KaiserScience

Start here

Gravitational repulsion and the Dipole Repeller

Ask Ethan: If Gravity Attracts, How Can The ‘Dipole Repeller’ Push The Milky Way?

Ethan Siegel, Contributor. Feb 4, 2017

Forbes.com Startswithabang 2017 Ask Ethan The Dipole Repeller

The relative attractive and repulsive effects of overdense and underdense regions on the Milky Way. Image credit: "The Dipole Repeller" by Yehuda Hoffman, Daniel Pomarède, R. Brent Tully, and Hélène Courtois, Nature Astronomy 1, 0036 (2017).

The relative attractive and repulsive effects of overdense and underdense regions on the Milky Way. Image credit: “The Dipole Repeller” by Yehuda Hoffman, Daniel Pomarède, R. Brent Tully, and Hélène Courtois, Nature Astronomy 1, 0036 (2017).

One of the most peculiar things about the Universe is how quickly the Milky Way appears to be moving. Despite having mapped out the cosmic masses nearby to unprecedented accuracy, there still doesn’t appear to be enough to cause the motion we actually experience. The idea of a “great attractor” doesn’t quite match up with what we see; what’s actually present isn’t quite “great” enough. But a new idea — that of a dipole repeller — might finally explain this longstanding conundrum. How would that work, and what it is, exactly? That’s what Darren Redfern wants to know:

What are the mechanics behind a dipole repeller? How can an area of space void of matter repulse galaxies to any meaningful extent (or at all?)?

If you were to look at all the galaxies accessible to us, you’d find, on average, that they were moving away from us at a specific rate: the Hubble rate. The farther away a galaxy is, the faster it appears to move away from us, and that’s a consequence of living in an expanding Universe governed by General Relativity. But that’s only on average. Each individual galaxy has an additional motion on top of that, known as peculiar velocity, and that’s due to the combined gravitational influence of every imperfection in the Universe on it.

The various galaxies of the Virgo Supercluster, grouped and clustered together. On the largest scales, the Universe is uniform, but as you look to galaxy or cluster scales, overdense and underdense regions dominate. Image credit: Andrew Z. Colvin, via Wikimedia Commons.

The various galaxies of the Virgo Supercluster, grouped and clustered together. On the largest scales, the Universe is uniform, but as you look to galaxy or cluster scales, overdense and underdense regions dominate. Image credit: Andrew Z. Colvin, via Wikimedia Commons.

The closest large galaxy to us, Andromeda, is actually moving towards us, thanks to the Milky Way’s gravitational pull. Galaxies in the closest giant cluster of galaxies — the Virgo cluster — get extra speeds of up to 2,000 km/s on top of the Hubble flow we see. And when we look at the Big Bang’s leftover glow, the Cosmic Microwave Background, we’re able to measure our own peculiar motion through the Universe.

The CMB dipole as measured by COBE, representing our motion through the Universe relative to the CMB's rest frame. Image credit: DMR, COBE, NASA, Four-Year Sky Map.

The CMB dipole as measured by COBE, representing our motion through the Universe relative to the CMB’s rest frame. Image credit: DMR, COBE, NASA, Four-Year Sky Map.

This “cosmic dipole” we see is redshifted in one direction (meaning we’re moving away from it) and blueshifted in the other (meaning we’re moving towards it), and we can reconstruct the motion of the entire local group as a result. Us, Andromeda, Triangulum and everything else is moving at a speed of 631 km/s relative to the Hubble flow, and we know that gravitation must be the cause of this. When we look out at where the galaxies are located, we can map out their masses and how much of an attractive force they exert.

 two-dimensional slice of the overdense (red) and underdense (blue/black) regions of the Universe nearby us. Image credit: Cosmic Flows Project/University of Hawaii, via http://www.cpt.univ-mrs.fr/.

two-dimensional slice of the overdense (red) and underdense (blue/black) regions of the Universe nearby us. Image credit: Cosmic Flows Project/University of Hawaii, via http://www.cpt.univ-mrs.fr/.

Thanks to the recent Cosmic Flows project, we’ve not only mapped out the nearby Universe to better precision than ever before, we discovered that the Milky Way lies on the outskirts of a giant collection of galaxies pulling us towards it: Laniakea. This is a significant contributor to our peculiar motion, but it isn’t enough to explain all of it on its own. Gravitational attraction is only half the story. The other half? It comes from gravitational repulsion. Let me explain.

Imagine you have a Universe where you have an equal number of masses evenly spaced everywhere you look. In all directions, at all locations, the Universe is filled with matter of even density. If you put an extra mass a certain distance to your left, you’ll be attracted towards your left, because of gravitational attraction.

But if you remove some of the mass that same distance to your right, you’ll also be attracted towards your left! In a perfectly uniform Universe, you’d be attracted to all directions equally, and that attractive force would cancel out. But if you remove some mass from one particular direction, it can’t attract you as strongly, and so you’re attracted preferentially in the other direction.

