Posts Tagged time travel

“An Epic Time Travel Romp,” says NY Times

Wednesday, November 3, 2010
Describe the plot of the next book you want to read, even if the book doesn’t exist yet.

I have actually been noodling with the following plot for a while, although I originally envisioned it in movie form.  Could be both!  Of course, those of you know who me or who have been reading along know I’m a sucker for a time travel story.  So that is of course the crux of the book I imagine: the protagonist is a time traveler.  The twist is, he (in my imagination, it’s me) doesn’t start the story that way!

I see the plot spanning two parts.  The first is where our hero is still mild-mannered, and finds himself descending quickly into a conspiracy plot but doesn’t know why, a la a Dan Brown novel, or maybe like, one of the Bourne series.  Extremely odd and improbable things happen around him, and he and his allies narrowly escape danger in situations where all of the dramatic build-up indicates it shouldn’t work that way.  Ideally, this phase of the book would be most akin to a mystery/thriller.

The second part begins with our hero capable of time travel.  I haven’t worked out *why* he begins to time travel – I imagine that at least part of the mystery of the first part is mundane/actual conspiracy in nature, and the culmination of that part of the action is heroic transformation into time traveler.  Perhaps it’s like a video game where there’s miniboss (local conspiracy) before big-boss (time traveling conspiracy).  The action in the second half of the book would be explaining what happened and taking on a sci fi/fantasy bent as the hero allies with past-himself (unknowingly) to take on the greater threat and explores the limits of his newfound powers.  Maybe even superhero-esque plot, at this point.

Anyway, that’s the book I’d like to read next.  Maybe I’ll have to write it myself.

p.s. spoilers

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Review: Vacuum Diagrams

When I made trips up and down the length of California, to visit home in Santa Cruz area while I went to school in Los Angeles area, I would sometimes stop at a highway convenience exit for food, bathroom, etc.  At one such stop, I ended up finding a Wendy’s and a bookstore within a gas station convenience store, and I picked up a collection of short stories called Vacuum Diagrams, by Stephen Baxter.  I really enjoyed reading them, having been hooked by the first couple of stories involving sentient creatures on an ice asteroid that had superfluid blood, and metamathematical nanobots as part of an experiment in quantum phenomena that ended up breaking free of the experiment to become grey goo.  I was in love with his universe.

Baxter writes hard sci fi, which is to say that he attempts to remain consistent to known or extrapolatable principles of science in his writing.  I eat this up because of my unique position as a former student of science and as a lover of high-tech fiction.  Vacuum Diagrams in particular is so great because it sketches out a cosmology and a wider universe around humans in the future through a number of interconnected short tales that are compelling on their own.  Not to spoil too much, but his primary conceit of an ancient elder race that’s kind of patronizing toward humans, and another ancient elder race of true aliens that (as a by product of their life cycle) are destroying the universe is really interesting to watch unfold over the course of (essentially) human’s future-history.

I recommend picking it up if (a) you enjoy seeing some of the weird parts of real science woven (faithfully) into fiction, and (b) you enjoy seeing a science-fiction world constructed from a series of stories that are each wonderful on their own.  Reading Vacuum Diagrams inspired me to pick up another one of his novels, Ring, which occurs in the same universe – it was okay, but not amazing – and I should see if Timelike Infinity, another in this universe, is any good.

Overall: A-
Number of Short Stories (Approx): 20
Secret to Ancient Elder Race’s Superiority: Time travel (obviously)

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The Kerr Metric

In the midst of a fun conversation about cosmological phenomena (and observability, and Objectivism, and the Rapture) with Zac and Erik today at lunch, I remembered some stuff about black holes and particularly rotating black holes doing something funky.  So, when I got back to a computer, I investigated – indeed, there is a phenomenon called frame dragging predicted by general relativity.  It’s kind of like the fact that space can rotate if enough mass is applied, because the massive object bends spacetime.  This has a peculiar effect on bodies in the vicinity of the rotating mass, and it is clearest from the rotating solution for a black hole, called the Kerr Metric after Roy Kerr, who found this particular solution to Einstein’s field equations.

So how do black holes work?  When an object is so massive that the structure of the object can’t resist the force of gravity causing it to implode, and if the mass is large enough, no force is sufficient to prevent its collapse to a singularity – a point in space, that’s like a rip in spacetime.  The region surrounding a singularity is bounded by an event horizon – within this region, light can’t escape the pull of gravity from the singularity.  But when the singularity is rotating (that is, the body that collapsed but had large angular momentum – rotational energy), it generates TWO horizons – the static event horizon, and the ergosphere, an ellipsoid region of frame dragging surrounding the spherical horizon of the singularity.

The ergosphere’s boundary is the point at which space is dragged around at the speed of light.  But in between that and the event horizon, space is being dragged at MORE than the speed of light – so all objects within that volume must co-rotate with the singularity.  They actually gain energy and can emit into the outside universe (since they are outside the event horizon), hence the name: ergo = work.  Incredibly crazy and cool, and only one of the crazy properties of the Kerr Metric solution: it can also allow for time travel (a closed timelike curve).

Anyway, I thought to myself, I should flex some real physics muscles and derive these results myself, but uh, I was unable to.  Just looking at the equations involved and the number of coordinate transforms being invoked makes my head spin.  Super cool though!

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Review: Hot Tub Time Machine

This movie made a promise.  A promise of hot tubs, and of time machines, and probably some relationship between the two.  And on that promise, it delivered.  I thought this movie was very enjoyable – the humor was a bit juvenile, but it did itself a great service by proclaiming right there in the title how ludicrous the premise was, and therefore had already groomed its audience for the right mindset.

