Nonobvious DNS record details (MX and CNAME): Add the trailing dot!

It's probably common that you have mail server hosting external to your main web server. In my case, I'm using a free email account from GoDaddy while hosting my site at alwaysdata, a very Django-friendly (via FastCGI) host in France.

I changed my DNS records to point to alwaysdata, which broke my mail record connection to GoDaddy. So I edited the MX and CNAME records as follows:

Type	Hostname	Value
CNAME	mail	pop.secureserver.net
CNAME	email	email.secureserver.net
MX	mailstore1	10 mailstore1.secureserver.net
MX	smtp	0 smtp.where.secureserver.net

This didn't work, though. No CNAME redirects, no MX pass-throughs. A little more research uncovered the nonobvious:

DNS domain names need a trailing dot!

(e.g., pop.secureserver.net.)

Configuring Apache 2.0.55 (ppc) with mod_python and Django - Part 1

The first of many in getting my Apache installation online. I just purchased the domains jaywhy.info and jaxwhy.info. I'm using mod_python to get Django online. The home directory is throwing a 500 server error, with the following in /var/log/apache2/error.log:

[Sat Nov 29 22:10:05 2008] [error] [client 192.168.xx.xx] PythonHandler

django.core.handlers.modpython: ExtractionError: Can't extract file(s) to egg cache

The following error occurred while trying to extract file(s) to the Python egg\ncache:

[Errno 13] Permission denied: '/var/www/.python-eggs/MySQL_python-1.2.2-py2.4-linux-ppc.egg-tmp'

The Python egg cache directory is currently set to:

/var/www/.python-eggs

Perhaps your account does not have write access to this directory? You can
change the cache directory by setting the PYTHON_EGG_CACHE environment
variable to point to an accessible directory.

A brief look-see showed that the Apache user ('nobody', by default) doesn't have access to this low-level directory while attempting to unzip the egg. Use this link to create 'apache' users and groups (and other useful security tips) and add the following to the top of your apache.conf:

User apache
Group apache

My efforts here petered out and I was back to school with a very thorough Apache/mod_python/Django intallation tutorial and Django's golden documentation and the end of the Django book.

Zeno's Paradoxes: Part 3

This installment concludes the series on Zeno's paradoxes (see Part 1 and Part 2).

The Arrow Paradox

This paradox investigates the motion of an arrow, and prior to the previous two paradoxes, focuses on the divisibility of time as an argument against motion. Again, Aristotle analyzed the validity of Zeno's reasoning in Physics, VI.9.

The Story

Say an arrow is in flight in midair. As is characteristic from human observation, divide time into a rapid succession of static moments (think of a flipbook, e.g.). Now zoom in on a given moment, representing the present. In this state, the arrow is motionless, traveling no distance. Assuming every point in the past and future passes through this 'present' state, we're left with a series of static arrows, preventing it from ever being in motion.

The Implications

Motion itself is an illusion, being physically impossible. But of course we have the sensation of traversing distance, leading to yet another paradox.

Proposed Solution

This paradox, like the others, relies on linear assumptions about the time-space continuum, as well as its infinite divisibility. This seems very Newtonian. Luckily, twentieth century physics seems to have provided us with some tools to address these apparent inconsistencies. Einstein's general relativity introduced us to the notion of wormholes, where one doesn't necessarily have to travel through every continuous point in space and time. Likewise, quantum mechanics is able to place a limit on the divisibility of space and time. The so-called Planck length and Planck time are defined as 1.62×10^-35 m and 5.39×10^-44 s, respectively. Providing a bound on physical values leads to another limit: the ratio of the Planck-length to Planck-time is the definition of the speed of light in a vacuum, the upper bound for motion.

Zeno's Paradoxes: Part 2

This continues the series on Zeno's paradoxes, starting with Part 1, which covered Achilles and the tortoise. More at Part 3.

Dichotomy Paradox

This post covers the so-called Dichotomy Paradox, which (obviously) relies on dichotomy, the division of an entity into two mutually exclusive objects. Aristotle commented on this paradox's ramifications in Physics, VI.9.

