Search found 3699 matches

by PM 2Ring
Tue Jun 18, 2019 1:48 pm UTC
Forum: Science
Topic: Relativity question.
Replies: 21
Views: 1493

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: 1493

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: 53602

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: 60140

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: 895

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: 5707

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: 1931

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: 1931

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: 1490

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: 1490

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: 5223

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: 2350

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: 6106

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: 48587

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: 124763

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: 9233743

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: 9233743

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: 9003

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: 124763

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: 9003

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: 24462

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: 20522

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: 20522

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...
by PM 2Ring
Sun Mar 31, 2019 3:08 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2130: "Industry Nicknames"
Replies: 28
Views: 4911

Re: 2130: "Industry Nicknames"

Wolves have lost federal protection under the Endangered Species Act, due to the influence of Big Bad Wolf.
by PM 2Ring
Sun Mar 31, 2019 3:01 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2129: "1921 Fact Checker"
Replies: 49
Views: 9045

Re: 2129: "1921 Fact Checker"

I doubt that the oil was cooking oil. It was much more likely to have been lamp oil. Although olive oil has been consumed in Mediterranean regions since ancient times, Britons in the era of the Pilgrims used animal fats for cooking. The use of vegetable oil in Britain for cooking is a relatively rec...
by PM 2Ring
Wed Mar 27, 2019 2:42 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 2129: "1921 Fact Checker"
Replies: 49
Views: 9045

Re: 2129: "1921 Fact Checker"

In British English, "corn" is a generic term for grain.
Oxford Living Dictionaries wrote:British
The chief cereal crop of a district, especially (in England) wheat or (in Scotland) oats.
by PM 2Ring
Wed Mar 27, 2019 4:59 am UTC
Forum: Individual XKCD Comic Threads
Topic: 2128: "New Robot"
Replies: 40
Views: 6739

Re: 2128: "New Robot"

Also see Vacuum Zeppelin.
by PM 2Ring
Tue Mar 26, 2019 4:53 pm UTC
Forum: Science
Topic: Verifying physics at home
Replies: 15
Views: 2857

Re: Verifying physics at home

"Time hacker" Tom Van Baak (& his kids) did an amateur test of gravitational time dilation using caesium atomic clocks on Mt Rainier in 2005, the 100th anniversary of Einstein's first paper on Relativity. See http://leapsecond.com/great2005 Also see Most Accurate Wristwatch  - the firs...
by PM 2Ring
Sat Mar 16, 2019 12:59 am UTC
Forum: Fictional Science
Topic: A Universe that's just two massive balls... fnar
Replies: 24
Views: 3038

Re: A Universe that's just two massive balls... fnar

They wouldn't collide at anywhere near C unless they were black holes. You could get close to c if they were neutron stars. And of course, if the combined mass & kinetic energy were high enough (after emitting some shrapnel & gravitational waves), the resulting object would very quickly col...
by PM 2Ring
Sun Mar 10, 2019 11:15 am UTC
Forum: Science
Topic: Extracting energy from a black hole via gravitational blueshift
Replies: 20
Views: 3727

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: 7711

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: 7711

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: 9990
Views: 2009917

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: 5705

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: 29569

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.

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