Dipoles are most common in electromagnetism, where we think of negative as attractive and positive as repulsive. If you thought of this gravitationally, negative would be 'extra mass' and therefore attractive, while positive would be 'less mass' and therefore, relative to everything else, repulsive. Image credit: Wikimedia Commons user Maschen.

Dipoles are most common in electromagnetism, where we think of negative as attractive and positive as repulsive. If you thought of this gravitationally, negative would be ‘extra mass’ and therefore attractive, while positive would be ‘less mass’ and therefore, relative to everything else, repulsive. Image credit: Wikimedia Commons user Maschen.

 

It’s not technically a gravitational repulsion, since gravitation is always attractive, but you’re less attracted to one direction than all the others, and so an underdense region effectively acts as a gravitational repeller. You can even imagine a situation where you have an overly dense region on one side of you with an underdense region on the other side. You’d experience the greatest magnitude of attraction and repulsion simultaneously. This is what the idea of the dipole repeller is.

The gravitational attraction (blue) of overdense regions and the relative repulsion (red) of the underdense regions, as they act on the Milky Way. Image credit: "The Dipole Repeller" by Yehuda Hoffman, Daniel Pomarède, R. Brent Tully, and Hélène Courtois, Nature Astronomy 1, 0036 (2017).

The gravitational attraction (blue) of overdense regions and the relative repulsion (red) of the underdense regions, as they act on the Milky Way. Image credit: “The Dipole Repeller” by Yehuda Hoffman, Daniel Pomarède, R. Brent Tully, and Hélène Courtois, Nature Astronomy 1, 0036 (2017).

It’s difficult to measure where an underdense region is, since regions of average density are fairly devoid of galaxies as well as the underdense ones. But a recently discovered cosmic void relatively nearby, and in the opposite direction to the large concentration of galaxies attracting us, seems to be responsible for roughly 50% of our peculiar motion, which is exactly the amount that was unaccounted for by the overdense regions alone.

Youtube video: The Dipole Repeller video, by Daniel Pomarède.  produced as part of the following publication: “The Dipole Repeller” by Yehuda Hoffman, Daniel Pomarède, R. Brent Tully, and Hélène Courtois, Nature Astronomy 1, 0036 (2017).

At long last, this could be the solution to why our Sun, galaxy and local group all exhibit the motion that they do. Gravity is never repulsive, but a less attractive force in one direction than all the others behaves indistinguishably from a repulsion. We might distinguish between a pull in one direction and a push in the opposite direction, but in astrophysics, it’s all the same thing: forces and acceleration. It doesn’t have anything to do with dark energy or a mysterious fifth force; it’s simply having an excess of matter in one direction and a dearth of matter in nearly the exact opposite direction. The result? We move through the Universe in our own particular, peculiar fashion.

Reference: The dipole repeller, Yehuda Hoffman, Daniel Pomarède, R. Brent Tully & Hélène M. Courtois, Nature Astronomy 1, Article number: 0036 (2017).

Ethan Siegel, Contributor. Feb 4, 2017

Forbes.com Startswithabang 2017 Ask Ethan The Dipole Repeller

 

Why learn computer programming

Why Johnny can’t code

By David Brin, Salom Magazine, Sept 14, 2006

from Barron’s Dictionary of Computer and Internet Terms for: BASIC

BASIC used to be on every computer a child touched — but today there’s no easy way for kids to get hooked on programming.

Also see our main page on What is mathematics, really? Is it made by humans or a feature of the universe? Math in art & poetry.
____________________________________________

For three years — ever since my son Ben was in fifth grade — he and I have engaged in a quixotic but determined quest: We’ve searched for a simple and straightforward way to get the introductory programming language BASIC to run on either my Mac or my PC.

Why on Earth would we want to do that, in an era of glossy animation-rendering engines, game-design ogres and sophisticated avatar worlds? Because if you want to give young students a grounding in how computers actually work, there’s still nothing better than a little experience at line-by-line programming.

Only, quietly and without fanfare, or even any comment or notice by software pundits, we have drifted into a situation where almost none of the millions of personal computers in America offers a line-programming language simple enough for kids to pick up fast. Not even the one that was a software lingua franca on nearly all machines, only a decade or so ago. And that is not only a problem for Ben and me; it is a problem for our nation and civilization.

Oh, today’s desktops and laptops offer plenty of other fancy things — a dizzying array of sophisticated services that grow more dazzling by the week. Heck, I am part of that creative spasm.

Only there’s a rub. Most of these later innovations were brought to us by programmers who first honed their abilities with line-programming languages like BASIC. Yes, they mostly use higher level languages now, stacking and organizing object-oriented services, or using other hifalutin processes that come prepackaged and ready to use, the way an artist uses pre-packaged paints. (Very few painters still grind their own pigments. Should they?)

