2,865 reputation
1119
bio website vyznev.net
location Helsinki, Finland
age
visits member for 2 years, 9 months
seen 21 hours ago

I like programming in Perl and C. I know Java and PHP too (I'm a MediaWiki developer), but I can't really say I like them. I keep meaning to learn Python some day, but never seem to get around to it.

I'm working on a Ph.D. in biomathematics. I also like programming puzzles and cryptography.

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.


May
1
comment Why are expressions such as $\operatorname{ln}T$ used in thermodynamics where $T$ is not dimensionless?
Almost duplicate: physics.stackexchange.com/questions/13060/…
Apr
30
comment Does the unit of a quantity change if you take square root of it?
Yes. If the unit of $m$ is $\rm kg$, then the correct unit of $\sqrt m$ is $\rm kg^{\frac12}$. That's simply a fact, not a matter of choice.
Apr
30
revised Does the unit of a quantity change if you take square root of it?
added 274 characters in body
Apr
30
answered Does the unit of a quantity change if you take square root of it?
Apr
23
comment Can vorticity be destroyed?
It sounds like you've answered your own question. What, exactly, would you still like clarified?
Apr
21
answered Is it possible that 5 planets can revolve around a single star in a single orbit?
Apr
21
comment Two planets in same orbit - not planets?
Ps. No on-line discussion of co-orbital satellites would be complete without a link to Bob Jenkins's Java applets. In particular, the "tag-team orbit" examples near the bottom of the page model pretty much this situation.
Apr
21
revised Two planets in same orbit - not planets?
added 84 characters in body
Apr
21
comment Two planets in same orbit - not planets?
I'd consider Janus and Epimetheus to be a much better example; see my answer below.
Apr
21
answered Two planets in same orbit - not planets?
Apr
1
revised Why doesn't fusion contradict the 1st law of thermodynamics?
texify E=mc^2, correct what seems to be a typo ("is" -> "it") and expand ("it" -> "the question")
Apr
1
suggested suggested edit on Why doesn't fusion contradict the 1st law of thermodynamics?
Mar
31
awarded  Nice Answer
Mar
31
comment Is Feynman's explanation of how the moon stays in orbit wrong?
@mtanti: The tangential velocity stays constant, as you can see from the picture. As for why $v_1$ should depend on $a_1$, remember that the acceleration vector is changing continuously from $a_0$ to $a_1$ as the moon moves from $x_0$ to $x_1$. Taking the mean of $a_0$ and $a_1$ in the approximate formula for $v_1$ is just a linear approximation of this gradual change.
Mar
31
comment Is Feynman's explanation of how the moon stays in orbit wrong?
@becko: I drew it in GeoGebra. Here's the worksheet file, if you want to play with it. (Try dragging the $x_1$ point around!)
Mar
31
answered Is Feynman's explanation of how the moon stays in orbit wrong?
Mar
29
comment Does the sun rotate?
@endolith: To be honest, I don't know, but I'd guess it must have something to do with the much greater heat flux out from the Sun driving more vigorous convection.
Mar
28
comment Does the sun rotate?
@Mark: It's not, though: the Sun's rotation speed varies between 10 to 15 degrees per day depending on latitude, compared to just under one degree per day for the Earth's orbit. Larger, yes, but hardly much larger.
Mar
28
comment Does the sun rotate?
@Mark: Actually, I don't think the latter part of your statement is true. The change in distance between the Earth and various points on the Sun's photosphere -- and thus the observed Doppler effect -- is purely a function of the difference between the relative angular velocities of the Sun's rotation and the Earth's orbital motion. In particular, if the Sun were a rigid body rotating with a period of exactly one year (which it of course is not), we wouldn't observe any net Doppler effect. Still, as you note, the Earth's orbital motion is well known and easy to compensate for.
Mar
27
comment What would be the effects if Jupiter was to blown up?
Also, if Jupiter's moons stick around, I doubt their initial orbits will be stable: the four big moons would end up in nearly intersecting eccentric orbits, and would likely start a game of gravitational billiards with each other, and possibly with other bodies in the solar system, until at least some of them got ejected or crashed into something. However, I also suspect that a blast capable of totally dispersing Jupiter might well transfer enough energy to the moons to put them on direct escape trajectories as well; after all, they'd be hit with quite a bit of fast-moving ejecta.