xkcd

PM 2Ring

FWIW, Google Calculator can do that calculation: (1 joule / kelvin) / (ln(2) * boltzmann constant) 1.04494013 × 10 23 I guess it's just a coincidence that it's within an order of magnitude of Avogadro's number: ((1 joule / kelvin) / (ln(2) * boltzmann constant)) / (avogadros number) 0.173516388 whic...

PM 2Ring

Unfortunately, converting those digit sequences to card sequences is a little tedious, and (AFAICT) you have to generate the whole 20 digit sequence before you can decide that it's invalid. Actually, you don't have to generate the whole sequence before you can decide that it's invalid; I should kno...

PM 2Ring

Am I missing something or are people way overthinking this? Just put the numbers 1 through 52 in an array and shuffle it. Dealing cards is as simple as pulling out elements starting from the first index and working your way down. The problem is that the OP's TRNG (true random number generator) only...

PM 2Ring

Inside the electrons are quarks, [...] In the Standard Model, electrons, like all leptons , are fundamental particles in their own right, they aren't composed of quarks. Quarks (and gluons), and particles composed of quarks, feel the strong nuclear force, but leptons are oblivious to that force. Ho...

PM 2Ring

This is related to the topic of perfect numbers and aliquot sequences . If we continue your sequence that starts with 62447, the next number after 15505 is 5807, which is prime, so it must be followed by 1. If we start at a perfect number, eg 6 or 28, then the next number is the same number we start...

PM 2Ring

If quantum field theory in curved space could be reasoned about successfully with fractions, I'd have gotten my PhD in fourth grade. :D If you want to know what Hawking radiation looks like to an infalling observer rather than one at infinity, just do the Bogolyubov transformation for that intrepid...

PM 2Ring

Here's a pertinent quote from Yes, Minister (Series One, Episode Six: The Right to Know): Sir Humphrey : Minister, I have something to say to you which you may not like to hear. Jim Hacker: Why should today be any different? Sir Humphrey: Minister, the traditional allocation of executive responsibil...

PM 2Ring

Yes, it is a tough one. And I was about to start writing some GeographicLib code before I noticed that this question is 5 years old. :) The OP mentioned Vincenty's formulae, which are commonly used for ellipsoid geodesic calculations. However, for the benefit of other readers who might find this thr...

PM 2Ring

This is the integer division thing I was talking about. I love the way it seems to make sense to begin with, with recognisable numbers like 52 and 365... but then you start getting crazy shit like 306 and 10. All division is integer division, operator % is modulus. Given integer y, m, d, calculate ...

PM 2Ring

New to OOP - quick question. [...] What is the canonical way to implement a function that is identical in a bunch of unrelated classes? And does python implement this? Just a quick note on terminology. A function that's defined inside a class is called a method. As Flumble said, if these classes al...

PM 2Ring

What phlip said. It's definitely a much better strategy these days to learn Python 3. You should start with the official Python tutorial , since it's aimed at people who already know how to program. If you want to be able to read old code &/or use old libraries properly you will eventually need ...

PM 2Ring

Are those sequences related to any other problem in number theory? Probably not. As Conman said earlier, sequences like this don't usually reveal anything particularly deep about the numbers involved because the results depend on the base you're using to represent the numbers. There's nothing of pa...

PM 2Ring

FWIW, Greg Egan created some nice diagrams, images, and a Java applet illustrating the neighbourhood of a pure GR Schwarzschild black hole to accompany his short story the Planck Dive . I guess it'd be nice to have graphics that somehow illustrated Hawking radiation, but it's not exactly easy to see...

PM 2Ring

If we can build a diophantine equation giving all the prime numbers even if it is not workable then why not trying to build functions or sequences or polynomials giving ONLY all the composite numbers. I started some ideas to find such way to solve this problem using some binary partition. A much si...

PM 2Ring

Conservation of momentum is very native and natural to us, much moreso than conservation of energy. So in fiction, conservation of energy often goes out the window but conservation of momentum will be preserved to a degree, since things would look strange without it. I guess so. OTOH, it's because ...

PM 2Ring

I don't believe that it's possible to do what you want with a finite degree polynomial without overlapping: the structure of the primes is too rich for that. On a closely related note, there is the Diophantine Representation of the Set of Prime Numbers by James P. Jones, Daihachiro Sato, Hideo Wada ...

PM 2Ring

I'm used to the concept that, say, sound waves and light waves travel at a constant speed in a constant medium, unaffected by either frequency or amplitude That's not true: wave speeds in a given medium generally are dependent on frequency / wavelength. One well-known manifestation of this is the d...

PM 2Ring

Your password page could have an embedded client-side password hasher, eg Xanthir's SHA-1 password hasher , (maybe with a slightly simplified, more user-friendly UI), with clear instructions on how to use it. And I guess you could include a brief explanation of why it's secure: it does its calculati...

PM 2Ring

siara wrote:By the way, how were you able to post URL in the reply? I couldn't.

The answer to that question can be found in the xkcd Forum Rules, along with other useful information.

PM 2Ring

BlackSails wrote:Positions of planets cant be accurately predicted to more than a few tens of millions of years.

p1t1o wrote:Not necessarily, as linked above.

