I gave a talk yesterday at the Center for Inquiry branch here in LA. It was a popular-level spiel on The Origin of the Universe and the Arrow of Time; click for slides. If I had been thinking, I would have advertised the existence of the talk before I had given it, rather than afterward. Either that, or I was trying to smoke out time-travelers.
But the real reason I’m even bringing it up is to give credit to this great YouTube video, found via Swans on Tea.
I was literally zipping through blogs yesterday morning while drinking coffee and preparing for the upcoming talk, when up popped this wonderful illustration of entropy and the arrow of time, which naturally I showed at the talk. And it features a kitty. (Schrodinger has his own cat, why shouldn’t Boltzmann?)
Ooooh! Cool! Seems like whoever does this has a lot of time and imagination. (Apparently so have I – not the imaginations, the time – since I looked at most of his other videos.)
-A lurker until now.
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I enjoyed your set of slides. Your statement on entropy driving metabolism made me think you might enjoy my thesis here on how entropy can be used to derive a definition for life:
http://meshula.net/wordpress/?p=195
Sean,
great video! And it can also be used to illustrate our financial system.
My personal crazy (crackpot?) theory of re-inflation. Please edumacate my ignoramusience!
As the universe expands and becomes more empty, the matter that is left in the spaces between, or the particles that pop up in the void, are so alone that their velocity can only be measured by distant objects. Since their velocity relative to distant objects is very high, they acquire increased mass. “Run once, run anywhere,” or something, and so the increased mass causes any nearby matter or particles to coalesce. These little lumps then have relative velocity measured by distant objects receding at closer and closer to the speed of light, so their mass (relative to “the universe”) becomes very high. Eventually the high mass energy lumps become black holes in the void, and evaporate their velocity-increased energy into particles that form clouds of new matter, form stars, etc. Since high relative velocity increases mass, it seems like an expanding universe would self-correct its own entropy.
But I dunno. ???
There’s a big difference in the way astronomers and biologists refer to evolution. Astronomers use the traditional definition of evolution that refers to individual things changing over time. That why stars and the universe can evolve.
But in biology single organisms don’t evolve. A person may change significantly from the time they’re born until the time they die but we don’t call that change “evolution.” Biological evolution only refers to heritable changes in an entire population (species) and not changes in an individual.
There are several articles that contrast stellar evolution and biological evolution pointing out that they are not the same.
Well … sure. The evolution of stars is obviously not the same as the evolution of species; nor is it the same as the evolution of individuals, or the universe, or sports cars. But all share the same non-technical sense of evolution as “change through time,” which is all I was using here.
And for a good related illustration of entropy leading to greater complexity, there is this excellent commercial:
http://www.youtube.com/watch?v=jEmbjiaA3E0
The video also demonstrates something very unrelated to its purpose but also very interesting: even though the impetus of the collapse of each block building contains a considerable lateral component of force, each colored building pretty much falls down into its own footprint. Take that, 9/11 “Truthers”.
Sean, I’m having trouble intuitively understanding how inflation and baby universes solve the time asymmetry puzzle. First of all, I don’t see how the idea is time-symmetric. If in one direction, the universe undergoes inflation, followed by giving birth to baby universes, then it would seem to me that time symmetry would require that deflation would also be possible, and that it should also be possible for baby universes to reenter the womb, so to speak. I suppose that you could define the direction of time pointing towards production of baby universes to be “the future”?
Certainly we can’t just intone “baby universes!” and solve the problem. In our model, both BU creation and the time-reversed process do indeed occur, but on opposite ends of the evolution of the multiverse. There is no equilibrium state, so there is no requirement of detailed balance of processes and anti-processes at any one time.
Sean
Looking at slide 20, I don’t see any time symmetry. I see expanding objects moving off in opposite directions in some unspecified dimension. Since entropy is dependent on the expansion, and time is dependent on entropy, your picture still shows a highly asymmetric vision of time.
The only alternative interpretation is that the picture shows some sort of hyperbolic universe, moving either left to right or right to left.
Perhaps you can clarify.
That unspecified dimension is time; it runs horizontally in that picture.
Yeah, that’s a cool video and I like the colored dominoes instead of just black and white (but then are they “real dominoes”?) One cute feature is the black and white cat walking among the sets before they go down – it reminded me of notable liberal blogger Kevin Drum’s cat named “Domino” – not so much a close look-alike as the general concept and name, and walking among dominoes under the title “Oh, oh, Domino”.
Check out his blog at the new address, http://www.motherjones.com/kevin-drum/. Th commenters are rather literate and witty, as they still also are his old digs http://www.washingtonmonthly.com/.
BTW if you really believe in the reality of wave functions, then time is asymmetric since the WF wouldn’t suddenly expand from the location of what used to be an absorber (turned into an “emitter”) and then condense down on top of the now-absorber (used to be the emitter.) Instead, the WF has to expand from the actual “emitter” regardless of what used to be what in another way of running time. That’s because there’s no way there can suddenly be a chance of the particle being far away, but in normal time sequence the WF can suddenly vanish after an absorption and localize into a point (well, that doesn’t make “sense” either, but certainly the WF can’t run backwards symmetrically whatever it is.) And if you don’t believe “in the reality of wave functions”, then what the heck is actually going through space? Well?
If volume of the universe when the two long lines are closest is at some sort of minimum, are you are saying that entropy increases despite your direction in time?
Does that mean that there are two dimensions of time as depicted by the graph, or perhaps one dimension of time, and one additional parameter of time that is dependent on entropy?
Yes, the entropy is at a minimum in the middle, and increases in either direction. There is only one time dimension, but the arrow of time points in different directions locally. In the background there is no arrow of time at all, and in the baby universes entropy increases from the creation toward the expansion.
