Author Archives: Marcus

Microsoft Project Lessons

Here are some tips for using MS Project in particular and project management in general that I picked up, which have either proven useful or which sound reasonable and which I plan to try out in the future. Feel free to add yours in the comments. Leave Buffers Since no project ever goes according to […]

Adventures in JavaScript: Number Bases

Here’s just a quick little JavaScript that will convert numbers between different bases. It grew out of the idea that numbers in a system based on π would be much more useful in engineering that the regular old ones. Well, just because one can do it doesn’t mean it’s a good idea, but it was […]

Adventures in JavaScript: Humidity

You thoroughly air out your rooms during winter time and watch the humidity inside drop in the process (provided you own a hygrometer). But where will it stop? This little gadget will tell you. Just enter the outside temperature and humidity and the temperature the air will be heated up to inside.   References [1] […]


The previous post on the Gaussian beam noted that this beam is a solution to the paraxial wave equation and thus only accurate for small divergence angles. The limit given in [1] was $w_0 \gt 2\lambda/\pi$ or $\theta \lt 0.5\mathrm{rad}$ or $\approx 29^\circ$. The Gaussian beam model is of course not exact up to that […]

the Gaussian beam (interactive)

The Gaussian beam “is a convenient, widespread model in laser optics.” [1] It is indeed convenient that such a mathematically relatively simple model can describe the evolution of laser light in free space so well. Given the wavelength of the laser, it can be described by a single parameter. This can be either the beam […]

TiddlyWiki – EditSectionPlugin Keyboard Shortcuts

Like so many of his plugins, Eric Shulman’s EditSectionPlugin for TiddlyWiki is quite awesome. Especially in long tiddlers it can save you a lot of scrolling and searching. One thing I was missing, though, were the keyboard shortcuts ESC to cancel editing and CTRL+ENTER to finish editing, like the ones you have when editing the […]

The Coupon (Sticker) Collector

Supermarket chain Edeka currently runs this sticker collecting racket – which used to be smurf collecting – where you get four stickers with animal pictures for every €10 spent. The kids are collecting like crazy, I am told, even though the pictures are mediocre at best. Anyway, as geeks we don’t care much about the […]

Summer of Code

Dabbling in JavaScript has been my new pasttime for the last few weeks. After a lot of poking in the dark trying to customize my TiddlyWiki, I thought that I could use my newfound JavaScript powers to make more useful stuff. So I sat down and wrote a bunch of scripts that add features to […]

shopping for a NAS

So I have this internal 500GB HDD drive that holds the backup for my personal data and photos and whatnot. Not only is it 98 percent full, but also very noisy, even when spinning idly. Since some Windows process always seems to access it regularly, it also never spins down. To get some peace of […]

the Doppler effect (relativistic)

Christian Doppler in 1942 predicted the Doppler effect for all kinds of waves, not only sound waves. The Doppler effect for light was demonstrated in 1948 by Fizeau. In conjunction with the article on the classical Doppler effect, as it occurs e.g. for sound waves, we will here examine the relativistic Doppler effect which is […]