Search found 3711 matches

by PM 2Ring
Wed Jul 10, 2019 8:54 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2172: "Lunar Cycles"
Replies: 19
Views: 1549

Re: 2172: "Lunar Cycles"

Your lunar cycle will also need to deal with the dreaded moon dust . It's much grittier than earth dust, since it hasn't been eroded by processes that polish off the pointy bits. It contains very fine particles, so it gets everywhere, and due to the lack of water it's chemically harsher than typical...
by PM 2Ring
Wed Jul 10, 2019 8:25 am UTC
Forum: News & Articles
Topic: In other news... (humorous news items)
Replies: 15152
Views: 2669903

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

I wouldn't be surprised if she could still change a wheel.
When the Queen was a truck mechanic.
by PM 2Ring
Thu Jul 04, 2019 7:06 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2170: Coordinate Precision
Replies: 70
Views: 3679

Re: 2170: Coordinate Precision

https://en.wikipedia.org/wiki/Hungarian_notation an intensely annoying coding convention used by stuff like Visual Basic back in the Visual Studio 6 days. Nothing like having to type dim integer intNum intNum = 12 even for stuff like loop iterators. "intI" or "intIter" instead o...
by PM 2Ring
Thu Jul 04, 2019 6:50 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2170: Coordinate Precision
Replies: 70
Views: 3679

Re: 2170: Coordinate Precision

In 2018 NIST announced that they could measure time with a bit more than 18 digits of accuracy using yet another flavor of atomic clock, this one is based on ytterbium. http://blogs.discovermagazine.com/d-brief/2018/11/28/atomic-clocks-so-accurate-they-can-measure-gravity This can measure altitude ...
by PM 2Ring
Sat Jun 29, 2019 12:59 am UTC
Forum: Fictional Science
Topic: Asimov's 3 laws
Replies: 39
Views: 9780

Re: Asimov's 3 laws

Isaac Asimov was invited to an early screening of 2001: A Space Odyssey . When HAL started to misbehave he loudly exclaimed "They're breaking the First Law!" (or words to that effect), to the chagrin of his wife. Sorry, I can't remember the exact details. I tried searching in my Asimov col...
by PM 2Ring
Thu Jun 27, 2019 5:01 am UTC
Forum: Fictional Science
Topic: Giant Insects Aliens
Replies: 12
Views: 4028

Re: Giant Insects Aliens

Then again, at the dimensions of a fly the Reynolds number must be pretty low so I'm not sure usual aerodynamic rules apply. Wikipedia's article on insect flight is quite detailed, with nice diagrams. Here's a snippet of some relevant info: Most insects use a method that creates a spiralling leadin...
by PM 2Ring
Sun Jun 23, 2019 6:06 pm UTC
Forum: Coding
Topic: Puzzle: Find integer not present in an array
Replies: 9
Views: 1565

Re: Puzzle: Find integer not present in an array

You don't need a bitmask over 2^32 numbers. If your array contains n numbers, then you just need a bitmask over n+1 numbers. After crossing out all the wrong numbers, at least one is guaranteed to remain. Can you please elaborate? I don't get how this works. In particular, how do you associate an a...
by PM 2Ring
Sun Jun 23, 2019 1:45 pm UTC
Forum: Coding
Topic: Puzzle: Find integer not present in an array
Replies: 9
Views: 1565

Re: Puzzle: Find integer not present in an array

Flumble wrote:One method is to take every number modulo n+1. (I think I'm feeling your facepalm. :mrgreen: ) That gives you n+1 holes for n elements.

