Search found 3665 matches

by PM 2Ring
Sun Mar 10, 2019 11:15 am UTC
Forum: Science
Topic: Extracting energy from a black hole via gravitational blueshift
Replies: 19
Views: 647

Re: Extracting energy from a black hole via gravitational blueshift

Gravity is a conservative force , so the net work over a closed loop must be zero. Conservation of momentum is certainly important, but I don't think that's the solution to this puzzle, since we can make the masses of the satellites huge, so they have large momenta relative to that of the beams of l...
by PM 2Ring
Sun Feb 24, 2019 3:59 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2115: "Plutonium"
Replies: 34
Views: 3497

Re: 2115: "Plutonium"

On the "l" vs "r" thing: even in English, the distinction isn't always clear. Eg, the "l" in "walk" & "talk" is pretty close to a (non-rhotic) "r" sound, but I expect most native English speakers don't usually notice that "l" ...
by PM 2Ring
Sun Feb 24, 2019 3:50 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2115: "Plutonium"
Replies: 34
Views: 3497

Re: 2115: "Plutonium"

I mean it helps that plutonium is FANTASTICALLY toxic. Just like the best at making people deadsies. Bonus, even if you keep it contained, if you get enough of it together, it'll create a self sustaining pile and start their own spontaneous fissioning will irradiate you, causing you to die in extre...
by PM 2Ring
Thu Feb 07, 2019 10:47 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9943
Views: 1905812

Re: Coding: Fleeting Thoughts

Image
by PM 2Ring
Wed Feb 06, 2019 2:25 pm UTC
Forum: Mathematics
Topic: The frog riddle
Replies: 23
Views: 2789

Re: The frog riddle

I didn't watch the video, so I'm not 100% certain of the details of this frog riddle, but it sounds like it's closely related to the Boy or Girl Paradox.
by PM 2Ring
Sat Jan 26, 2019 10:27 am UTC
Forum: Science
Topic: Consequences of climate change
Replies: 90
Views: 21612

Re: Consequences of climate change

p1t1o wrote:Sounds deep but doesnt hold water. We could easily still have capitalism with clean energy.

Indeed. Capitalism doesn't intrinsically imply that you're free to pursue your economic goals without cleaning up any messes you create in the process.
by PM 2Ring
Sat Jan 26, 2019 10:20 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2103: "Midcontinent Rift System"
Replies: 28
Views: 3479

Re: 2103: "Midcontinent Rift System"

I'd have thought that something that split red from blue would be more popular. At least with general voters; possibly not with people who believe that their position relies on exploiting the other colour... There's a SB thread about that, although it doesn't involve an actual geophysical split. ht...
by PM 2Ring
Fri Jan 25, 2019 2:12 am UTC
Forum: Language/Linguistics
Topic: Has anyone ever made a word square?
Replies: 31
Views: 11162

Re: Has anyone ever made a word square?

I discovered EAT ATE TEA in the early 1970s. Notice that you can extend it to a cube. And a tesseract. Etc. I've done lots of 3, 4 & 5 letter word squares, and I can still do 3 letter ones from the 1st word almost instantly, but I must admit I haven't done many manually since I wrote C code to g...
by PM 2Ring
Tue Jan 15, 2019 7:19 am UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 427
Views: 139573

Re: Math: Fleeting Thoughts

Wikipedia has lots of info on cousin marriage, including various maps. Also see cross cousin marriage from the University of Manitoba.
by PM 2Ring
Sat Jan 12, 2019 6:18 am UTC
Forum: Science
Topic: Science fleeting thoughts
Replies: 191
Views: 34651

Re: Sea level

Big G: 6.6719 * 10^-11 m^3 / s^2 kg Earth: 5.972 * 10^24 kg Product: 3.98445868 * 10^14 m^3 / s^2 It's difficult to get high precision values for the masses of astronomical bodies because it's hard to make precise measurements of big G. But we can measure orbital periods quite well, so we have good...
by PM 2Ring
Thu Jan 10, 2019 10:25 am UTC
Forum: Science
Topic: Stars in background of deep-sky photos are in foreground
Replies: 21
Views: 2337

Re: Stars in background of deep-sky photos are in foreground

Eebster the Great wrote:I think his statement would be correct though if the distance to the moon were not so much greater than its diameter.