I thought the actors did not really feel like they were comfortable as a group until a good way through the movie, but the sheer assholeness of Rob Corddry’s character helped that along quite a bit.  There were some great bits that utilized time travel in unexpected ways – lots of hilarity derived from things the group “knew” was supposed to happen, and then having that in-character expectation fulfilled/not fulfilled.  Their conception of time was just right for a clearly-comedy movie, and I was not disappointed at the end by how things were wrapped up.

If anything, what I would have changed about this movie would have been focusing less on the start and “return to the present” parts of the plot, and just do more with the humor of the situation of being back in the past.  Those parts were well-done, and considering the suspension of disbelief already necessary for us to accept the titular device, I think there could have been a little less mystical hot tub repair guy / whining about needing to “preserve the space-time continuum” (bah!) and a little more everything else.

Final grade: B+

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Time Travel 2

The mutable scenario is nice because it neatly sidesteps most paradoxes.  Time CAN change, in this scenario, and the resulting timeline is {past previous to the change} + {changed timeline that includes a time traveler}.  Of course, in order to understand what’s going on in the changed timeline, we have to consider (as Mark and I discussed the other day) the two unique constructions of mutable time: replacement, and multiply.

The replacement timeline is where the changed timeline just wholesale replaces the original timeline, past the change.  Any time travelers will still “remember” the old unchanged timeline if they lived through it, because their proper worldline (their path through time) – although loopy – is still internally consistent.  This is the first major divergence from the immutable construction, because in that world, there only ever was one timeline (talking of “alternate histories” is sort of meaningless in immutable time).

The multiply timeline is the one I am fond of: in this construction, each change to the timeline splits it in two, and the two resulting timelines are separate universes, A and B.  What is the change we’re talking about?  The introduction of a time traveler, of course!  This implies that a time traveler can’t ever “return” to the original timeline from which he or she originated, but one can assume that if the time traveler is going back and wreaking havoc changing things, going back isn’t foremost in the planning.

It is interesting how the multiply timeline shares traits with the Many Worlds theory of quantum mechanics: basically, that multiple-possibility states (Schroedinger’s Cat is both alive and dead inside the box) do not become one or the other via observation, but exist simultaneously in separate, noninteracting universes.  Observation merely tells the observer which of the many possible universes he or she is in.  The relationship between a quantum observer and a multiply-timeline time traveler feels weird to me: they clearly share properties, but the time traveler seems both more powerful (can move from one universe to another) and more constrained (can’t get into universes where time travelers aren’t).

Time travel is fun to think about.

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Time Travel 1

In this and future time travel posts, I’m going to “think out loud” (e.g. do exactly what I always do on this blog) about some possible ways in which time travel might work, were it possible, and resulting implications.

When I think about time travel, I consider two potential timeline scenarios – immutable and mutable.  In the immutable scenario, there is only one timeline – that is, One True Time.  Imagine I go back in time and kill someone (like, e.g., my grandfather).  Since there is only one timeline, it must be true that I didn’t change anything – it was always the case that I arrived at that moment in time and killed that person. “How is this possible,” one might ask, since killing my own grandfather would seem rather paradoxical.  Well, in One True Time, if I did actually kill someone, it can’t have been my actual grandfather – events will have seemed to have conspired to make that true.

This version of time is fatalistic, in a similar sense to the biomachine-free-will argument: although people believe that they are making meaningful choices, they are really just acting out the programming, which in this case is the way Time “ought to be”.  An interesting conundrum with this sort of timeline is — who determined what the fixed timeline looked like, once time travelers were added to the mix (or what, or why, or at least how)?  The term “closed causal loop” stems from this conundrum: events that seem fated to happen don’t really have a cause, since their cause and their effect become blurred.  If I find a time machine, deconstruct it and make detailed instructions on how to build one, go back and give the plans to an inventor, and that inventor creates a time machine and leaves it for me to find, who created the time machine?

Immutable time is tidy, but not particularly interesting to me.  It can make for very dramatic science fiction – since conflicts can easily be railroaded via time travel to terrible, tragic conclusions (or beautiful, “serendipitous” conclusions), it works quite well.  But in terms of usefulness, I think it falls short.  Just as I don’t like considering lack of free will, I also don’t like considering predetermination of events.  Although… I suppose it’s still an open question as to whether events are predetermined BEFORE time travel is possible!

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Time Travel 0

I am fascinated by time travel.  At its heart, time travel is about breaking the rule of commitment – normally, once you do something, you have committed the act and can’t undo it.  (You can sometimes change the facts by applying more action, but you can’t remove the action you have already taken.)  Time travel allows for risk-free action, since you can (potentially, depending on how exactly time travel works) take action and then later undo the action.

I think there are three things that drive me to interest in the possibility of time travel – the first is the allure of risk-free action, described above.  The second is the examination of the fundamental meaning of human experience – that is, normally we think of what a person has experienced as immutable, but time travel breaks that thinking.  And finally, it pushes the boundaries of science (often the fictional, hypothetical part) in a way that tickles my brain.

I said in my 25 things on Facebook (a meme from a while ago where people said 25 random things about themselves) that “I don’t believe humans will ever be able to time travel.”  Part of the reason I believe this is that I think our concept of human beings would need to shift considerably to still make sense with respect to a world in which time travel is possible and frequent.  The other part of the reason I’ll explain in Time Travel 2 (Multi-Stream Time Travel), so stay tuned!  One of my favorite game systems, Continuum, is a time-travel RPG that is an interesting (if flawed) study of a society of time travelers.  I wish more science fiction did that sort of treatment.

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