And yet the thought processes that today’s best programmers learned at the line-coding level still serve these designers well. Renowned tech artist and digital-rendering wizard Sheldon Brown, leader of the Center for Computing in the Arts, says:

“In my Electronics for the Arts course, each student built their own single board computer, whose CPU contained a BASIC ROM [a chip permanently encoded with BASIC software]. We first did this with 8052’s and then with a chip called the BASIC Stamp. The PC was just the terminal interface to these computers, whose programs would be burned into flash memory. These lucky art students were grinding their own computer architectures along with their code pigments — along their way to controlling robotic sculptures and installation environments.”

But today, very few young people are learning those deeper patterns. Indeed, they seem to be forbidden any access to that world at all.

And yet, they are tantalized! Ben has long complained that his math textbooks all featured little type-it-in-yourself programs at the end of each chapter — alongside the problem sets — offering the student a chance to try out some simple algorithm on a computer. Usually, it’s an equation or iterative process illustrating the principle that the chapter discussed. These “TRY IT IN BASIC” exercises often take just a dozen or so lines of text. The aim is both to illustrate the chapter’s topic (e.g. statistics) and to offer a little taste of programming.

Only no student tries these exercises.

Not my son or any of his classmates. Nor anybody they know. Indeed, I would be shocked if more than a few dozen students in the whole nation actually type in those lines that are still published in countless textbooks across the land. Those who want to (like Ben) simply cannot.

Now, I have been complaining about this for three years. But whenever I mention the problem to some computer industry maven at a conference or social gathering, the answer is always the same: “There are still BASIC programs in textbooks?”

At least a dozen senior Microsoft officials have given me the exact same response. After taking this to be a symptom of cluelessness in the textbook industry, they then talk about how obsolete BASIC is, and how many more things you can do with higher-level languages. “Don’t worry,” they invariably add, “the newer textbooks won’t have any of those little BASIC passages in them.”

All of which is absolutely true. BASIC is actually quite tedious and absurd for getting done the vast array of vivid and ambitious goals that are typical of a modern programmer. Clearly, any kid who wants to accomplish much in the modern world would not use it for very long. And, of course, it is obvious that newer texts will abandon “TRY IT IN BASIC” as a teaching technique, if they haven’t already.

But all of this misses the point. Those textbook exercises were easy, effective, universal, pedagogically interesting — and nothing even remotely like them can be done with any language other than BASIC. Typing in a simple algorithm yourself, seeing exactly how the computer calculates and iterates in a manner you could duplicate with pencil and paper — say, running an experiment in coin flipping, or making a dot change its position on a screen, propelled by math and logic, and only by math and logic:

All of this is priceless. As it was priceless 20 years ago. Only 20 years ago, it was physically possible for millions of kids to do it. Today it is not.

In effect, we have allowed a situation to develop that is like a civilization devouring its seed corn. If an enemy had set out to do this to us — quietly arranging so that almost no school child in America can tinker with line coding on his or her own — any reasonably patriotic person would have called it an act of war.

Am I being overly dramatic? Then consider a shift in perspective.

First ponder the notion of programming as a series of layers. At the bottom-most level is machine code. I showed my son the essentials on scratch paper, explaining the roots of Alan Turing’s “general computer” and how it was ingeniously implemented in the first four-bit integrated processor, Intel’s miraculous 1971 4004 chip, unleashing a generation of nerdy guys to move bits around in little clusters, adding and subtracting clumps of ones and zeroes, creating the first calculators and early desktop computers like the legendary Altair.

This level of coding is still vital, but only at the realm of specialists at the big CPU houses. It is important for guys like Ben to know about machine code — that it’s down there, like DNA in your cell — but a bright kid doesn’t need to actually do it, in order to be computer-literate. (Ben wants to, though. Anyone know a good kit?)

The layer above that is often called assembler, though there are many various ways that user intent can be interpreted down to the bit level without actually flicking a series of on-off switches. Sets of machine instructions are grouped, assembled and correlated with (for example) ASCII-coded commands. Some call this the “boringest” level. Think of the hormones swirling through your body. Even a glimpse puts me to sleep. But at least I know that it is there.

The third layer of this cake is the operating system of your computer. Call it BIOS and DOS, along with a lot of other names. This was where guys like Gates and Wozniak truly propelled a whole industry and way of life, by letting the new desktops communicate with their users, exchange information with storage disks and actually show stuff on a screen. Cool.

Meanwhile, the same guys were offering — at the fourth layer — a programming language that folks could use to create new software of their very own. BASIC was derived from academic research tools like beloved old FORTRAN (in which my doctoral research was coded onto punched paper cards, yeesh). It was crude. It was dry. It was unsuitable for the world of the graphic user interface. BASIC had a lot of nasty habits. But it liberated several million bright minds to poke and explore and aspire as never before.

The “scripting” languages that serve as entry-level tools for today’s aspiring programmers — like Perl and Python — don’t make this experience accessible to students in the same way. BASIC was close enough to the algorithm that you could actually follow the reasoning of the machine as it made choices and followed logical pathways.

Repeating this point for emphasis: You could even do it all yourself, following along on paper, for a few iterations, verifying that the dot on the screen was moving by the sheer power of mathematics, alone. Wow!

