists tend to blur them together in their minds.
The most important non-obvious stance I take in this chapter is to come down firmly on the side of an “eternalist” or “block universe” conception of time. The past, present, and future are equally real. Philosophers and other deep thinkers have been arguing about this for years, and I kind of dismiss the whole discussion in a couple of paragraphs. Sorry, philosophers! It’s an important issue, but we have other conceptual fish to fry.
So let me know what you thought, and what questions still remain — either about the substance of the chapter, or the stylistic choices made along the way. I’ll try to respond, although I reserve to right to say “hold that thought until we get to Chapter X.” And of course everyone else is encouraged to chime in, too.
The discussion of perceived time is too simple. We look down, see a broken coffee cup, and we remember the cup fell a moment ago and broke. That’s the past. But that’s also a very simple (and too simple) description of time.
– 1861 was in the past. Does anyone remember 1861? No. None of us can personally remember that year. We know from teachers and books that the US Civil War started at Ft. Sumter in 1861. But even that isn’t clear. All we know as a fact is that there was a blockade and cannon fire. But what happened in the Civil War? That isn’t a “fact” in the same way that my broken coffee cup is a fact. The meaning of the “Civil War” changes every few decades. If you read books and articles written at the time, you’ll realize that what we “know” about the past is different from what they experienced at the time. Thus the perceived past can change: it can evolve (look at the change in understanding over the Great Depression), it can change radically (the War Between the States, which was fought over states’ rights, is now seen as a war over slavery), and it can even disappear (the history of the USSR is disappearing).
– Did the past ever exist? Christians say the world was created by their sky god in seven days. Archbishop Ussher calculated this to a late afternoon on Sunday, October 23, 4004 BC. They know the past quite clearly (and you have any doubts, just try talking with a fundamentalist Christian). But for everyone else, their “past” never existed.
What about the “past” of science? That’s clearly defined, isn’t it? But 200 years ago, we had no idea of galaxies. 100 years ago, we realized how far away they were. Ten years ago, the issue of the expansion of the universe was solved. Our scientific, objective past itself is changing radically, constantly being updated.
The past itself is as malleable and up-for-grabs as the future, according to politics, religion, and cultural trends. A few things can be said with certainty (such as “Sean Carroll was born in 1966”), but even that can change (“Carroll, the 2018 Nobel Prize winner, was born Oct. 5, 1966″) (or… The modern Age of Carroll started as the year zero, which replaced the previous Gregorian Calendar, previously known as 1966.”).
What about the broken coffee cup? Isn’t that clearly “in the past”? Not if your house has three kids, two dogs, and a cat. You’ll get 24 different explanations why your Nobel Prize coffee cup got broken until you finally give up and switch to whiskey.
So, it’s only for very simple (and very trivial) events that we can talk with certainty about a past. Everything else recedes into a fog of conflicting interpretations.
All of this applies to the future as well. “The future isn’t what it used to be” captures it very well: The expected perception of the future is a cultural construct, and it changes as well. 2010 certainly isn’t what we expected back in 1980. We construct and maintain the future, just as we construct and maintain the present and the past.
Thus I find it very problematic (okay, wrong) when Sean writes “we remember the past due to entropy” (p.40-41). How does entropy explain different pasts (Bishop Ussher vs. Charles Darwin) or that the understanding of the French Revolution has changed several times? And we very well can remember the future: Back in the 80s, the future had flying cars, house robots, and no web.
So the discussion of time in these opening chapters isn’t useful. Too many issues are mixed up; there isn’t a clear analysis.
Andreas– I’m not sure if there’s a particular point in there you’d like me to answer. General tip: to increase the likelihood of a useful response, keep the questions relatively pithy!
By the way, I read Slaughterhouse-Five a week before I started reading this book and was excited to see the reference to it. I was also thinking of how the Grand Canyon gives us the ability to see all events at once (maybe not the future, but if we pick a spot in the middle then we could see past present future with a little help from our imagination). You can see millions of years at once if you know how to ‘read’ the walls and rocks.
I am coming to this book as a complete and total laymen, interested in the subject of time and eager to go on this quest for the ultimate theory, but a little frightened by how smart all of you are!
That being said, I thoroughly enjoyed the first chapter. The only place that I stumbled was when you said, “For subtle concepts such as entropy…” and I thought to myself, “Oh crap, I have no idea what entropy is.” I tried to have someone explain it to me and I managed to somehow understand how human beings are the anti-entropy, but the concept is still lost on me. But I guess you’ll be getting more into that in the second chapter?
Anyway, being that I didn’t feel at all lost or bored in this chapter means that I think you’ve done a really excellent job.
Excited to read and discuss more.
Oh! I also wanted to say that imagining myself as Dr. Manhattan really helped in understanding a lot of the chapter. I sort of wanted to leave a comment in the book club announcement that said, “It’s 3:34 on April 19th and I’ve already finished reading the book.”
Also – for those of you having a hard time finding it at B&N – I’m pretty sure the stores have the books modeled in on a display, so if you go to bn.com and click the find in store option, it should give you a list of other stores near you that have the book.
