5,780 reputation
11624
bio website vyznev.net
location Helsinki, Finland
age 35
visits member for 4 years, 1 month
seen 53 mins 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'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:

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.


Aug
17
comment What does it mean if a = g in this situation?
Alas, it looks like ImageShack has deleted your image, and replaced it with an ad banner. If you can, please reupload the image (or something equivalent) using the image upload button in the editor toolbar (which will upload it to Stack Exchange's imgur account).
Aug
13
comment Can a Skydiver Land On a Large Slide and Survive?
See also: ski jumping.
Aug
2
comment What is the smallest distance possible between two stars?
en.wikipedia.org/wiki/Contact_binary
Jul
30
comment Conical train wheels
Also, I'm pretty sure the center-of-mass argument is backwards. It really doesn't matter whether the CoM moves left or right; what matters for stability is whether it moves up or down, and that's not so obvious from the geometry. (In particular, it depends on the curvature of the wheel surfaces, not just on their slope.) But, of course, the wheel radius effect described by @Kyle probably dominates this anyway.
Apr
29
comment Does a truck stop faster if the stack on the back of truck is stable or if it moves forward?
Short answer: If the stack slides, the truck will stop faster, but the stack will stop slower. Depending on what the stack consist of, that may or may not be desirable.
Apr
24
comment Paradox in applying Newton's second law
Why the hidden spoilers?
Apr
1
comment Why doesn't light affect a compass?
Technically, light does cause (bits of) the needle (mostly, the electrons) to wiggle at around 400-800 THz, which is why we can see it in the first place. If it didn't interact with visible light at all, it would be totally transparent.
Mar
2
comment Why doesn't a cigarette lighter generate thrust?
The combustion will also generate some minimal thrust, since it will heat the gas, causing it to expand, and some of that expanding gas will push against the lighter. Still, the combustion geometry is very poor (and the amount of fuel minimal anyway), so you won't get much thrust out of it.
Jan
21
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@MarkEichenlaub: The scrambled cube has about $2^{65}$ possible states; the solved one has only one. On the microscopic level, physics is reversible, so when the cube is solved, the information needed to reverse the solution and reconstruct the original scrambled state from the solved one must go somewhere. That means it either has to be stored in some part of the system, or emitted from it (as heat).
Jan
6
comment What does 1714 mean in hydraulics?
@imallett: If you consider radians dimensionless, then degrees are also dimensionless, with the conversion factor $1\text{ degree} = \frac{\pi}{180} \approx 0.0174533$.
Jan
3
comment Why are porcelain teeth strong?
@Jez: If you hit your teeth "even lightly with a hammer", you'll probably break some or knock them off. (Note: Please do not attempt to test this.)
Dec
13
comment How would night sky look like if the speed of light was infinite?
Do you also believe that it is infinite in spatial extent (which, combined with finite mass and non-zero local density, necessarily implies non-homogeneity)? If not, you'll still get the same problem, since an infinitely fast light ray can wrap arbitrarily many times around a finite universe before hitting a target. Thus, no matter which way you looked in such a universe, you should see something other than empty space, whether it be a star, a gas cloud, a planet, or the back of your own head.
Dec
12
comment How would night sky look like if the speed of light was infinite?
What about Olbers' paradox, as noted by Chris White? With infinite $c$, the observable radius should also be infinite. (If the universe itself is finite, this would just mean that we could observe infinitely many images of it, as light rays wrapped around the universe.) If the universe is also homogeneous at large scales (or, as noted above, finite) and contains stars, we should be able to look in any direction and eventually see the surface of a star (or some other opaque object, which, by the same argument, should also be bathed in starlight and thus heated to incandescence).
Dec
7
comment Gravity is curved geometry: A fact of nature or model-dependent interpretation?
Arguably, the existence of space (and time), curved or not, is itself a "model-dependent interpretation", at least as much as its curvature is.
Nov
13
comment Why does an atom remain uncharged after emission of an alpha particle?
@ratchetfreak: In fact, that is where most of the helium on Earth comes from. That party balloon you bought is filled with the decay products of unstable nuclei.
Nov
13
comment Have we proven that higher dimensions exist?
Hmm, I can think of plenty of meaningful and non-trivial physics theories of the form "X exists", where X is, say, any hypothesized object, particle, interaction or state, and these are, in fact, frequently confirmed by observations (to a varying degree, depending on the reliability and unambiguity of the observations). For instance, the existence of atomic nuclei was pretty directly confirmed by the Rutherford gold foil experiment. Going a bit further afield, there are plenty of examples in, say, chemistry or astronomy (which, if not considered physics as such, are at least very close).
Nov
13
comment Have we proven that higher dimensions exist?
While trying not to get all epistemological here, I should note that theories of the form "an X exists" can, in fact, be experimentally proven true by directly observing an X. In fact, such existential statements can never be experimentally proven false, since it's always possible that an X exists but we just haven't found it yet. (Of course, technically, we can never be 100% sure that our observations of an X are correct, either, but sometimes the evidence can be fairly overwhelming. For example, I'm pretty sure that computers exist, because I'm typing this comment on one.)
Nov
13
comment Solving Optics problem with and without differentiation result in different results
Completely unrelated, but I just noticed that the lens outline in your image is just slightly wobbly. Was this maybe scanned and vector-traced from a printed version, or did someone actually draw that lens by hand? o_O
Nov
10
comment Why does correlation length diverge at the percolation threshold?
Related: physics.stackexchange.com/questions/59678/…
Nov
5
comment Do the probability density and the probability current density have a unit
By "(probability) current density", I assume the OP was referring to (probability) flux, which would have units of base quantity per "area" (= surface of a "volume") per time. Of course, $A/m^2 = C/m^2/s$ is a unit of (electric charge) flux, the 1/time part is just hidden inside the definition of the ampere.