Ok. That works. :face duly palmed: :D
by PM 2Ring
Sun Jun 23, 2019 1:16 pm UTC
Forum: Coding
Topic: Puzzle: Find integer not present in an array
Replies: 9
Views: 1565

Re: Puzzle: Find integer not present in an array

Nice question. How big is the array? I suspect that for smallish arrays (like n < 2^20) a sorting based approach, eg using radix sort, will be fastest. Or maybe even a modified version of an algorithm that finds the minimum & maximum values. You don't need a bitmask over 2^32 numbers. If your ar...
by PM 2Ring
Sun Jun 23, 2019 12:49 pm UTC
Forum: General
Topic: Hifaleetin' thoughts
Replies: 90216
Views: 9233228

Re: Hifaleetin' thoughts

[...] I kind of think using pneumatic tyres on ultra-narrow wheels is bullshit too, since they're pumped to such high pressure that you might as well have tyres filled with solid rubber or cork granules. That sounds like it could be a good thread on the Science forum. My guess is that even though h...
by PM 2Ring
Fri Jun 21, 2019 6:05 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2958
Views: 722902

Re: Miscellaneous Science Questions

Yes, the energy of gravitational waves creates gravity. This makes them non-linear, Oh huh, I would phrase it the opposite -- gravitational waves are linear perturbations of a metric, and full GR is nonlinear, but if you're in a regime where you need the higher order terms you are no longer working...
by PM 2Ring
Fri Jun 21, 2019 12:03 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2958
Views: 722902

Re: Miscellaneous Science Questions

Yes, the energy of gravitational waves creates gravity. This makes them non-linear, so calculations involving extremely intense gravitational waves are hard. But fortunately, most gravitational waves don't carry much energy, so we only need to worry about this for things like colliding black holes, ...
by PM 2Ring
Tue Jun 18, 2019 1:48 pm UTC
Forum: Science
Topic: Relativity question.
Replies: 21
Views: 1470

Re: Relativity question.

Any deviation from “constant subjective acceleration equals linear subjective increase in delta-v” would constitute information about my velocity with respect to c, which by the Equivalence Principle can not be obtainable without looking outside of my starship. The others have given great replies, ...
by PM 2Ring
Sat Jun 15, 2019 9:50 am UTC
Forum: Science
Topic: Relativity question.
Replies: 21
Views: 1470

Re: Relativity question.

Modern treatments of special relativity avoid the concept of relativistic mass. It can be confusing and misleading, unless you know exactly what you're doing. For example, it can lead to erroneous conclusions like the OP's "any vessel approaching the speed of light would crush itself under its ...
by PM 2Ring
Thu Jun 13, 2019 3:21 pm UTC
Forum: Language/Linguistics
Topic: Language fleeting thoughts
Replies: 163
Views: 53599

Re: Language fleeting thoughts

In central Australia, we have the Todd River, famous for the Henley-on-Todd Regatta, which is dry most of the time. Wikipedia calls it an ephemeral river.
by PM 2Ring
Wed Jun 12, 2019 6:22 am UTC
Forum: Science
Topic: Science fleeting thoughts
Replies: 381
Views: 59906

Re: Science fleeting thoughts

Having seen* ball lighting when I was about five years old, I am fascinated by it. Wow! That's fantastic. And I'm totally not jealous. :D BTW, there's been an update to the What-If 0085: "Rocket Golf" thread: I can confirm that we are indeed a family of physicists who managed to turn scre...
by PM 2Ring
Tue Jun 11, 2019 12:16 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2160: "Ken Burns Theory"
Replies: 18
Views: 2426

Re: 2160: "Ken Burns Theory"

Still makes more sense than the GoT timeline. Where's the damn winter they promised us? If you want winter, see The Donner Party , by Ken's brother Ric. I think I'll watch that movie tonight - what should I make for dinner to eat while watching the movie? Donner kebabs, of course. On a more serious...
by PM 2Ring
Sat Jun 08, 2019 10:46 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2160: "Ken Burns Theory"
Replies: 18
Views: 2426

Re: 2160: "Ken Burns Theory"

cellocgw wrote:Still makes more sense than the GoT timeline. Where's the damn winter they promised us?

If you want winter, see The Donner Party, by Ken's brother Ric.
by PM 2Ring
Fri May 31, 2019 9:30 pm UTC
Forum: Mathematics
Topic: Help finding an arccotan website
Replies: 3
Views: 893

Re: Help finding an arccotan website

eta oin shrdlu beat me to it. But you've reminded me of this thread
viewtopic.php?t=109967#p3656720
by PM 2Ring
Wed May 29, 2019 9:07 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2153: "Effects of High Altitude"
Replies: 56
Views: 5705

Re: 2153: "Effects of High Altitude"

Let's not forget Felsius.

