Sunday, July 13, 2008

The Spacetime Tree

A direct link to the above video is at

Last blog we looked at the annotated version of the Imagining the Tenth Dimension video, which provides a running commentary introducing ideas from the website and the book to people who are already familiar with the original animation. This time, let's continue with a discussion of some of the basic ideas that stem from this way of visualizing reality.

The "spacetime tree" is a phrase that was first introduced to me by visitors to the Imagining the Tenth Dimension forum. I like this phrase because it immediately evokes a useful image of what the Many Worlds Interpretation tells us about our reality - that from this particular "now" there is not just one line of time. Rather, there is a bush-like branching structure of possible outcomes, and this has been confirmed by Anton Zeilinger and his team in Vienna as being more than just thought experiment: amazingly, this means that Schrödinger's cat really is simultaneously alive and dead until one state or the other is observed. The fact that the David Deutsch team at Oxford published a proof equating this at both the quantum and macro levels does indeed seem to put Everett's idea of a wave function that exists outside of time and space, and which we are merely "observing" rather than "collapsing" on a very solid footing.

In a blog entry called Time in Either Direction, I talked about Sean Carroll's ideas of an equilibrium state that exists outside of time and space, and how the entropy-derived line of branching choices that create what we experience as "time" is only one of the possible directions for a universe to be viewed. Thinking of the trunk, limbs, branches, and twigs of a spacetime tree gives us another way to visualize this - and also shows us how the move from the highly ordered "base" of the tree trunk to the many branches is equivalent to the universe we live in, where eggs do not unscramble themselves and broken mirrors do not reassemble: once you have moved out to a branch, you are no longer on the trunk, and so on. Here is a freaky-looking video blog of "Time in Either Direction":

A direct link to this video is at

The spacetime tree is also a useful phrase because it immediately puts one in the mindset of thinking in a more timeless mode, where all possibilities exist simultaneously. In a blog entry called Anime, Gaming, and Cusps I used the metaphor of the branching scenarios of video games as a starting point for imagining the many branches of our spacetime tree, which we would be able to see if we could somehow move our observation out to this timeless perspective. Here is a video blog entry of that discussion:

A direct link to this video is at

Finally, one of the assumptions that I make in this project is that the fourth dimension has (as Sean Carroll also says) two directions, one of which is time as we know it, and the other which would be the time-reversal version of that fourth dimension. If our spacetime tree was one single trunk from beginning to end that would be the end of the story, but since we now have scientific evidence that the branches do exist, the fifth dimension is where I place the spacetime tree for our particular universe as it exists in our current "now", and the sixth dimension is where I place the other spacetime trees which are logically/probabilistically incompatible with our current "now". In both cases I am using the moral/probabilistic branches created by chance and choice as ways to describe the extra dimensions, and some will insist that because of this I'm not talking about spatial dimensions, I'm talking about temporal dimensions. In Hypercubes and Plato's Cave, I made what I believe to be a convincing argument for why our experience of the extra spatial dimensions can be incorporated into a temporal model, because ultimately we are 3D creatures moving on a 4D line, and because of that our ability to perceive any of the extra dimensions requires us to acknowledge the spatial nature of time: without time, we 3D creatures are stuck in one single frame of our universe with no way to witness or experience the fourth dimension and above. Here is a video blog of that discussion:

A direct link to this video is at

The spacetime tree for our particular universe, then, at this particular moment, is in the fifth dimension. The spacetime tree for some other version of our universe, then, like the one where it's 2008 and gas is free, is inaccessible to our spacetime tree unless we move through the sixth dimension to get there. The logic of such reasoning is consistent with the general idea of dimensions - each dimension that we add gives us a way to get to states that were unavailable from the dimension we were in, and that is consistent with the most basic definition of the word "dimensions" that is commonly used.

Enjoy the journey!

Rob Bryanton

Related Links:
The Annotated Tenth Dimension Video
What Would a Linelander Really See?
How to Make a Universe
The Omniverse

Next: Dark Energy, Linelanders, and the LHC

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