(Indeed, I would love to sit with my son and write “Pong” from scratch. The rule set — the math — is so simple. And he would never see the world the same, no matter how many higher-level languages he then moves on to.)

The closest parallel I can think of is the WWII generation of my father — guys for whom the ultra in high tech was automobiles. What fraction of them tore apart jalopies at home? Or at least became adept at diagnosing and repairing the always fragile machines of that era? One result of that free and happy spasm of techie fascination was utterly strategic. When the “Arsenal of Democracy” began churning out swarms of tanks and trucks and jeeps, these were sent to the front and almost overnight an infantry division might be mechanized, in the sure and confident expectation that there would be thousands of young men ready (or trainable) to maintain these tools of war. (Can your kid even change the oil nowadays? Or a tire?)

The parallel technology of the ’70s generation was IT.

Information technology (IT) is the application of computers to store, study, transmit, and manipulate data, often in the context of a business or other enterprise.

Not every boomer soldered an Altair from a kit, or mastered the arcana of DBASE. But enough of them did so that we got the Internet and Web. We got Moore’s Law and other marvels. We got a chance to ride another great technological wave.

So, what’s the parallel hobby skill today?
What tech-marvel has boys and girls enthralled, tinkering away, becoming expert in something dazzling and practical and new?
Shooting ersatz aliens in “Halo”?
Dressing up avatars in “The Sims”?

Oh sure, there’s creativity in creating cool movies and Web pages. But except for the very few who will make new media films, do you see a great wave of technological empowerment coming out of all this?

OK, I can hear the sneers. Are these the rants of a grouchy old boomer? Feh, kids today! (And get the #$#*! off my lawn!)

Fact is, I just wanted to give my son a chance to sample some of the wizardry standing behind the curtain, before he became lost in the avatar-filled and glossy-rendered streets of Oz. Like the hero in “TRON,” or “The Matrix,” I want him to be a user who can see the lines that weave through the fabric of cyberspace — or at least know some history about where it all came from. At the very minimum, he ought to be able to type those examples in his math books and use the computer the way it was originally designed to be used: to compute.

Hence, imagine my frustration when I discovered that it simply could not be done.

Yes, yes: For three years I have heard all the rationalized answers. No kid should even want BASIC, they say. There are higher-level languages like C++ (Ben is already — at age 14 — on page 200 of his self-teaching C++ book!) and yes, there are better education programs like Logo. Hey, what about Visual Basic! Others suggested downloadable versions like q-basic, y-basic, alphabetabasic…

Indeed, I found one that was actually easy to download, easy to turn on, and that simply let us type in some of those little example programs, without demanding that we already be manual-chomping fanatics in order to even get started using the damn thing. Chipmunk Basic for the Macintosh actually started right up and let us have a little clean, algorithmic fun. Extremely limited, but helpful. All of the others, every last one of them, was either too high-level (missing the whole point!) or else far, far too onerous to figure out or use. Certainly not meant to be turn-key usable by any junior high school student. Appeals for help online proved utterly futile.

Until, at last, Ben himself came up with a solution. An elegant solution of startling simplicity. Essentially: If you can’t beat ’em, join ’em.

While trawling through eBay, one day, he came across listings for archaic 1980s-era computers like the Apple II. “Say, Dad, didn’t you write your first novel on one of those?” he asked.

“Actually, my second. ‘Startide Rising.’ On an Apple II with Integer Basic and a serial number in five digits. It got stolen, pity. But my first novel, ‘Sundiver,’ was written on this clever device called a typewrit –”

“Well, look, Dad. Have you seen what it costs to buy one of those old Apples online, in its original box? Hey, what could we do with it?”

“Huh?” I stared in amazement.

Then, gradually, I realized the practical possibilities.

Let’s cut to the chase. We did not wind up buying an Apple II. Instead (for various reasons) we bought a Commodore 64 (in original box) for $25. It arrived in good shape. It took us maybe three minutes to attach an old TV. We flicked the power switch … and up came a command line. In BASIC.

Uh. Problem solved?

I guess. At least far better than any other thing we’ve tried!

We are now typing in programs from books, having fun making dots move (and thus knowing why the dots move, at the command of math, and not magic). There are still problems, like getting an operating system to make the 5141c disk drive work right. Most of the old floppies are unreadable. But who cares? (Ben thinks that loading programs to and from tape is so cool. I gurgle and choke remembering my old Sinclair … but whatever.)

What matters is that we got over a wretched educational barrier. And now Ben can study C++ with a better idea where it all came from. In the nick of time.

Problem solved? Again, at one level.

And yet, can you see the irony? Are any of the masters of the information age even able to see the irony?

This is not just a matter of cheating a generation, telling them to simply be consumers of software, instead of the innovators that their uncles were. No, this goes way beyond that. In medical school, professors insist that students have some knowledge of chemistry and DNA before they are allowed to cut open folks. In architecture, you are at least exposed to some physics.

