4,519 reputation
11521
bio website vyznev.net
location Helsinki, Finland
age
visits member for 3 years, 1 month
seen 6 hours ago

I'm a PhD student in biomathematics, working on stochastic individual-based models of evolution in spatially structured populations. My other interests include cryptography, programming games and puzzles, photography and graphic design.

I started programming (in AmigaBASIC) when I was 10 years old. Nowadays, I'm most comfortable using Perl, C and JavaScript. I know Java and PHP too, but I can't really say I like them. I also know some Python, but not as much as I'd like.


CC-Zero Please consider any (original) code I post to Stack Overflow and other Stack Exchange sites to be released under CC-Zero unless stated otherwise. You may do whatever you want with it and don't have to credit me in any way, although of course that would be nice.


I'm the main author and maintainer of the Stack Overflow Unofficial Patch (SOUP), a user script for browsers with GreaseMonkey-compatible user script support (Firefox, Chrome, Opera, possibly Safari) that fixes or works around a number of outstanding issues with the Stack Exchange user interface.

I tend to answer a lot more questions than I ask. Some answers I'm rather proud of:


Jul
30
comment Why aren't units with powers, like cm³, surrounded by parentheses?
@supercat: The IEC binary prefixes exist precisely for that purpose. If you mean $16 \times 2^{20}$ bytes, write 16 MiB; if you mean $16 \times 10^{6}$ bytes, write 16 MB without the "i".
Jul
29
comment Why aren't units with powers, like cm³, surrounded by parentheses?
@supercat: According to the current ISO/IEC standard, $4\,{\rm kB/s}$ $=$ $4{,}000\,{\rm B/s} $ $\ne$ $4{,}096\,{\rm B/s}$ $=$ $4\,{\rm KiB/s}$.
Jun
6
comment Of all the electrical energy used in a home, is there any portion that won't eventually become thermal energy in the home?
@Klik: It goes outside. Usually mostly into the air, although some setups might also transfer heat into the ground.
Jun
2
comment Why don't two musical instruments sometimes generate destructive interference?
@user6972: Wait, what? How do you get "fundamental tone" from "first five harmonics bins"? Looking at the paper (e.g. Figure 2), it seems pretty clear that they're saying that most of the signal power is in the first five harmonic frequencies, i.e. from the fundamental to the fourth overtone; that's not the same as saying that the signal power would be concentrated in the fundamental frequency alone.
May
30
comment Power fit to some experimental data
NLLS is only (strictly) appropriate if your measurements have additive normally distributed errors. If the errors are mostly multiplicative and log-normal, you do want to use LLS in log space; if they're something more complicated, you either need more advanced methods, or you just pretend your errors are nice and normal / log-normal, even if they really aren't, and hope that your data is clean enough to still give you a decent fit. The real problem isn't so much finding the right fitting method, but that the right method depends on the error distribution, and you usually don't know that.
May
21
comment In the case of riding a bicycle, why can the system of the bicycle and rider be accelerated if no external net force?
@tpg2114: Trust me, a cyclist on a really smooth sheet of ice does accelerate. On average, downwards. Briefly. BTDT.
May
19
comment What will I see in this scenario? Will this be faster than the speed of light?
I'm going to have to give this a -1 as it stands. The answer in your last paragraph is correct, but you seem to have taken a pretty strange and convoluted route to get there.
May
18
comment How does light bend around my finger tip?
@Samuel: Depends on exactly what you mean by a "parallax effect"; even after reading your answer, that's still not 100% clear to me. The bending effect arises because the light from each point in the background arrives at the lens through multiple paths, some of which can be occluded by the foreground object, and because, with the lens not in focus, each of those paths generates a different part of the blurred image. That's a kind of a parallax effect, or at least something related, but not quite what I'd typically think of when speaking of parallax e.g. in photography.
May
8
comment How does light bend around my finger tip?
@MattWilko: Actually, that does not appear to be the case; the observed effect can be fully explained and reproduced by ray optics, with no need for diffraction or other wave effects.
May
8
comment How does light bend around my finger tip?
@BrianFunt: This does not actually seem all that surprising: the human eye has some chromatic aberration, which causes different colors to be in slightly different focus, and thus to experience the bending effect in different amounts. I suspect that photographing this effect would be easiest with a really low-quality camera lens with significant chromatic aberration; a good achromatic lens will defeat your efforts here.
May
7
comment Could a hard drive actually have been erased as described in Cryptonomicon?
@BrandonEnright: I thought so too, at first, but I rather doubt it. The thing is, even an alternating magnetic field still attracts ferromagnetic materials, since the ferromagnet's polarity simply tracks the external field. At least, this holds up to the point where the frequency gets too high for the magnetic domains in the ferromagnet to follow, but at that point the field also becomes an inefficient degausser (since flipping the magnetization in the disks is what you want to do).
May
7
comment How does light bend around my finger tip?
@Navin: Probably an hour or two of actual work (mostly playing around with POV-Ray and Inkscape, and later with with my camera, plus writing). If you count the total elapsed time from "you know, I think I could answer this" to the "finished product" (whatever it'll be), though, it's so far three days and running. (I'm still planning to summarize the discussion about nearsightedness that was here before the comments were cleaned up by the mods.)
May
4
comment How does light bend around my finger tip?
@Virtlink: I just did.
May
1
comment Could a hard drive actually have been erased as described in Cryptonomicon?
If the field strength is indeed "half of typical MRI scanners", the effects would be interesting indeed. As in, any police walking through that door would've likely had their badges, guns, belt buckles and any other ferromagnetic metal objects they were carrying (not to mention the hard drives themselves) violently ripped off and slammed against the door frame. There's a reason why they make really sure you don't bring anything metallic close to an active MRI scanner.
Apr
25
comment Is there no radioactive decay between nuclear fusion and solid material formation?
Your confusion is due to a misunderstanding of how nuclear decay works. See How does a half-life work? for what's essentially the question you should've asked.
Apr
20
comment Birds sitting on electric wires: potential difference between their feet
Having the bird spread its legs will (very slightly) increase both the current and the voltage through the bird (as one would intuitively expect), not decrease them: increasing $R_{wire}$ increases both $I_{bird} = I_{wire} \dfrac{R_{wire}}{R_{bird}}$ and $V_{bird} = V_{wire}$.
Apr
16
comment Does the mass of a star change as it collapses into a black hole?
@trysis: On the surface. And no, it doesn't account for the presence of the atmosphere, so it's not actually sufficient to escape the Earth's gravity if you're starting from the surface. (In fact, an object moving at 11.2 km/s or faster near the Earth's surface would most likely shortly turn into a ball of incandescent gas due to aerodynamic heating. To actually get into space from the Earth's surface, you need to start relatively slowly until you've cleared most of the atmosphere.)
Mar
29
comment Where does a string tighten when you pull it?
The behavior you describe is fairly typical if the string is lying on the ground, so that there's significant static friction resisting its movement. If the string is in free-fall, or, say, floating on/in water, things can be very different.
Mar
9
comment If I take a bottle of air into space, and open it, where does it go?
@XièJìléi: That just means you need a stronger balloon.
Mar
7
comment How does a half-life work?
Dammit, accepted. And just when I was this close to getting a Populist badge... ;-)