And if the Moon's orbital plane were near Earth's equatorial plane rather than being a few degrees off the ecliptic plane.
by PM 2Ring
Thu Jan 10, 2019 9:53 am UTC
Forum: Science
Topic: quarkcosh1's miscellaneous science posts
Replies: 73
Views: 8372

Re: quarkcosh1's miscellaneous science posts

BTW, if the digits of pi contain every finite sequence of digits, then pi is a normal number. That may be true, but we currently don't know how to prove that a given real number is normal.
by PM 2Ring
Tue Jan 08, 2019 1:50 pm UTC
Forum: Science
Topic: Science fleeting thoughts
Replies: 191
Views: 34651

Re: Science fleeting thoughts

(And I imagine that if you don't watch out, doubling up and doubling up a RTG either in scale or by banking more units together will start to create something that, while maybe staying subcritical by keeping spot density down, does start to go through the prompt phase, requiring extra shielding. Or...
by PM 2Ring
Mon Dec 31, 2018 1:34 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9943
Views: 1905812

Re: Coding: Fleeting Thoughts

Reading uninitialised memory is undefined behaviour, so any program that does that is already skating on very thin ice.
by PM 2Ring
Sat Dec 15, 2018 9:41 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2083: "Laptop Issues"
Replies: 27
Views: 5156

Re: 2083: "Laptop Issues"

Just occurred to me: The One Ring was a Horcrux. (Or, rather, the Horcrii/Horcruxen were as derivative of such older examples as most of the rest of the stories.) From the Science Fiction & Fantasy Stack Exchange : Tolkien took many influences from JRR Rowling - think of the Ring like a Horcrux...
by PM 2Ring
Sun Nov 11, 2018 10:58 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2070: "Trig Identities"
Replies: 18
Views: 4216

Re: 2070: "Trig Identities"

What rmsgrey said. Iterated trig functions are pretty rare, compared to powers of trig functions. I guess iterated trig functions can be used to make fractals, and of course there's the Dottie number, but there's not much practical application for them.
by PM 2Ring
Tue Oct 30, 2018 3:37 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2063: "Carnot Cycle"
Replies: 27
Views: 5599

Re: 2063: "Carnot Cycle"

And thus the Carnot cycle merges with the Pornot cycle.
by PM 2Ring
Fri Oct 19, 2018 7:23 am UTC
Forum: Coding
Topic: write a C++ please
Replies: 18
Views: 6227

Re: write a C++ please

gd1 wrote:q=(s*s)+p(s-x)*(p+y);
This is the final calculation that does some mathematics and stores the result in the variable q.

You should fix that typo. p isn't callable.
by PM 2Ring
Fri Oct 19, 2018 12:45 am UTC
Forum: Language/Linguistics
Topic: Language fleeting thoughts
Replies: 135
Views: 40418

Re: Language fleeting thoughts

In this recent Stack Exchange Physics question about a home-made cloud chamber, the OP mentioned he was using IPA, meaning isopropyl alcohol. Some readers thought he meant India Pale Ale.
by PM 2Ring
Mon Oct 15, 2018 11:47 pm UTC
Forum: Science
Topic: Why does dry ice sublimate?
Replies: 12
Views: 2814

Re: Why does dry ice sublimate?