But in the high-tech, razzle-dazzle world of software? According to the masters of IT, line coding is not a deep-fabric topic worth studying. Not a layer that lies beneath, holding up the world of object-oriented programming. Rather, it is obsolete!

Or, at best, something to be done in Bangalore. Or by old guys in their 50s, guaranteeing them job security, the same way that COBOL programmers were all dragged out of retirement and given new cars full of Jolt Cola during the Y2K crisis.

All right, here’s a challenge. Get past all the rationalizations. (Because that is what they are.) It would be trivial for Microsoft to provide a version of BASIC that kids could use, whenever they wanted, to type in all those textbook examples. Maybe with some cool tutorial suites to guide them along, plus samples of higher-order tools. It would take up a scintilla of disk space and maybe even encourage many of them to move on up. To (for example) Visual Basic!

Or else, hold a big meeting and choose another lingua franca, so long as it can be universal enough to use in texts, the way that BASIC was.

Instead, we are told that “those textbooks are archaic” and that students should be doing “something else.” Only then watch the endless bickering over what that “something else” should be — with the net result that there is no lingua franca at all, no “basic” language so common that textbook publishers can reliably use it as a pedagogical aide.

The textbook writers and publishers aren’t the ones who are obsolete, out-of-touch and wrong. It is people who have yanked the rug out from under teachers and students all across the land.

Let me reiterate. Kids are not doing “something else” other than BASIC. Not millions of them. Not hundreds or tens of thousands of them. Hardly any of them, in fact. It is not their fault. Because some of them, like my son, really want to. But they can’t. Not without turning into time travelers, the way we did, by giving up (briefly) on the present and diving into the past. (I also plan to teach him how to change the oil and fix a tire!) By using the tools of a bygone era to learn more about tomorrow.

If this is a test, then Ben and I passed it, ingeniously. In contrast, Microsoft and Apple and all the big-time education-computerizing reformers of the MIT Media Lab are failing, miserably. For all of their high-flown education initiatives (like the “$100 laptop”), they seem bent on providing information consumption devices, not tools that teach creative thinking and technological mastery.

Web access for the poor would be great. But machines that kids out there can understand and program themselves? To those who shape our technical world, the notion remains not just inaccessible, but strangely inconceivable.

– David Brin is an astrophysicist whose international best-selling novels include “Earth,” and recently “Existence.” ” The Postman” was filmed in 1997. His nonfiction book about the information age – The Transparent Society – won the Freedom of Speech Award of the American Library Association. (http://www.davidbrin.com)

http://www.salon.com/2006/09/14/basic_2/

This website is educational. Materials within it are being used in accord with the Fair Use doctrine, as defined by United States law.

§107. Limitations on Exclusive Rights: Fair Use.  Notwithstanding the provisions of section 106, the fair use of a copyrighted work, including such use by reproduction in copies or phone records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use, the factors to be considered shall include: the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; the nature of the copyrighted work; the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and the effect of the use upon the potential market for or value of the copyrighted work. (added pub. l 94-553, Title I, 101, Oct 19, 1976, 90 Stat 2546)

Coal releases more radioactivity than nuclear power

 

Coal Ash Is More Radioactive Than Nuclear Waste

By burning away all the pesky carbon and other impurities, coal power plants produce heaps of radiation

By Mara Hvistendahl on December 13, 2007

PWR_nuclear_power_plant_diagram

The popular conception of nuclear power is straight out of The Simpsons: Springfield abounds with signs of radioactivity, from the strange glow surrounding Mr. Burn’s nuclear power plant workers to Homer’s low sperm count. Then there’s the local superhero, Radioactive Man, who fires beams of “nuclear heat” from his eyes. Nuclear power, many people think, is inseparable from a volatile, invariably lime-green, mutant-making radioactivity.

Coal, meanwhile, is believed responsible for a host of more quotidian problems, such as mining accidents, acid rain and greenhouse gas emissions. But it isn’t supposed to spawn three-eyed fish like Blinky.

Over the past few decades, however, a series of studies has called these stereotypes into question. Among the surprising conclusions: the waste produced by coal plants is actually more radioactive than that generated by their nuclear counterparts. In fact, the fly ash emitted by a power plant—a by-product from burning coal for electricity—carries into the surrounding environment 100 times more radiation than a nuclear power plant producing the same amount of energy. * [See Editor’s Note at end of page 2]

At issue is coal’s content of uranium and thorium, both radioactive elements. They occur in such trace amounts in natural, or “whole,” coal that they aren’t a problem. But when coal is burned into fly ash, uranium and thorium are concentrated at up to 10 times their original levels.

Fly ash uranium sometimes leaches into the soil and water surrounding a coal plant, affecting cropland and, in turn, food. People living within a “stack shadow”—the area within a half- to one-mile (0.8- to 1.6-kilometer) radius of a coal plant’s smokestacks—might then ingest small amounts of radiation. Fly ash is also disposed of in landfills and abandoned mines and quarries, posing a potential risk to people living around those areas.

https://www.scientificamerican.com/article/coal-ash-is-more-radioactive-than-nuclear-waste/

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Nuclear Danger Still Dwarfed by Coal
By Christopher Wanjek, LiveScience, 4/26/11

One must accept a risk of radiation exposure when flying in and out of Narita International Airport, the busiest airport in Japan, just east of Tokyo, but perhaps not for the reason you are thinking.