I suspect that you misread BlackSails's post, p1t1o.

PM 2Ring

If a car gets a signal to pick someone up, but is blocked by other self driving cars, it could transmit a "I need to leave now" signal to nearby cars, which would then move out of the way, then shuffle back into the available parking space. The image of a parking lot stuffed full of self-...

PM 2Ring

Trying to read Ulysses [...] Kinda reminds me of Deva and addams' posts. Na-Uh! No! No Way! Deva and I are both easier to read than Ulysses is. oh, dear God! That's what you see when I post?? I should seriously consider Not posting. The world is difficult enough to understand. It is Wrong to needle...

PM 2Ring

[...]Water, on the other hand, can hold quite a bit of hydrogen. (They call it hydrogen peroxide, you know.)[...] Not quite. Hydrogen peroxide is H 2 O 2 . Hydrogen peroxide is a powerful oxidizing agent and somewhat unstable due to the O-O (peroxide) bond. FWIW, when it decomposes it tends to give...

PM 2Ring

Then you can prove that zeta(1)=infinity, without assuming that there are infinitely many primes. (though that's hard, and the usual easy proof uses the fact that there are infinitely many primes) Huh? The usual easy proof of the divergence of zeta(1) is Nicole Oresme's proof using comparison of th...

PM 2Ring

[...] the light source here (gigantic ball of explosion far older than life on this planet, not shown) [...] The Sun's not as explosion-y as you might think. The Sun's atoms certainly have a lot of kinetic energy , and sure, it has nuclear fusion reactions happening in its core, but those reactions...

PM 2Ring

FWIW, I have XP on this machine for those very rare occasions when I need Windows, but since XP was discontinued I turn off my ADSL modem before booting into XP. Another useful anti-malware program that still works on XP is AdwCleaner - it can occasionally find things that MBAM misses. Obviously, I ...

PM 2Ring

I wouldn't call a 10% difference negligible, but YMMV. But do I agree that 25 microseconds is negligible. The relative speed difference of the two methods depends on the speed of the computation inside the list comp / gen exp: if that computation is slow it may dominate the total time, hiding the di...

PM 2Ring

How about 4π² AU³/yr² ?

But what's a minor constant of proportionality between friends?

PM 2Ring

One problem with Runge–Kutta methods is that they don't conserve energy, and that could be killing your filaments. Try using a symplectic integrator like Verlet, or Leapfrog . I generally use the synchronized version of Leapfrog (for doing simple orbit sims) but the standard version's probably adequ...

PM 2Ring

A minor correction: G is normally called the gravitational constant ; the term "gravitational parameter" or standard gravitational parameter normally denotes the product GM. In celestial mechanics, the standard gravitational parameter μ of a celestial body is the product of the gravitation...

PM 2Ring

ETA: yep, it's perfect. Thanks! No worries. When you're done, it'd be great if you could let us know what you think of svg_stack. OTOH, since your SVG files are all nearly identical it probably wouldn't be too hard to write a bit of Python to do the tiling yourself, assuming that the files were bui...

PM 2Ring

I have a large amount of SVG files (all nearly identical) which I want to put on a single page in a simple rectangular tiled layout. I assume you want to tile all these files into a single SVG file, rather than into a HTML / XHTML Web page. If so, svg_stack may be helpful. svg_stack combines multip...

PM 2Ring

I wasn't aware that list comps create their own scope, now. Lots of people have been bitten by the "scope-leaking" of Python 2 list comps. Most of us just learned to live with it, but enough people complained that it was changed for Python 3, even though it makes list comps slightly less ...

PM 2Ring

@MostlyHarmless What they said. Generators (including generator expressions) run slightly slower than list comprehension and take more setup time, so list comprehensions will beat them for stuff like this unless you're processing ridiculously huge strings of digits. BTW, in general, don't use `chr` ...

PM 2Ring

You could do a Death Star cake and if someone asks which moon it is your SO can reply
"That's no moon".

PM 2Ring

FWIW, the Wikipedia article on the Fermat point (the point such that the total distance from the three vertices of the triangle to the point is the minimum possible) invokes without proof "the dogleg rule" which asserts that if a triangle and a polygon have one side in common and the rest ...

PM 2Ring

As I've mentioned before, I'm rather fond of Cramer's Transactional Interpretation of quantum mechanics. Roughly speaking, Cramer postulates that the normal past-to-future causality is complemented by future-to-past causality, so when atom A emits a photon that's absorbed by atom B, the actual traje...

PM 2Ring

Speaking of liquid conductors & motors, check out the mercury "motor" . It's not very practical, but it is rather cute. WRT Carbon: it conducts, but rather poorly. Try running an electric current through a stick of pencil lead and see what happens! True, but graphite is a great lubrica...

PM 2Ring

Echo244 wrote:I think they're invasive in Australia, and a bit tricky to get rid of.

They are. Also, blackberries can harbour rabbits, another invasive species.

PM 2Ring

Maybe something based on the inverse hyperbolic tangent?
Eg y = ln((7-x)/(x-1))/2

Search found 3662 matches