I got a Kindle for Christmas and this was the second book I put on there. The notes work great on it! I, like Tom, would have liked to have seen more on the block universe concept, but I can live with that given the way the perception of time was broken down into the 3 aspects. I had long ago given up trying to wrap my head around the “the medium through which we move” and was quite happy counting ticks and plotting points. It was good to revisit and I look forward to seeing the 3 aspects get tied closer together (at least I hope they get tied closer together) as the book progresses.
TS– digging up the literary references was lots of fun.
NicoleS– more on entropy in Chapter Two, and *lots* more in Chapters 8, 9, 10. If nothing else, you’ll know what entropy is when we’re all done. (It’s [the logarithm of] the number of ways you can re-arrange a system without changing its macroscopically observable features.)
J– hopefully things will be tied more together. And I agree, the Kindle works well.
Andreas:
The purpose of science is to solve problems. So the assuption of an actual past makes solving questions about it a lot easier. Geologists regularly use multiple working models for particular past (and present) problems where different methods of analysis produce different results. But the assumption of anything other than a single tractable reality decreases our ability to constrain that reality, so it is not a productive approach.
Here is a practical example: A decade ago, the two main radiological methods of determining time (The uaranium/ lead and potassium argon systems) systematically differed by 1-2%. Assuming a single “real” timescale allows two thigs: firstly, an intercalibration between the two systems can be produced. Secondly, the assuption that one or both is wrong can lead to attempts to improve them by refining analytical procedures and the physical constants used in those procedures. It is not clear to me how a different view of time would increase the tarctability of the problem. Since science is ultimately a utilitarian endeavor, we pick the approach that works best.
In fact, the appeal to utilitarianism is useful not only here, but for confronting anti-evolutionary and other antiscientific suggestions as well.
Sean,
Do you go into the history of entropy at all? The thing I lvoe about it is that it was defined and put into routine use decades before atomic theory was accepted. So the
I go into the pre-Boltzmann history a bit in Chapter 2, and the Boltzmann history a lot in later chapters.
I am surprised that with all the recent recourse to dualism nobody has stated the obvious; that the presentism and eternalism views are dual descriptions of the same concept (time). The analogy to wave-particle duality is self evident. I think Orzel’s dog figured that out in chapter one of his book.
I see in Chapter One the same thoroughness I liked so much in your dark energy lectures. Sometimes I think I understand a concept, sometimes not. But I know that if I keep at it I WILL understand it, because it is All there. One idea, discussion around it, next idea more explaination, and so on. Each one a block of thought, that I can return too. And the layering of ideas is useful. Since I only read, or even “think deeply”, in bits and pieces, I often have to go back over things many times. But in this back and forth manner I have learned a lot. I hope I am correct in thinking this book will lend itself to that method. To help out I have the book, and the audio book is ordered. I do expect you to be reading it.
Susan, thanks, I hope the book lives up to it! I’m not the one reading the audio book; the guy who is doing it is a professional who is frankly better at it than I would have been.
Lab Lemming writes that it’s useful to assume an actual past. He means “an actual physical past”, namely, the history of broken cups and factual, physical things.
I’m pointing out that Sean is moving back and forth between “physical past in memory” (I remember my cup fell and broke) and “the social past in memory” (the various interpretations of the Civil War.)
The second one isn’t something that physics can address. I don’t see how entropy has to do with that type of memory, since it changes according to politics, historians, etc. There simply isn’t an objective historical past in the Newtonian sense.
The first type of past (physical events) is also a problem. Let’s say ten minutes ago, Xsdf (who lives on a planet around Sirius) broke his coffee cup. Sirius is about eight light years away, which means Xsdf is outside our light cone. There is no meaningful way for us to say Xsdf’s cup fell ten minutes ago in our past. There is no objective Newtonian past. We can’t assume an actual physical past.
Sean asked if I’m asking a question. It’s not a question. I’m pointing out that the common sense ideas of past and memories are very complicated (or, better said, very muddled). Sean’s book is forcing me to think about these. I’ll admit: I want to say that Xsdf’s cup broke ten minutes ago, but Einstein’s ideas tell me I can’t do that.
Here’s another note: A few months ago, I converted our family’s Super8mm films into digital files and began editing them on my computer. I haven’t seen these movies in 20-30 years. If you ask me what is in my memory, it’s a series of fuzzy scenes, somewhat like what I see in dreams. When I watch the videos, it doesn’t match my memory at all. I have to adjust my memory to match the video. I bring this up because Sean writes quite a bit about memory and entropy, but that doesn’t match my experience of memory, that is to say, my experience of the past.