We can look at the phase diagram of CO 2 to see how it behaves, but of course that doesn't explain why it behaves that way. Courtesy of Wikipedia (click the image for a SVG). https://upload.wikimedia.org/wikipedia/commons/thumb/1/13/Carbon_dioxide_pressure-temperature_phase_diagram.svg/636px-Carbon_...
by PM 2Ring
Thu Sep 27, 2018 7:59 am UTC
Forum: Serious Business
Topic: Class vs class
Replies: 69
Views: 10018

Re: Class vs class

In Australia and New Zealand, the term bogan is used to refer to that class of person you're not comfortable with. I've always thought that "bogan" was the Aussie equivalent to the American "redneck", although of course there are some differences. In particular, "redneck&quo...
by PM 2Ring
Sat Sep 15, 2018 2:35 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2046: "Trum-"
Replies: 38
Views: 6418

Re: 2046: "Trum-"

I'm waiting for The Trump Show, starring Drew Carey. Or Mariah.
by PM 2Ring
Mon Sep 10, 2018 3:52 am UTC
Forum: Science
Topic: Laser recoil, relativistic momentum and whether mass counts
Replies: 4
Views: 2308

Re: Laser recoil, relativistic momentum and whether mass counts

Right, then. Momentum does not, in fact, equal mass times velocity. Wow. Thank you, chenille. Exactly. p = mv is just a Newtonian approximation. OTOH, momentum is velocity times relativistic mass, but in modern treatments of SR relativistic mass is a deprecated concept because it can be misleading,...
by PM 2Ring
Mon Sep 10, 2018 3:40 am UTC
Forum: Science
Topic: Half full or half empty?
Replies: 41
Views: 6116

Re: Half full or half empty?

But for a given volume/radius of black hole, you cannot add anything more without it becoming greater in volume/radius, so in that sense any size black hole is “full”. Sure, but that's just talking about the event horizon, which is a mathematical surface, it's not a physical object. Inside the EH, ...
by PM 2Ring
Sat Sep 08, 2018 3:31 am UTC
Forum: Computer Science
Topic: a neat picture based on recursive number
Replies: 11
Views: 4614

Re: a neat picture based on recursive number

Also see Dyck words . In the theory of formal languages of computer science, mathematics, and linguistics, a Dyck word is a balanced string of square brackets [ and ]. The set of Dyck words forms Dyck language. Dyck words and language are named after the mathematician Walther von Dyck. They have app...
by PM 2Ring
Tue Sep 04, 2018 8:28 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2040: Sibling-in-law
Replies: 52
Views: 9116

Re: 2040: Sibling-in-law

Wikipedia says The Serbo-Croatian standard languages (Croatian, Serbian, Montenegrin and Bosnian) have one of the more elaborate kinship(srodstvo) systems among European languages. [...] There are four main types of kinship in the family: biological aka blood kinship, kinship by law (in-laws), spir...
by PM 2Ring
Thu Aug 30, 2018 1:07 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2038: "Hazard Symbol"
Replies: 46
Views: 11963

Re: 2038: "Hazard Symbol"

For extra fun, make the chlorine trifluoride using 36 Cl, which is a beta emitter with a half-life of around 300,000 years, and a maximum decay energy around 709 keV. I guess you could just get some regular ClF 3 and put it inside a fission reactor to irradiate it with neutrons, but the reactor peop...
by PM 2Ring
Mon Aug 20, 2018 12:35 pm UTC
Forum: Mathematics
Topic: Cross-continuousness in higher dimensions,
Replies: 4
Views: 2060

Re: Cross-continuousness in higher dimensions,

Did someone say rhombic dodecahedron? I'm rather fond of those, as you might be able to tell from my avatar. :) The spoilered image shows the relationship between the cube, octahedron and rhombic dodecahedron (ray-traced using POV-ray). http://i2.photobucket.com/albums/y43/PM2Ring/RhombicH3S.jpg As ...
by PM 2Ring
Sun Aug 19, 2018 5:50 am UTC
Forum: Science
Topic: Gravitation 'Beach'
Replies: 11
Views: 3131

Re: Gravitation 'Beach'

Could gravitational waves not be slowed by passing through masses interacting with them, much like light itself can be slowed moving through a medium? A "gravitation beach" would then be some kind of ginormous wall of mass, somehow? I don't think so, because matter is essentially transpar...
by PM 2Ring
Tue Aug 07, 2018 1:29 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2028: "Complex Numbers"
Replies: 48
Views: 7770

Re: 2028: "Complex Numbers"

