Yes, there's a lot wrong with that old rubber sheet analogy. As a zillion previous/.ers have stated, it's just a simple crude means of making an intuitive point, that in some general way curvature affects objects moving about in the arena they inhabit.
Of course the biggest bit of silliness is that the analogy relies on gravity in order to explain gravity. Duh.
Some have mentioned that marbles rolling about on a curved rubber sheet are _rolling_, and that has no analogy with reality. But we can ignore that.
Rubber, or whatever more or less solid type of "fabric of space-time" one uses, allows longitudianal motions, stretching and jiggling tangentially along the surface. This has no analog in reality. We can just ignore that too. A better way to think of curved space is as liquid, in an analogy with soapy water films and bubbles. There's no stretching, as liquid readily flows to fill in areas being pulled apart. There's only curvature and boundary conditions as the films of liquid find minimal surface area.
But then, even that fails, as gravity as we deal with it in the real world is almost entirely explained by the time-time component of the metric. Curvature of space is secondary, hard to measure, and a matter for precision experiments involve spacecraft and lasers. It's the differential rate of progress of time between nearby points that "explains" gravity. But to explain it intuitively to the layman, that I'm not so sure about.
Practical book giveaway: Ruby vs. D
on
Is Ruby Dying?
·
· Score: 1
FWIW, at one place I worked there was a table anyone could dump a book on for others to "borrow". No real expectation of getting it back, but a way to pass on unwanted books to someone who might find it useful.
I wanted to reduce my collection of books. So I dumped a less-popular Ruby book onto that table. It vanished before the end of the day. I dumped a couple other ruby books, including The Ruby Way and some book on Ruby brain-teaser quizes, something like that. Poof, as if done by a magician trying to impress members of the opposite sex, they vanished quickly and completely, by the next time I passed through that room. Interesting.
Then I dumped Andrei Alexandrescu's The D Programming Language. It sat for a day, then another day, and another. After a week it was still there. Eventually someone took it. At least at this one company, D is 1/100th as popular as Ruby. Neither language is used officially on company projects - it's all Java, C++, C# and Python. Internal web sites do not use RoR that I know of.
Ruby is a fine language, but in practical implementation other languages, in particular, Python run circles around it. A circle. Maybe half a circle, but you know what I mean - Ruby is fine but never in first place. I still use it for some electronics graphics (http://www.darenscotwilson.com/spec/stereo888/stereo888.html) It's certainly not dying if there are such quick book-snatchers in a company not using it.
OTOH, those who know of D like it quite well, actually use it, try to spread the word, and that includes me. Maybe D is in the stage of early growth outside it's originating community, where Ruby was in 199x where I'm not sure what 'x' is.
D is clearly growing, but has a long way to go, while Ruby is way up there, and has a long way to go if it is in fact shrinking.
When I am a multi-billionaire, I will build a giant monument, 100 miles wide, fifty tall, and engrave on it all over every tweet and facebook post ever written since the 1990s, through all of the 21st century, so our descendants one thousand years in the future will not lose all that precious wisdom and insight into our culture.
When my university's library expanded in the late 1980s, I wondered about two things: in another two or three decades, will they need to expand again? Of course. And also: Who is going to read or look up info in all those books? Of course, there will always be specialists and indexes and catalogs, but if the trend continues for all the 21st Century, and all of the 22nd Century,..., at some point there will be far too much "literature" even in a very narrow academic specialty for any human to make use of. Then what about all the non-academic stuff, cheap romance novels and mysteries and memoirs of flash-in-the-pan pseudo-celebrities?
It's not that we need a good ol' roaring book-burning now and then like at Alexandria long ago, but somehow the best needs to be brought to the top, and the most of the mediocre disposed of. And maybe keep mediocre writers from ever starting. (Stuff that's actually *bad* not merely mediocre - keep some as examples and for the entertainment value!)
So now we have disks and all manner of extremely dense storage materials. This changes nothing, aside from the physical space requirements are reduced to near nothing. Even with intelligent indexes and indexes of indexes, or miraculously good search engines such as Google, or whatever we'll have in fifty years - it's mind-boggling to wonder how such a huge growing pile of information will be utilized.
"Research scientists could learn an important thing or two from computer scientists,..."
What is the error bar on "a thing or two"?
As someone with a foot in each camp, I believe it's more like fifty or a hundred. The methods of scientists regarding computing are often built of slow evolutionary changes upon old familiar methods, while incorporating selected cutting edge hardware or algorithms. It is partly the nature of some science projects to carry out observations over many years, ideally with the same instruments, processing and management. In academic computer science, as well as real world IT, all layers and all aspects of any large system are always changing over time. ("All" = 100% give or take a few %) (And yes, somedays, it does seem like over 100%)
Would the chemistry leading to primitive life, and the very earliest life forms, need cooler places? If all of space is permeated by comfy temperatures, where could things happen needing to happen at cooler temperatures? Maybe evaporation in certain places could lead to that, or some other nonequilibrium situations.