Fukushima Daiichi, the tsunami-damaged nuclear reactor site about 150 miles (241 kilometers) to the north, as the foolish crow flies, continues to leak trace amounts of radiation. Radioactive iodine-131 made it into the water supply here last month. But most, as physics would have it, has since decayed into stable xenon.

So, few in this Tokyo region have been exposed to radiation levels as high as someone just hopping off a plane. The international flyer receives a dose of about 0.10 millisievert, or the amount of ionizing radiation in two dental X-rays, from the sun’s radioactive cosmic rays. That means that folks who left Tokyo because of the threat at Fukushima likely received more radiation on the airplane flight than they would have if they had stayed at home. [Mysterious Radiation May Strike Airline Passengers]

Such is the irony of nuclear energy, so potentially dangerous yet so much remarkably safer than most other energy sources, namely coal and other fossil fuels.

Dirty, dirty coal

As bad as Japan’s nuclear emergency could have gotten, it would never be as bad as burning coal. Coal is fantastically dangerous, responsible for far more than 1 million deaths per year, according to the World Health Organization.

Start with the coal miners, thousands of whom die from mine collapses and thousands more from various lung diseases. Next, add the hundreds of thousands of deaths in the public from breathing coal’s gaseous and particulate pollution, mostly from respiratory and heart disease.

Next, add the untold deaths and disabilities resulting from mercury in coal entering into the food chain. Then add the millions of acres of land, river and lake destroyed by mining waste.

Some of China’s citizens worried about a radioactive wind blowing over from Japan, but coal-burning power plants from China are causing far more health problems for both China and Japan.

Coal even releases more radioactive material than nuclear energy — 100 times more per the same amount of energy produced, according to Dana Christensen of the U.S. Department of Energy (DOE), as reported in Scientific American in 2007.

According to WHO statistics, there are at least 4,025 deaths from coal for every single death from nuclear power. Switch to “clean” natural gas? That’s still 100 times deadlier than nuclear energy. Oil is 900 times deadlier.

Not many are expected to die from the Fukushima Daiichi accident.

The U.S. DOE predicts a yearly dose of about 2,000 millirems for some people living northwest of the nuclear facility within 19 miles (31 kilometers), which could slightly increase their cancer risk if they haven’t left the area. But Japanese health authorities were quick to warn the public not to eat certain local foods with harmful levels of radioactivity, namely milk and spinach; people living within 12 miles (19 km) of the nuclear facility have been evacuated as a precaution; more are expected to be evacuated; and radiation levels continue to fall daily.

http://www.livescience.com/13876-nuclear-energy-dangers-coal.html

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Coal and Gas are Far More Harmful than Nuclear Power
By Pushker Kharecha and James Hansen — April 2013
NASA Science Briefs, Goddard Institute for Space Studies

In a recently published paper (ref. 1), we provide an objective, long-term, quantitative analysis of the effects of nuclear power on human health (mortality) and the environment (climate). Several previous scientific papers have quantified global-scale greenhouse gas (GHG) emissions avoided by nuclear power, but to our knowledge, ours is the first to quantify avoided human deaths as well as avoided GHG emissions on global, regional, and national scales.

The paper demonstrates that without nuclear power, it will be even harder to mitigate human-caused climate change and air pollution. This is fundamentally because historical energy production data reveal that if nuclear power never existed, the energy it supplied almost certainly would have been supplied by fossil fuels instead (overwhelmingly coal), which cause much higher air pollution-related mortality and GHG emissions per unit energy produced (ref. 2).

Using historical electricity production data and mortality and emission factors from the peer-reviewed scientific literature, we found that despite the three major nuclear accidents the world has experienced, nuclear power prevented an average of over 1.8 million net deaths worldwide between 1971-2009 (see Fig. 1). This amounts to at least hundreds and more likely thousands of times more deaths than it caused. An average of 76,000 deaths per year were avoided annually between 2000-2009 (see Fig. 2), with a range of 19,000-300,000 per year.