To me they don’t. I would bet that the line of maximum density of the debris is shifted forward form the center of the footprint, close to the “next” building.
I really enjoyed that powerpoint. I didn’t know of the idea of baby universes “pinching off” the main one.
I’ve been lurking at your site for a few months now. Nice blog!
Sean, you are proposing a physical reality that has not started to exist. Just like an eternal god. For example, how do you propose this reality has obtained the properties it actually has?
Sean
Last question
Does the transformation from a right moving arrow to a left moving arrow imply that there is an additional rotational degree of freedom?
I think there has to be, even if it is heavily suppressed, and even if there are no intermediate orientations for the arrow.
Speaking of new universes “pinching off” another one, in the manner of soap bubbles etc. – what holds “spaces” once we start imagining multiplicity and/or curvature of fundamental spaces? (Based on a comment at Uncertain Principles, in “Everything is Relative”)
The idea of “space-time” led, in General Relativity, to the idea of space as being like a “rubber sheet” than could be curved as the basis of gravity. So people asked, what does “space” curve through unless there’s more space (hyperspace) around it. That led to many diagrams showing a surface in emptiness, and the notion we can generalize to a three-surface curved into a four-space (sic) etc.
But here’s a fundamental problem I and surely others have with thinking of “space” (in effect, the constraint domain of the movement of matter and radiation, right?) as being like a “sheet” (rubber or otherwise) that can be inside another “space” with more dimensions. Here I mean a macro space with more dimensions to “hold” a space with fewer, and not confusing with time either (so: a four-space dimensional manifold to “hold” a curved 3-D space within it.) Sure, in math I can just specify a manifold, a surface or space as part of another space by stating the rule for the locus of points. I can say, “the locus of points equidistant from a given point” which creates by semantic fiat a spherical shell in any space. The shell is literally curved (showing intrinsic non-Euclidean geometry), and has dimensionality one less than the parent space.
Some physicists and philosophers of science say, there really isn’t (or “doesn’t need to be,” seen as the same point to the empirical minded) some hyperspace that our space has to be “curved into”, it’s just a way of talking about what happens here. Hence you can imagine that space doesn’t really pucker around a mass, but rather that rulers shrink in the radial direction. Some writers literally phrase it that way. That effect would effectively seem to be space curvature (e.g., more rulers can be placed = more distance to travel, when going through the pucker versus around it, etc.) But even if curvature can be “simulated” by distorted rulers “on a flat space,”: don’t you need “real curvature” and not just the equivalent distortion on a flat surface, in order to get closed, finite volumes of space? (Otherwise, the mapping doesn’t work out does it?)
So as far as physics goes, in what sense is the “space” that holds how matter can move distinguished from the equally empty “space” that holds the first space? I know, there are quantum issues and maybe gravitons work differently, but we still can’t merely draw pictures of surfaces inside another “space” and think we’ve explained anything. Like I said, with mathematics you get to specify loci literally by saying so, but in a natural world there’s “something” that has to keep objects held inside a locus of points defined within a more bountiful (in whatever sense) “space”.
IOW, if there’s no difference in “kind” about space and its containing “hyperspace” then it’s just like trying to have water surfaces distinguished inside of water etc. – what makes the difference between them (unless you follow Tegmark’s modal realism.) So, what does that job? What keeps particles etc. penned in when there’s “more room” available in principle? (Please, no circular arguments or semantic tricks. And it isn’t just “metaphysics” to ask this, if a theory employs “spaces” as a physical constituent in any manner.)
Sean.
Did any time-travellers attend?
Hi,
Interesting presentation, sparked a blog entry for me: http://ysfk.blogspot.com/2008/09/beginning-of-universe.html
I always thought it would be more elegant for our Creator to create things by defining the process and setting the right preconditions to make sure they happen.
Time/Entropy = the Process
Regards,
Yusuf
The thing which distiguishes biological evolution from basic “change over time” is a selection mechanism. Genes can mutate or transpose with other genes, but whether the phenotypic expression works depends upon whether this is selected for or against. This exists because the Earth’s surface and environment is an open thermodynamic system. This is what permits the evolution of some line of species to greater complexity, given we can’t define complexity very well. However, humans, whales and magnolia trees are more complex than a bacillus. Yet in spite of our “complexity hubris we should bear in mind this planet is really in fact a bacteria planet, and even complex eukaryotic cells and complex organisms are in a way just associations of prokaryotes.
When it comes to the whole universe, we don’t know enough to make definative statements, and in fact time itself is something rather strange. In some way the universe emerged with a local definition of time from a vacuum state or configuration (false vacua etc) we don’t fully understand, by mechanisms (Higgs, inflatons, landscapes) we only have a cursory understanding of. In fact we are waiting for the LHC to give us our first data set on that second part.
Lawrence B. Crowell
Sean
You probably won’t read this, but I find it useful to document my thoughts were I can find them in the future.
I think that macroscopically, our future does look like our past.
When we stare off into the cosmos (into the past) at the extreme edges of our “hubble bubble” we see fewer objects that have large angular distances between them.
If instead, when I stared off into the cosmos, I was staring into the future, I would see fewer objects that have large angular distances between them.
If I lived in the universe where time was a small curled dimension, in that universe, the real past or future would be only a short “distance” from where I am at. The evolution of the universe would then depend on which direction I went around the circle (determining whether I was matter or antimatter) as well as how many times I went around the dimension (a parameter).
My perception of space would appear to be a superposition of states, ordered based on the relative number of times “distant” regions have traveled around the dimension.
If I imagine these states being side by side forming a tube, where time is motion around the tube, and space is down the length. Then either way I looked, I would see a superposition of continuously lower entropy states.
Time in this universe would be symmetric, since locally, time could be running backwards (and would look like a patch of antimatter), but that fact would not upset the global view from wherever I was.