Yup. Though there can be big differences in the benefit for effort depending on if the candidate is modestly experienced, more experienced, a near-master, or what, and if the nature of the work is "concave" or "convex" as described by Michael O Church http://michaelochurch.wordpress.com/2013/04/03/gervais-macleod-21-why-does-work-suck/ In certain cases it may really be better for the company to wait it out for superb talent - but surely this accounts for only a few % of all open positions. What kinds of jobs are "concave"? As far I understand, professional athletes, pop celebrities (their agents and marketers not the singers/dancers/actors themselves being the actual "talent"). Symphony bassoonists too, I imagine. Video game designers, language and framework designers.
For almost all other cases, in real life, I look around and see people with skills of any kind at any level above zero, would be happy to learn new things. And there's a lot of "convex" work in IT and software development (and many entirely different fields) where being not in the top 1% or 10% is okay - being 40% or 50% down means work that is just about as good. Convex work would include stuff like maintaining servers or grinding out more GUI frontends to ever-shifting enterprise databases.
A lot of talented and near-talented and half-talented people could be contributing, earning money, and reviving the economy of (fill in blank with whatever country has a slow economy and companies holding out for superstars), if companies understood that they'd be just fine in any of those "convex" jobs.
"...choose whether you want to be part of the herd near the edge looking for the wolves, or oblivious somewhere the middle, or if you want to be a wolf"...or the vulture to clean up the carcass after the wolf's feast, or the fleas who bother all furry/hairy animals, or the dung beetles to carry away you-know-what, or the penguins who are so far away, so aloof they don't know or care about the herd, or....
And the edge of the herd is more than an early warning system against predators, but also where new feeding grounds, water, and various good things are first observed.
A two or three week vacation in the spring (best for travel) and a couple in the fall, and a couple during the coldest part of the year (to save heating costs) and another in the hottest part of the year (to save cooling costs). These may vary from one part of the country to another, which is good. Families on vacation won't be all crowding the hot tourist spots all at once.
There's no good reason to take as much as a full month off, and certainly not more, although in places with the harshest winters an exception to that rule would be fine.
(Just leave my Nobel Prize in Education on the back porch. I'll drag it in when I get around to it.)
Go to YouTube, search with some keywords like "russia car accident", and you can watch 10,000 dashcam videos of "interesting events". I wonder how well Nissan's car would handle any of those?
You take a risk by saying something intelligent on slashdot!
My personal experience with bicycle helmets is that it's more dangerous to wear a helmet than not. I have never had a serious injury from a bicycle incident. A semi-serious injury to my hand once, with no permanent damage. (Checking... 1, 2, 3, 4, 5. All fingers still there.)
But one fine year I decided to do the right thing and wear a helmet. There was a situation where the wheel slipped and I landed the way I normally do on those rare occasions. Except this time, the ground shoved the helmet against my head and the edge of it bashed my forehead right above an eye. A bump grew, and I went to the nearest emergency room. Turned out okay, just the swelling you get from any whack.
Interesting, that the one time I wear a helmet, it causes more injury than if I hadn't worn it. Also interesting that bicycling injuries, except for that one helmet incident, are always to my hands. What are we supposed to wear over our hands? Is it law?
This is just my personal experience. YMMV, of course. Do not try this at home, do not operate heavy women while under the influence of pregnant machinery, I'm not a real doctor just tell women at the bar that I play one on TV, I may have guardian angels with oddball senses of humor, etc etc etc.
How often have those massive overreactions lead to trouble leading to lawsuits?
Seems like a few clever lawyers could apply some equal and opposite legal forces to herd the authorities and decision-makers into a reasonable direction.
Yup. Phil Plait, the Bad Astronomer explained it well. What goes for Hubble, goes pretty much the same for Cassini (I know, I worked for CICLOPS) and for many other planetary missions.
Physics grad students (and grad students in other sciences and engineering) actually help build instruments, interpret data, and contribute to mankinds store of knowledge.
Athletes hoping for superstardom but not making it out of high school football/whatever provide some entertainment for local football/whatever fans, but don't really contribute to mankind's anything. They're doing good, nonetheless - developing teamwork skills, performing in front of a crowd, organizing, following a strategy, staying healthy. But so do grad students, albeit a different kind of team, different kinds of strategies. (And maybe not so much interest in staying healthy.)
