## Oh, god I hate PDF for on-screen viewing

Honestly, I don’t understand how somebody can prefer PDF to HTML for on-screen viewing. Really? That is possible? If you’re one of them, can you help me understand?

## Increased surveillance is considered a positive by many? Yikes…

Here in Denmark, we’ve just had an election, and the previous government has been replaced.

A newspaper article [lang="da"] looks back at what people liked and disliked about what the previous government did.

I have trouble believing, much less understanding, that 68% consider increased surveillance to have had a positive effect for Denmark, 16% believe the effect to be neutral and 16% believe it to be negative.

Wow. The people who believe that our society is better off when the government monitors us more out numbers people like me 4 to 1? Yikes. Has nobody read 1984 or seen Das Leben der Anderen? Doesn’t anybody remember DDR or the Soviet Union? Perhaps China will open source the great firewall too, so we can install it here!

Edit on 2011-10-20. Oh no, it keeps getting worse [lang="da"].

## NSA Open Sources an internally developed project

This is a big deal (at least in my book) because it demonstrates that the NSA does not believe in security by obscurity.

## 34 Cleverly Designed Inventions

Really cool list of 34 Cleverly Designed Inventions. I especially liked the USB connector, the stair case drawers, and the crawling lamp on the wall.

Thanks to the Userfocus Usability Newsletter for the link. The site also has lovely 32 Pictures To Help You Appreciate The Awesomeness Of Nature but I better let you go now .

## How much do we trust posts on website forums?

A Danish Minister approves an ad-agency to pose as real users and stuff a forum with bogus posts to kick-start it. I’m appalled, surprised at my own ignorance and worried about the lack of credibility of even government-funded sites. Continue reading ‘How much do we trust posts on website forums?’ »

## Natural Sort

Why doesn’t every programming language have “Natural Sorting” built in, out of the box? Natural sorting is the way humans sort, where number substrings are sorted numerically, everything else alphabetically:

Sorted “Asciibetically” (normal computer sort) Sorted “Naturally” (what humans prefer)
foo1bar
foo10bar
foo2bar
foo1bar
foo2bar
foo10bar

Notice how 10 comes before 2 in asciibetical “normal computer sorting” ? Haven’t we all seen user interfaces that like that? Its just plain wrong.

Dave Koelle’s Alphanum Algorithm sorts naturally, but instead of analyzing each array element O(log(N)) times, I present a modified Perl version that allows for Schwartzian transforms, yielding huge performance improvements.

## Refresh your browser automatically during web development

Did you ever find that while editing files for the web (e.g. HTML, Javascript, Java/Flash/Ruby, whatever) that it would be cool to have your browser reflect any changes as soon as you hit Save in your IDE without having to Alt-Tab to the browser and hit refresh (Ctrl-R)? That way, you could stay entirely in your browser and just move your eyes to the browser as it refreshes automatically showing you the results of your newest changes.

Well, now you can! I’ve developed a pair of tools for that allow this when used in concert. Both are Open Source, of course.

## Forwarding SNMP ports over SSH using socat

Here is an example of the problem we need to solve: We have SSH access to a network, but want to access an SNMP agent in that network from a local client. We use SNMP here in this example, but it could be any other protocol that uses UDP, such as DNS or TFTP.

We’ll forward the SNMP traffic in a TCP port like this, with “socat” doing the UDP-in-TCP tunneling:

## Subversion: Setting the repository path for svn+ssh://server/repos

For some reason, it doesn’t seem to be possible to set up a path for your repository when using subversion as: svn+ssh://server/repos out of the box. So you end up having to specify svn+ssh://server/some/path/repos.

But it really isn’t that hard to do. Here is how I do it. Beware that you’re going to be making system-wide changes to how svnserve operates. The basic idea is to replace svnserve with our own version, that calls the original one with a -r parameter.

## Classical Mechanics: Why does Power depend on frame of reference?

Imagine we’re in a rocket.

We have an imaginary engine, that provides a constant amount of thrust. How much power does such an engine provide? In essence the power depends linearly on the velocity:

$\\ P = \frac{dW}{dt} \wedge W = \int F \cdot ds \Leftrightarrow \\ P = F \cdot \frac{ds}{dt} \Leftrightarrow \\ P = F \cdot v$

And the velocity depends (by definition) on the frame of reference.

So imagine that we started from a planet a while back. Our thrust is constant (remember?) so our acceleration is constant, and so velocity grows linearly.

Does that make sense?

If this was a classical rocket engine (and we can somehow neglect that our rocket looses mass), then the Power would continue to grow. At some point, the power will exceed the power present in the fuel (power = energy/time). That doesn’t make sense to me.

Also, lets say we hook up with another rocket that has the same velocity as us. After having drinks and dinner together, we start up our engine and head off. Depending on our frame of reference, we either have enormous power (if we keep our original frame of reference – the planet we started from) or very little power (if we use the other rocket as a frame of reference). That also makes no sense.

Our assumption was that we have an imaginary engine that provides a constant amount of thrust. When faced with conclusions that make no sense, it is customary to question the assumptions. Our imaginary engine.

So, have I then proved that it is impossible to create such an imaginary engine? Really?

Related to the above, we have the definition of kinetic energy:

$E_{kin} = \frac{1}{2} \cdot m \cdot v^{2 }$

Here again, we have that the energy depends on the frame of reference. Energy seems such a crucial cornerstone of physics, that I don’t understand how it can depend on the frame of reference. When e.g. the energy content of fuel or batteries or whatever are absolutes values.

I’ve been toying with this for years, never taking it seriously, but I am perplexed. I was just trying to explore the characteristics that such an imaginary engine would have and I don’t know what to make of it. Do you?