In Fahrenheit and Rankine, between the freezing and boiling points of water there are 180° or π radians. :wink:
by PM 2Ring
Tue May 28, 2019 8:03 pm UTC
Forum: Science
Topic: mark mccutcheon final theory
Replies: 27
Views: 1902

Re: mark mccutcheon final theory

Going on a tangent here: a = GM/r² is true in the centre of mass frame, but when the second body has considerable mass relative to the first, then we also need to consider the acceleration of the first body towards the second. See Don't heavier objects actually fall faster because they exert their ...
by PM 2Ring
Mon May 27, 2019 5:01 pm UTC
Forum: Science
Topic: mark mccutcheon final theory
Replies: 27
Views: 1902

Re: mark mccutcheon final theory

Right. Kepler derived his laws empirically, it was about seven decades later that Newton derived them from his laws of motion & gravitation. a = GM/r² is true in the centre of mass frame, but when the second body has considerable mass relative to the first, then we also need to consider the acce...
by PM 2Ring
Mon May 27, 2019 4:42 pm UTC
Forum: Science
Topic: Life in hyperbolic space
Replies: 9
Views: 1479

Re: Life in hyperbolic space

Indeed! My introduction to hyperbolic space was via Escher; I had a book of Escher prints in my teens, which I sadly lost some time in my late 20s. I've written a couple of clunky programs to do simple hyperbolic geometric constructions on the Poincaré disc. But to do "Circle Limit" style ...
by PM 2Ring
Mon May 27, 2019 8:59 am UTC
Forum: Science
Topic: Life in hyperbolic space
Replies: 9
Views: 1479

Re: Life in hyperbolic space

You'd have a lot more options for floor tiling patterns. See
Uniform tilings in hyperbolic plane and the links there. Eg,
Spoiler:
Image
by PM 2Ring
Tue May 21, 2019 4:25 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2152: "Westerns"
Replies: 56
Views: 5222

Re: 2152: "Westerns"

The British film Moon Zero Two from 1969 was shamelessly promoted as 'The first moon "western"'. I guess it was a bit cheesy, but I enjoyed it, although it wasn't very successful. I suspect it hasn't aged well...
by PM 2Ring
Wed May 15, 2019 5:51 am UTC
Forum: Mathematics
Topic: a recursive factoring algorithm?
Replies: 31
Views: 2349

Re: a recursive factoring algorithm?

FWIW, Fermat devised a factorization method that uses (a + b)(a - b) = a² - b². See https://en.wikipedia.org/wiki/Fermat%27s_factorization_method In its simplest form, Fermat's method might be even slower than trial division (worst case). Nonetheless, the combination of trial division and Fermat's i...
by PM 2Ring
Thu May 02, 2019 11:01 am UTC
Forum: Science
Topic: Is it possible to escape from a black hole using another black hole?
Replies: 56
Views: 6047

Re: Is it possible to escape from a black hole using another black hole?

Here are some relevant Physics Stack Exchange questions.

Black hole collision and the event horizon. The top answer there has links to several diagrams.

Why stop at lava vs ice when you can do matter vs antimatter?
What happens if you dump antimatter into a black hole?
by PM 2Ring
Tue Apr 30, 2019 1:33 pm UTC
Forum: Mathematics
Topic: Analytic/ asymptotic size of rationals
Replies: 4
Views: 2155

Re: Analytic/ asymptotic size of rationals

On a closely related note, see Farey sequence.
The Farey sequence of order n is the sequence of completely reduced fractions, either between 0 and 1, or without this restriction, which when in lowest terms have denominators less than or equal to n, arranged in order of increasing size.
by PM 2Ring
Fri Apr 26, 2019 7:56 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2142: "Dangerous Fields"
Replies: 35
Views: 5880

Re: 2142: "Dangerous Fields"

strix99 wrote:Well good, I was afraid I was suffering from an irrational fear of the elderly. It turns out I have a completely healthy fear of the elderly brutally beating their caregivers to death with canes and walkers.