Likewise, we calculated that nuclear power prevented an average of 64 gigatonnes of CO2-equivalent (GtCO2-eq) net GHG emissions globally between 1971-2009 (see Fig. 3). This is about 15 times more emissions than it caused. It is equivalent to the past 35 years of CO2 emissions from coal burning in the U.S. or 17 years in China (ref. 3) — i.e., historical nuclear energy production has prevented the building of hundreds of large coal-fired power plants.

https://www.giss.nasa.gov/research/briefs/kharecha_02/

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 

 

brachistochrone

brachistochrone – curve of quickest descent.
A curve on which a bead slides frictionlessly, under the influence of gravity, to an end point in the shortest time.

tautochrone- the curve for which the time taken by an object sliding without friction in uniform gravity to its lowest point is independent of its starting point.

details to be added

brachistochrone-and-tautochrone-curve

Demonstration of the Brachistochrone Curve & the Tautochrone Curve.

vSauce The Brachistochrone

 

MCAS Heat problems

Problems on heat and thermodynamics: Massachusetts Physics MCAS

2015 MCAS Physics Exam

#4. The graph below shows how the temperature of a sample of water changes as energy is added to the sample.

heating-of-water-curve

During which interval does a gas form?
A. Q to R
B. R to S
C. S to T
D. T to U

_ _ _ _ _ _ _ _ _ _ _ _ _  _

#21. Sunlight warms an area of Earth’s surface. Winds then carry thermal energy from this area to another location. Which two heat transfer processes are primarily involved in this situation?

A. radiation and convection
B. radiation and evaporation
C. conduction and convection
D. conduction and evaporation

_ _ _ _ _ _ _ _ _ _ _ _ _  _

#24. Frozen food is submerged in a small insulated container of 95°C water. Which statement best describes the temperature of the food after two hours, assuming no heat is lost outside of the insulated container?

A. The temperature of the food will be 95°C.
B. The temperature of the food will be 100°C.
C. The temperature of the food will be the same as the temperature of the water.
D. The temperature of the food will be greater than the temperature of the water.

_ _ _ _ _ _ _ _ _ _ _ _ _  _

#31 A student heats 200 g of water from 20°C to 70°C. How much heat did the student add to the water if the specific heat for water is 4.2 J/g C •° ?

A. 10,000 J            B. 14,000 J

C. 42,000 J            D. 76,000 J

_ _ _ _ _ _ _ _ _ _ _ _ _  _

#44 A student was investigating cooling times for two pots made of different materials. One pot was stainless steel and the other pot was iron. The pots were placed on a table in a 25°C room. The pots were roughly the same size and shape, and contained the same amount of water. The pots and water were originally at 100°C. The student recorded the temperature of the water in each pot over time. The graph below shows the results.

stainless-steel-iron-heating

a. Determine the amount of time it took the water in the iron pot to cool from 100°C to 60°C.

b. Based on the graph, which pot, the iron pot or the stainless steel pot, was a better conductor of thermal energy? Explain your answer.

c. Identify two methods of heat transfer that occurred as the water in the pots cooled, and describe how the transfer of heat occurred for each method.

d. Describe when the pots no longer experienced a net loss of thermal energy.

2016 MCAS Physics Exam

A 1 kg sample of liquid water and a 1 kg sample of ice are placed on a table. Which of the following statements best compares these two samples?

A. The liquid water has a larger volume than the ice.
B. The liquid water has a greater weight than the ice.
C. The liquid water has more thermal energy than the ice.
D. The liquid water has more gravitational potential energy than the ice.

_ _ _ _ _ _ _ _ _ _ _ _ _  _

6. Two U.S. quarters, initially at the same temperature, are heated with a flame. One of the quarters was made before 1965 and is composed of silver. The
other quarter was made after 1965 and is composed mostly of copper.
What information is needed to determine which quarter will heat up faster?

A. the specific heats of the metals and the mass of each coin
B. the initial temperature of the coins and the mass of each coin
C. the temperature of the flame and the specific heats of the metals
D. the initial temperature of the coins and the temperature of the flame

_ _ _ _ _ _ _ _ _ _ _ _ _  _

16. A fan enables a computer’s processor to run for long periods of time without overheating. Which of the following forms of heat energy transfer does this
example best represent?

A. condensation
B. convection
C. evaporation
D. radiation

_ _ _ _ _ _ _ _ _ _ _ _ _  _

18. A small steel rod is placed in 5 L of water. The initial temperature of the steel rod is 120°C, and the initial temperature of the water is 10°C. When does heat stop flowing between the steel rod and the water?

A. when the steel rod reaches 65°C
B. when the water reaches its boiling point
C. when the steel rod reaches 10°C and the water reaches 120°C
D. when the steel rod and the water reach the same temperature

_ _ _ _ _ _ _ _ _ _ _ _ _  _

27. Two identical objects, one hot and one cold, are placed near each other in a closed system. Which of the following graphs shows what happens to the temperatures of the objects over time?

_ _ _ _ _ _ _ _ _ _ _ _ _  _

44. During cold periods, many orange growers repeatedly spray their trees with water to prevent the oranges from freezing. If the air is cold enough, the sprayed water freezes around the oranges, leaving the oranges themselves unfrozen.

a. Identify a measurement tool that orange growers use to measure the average kinetic energy of the air.
b. Describe what happens to the average molecular kinetic energy of the sprayed water
as it cools before it freezes.
c. Describe what happens to the average molecular kinetic energy of the sprayed water
as it freezes.
d. Explain how the phase change of the sprayed water may protect the oranges from freezing.

