# the universal tree thing

This cosmology rests on a metaphor of time as an extra spatial dimension. If you have never been exposed to the idea of higher spatial dimensions, explained using the analogy of a 2-dimensional creature picked up into a 3-d world, you should read more books. Edward Abbott gets credit for originating the analogy with his book Flatland, published 1884. (http://www.alcyone.com/max/lit/flatland/).

That it is useful and valid to think of time as an extra spatial dimension has not been disputable since Einstein. In case you aren’t sure what Einstein said, here is my one paragraph summary of special relativity based on algebra: We have the equation Speed = Distance/Time; every kid learns this in grade-school. Einstein showed that only the left side of the equation (the speed of light) is a constant, and that the things on the right side, including the units of measurement, are variables which we can play around with as long as the relation works out the same. The top and bottom of a ratio can both be multiplied by two or divided by miles-per-hour without changing the equality; if we multiply the ratio by certain things it might simplify the denominator while making the numerator more complicated, or if we’re clever we might find a divisor that simplifies both. The important point is that we end up having to treat them together, to deal with space and time as inseparable.

And that’s how we get the idea of space-time, space and time pushed into a single concept in a way that completely confuses our intuition about both. Mathematicians and physicists are still working out all of the implications of the merger, but the rest of us needn’t concern ourselves with the details. The big picture is that there’s another way of looking at space and time that is just as valid as our intuitive way of looking at them (many of the most important inventions of the last 50 years are based on the new way of looking), and which treats them (space and time) as basically the same kind of thing.

Now think about the way we experience space and time. From the perspective of our lived experience, space and time are completely different kinds of things. Space is like a field, far larger than ourselves, in which we can move around more or less at will. Time, on the other hand, is like a tiny capsule in which we are carried along whether we want to be or not. We are not free to move about in time the way we can in space. Wise people are always telling us to embrace that constraint, to “live in the moment,” which really means to stop daydreaming about what life would be like if we could escape the present.

The view of the universe I’m about to describe is one of those daydreams. Not a daydream about being locked in a different moment in the past or future, but about being able to move freely through moments and perceive all of time in a way similar to the way we perceive space.

In this moment, that is, in this cross section of four dimensional space-time, you look like a person sitting in a chair looking at a computer screen. In another cross section you will look like a person laying in a bed. Now imagine that you can experience time as a continuous field, just the same way you experience space. Imagine that you can see all the moments, all the cross-sections of time, that lead you from the chair to the bed.

The first thing you would notice is that those moments are connected without any discontinuity. Between the time you sat in the chair and the time you laid in the bed you were moving around in space-time without any breaks, without ever disappearing and reappearing again. You would look like a long, human shaped tube, colored pink or brown or whatever color you are. If you could see that whole tube all at once, the whole curve of your life, it would follow an amazingly complicated path full of spirals (where you kept leaving and returning to the same place), sudden jags (where you traveled a distance quickly), and straight sections (where you stayed in the same place for a while, your only motion through the time dimension). If you followed your tube all the way to its beginning, you would find that it grows smaller and smaller until it meets up with another tube from which it first emerged, like a branch from a tree. That other tube is your mother. If you follow her tube just a little way back you’ll see it bumping up against another tube. That’s your dad.

In this way all of humanity is connected like a big, crazy tree. Billions of little human-tubes which travel along singly and in groups and join together and branch apart and spin and weave and spiral around each other in a shape more complicated than anything we can imagine in just 3-dimensions. But the shape is still basically a tree. It branches; that is basic character. It bifurcates through time, so that if we trace the tendrils backwards through human history and prehistory we would see them fuse together and become less numerous the farther back we went. We would also see that the branches are different as we move back in time, or rather, we would notice that the average branch at one time is different from the average branch at another time. If we kept tracing the branches of the human tree backwards in time, at a certain point there would be a relatively small number (tens or hundreds of thousands, perhaps) of them that looked significantly different from the (6 billion) branches at the end. They would look different enough that we would say we are no longer looking at humans, but at Australopithecines.

And if we traced those branches back we would find them fusing and changing again into yet other species, which occasionally send different branches forward in time all the way to the present. In fact, now that we have got to the idea of other species, we should reexamine the tree in the present and notice that the tree of humanity is actually coexistent in space with thousands of other species-trees (really branches of the same tree), some of which look quite different from our own. Some of those trees (the plant species) appear to be discontinuous until we look very closely and see that each branch (each organism) really is connected to another before it, if only by a tiny seed. If we look still closer we would see another class of organism (bacteria) which are really densely interconnected, branching and merging again, and sharing little bits of themselves without having to branch or die (Bacteria stretch the tree metaphor. They are more like a densely connected graph. In computer science, a tree is a special case of a graph, which is just a data structure composed of nodes and branches.). And all those species-trees interact in complicated ways. Human-branches gobble up cow-branches. The bacteria-tree grows in and around the human-tree like dense webbing.

It’s interesting to notice that by thinking about time this way we can continue going backwards right to the very beginning and it’s trees all the way down. All of the life that we’ve been talking about so far is happening on the surface of the Earth, but the Earth wasn’t always here. All of the matter in our solar system came from somewhere else, and all of that matter came from yet another place, until we get back to the big bang. So, all of the objects in the universe, which our human, time-locked perceptions interpret to be discrete, become parts of one big tree from the perspective of this four-dimensional space-time view. All the life on Earth is just like a moss covering the tip of one branch of the universal tree-thing.

I think this is a wonderful view of the universe. It comes from my friend Isaiah and I have only elaborated on it a little bit here. Isaiah, if you read this would you add something in a comment? This whole conversation happened because we saw a bum sleeping by the river and I said that made me sad and you said you weren’t bothered but I can’t remember the connection between that and this well enough to write it down.

One thing that occurs to me to wonder is whether observations about the topology of the tree might lead anywhere useful. For example, consider the way the topology of the human-tree has changed with urbanism. These days there are sky-scrapers full of cubicles which fill up with people every day. This is like thousands of branches coming together in a 3-d grid, traveling in parallel through time for 8 hours, dispersing into a big knot at night, and repeating it the next day. Clearly there are things we already know about that kind of structure (that it is weak against an attack like 9/11, for example), but what I’m curious about is whether observations about the structures (topology) we see today, or about trends in the way the topology is changing, might lead to predictions about what the whole tree will look like in the future.

-2005