Hi –
I guess I am a layman (I am a freshman in high school and I should probably be studying for finals right now… this is more fun though so whatever…), but I love reading books like this (I just finished A Brief History of Time and Why Does E=mc^2, both of which I would highly recommend to anyone who likes this sort of book). I do have a few questions from the start of the book, both of them about entropy, so I guess I should wait until next week but one of them is more directly related to time, so here it is: I completely understand that the Second Law of Thermodynamics combined with the fact that entropy must have originally been very low leads to the Arrow of Time and thus why we seem to move from and remember the past while journey (so to speak) into the future. My question though is this: if a universe were to evolve in which the reverse were true (perhaps this is impossible and a silly hypothetical, but it seems conceivable), i.e. the universe started with high entropy and entropy decreases, what would that mean for perception? Would we “remember” the future and forget the past? Also would this universe actually seem no different, just as if every timekeeping device of any sort slowed down, you wouldn’t notice?
This is something else that I find interesting but isn’t really a question: if one were to apply the concept of slowing down all the time-keepers to a single individual, it seems to me analogous to the idea of one person seeing everything in negative; the person who experiences time slower would be like the person who sees everything in negative relative to everyone else. If someone else were to experience time or see color the way the special person does, they would notice the difference, but if they were to just talk, it would be impossible to tell the difference. As I’m sure you know the idea of seeing in negative is a famous philosophical concept, and although I mean not be explaining it well, I was wondering if you agree that the same idea applies to time.
Thanks,
Sam
Sorry if my first question should have waited for the next chapter, but I am already saving one and I just had to ask.
Sam– the direction in which time points is ultimately arbitrary. What is real and measurable is the direction in which entropy increases. Everything goes along with that; so in any particular universe, inhabitants would always think of the direction of lower entropy as “the past,” and that’s what they would remember. There would be absolutely no difference between that type of universe and the one in which we live. (In fact, there’s nothing to stop you from using a time coordinate that runs in the opposite direction of the usual one — coordinates aren’t very meaningful, they’re just labels.)
My only quibble with the book so far is I’d have preferred foot notes to end notes. I don’t like having to flip back and forth, but I’m sure the choice wasn’t made haphazardly (maybe footnotes scare people off like equations).
I also vastly prefer footnotes to endnotes. Those who aren’t interested can ignore either one; those who are have a more difficult time with the endnotes. After reading a book, sometimes I want to go back and re-read something, and have a feel for where it was in the book. With footnotes, I’ll find it easily, whether it was in the main text or not, but with endnotes it is more difficult.
The most important non-obvious stance I take in this chapter is to come down firmly on the side of an “eternalist” or “block universe” conception of time.
I used to be rather sceptical of the many-worlds interpretation due to the “but where are they” argument. However, while reading Deutsch’s The Fabric of Reality, I realised that this question is no more puzzling than asking where the many worlds (infinitely many, or perhaps finitely separated by the Planck time or whatever) of the past are.
Comments?
Philip– yes, I feel the same way, and we talk about it a bit in Chapter 11.
I’m interested in the concept of “nowhen”, but it seems to me that everyone’s nowhen is unique. An earlier poster asked about the concept of “past” in the context of far removed locales, and you promised we would get into it more in later chapters. But does the role of the observer have similar effects on time as it does on quantum mechanics? I’m probably not making sense, but it seems to me that my perception of time (past, present or future) must be different than an observer (hypothetical) in the Andromeda galaxy. Really looking forward to chapters 4 and 5!
Huh. I waited until the bottom of p. 35 to kill off a character. No wonder my sales have been so slow.
<John Hammond voice> “Next time, it will be flawless!”
I got my copy just in TIME to join in. First chapter is very solid except I have no idea who or what a “running back” is or why they would run around like that 🙂
You said above that you dont have “any specific suspicions that extra dimensions will change the way we view time”. Of course if there were extra time dimensions (as in F-theory) then that would have some influence on the way people view time. Some ideas about time would not make sense if there were actually more than one time dimension even if they only show up at very small scales. For example a lot of what Lee Smolin says about time being more fundamental and different from space would be hard to justify. I prefer the viewpoints that would not fall apart in the face of many time dimensions.
Will– time is not an observable in quantum mechanics; the wave function takes on values at every different moment of time. But the perception of time depends on lots of things, including the arrow of time based on entropy. For most purposes, there’s every reason to think that the perception of time is similar at all points within the observable universe, but in regions where they might not be an arrow of time it’s hard to know what that would even mean.
Blake– study your Dan Brown, and get back to me.
PhilG– sorry about the running back business; the only current edition of the book is aimed at Americans. The number of time dimensions is of course an empirical question, to the extent that it’s a well-posed question at all. I tend to think that quantum mechanics is fundamental, so that there is just one time direction at a deep level, but obviously that’s a tentative opinion.
Your above quote ” time is not an observable in quantum mechanics” while the conventional view has always made me a little unconfortable especially with regard to relativistic QM. I love Mark Srednicki’s dicussion in his QFT text P. 10 about the two alternatives demoting space operators to parameters ( conventional QFT approach ) or promoting time to an operator – any thoughts about the second option?
Mark– I don’t have any very deep thoughts about it. It doesn’t seem obviously necessary to promote time to an operator; in quantum mechanics, time is very different from anything else, as the history of the wave function is a path through the Hilbert space as a function of time. I kind of like it that way.