5,143 reputation
11523
bio website vyznev.net
location Helsinki, Finland
age
visits member for 3 years, 5 months
seen 1 hour 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.


1d
revised Trying to show that the current is conserved
add \newcommand so the math will show up right even if viewed without the question
1d
revised Trying to show that the current is conserved
fix extra whitespace at top due to \newcommand
1d
comment If point is zero-dimensional, how can it form a finite one dimensional line?
It might help if you told us why, exactly, you find this counterintuitive. Otherwise, we'd just have to guess. (Also, could you please clarify what specific kind of process you're thinking of, when you speak of a point "forming a line"? My initial assumption would be that you're talking about how a point, moving continuously along a line, traces out that line -- but surely that should not be so hard to accept.)
Dec
17
revised Another condition of calculating work
more copyediting
Dec
17
reviewed Approve Another condition of calculating work
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
23
answered Force required to drive car
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
answered Why does correlation length diverge at the percolation threshold?
Nov
10
comment Why does correlation length diverge at the percolation threshold?
Related: physics.stackexchange.com/questions/59678/…
Nov
10
answered Solving Optics problem with and without differentiation result in different results
Nov
10
revised Solving Optics problem with and without differentiation result in different results
add missing line break
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.
Nov
5
revised Do the probability density and the probability current density have a unit
added 3099 characters in body
Nov
5
answered Do the probability density and the probability current density have a unit