The Story

Say you want to walk the nominal distance of 1 meter. Using logic based on space as a continuum, you must first reach the halfway point, or 0.5 m. Extending this argument backwards towards your starting point, you are faced with a dilemma. Before you reach 0.5 m, you must arrive at 0.25 m, which requires going 0.125 m, and 0.0625 m, and 0.03125 m, ad infinitum, ad nauseum. The challenge is not the magnitude of distance required for you to travel (for it is quite small, indeed, infinitely small), but the undefined nature of how to start. For every distance you decide to travel, you must first travel half that distance, so in principle, you have an infinite number of tasks to complete before you can even start.

The Implications

You cannot even begin to move! This, of course, fits nicely with Parmenides notion that all matter is fused into one entity, negating the existence of separate objects, let alone the possibility of motion. Zeno's paradoxes were devised to support Parmenides, which emphasizes the importance of full disclosure in so-called objective inquiries.

Zeno's Paradoxes: Part 1

While reading Wired's article on free products as the emergent business model (which I covered here), I ran across an intriguing quotation:

What's interesting is that transistors (or storage, or bandwidth) don't have to be completely free to invoke this effect. At a certain point, they're cheap enough to be safely disregarded. The Greek philosopher Zeno wrestled with this concept in a slightly different context. In Zeno's dichotomy paradox, you run toward a wall. As you run, you halve the distance to the wall, then halve it again, and so on. But if you continue to subdivide space forever, how can you ever actually reach the wall? (The answer is that you can't: Once you're within a few nanometers, atomic repulsion forces become too strong for you to get any closer.)

I'd like to elucidate Zeno's paradoxes, as well as some of modernity's proposed solutions.

Achilles and the Tortoise

The impetus for Zeno's paradoxes was to shore up one Parmenides' notion of material unity, requiring motion to be merely an illusion. This is Zeno's most famous paradox, appearing in Aristotle's Physics, VI.9.

The Story

Achilles and the (ubiquitously proverbial) tortoise agree to a footrace. Achilles, being the swift demigod warrior, agrees to give the slower tortoise a head start. *Bang!*, the tortoise is off at a constant pace. Say he gains 20 meters before Achilles begins at a more rapid, but constant, rate. Zeno argues that before Achilles passes the tortoise, he must first arrive at a point where the tortoise was previously. The race continues.

The Implications

By Zeno's logic, Achilles will never be able to catch the tortoise, because in the time it takes to reach one of tortoise's prior locations, the tortoise will be able to advance a finite distance, albeit increasingly infinitesimal. However, we have all observed faster objects overtake slower ones. Thus the paradox, and the dilemma over the true nature of motion.

More: Part 2 | Part 3

Obama: The Unregulated Democrat

It's nice to see a not-so-partisan partisan! At least he's able to approach a topic objectively, even if it means not walking the party line.

To quote Senator Obama:

I think that back in the '60s and '70s a lot of the way we regulated industry was top-down command and control, we're going to tell businesses exactly how to do things.

And you know, I think that the Republican Party and people who thought about the markets came up with the notion that, "You know what? If you simply set some guidelines, some rules and incentives, for businesses—let them figure out how they're going to, for example, reduce pollution," and a cap and trade system, for example is a smarter way of doing it, controlling pollution, than dictating every single rule that a company has to abide by, which creates a lot of bureaucracy and red tape and oftentimes is less efficient.

The New (Old) Business Model: Free!

Wired magazine has put forth another trendy, forward thinking assessment of technology's impact on our world. Entitled "Free! Why $0.00 Is the Future of Business", its thesis seems evident.

Some prominent examples of how free products generate business:

• Television and radio: the programs are free, while the advertisements generate revenue
  
• Linux: the software is free, while corporate-level support generates revenue
  
• Google: everything is free and top-notch, while it retains a choke-hold on internet advertising. They saw this quarter's profits rise 30% over last year.

The article elucidates six individual business models based around a free product:

1. "Freemium"
   
2. Advertising
   
3. Cross-subsidies
   
4. Zero marginal cost
   
5. Labor exchange
   
6. Gift economy

This new thinking is the epitome of the notion that too firm a grip inevitably results in things slipping through your fingers.