Scientists who don't make it to professorhood do a lot more for society as grad students and post-docs than athletes who don't make it to the pro teams.
Reminds me of the story about the Mercury astronauts. Originally, they'd just be cooped up in their tin cans with nothing to do. They insisted on having buttons to push, a joystick, levers to pull so they could be *pilots*, as they already were in their pre-astronaut careers. They got it, and it turned out to be useful. (At least, this is the story as told in books, movies and other sources.)
No one wants to do nothing, but we all want to be involved in some way, to have input, to have the means to push harder or more skillfully, and to be able to rescue ourselves from disaster in case the automated systems fail.
Another story, from the 1970s, science fiction but that's not important. Some characters wanted to go from ground to the top of some building or structure, not very tall, just a few floors. They had a choice: stairs or elevator? They took the stairs, because it feels like you're doing something, active, in a position of control and able to push a little harder if you want to get there sooner. Maybe the elevator would have been a bit faster, but the passive waiting, getting in, and then more passive waiting, is unpleasant to people who have things to do, goals, disasters to prevent. That insight from that one story has stuck in my mind ever since.
That said, of course, a four hour round trip as the one commenter described is wasted time that could go toward reading, sleeping, practicing guitar, answering question on internet forums, telling jokes or anything more fun than guiding a machine along an easy path.
Not practical anytime soon, but maybe someday, we could create materials with muons in place of electrons. Effectively much smaller atoms. Much denser, many more quarks per cubic cm to catch neutrinos. How to keep it stable instead of being ridiculously radioactive and going poof in a microsecond, and make bulk amounts, I have no idea. Crazy new things will be invented in the coming decades. We can't discount the possibility of some impossible-today new material that can catch neutrinos.
Yeah, there are many other very lucrative fields such as theater, fine arts, sociology, Lady Gaga Studies (seriously, proof there is no hope for humanity),...
Slashdot Mirror
Far worse: Climb the foothills near Boulder, and look at Denver.
People suffer effects of breathing carbon monoxide after driving through Denver on I25.
Yes, there's a lot wrong with that old rubber sheet analogy. As a zillion previous /.ers have stated, it's just a simple crude means of making an intuitive point, that in some general way curvature affects objects moving about in the arena they inhabit.
Of course the biggest bit of silliness is that the analogy relies on gravity in order to explain gravity. Duh.
Some have mentioned that marbles rolling about on a curved rubber sheet are _rolling_, and that has no analogy with reality. But we can ignore that.
Rubber, or whatever more or less solid type of "fabric of space-time" one uses, allows longitudianal motions, stretching and jiggling tangentially along the surface. This has no analog in reality. We can just ignore that too. A better way to think of curved space is as liquid, in an analogy with soapy water films and bubbles. There's no stretching, as liquid readily flows to fill in areas being pulled apart. There's only curvature and boundary conditions as the films of liquid find minimal surface area.
But then, even that fails, as gravity as we deal with it in the real world is almost entirely explained by the time-time component of the metric. Curvature of space is secondary, hard to measure, and a matter for precision experiments involve spacecraft and lasers. It's the differential rate of progress of time between nearby points that "explains" gravity. But to explain it intuitively to the layman, that I'm not so sure about.
FWIW, at one place I worked there was a table anyone could dump a book on for others to "borrow". No real expectation of getting it back, but a way to pass on unwanted books to someone who might find it useful.
I wanted to reduce my collection of books. So I dumped a less-popular Ruby book onto that table. It vanished before the end of the day. I dumped a couple other ruby books, including The Ruby Way and some book on Ruby brain-teaser quizes, something like that. Poof, as if done by a magician trying to impress members of the opposite sex, they vanished quickly and completely, by the next time I passed through that room. Interesting.
Then I dumped Andrei Alexandrescu's The D Programming Language. It sat for a day, then another day, and another. After a week it was still there. Eventually someone took it. At least at this one company, D is 1/100th as popular as Ruby. Neither language is used officially on company projects - it's all Java, C++, C# and Python. Internal web sites do not use RoR that I know of.
Ruby is a fine language, but in practical implementation other languages, in particular, Python run circles around it. A circle. Maybe half a circle, but you know what I mean - Ruby is fine but never in first place. I still use it for some electronics graphics (http://www.darenscotwilson.com/spec/stereo888/stereo888.html) It's certainly not dying if there are such quick book-snatchers in a company not using it.
OTOH, those who know of D like it quite well, actually use it, try to spread the word, and that includes me. Maybe D is in the stage of early growth outside it's originating community, where Ruby was in 199x where I'm not sure what 'x' is.