See Hell's Grannies.
by PM 2Ring
Mon Apr 22, 2019 3:27 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1455: "Trolley Problem"
Replies: 172
Views: 48581

Re: 1455: "Trolley Problem"

Image
by PM 2Ring
Sat Apr 13, 2019 5:59 am UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 590
Views: 124467

Re: Miscellaneous language questions

FWIW, some Anglophones quite like the sound of Dutch. But I must admit I can't tell the difference between the sound of Dutch and Afrikaans.
by PM 2Ring
Sat Apr 13, 2019 4:51 am UTC
Forum: General
Topic: Hifaleetin' thoughts
Replies: 90216
Views: 9233228

Re: Thoughts for ships

OTOH, if you average several different faces together, the resulting composite is (usually) more attractive than the originals. See examples here, and play with the interactive viewer.
by PM 2Ring
Fri Apr 12, 2019 1:29 pm UTC
Forum: General
Topic: Hifaleetin' thoughts
Replies: 90216
Views: 9233228

Re: Thoughts for ships

If you could be any startrek character from any of the tv series, which and why? I always thought the silicon-based Horta , first introduced in TOS episode The Devil in the Dark , were fascinating. But they do look rather ugly to us carbon-based life forms, so maybe I wouldn't like to actually be o...
by PM 2Ring
Fri Apr 12, 2019 1:12 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2135: M87 Black Hole Size Comparison
Replies: 42
Views: 9001

Re: 2135: M87 Black Hole Size Comparison

Soupspoon wrote:Incidentally, I'm sure Dr Bowman Bouman has consciously been avoiding telling us that it's full of stars…

I bet if there were a video on YouTube of Dr Katie Bouman looking at the M87* image on a computer monitor and saying "My God, it's full of stars!", it would go viral. :D
by PM 2Ring
Thu Apr 11, 2019 4:54 pm UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 590
Views: 124467

Re: Miscellaneous language questions

Another similar term we use in English (British, at least) is "brain surgery" (as something that something else is not). I can think of at least two comedy double acts that did a sketch about how an actual rocket scientist character meets (or mutually becomes aware of) an actual brain sur...
by PM 2Ring
Thu Apr 11, 2019 2:24 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2135: M87 Black Hole Size Comparison
Replies: 42
Views: 9001

Re: 2135: M87 Black Hole Size Comparison

From one of the best Stack Exchange Physics pages on singularities, Is a black hole singularity a single point? : A singularity in GR is like a piece that has been cut out of the manifold. It's not a point or point-set at all. Because of this, formal treatments of singularities have to do a lot of n...
by PM 2Ring
Wed Apr 10, 2019 7:41 am UTC
Forum: Computer Science
Topic: Favorite Programming Language
Replies: 32
Views: 24458

Re: Favorite Programming Language

I used to code in Advance Java during my venture in Wipro. Currently I think there are new concepts and languages like fll stack, mongo db, python and c# which are being used for developing complex projects. Are you talking about this Wipro ? BTW, Python isn't exactly new. It was conceived in the l...
by PM 2Ring
Wed Apr 03, 2019 9:23 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2131: “Emojidome”
Replies: 123
Views: 20506

Re: 2131: “Emojidome”

The official name of the winning emoji is Milky Way. Its Unicode codepoint is U+1F30C. As well as the official name, it has several synonyms: Galaxy, Night Sky, Space, Stars, & Universe. It has over a dozen different visual representations, which you can see on Emojipedia.
by PM 2Ring
Tue Apr 02, 2019 11:19 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2131: “Emojidome”
Replies: 123
Views: 20506

Re: 2131: “Emojidome”

AFP = alt.fan.pratchett ?
by PM 2Ring
Mon Apr 01, 2019 11:41 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2129: "1921 Fact Checker"
Replies: 49
Views: 9045

Re: 2129: "1921 Fact Checker"

EDIT: On the note above, I assume lamp oil was edible, right? What was the property of whale oil that made it so prized for lamps over other animal fats in the 18th and early 19th centuries, and did this make it inferior as a cooking oil? Was whale oil even used in the early 1600s? The lamp oil may...

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