Mathematicians used negative numbers for a long while, but they weren't considered to be proper numbers. They were just a bookkeeping trick that simplified calculation and algebra. But that's what numbers are . The lot of them! Jose Well, sure. But that's a fairly modern notion, and it took a lot o...
by PM 2Ring
Tue Aug 07, 2018 1:12 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2028: "Complex Numbers"
Replies: 48
Views: 7770

Re: 2028: "Complex Numbers"

Of course, another is the idea of negative numbers. Once you have negative numbers, complex numbers are a fairly small step... Oddly enough, the historical order was the opposite of that. Mathematicians used negative numbers for a long while, but they weren't considered to be proper numbers. They w...
by PM 2Ring
Fri Jul 20, 2018 10:53 pm UTC
Forum: General
Topic: Thoughts for ships
Replies: 90128
Views: 8682865

Re: Thoughts for ships

Not dumb. Saturn does have that photoshop look to it. I've seen lots of photos of Saturn, and saw it through a cheap telescope when I was a kid, but the first time I saw Saturn through a good scope I was blown away. Modern computer enhanced imaging techniques are great, and allow us to see high qual...
by PM 2Ring
Sat Jul 14, 2018 5:10 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2019: "An Apple for a Dollar"
Replies: 80
Views: 9735

Re: 2019: "An Apple for a Dollar"

When I was there in 2002-3, Australia had abandoned anything smaller than 5c - prices were still in any integer number of cents, but, at point of sale, if paying cash, the customer got to keep the odd cents (or the shop gave a few extra cents in change) to get to a multiple of 5c. I've heard someth...
by PM 2Ring
Sun Jul 08, 2018 2:31 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2013: "Rock"
Replies: 42
Views: 7538

Re: 2013: "Rock"

Soupspoon wrote:Everything was Created on Tuesday. Even this comic, and our memories of previously having read it…

Splitter. It was last Thursday.
by PM 2Ring
Mon Jun 25, 2018 9:42 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2009: "Hertzsprung-Russell Diagram"
Replies: 35
Views: 6833

Re: 2009: "Hertzsprung-Russell Diagram"

Surely an LED bulb has a lower effective temperature than a normal (incandescent) light bulb. They have about the same surface area, but an LED bulb emits less total EM radiation. LEDs only look "hot" because their spectrum is so different to that of a black body. It seems strange to me t...
by PM 2Ring
Mon Jun 18, 2018 12:25 pm UTC
Forum: Language/Linguistics
Topic: "Cactus plant"
Replies: 20
Views: 5884

Re: "Cactus plant"

I associate "cactus plants" with the song A Fine Romance composed by Jerome Kern with lyrics by Dorothy Fields, published in 1936. The song came from the popular Fred Astaire, Ginger Rogers movie Swing Time . A fine romance, my good woman My strong, aged-in-the-wood woman You never give th...
by PM 2Ring
Mon Jun 18, 2018 11:45 am UTC
Forum: General
Topic: Questions For The World
Replies: 2216
Views: 438273

Re: Questions For The World

Not to be confused with hyphae.
by PM 2Ring
Thu Jun 14, 2018 5:21 am UTC
Forum: News & Articles
Topic: In other news... (humorous news items)
Replies: 15108
Views: 2522544

Re: In other news... (humorous news items)

FWIW, a previous discussion on solar roads is here: viewtopic.php?f=7&t=123914
by PM 2Ring
Wed Jun 13, 2018 11:03 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2005: "Attention Span"
Replies: 78
Views: 10845

Re: 2005: "Attention Span"

I never encounter that "the reason being is" construction, and I really don't see why anyone would use it when they could just leave the "is" out and have something grammatically correct and shorter. E.g. "Unlike most people around here, Alice goes shopping every single day...
by PM 2Ring
Mon Jun 11, 2018 4:43 am UTC
Forum: Serious Business
Topic: Philosophy and science of gender and sex
Replies: 118
Views: 24693

Re: Philosophy and science of gender and sex

But none of that is enabled by definitions. We don't really need a precise definition of any subgroup to act appropriately towards someone we know. Well, sure. But clear agreed-upon definitions are useful if you're trying to have a technical discussion. Or if you just want to articulate your positi...

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