D is clearly growing, but has a long way to go, while Ruby is way up there, and has a long way to go if it is in fact shrinking.
When I am a multi-billionaire, I will build a giant monument, 100 miles wide, fifty tall, and engrave on it all over every tweet and facebook post ever written since the 1990s, through all of the 21st century, so our descendants one thousand years in the future will not lose all that precious wisdom and insight into our culture.
When my university's library expanded in the late 1980s, I wondered about two things: in another two or three decades, will they need to expand again? Of course. And also: Who is going to read or look up info in all those books? Of course, there will always be specialists and indexes and catalogs, but if the trend continues for all the 21st Century, and all of the 22nd Century, ..., at some point there will be far too much "literature" even in a very narrow academic specialty for any human to make use of. Then what about all the non-academic stuff, cheap romance novels and mysteries and memoirs of flash-in-the-pan pseudo-celebrities?
It's not that we need a good ol' roaring book-burning now and then like at Alexandria long ago, but somehow the best needs to be brought to the top, and the most of the mediocre disposed of. And maybe keep mediocre writers from ever starting. (Stuff that's actually *bad* not merely mediocre - keep some as examples and for the entertainment value!)
So now we have disks and all manner of extremely dense storage materials. This changes nothing, aside from the physical space requirements are reduced to near nothing. Even with intelligent indexes and indexes of indexes, or miraculously good search engines such as Google, or whatever we'll have in fifty years - it's mind-boggling to wonder how such a huge growing pile of information will be utilized.
"Research scientists could learn an important thing or two from computer scientists,..."
What is the error bar on "a thing or two"?
As someone with a foot in each camp, I believe it's more like fifty or a hundred. The methods of scientists regarding computing are often built of slow evolutionary changes upon old familiar methods, while incorporating selected cutting edge hardware or algorithms. It is partly the nature of some science projects to carry out observations over many years, ideally with the same instruments, processing and management. In academic computer science, as well as real world IT, all layers and all aspects of any large system are always changing over time. ("All" = 100% give or take a few %) (And yes, somedays, it does seem like over 100%)
Would the chemistry leading to primitive life, and the very earliest life forms, need cooler places? If all of space is permeated by comfy temperatures, where could things happen needing to happen at cooler temperatures? Maybe evaporation in certain places could lead to that, or some other nonequilibrium situations.
Amoebas gotta keep their primitive beer cold!
Problem solved - just resume production of these:
Gilbert U-238 Atomic Energy Lab
http://www.orau.org/ptp/collection/atomictoys/GilbertU238Lab.htm
Yup. Though there can be big differences in the benefit for effort depending on if the candidate is modestly experienced, more experienced, a near-master, or what, and if the nature of the work is "concave" or "convex" as described by Michael O Church http://michaelochurch.wordpress.com/2013/04/03/gervais-macleod-21-why-does-work-suck/ In certain cases it may really be better for the company to wait it out for superb talent - but surely this accounts for only a few % of all open positions. What kinds of jobs are "concave"? As far I understand, professional athletes, pop celebrities (their agents and marketers not the singers/dancers/actors themselves being the actual "talent"). Symphony bassoonists too, I imagine. Video game designers, language and framework designers.
For almost all other cases, in real life, I look around and see people with skills of any kind at any level above zero, would be happy to learn new things. And there's a lot of "convex" work in IT and software development (and many entirely different fields) where being not in the top 1% or 10% is okay - being 40% or 50% down means work that is just about as good. Convex work would include stuff like maintaining servers or grinding out more GUI frontends to ever-shifting enterprise databases.
A lot of talented and near-talented and half-talented people could be contributing, earning money, and reviving the economy of (fill in blank with whatever country has a slow economy and companies holding out for superstars), if companies understood that they'd be just fine in any of those "convex" jobs.
Best read of the day!
"...choose whether you want to be part of the herd near the edge looking for the wolves, or oblivious somewhere the middle, or if you want to be a wolf" ...or the vulture to clean up the carcass after the wolf's feast, or the fleas who bother all furry/hairy animals, or the dung beetles to carry away you-know-what, or the penguins who are so far away, so aloof they don't know or care about the herd, or ....
And the edge of the herd is more than an early warning system against predators, but also where new feeding grounds, water, and various good things are first observed.
A two or three week vacation in the spring (best for travel) and a couple in the fall, and a couple during the coldest part of the year (to save heating costs) and another in the hottest part of the year (to save cooling costs). These may vary from one part of the country to another, which is good. Families on vacation won't be all crowding the hot tourist spots all at once.
There's no good reason to take as much as a full month off, and certainly not more, although in places with the harshest winters an exception to that rule would be fine.
