Mail Lists, Diffs, XPD

For anyone potentially reading, I’ve set up new mail lists for GovTrack and my Thunderbird SPF Extension. If you have an interest in either thing, please visit the site and join the list.

I’ve also posted a library for diffing/merging/patching written in C#, based on the Perl module Algorithm::Diff. And I posted the source for XPD, the XML pipline document generation engine that I wrote to power GovTrack. These things have helped me; I hope they help you.

GovTrack is now set up on a new server, and it’s much much more responsive than it used to be. In fact, you can’t tell anymore that it’s doing lots of XSLT transformations on each request.

GovTrack’s Insides

I wrote an article about how GovTrack’s website works on the inside. The summary is:

Websites have some of the same design issues as programs. One common issue is how to avoid duplication, but while software developers have solved this issue with functions, website developers are still struggling for a solution., my new website, solves this problem using XSL transformations and the Mono framework.

In the interests of full disclosure, I wrote the article just so it would be blogged on Monologue, which it was, so I’m happy. Thanks, Miguel!

How We Exist

While updating my homepage, I wrote down my thoughts on how it is that we exist…

I think I’ve solved the mystery of why we’re “here.” 🙂 Think of this as a casual theory about why we’re living in The Matrix.

Tree Falls in an Empty Forrest

The problem, to me, is that there is no one to observe our universe from the outside. If our universe is truly all alone, then our universe might as well not exist in the first place. This is similar to the tree falling in a forest with no one around to hear it. Did it make a sound? If you would answer the question by falling back on the physics of sound, separate for the moment the notion of sound and vibration. Think of sound as just the sensation we perceive when we’re hearing something. If no one perceives a vibration, then by my definition of sound arguendo, there couldn’t have been a sound. Sounds only exist in the ears of the perceiver, and without perceivers there can’t be sound. If a tree falls in a forest an no one is around to perceive the resulting vibrations, then no sound was created.

Of course, this only applies for this narrow definition of sound. But, maybe it applies to everything. That is, nothing exists unless someone observes it (or can potentially observe it). Call this “nothing unobservable exists.” Maybe it’s true, maybe it’s not. For the sake of curiosity, I’ll assume it is true.

For everything we know in our world, and many things we don’t, the “nothing unobservable exists” line has no consequences. Everything around us we’ve either observed, or it’s possible someone will in the future.

Some things in our universe are potentially unobservable (i.e. scientists aren’t certain that they are unobservable). For instance, the innards of black holes might be unobservable since light cannot escape from black holes to indicate their contents. If black hole innards are in fact unobservable, then do the innards exist at all? Since a person at the center of a black hole, though physically impossible, could observe the contents of the black hole, then the contents are potentially observable to someone, so they can exist. Maybe.

No one outside of the black hole can observe the contents of the black hole. The presence of an observer within the black hole is unknowable to anyone outside of it, so as far as anyone outside of the black hole is concerned, the contents of the black hole might as well not exist.

Maybe it doesn’t matter what people outside of the black hole think about whether the contents of the black hole exist. But, maybe it does. Maybe the existence line was too weak. Maybe it should be “nothing externally unobservable exists.” Call this the strong hypothesis. If no one outside of the black hole can observe the inside of the black hole, then nothing at all exists within the black hole.

Observers on Our Universe

Who can observe our universe? We can. But, we’re in our universe, so under the strong hypothesis, we don’t count. If that line is true, then someone outside of our universe must be able to observe us.

Between two people, A and B, there are four states of observability that can obtain. 1) A and B can (potentially) observe each other. 2) Neither can observe the other (ever). 3) A can (potentially) observe B, but B cannot possibly observe A. And, 4) the reverse. Which is the relation between A, someone outside of our universe that can observe our universe, and B, someone in our universe? (2) and (4) are immediately ruled out. It doesn’t seem it can be (1) because if A and B can observe each other, then they are in the same universe. What’s left is (3), which tells us that if we find an observer who satisfies the strong hypothesis, then we can’t observe him.

This all seems pretty contradictory. Given the strong hypothesis, then there must exist someone who can observe us but we can’t observe him. Actually, it seems pretty spiritual.

Emergent Universe

To solve the problem of the strong hypothesis, one could postulate a god of some sort that exists at a level of existence outside of our universe. But, that explanation begs the question of how the god could exist, since someone must observe him too, and also if the god is not in our universe, how is he able to observe it? A better solution explains how the observer exists and how he is able to observe our universe.

Here’s the gist of my answer: Our universe is embedded in another, Matrix-style. This is the philosophically-loaded explanation. It’s a lot of hand-waving and is hardly a solid thesis. I’ll expand on it in the future.

Assume physicalism. Assume consciousness is the result of the functional state of the universe. Suppose that a copy of the physical state of the universe also copies its functional state. Encode the physical state of the universe in a computer simulation running in another universe. Since the functional state of the universe is preserved, our simulated equivalents will feel just as conscious and alive as we do. To them, they are in a universe — our universe.

Our simulated equivalents and ourselves are indistinguishable, so let’s assume we are them. We are being simulated in another universe. Does this help us find an observer of our universe ourside of our universe?

Anyone who can observe the computer simulation is, in a way, observing us. The people running our simulation in our “parent” universe can observe the simulation, and thus can observe us. They are also in their universe, and not ours. They satisfy the requirement that our universe have an external observer, and the way they can observe our universe is explained.

Then there is the second question to be answered about how these observers can themselves exist. They, too, can be simulated. There might be another way for their universe to be externally observable, but being simulated is one possible explanation.


The strong hypothesis is that nothing externally unobservable can exist. That is, given a self-contained system of some sort, if the system cannot be observed from outside of the system, then the system cannot exist. If the strong hypothesis is true, and if we believe physicalism, then one way our own universe can exist is if our universe is based on a computer-style simulation running in another universe. Since we can never observe our “parent” universe, there are no real consequences to believing the strong hypothesis.

A blog!

A loooong time ago, Aliza suggested that I blog… well, here it is. There isn’t really anyone who would be interested in reading my blog regularly – for now – and I don’t even have much to say.

If I can get to be successful, I might post comments about it here so visitors can see what’s new on the site.

I might post my linguistics research/thoughts here… maybe other Penn people will read it.

I’m working on a few Mono/.NET projects (, including a virtual file system library, a file browser based on the library, and the Mono documentation tools. Once I get them all posted somewhere, I might write here about their progress.