(Just leave my Nobel Prize in Education on the back porch. I'll drag it in when I get around to it.)
Go to YouTube, search with some keywords like "russia car accident", and you can watch 10,000 dashcam videos of "interesting events". I wonder how well Nissan's car would handle any of those?
You take a risk by saying something intelligent on slashdot!
My personal experience with bicycle helmets is that it's more dangerous to wear a helmet than not. I have never had a serious injury from a bicycle incident. A semi-serious injury to my hand once, with no permanent damage. (Checking... 1, 2, 3, 4, 5. All fingers still there.)
But one fine year I decided to do the right thing and wear a helmet. There was a situation where the wheel slipped and I landed the way I normally do on those rare occasions. Except this time, the ground shoved the helmet against my head and the edge of it bashed my forehead right above an eye. A bump grew, and I went to the nearest emergency room. Turned out okay, just the swelling you get from any whack.
Interesting, that the one time I wear a helmet, it causes more injury than if I hadn't worn it. Also interesting that bicycling injuries, except for that one helmet incident, are always to my hands. What are we supposed to wear over our hands? Is it law?
This is just my personal experience. YMMV, of course. Do not try this at home, do not operate heavy women while under the influence of pregnant machinery, I'm not a real doctor just tell women at the bar that I play one on TV, I may have guardian angels with oddball senses of humor, etc etc etc.
So, one wouldn't find much of this
http://youtu.be/65_m3Eyga0o
happening in Finland, then?
How often have those massive overreactions lead to trouble leading to lawsuits?
Seems like a few clever lawyers could apply some equal and opposite legal forces to herd the authorities and decision-makers into a reasonable direction.
Yup. Phil Plait, the Bad Astronomer explained it well. What goes for Hubble, goes pretty much the same for Cassini (I know, I worked for CICLOPS) and for many other planetary missions.
http://www.badastronomy.com/bad/misc/badhst.html
Physics grad students (and grad students in other sciences and engineering) actually help build instruments, interpret data, and contribute to mankinds store of knowledge.
Athletes hoping for superstardom but not making it out of high school football/whatever provide some entertainment for local football/whatever fans, but don't really contribute to mankind's anything. They're doing good, nonetheless - developing teamwork skills, performing in front of a crowd, organizing, following a strategy, staying healthy. But so do grad students, albeit a different kind of team, different kinds of strategies. (And maybe not so much interest in staying healthy.)
Scientists who don't make it to professorhood do a lot more for society as grad students and post-docs than athletes who don't make it to the pro teams.
If only Head of Microsoft were an elected office! You've got my vote.
Reminds me of the story about the Mercury astronauts. Originally, they'd just be cooped up in their tin cans with nothing to do. They insisted on having buttons to push, a joystick, levers to pull so they could be *pilots*, as they already were in their pre-astronaut careers. They got it, and it turned out to be useful. (At least, this is the story as told in books, movies and other sources.)
No one wants to do nothing, but we all want to be involved in some way, to have input, to have the means to push harder or more skillfully, and to be able to rescue ourselves from disaster in case the automated systems fail.
Another story, from the 1970s, science fiction but that's not important. Some characters wanted to go from ground to the top of some building or structure, not very tall, just a few floors. They had a choice: stairs or elevator? They took the stairs, because it feels like you're doing something, active, in a position of control and able to push a little harder if you want to get there sooner. Maybe the elevator would have been a bit faster, but the passive waiting, getting in, and then more passive waiting, is unpleasant to people who have things to do, goals, disasters to prevent. That insight from that one story has stuck in my mind ever since.
That said, of course, a four hour round trip as the one commenter described is wasted time that could go toward reading, sleeping, practicing guitar, answering question on internet forums, telling jokes or anything more fun than guiding a machine along an easy path.
An excellent book. Recommended by 100% of those who recommend this book.
That movie sounds like "A Bronx Tale", from 1993. A good movie that made several thoughtful philosophical points.
Not practical anytime soon, but maybe someday, we could create materials with muons in place of electrons. Effectively much smaller atoms. Much denser, many more quarks per cubic cm to catch neutrinos. How to keep it stable instead of being ridiculously radioactive and going poof in a microsecond, and make bulk amounts, I have no idea. Crazy new things will be invented in the coming decades. We can't discount the possibility of some impossible-today new material that can catch neutrinos.
Yeah, there are many other very lucrative fields such as theater, fine arts, sociology, Lady Gaga Studies (seriously, proof there is no hope for humanity), ...
Reminds me of old-time television cameras, from the 1950s and early 1960s, with the bright objects surrounded by a halo of dark.