_ _ _ _ _ _ _ _ _ _ _ _ _  _

Sample “Open Response” answers: Question 44: Open-Response

Question 44: Open-Response
Reporting Category: Heat and Heat Transfer
Standard: 3.1 – Explain how heat energy is transferred by convection, conduction, and radiation.

A student was investigating cooling times for two pots made of different materials. One pot was stainless steel and the other pot was iron. The pots were placed on a table in a 25°C room. The pots were roughly the same size and shape, and contained the same amount of water. The pots and water were originally at 100°C. The student recorded the temperature of the water in each pot over time. The graph below shows the results.

stainless-steel-iron-heating

a. Determine the amount of time it took the water in the iron pot to cool from 100°C to 60°C.

b. Based on the graph, which pot, the iron pot or the stainless steel pot, was a better conductor of thermal energy? Explain your answer.

c. Identify two methods of heat transfer that occurred as the water in the pots cooled, and describe how the transfer of heat occurred for each method.

d. Describe when the pots no longer experienced a net loss of thermal energy.

Scoring Guide and Sample Student Work
Select a score point in the table below to view the sample student response.

Score Description
4 The response demonstrates a thorough understanding of heat transfer by convection, conduction, and radiation and of thermal equilibrium.
The response correctly determines the time it took for water in the iron pot to cool to 60°C, and clearly explains which pot is a better conductor.
The response also correctly identifies and clearly describes two methods of heat transfer that occurred as the water cooled, and describes when the pots no longer experienced a net loss of thermal energy.
4
3 The response demonstrates a general understanding of heat transfer by convection, conduction, and radiation and of thermal equilibrium.
2 The response demonstrates a limited understanding of heat transfer by convection, conduction, and radiation and of thermal equilibrium.
1 The response demonstrates a minimal understanding of heat transfer by convection, conduction, and radiation and of thermal equilibrium.
0 The response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.

Note: There are 2 sample student responses for Score Point 4.

MCAS wave problems

MCAS Physics exam: Example Problems

buzzer-near-pendulum-doppler-mcas-2011

MCAS 2011

Which of the following describes and explains what the observer hears as the buzzer moves away from him?

A. a lower-pitched buzz than the buzzer’s normal sound because the sound waves are arriving less frequently
B. a higher-pitched buzz than the buzzer’s normal sound because the sound waves are arriving more frequently
C. a lower-pitched buzz than the buzzer’s normal sound because the velocity of the sound waves is reduced by the velocity of the swinging buzzer
D. a higher-pitched buzz than the buzzer’s normal sound because the velocity of the sound waves is increased by the velocity of the swinging buzzer

#25, MCAS 2011

longitudinal air wave in tube MCAS 2011.PNG

#32. Essay question, MCAS 2011

A large anchor is being lifted into a boat with metal sides. As the anchor leaves the water it
hits the side of the boat, making loud sounds and making waves on the surface of the water.

a. Describe the motions of the sound waves and the water waves.
b. Draw a diagram for each of the waves you described in part (a). Be sure to label each
diagram.
c. Describe how the wavelength is measured for the water waves

#35. Which of the following observations demonstrates that visible light waves are
electromagnetic and not mechanical?

A. Sunlight can pass through gas.
B. Sunlight can pass through solids.
C. Sunlight can pass through liquids.
D. Sunlight can pass through a vacuum.

#37, MCAS 2011
Which of the following statements best explains why lightning is seen before thunder is heard?

A. Electromagnetic waves travel faster than mechanical waves in air.
B. Electromagnetic waves have a higher frequency than mechanical waves.
C. Electromagnetic waves experience less interference than mechanical waves.
D. Electromagnetic waves form faster than mechanical waves during a thunderstorm.

#3, MCAS 2011
In a large room, a sound wave traveling from a violin produces a tone with a frequency of 264 Hz. The speed of sound in the room is 340 m/s.  What is the wavelength of the sound wave from the violin?

A. 0.004 m      B. 0.80 m      C. 1.3 m    D. 2.6 m

MCAS 2012

2. When music plays through the speaker, the speaker rapidly moves back and forth in the cabinet. Which of the following conclusions is best supported by this observation?

A. Sound travels only in air.
B. Sound is a transverse wave.
C. Sound is a longitudinal wave.
D. Sound travels at the speed of light

4. Which of the following statements best describes a difference between mechanical waves and electromagnetic waves?
A. Mechanical waves can produce colored light, while electromagnetic waves cannot.
B. Mechanical waves can travel in any direction, while electromagnetic waves travel only in one direction.
C. Mechanical waves travel only through a medium, while EM waves can also travel through a vacuum.
D. Mechanical waves travel only at the speed of light, while electromagnetic waves can travel at many different speeds.

6. A student is sitting on the edge of a swimming pool. The student repeatedly dips his foot in and out of the pool, making waves that move across the water. The student dips his foot slowly at first and then does it faster, each time to the same depth. Which of the following properties of the waves increases as the student dips his foot faster?

A. frequency
B. period
C. velocity
D. wavelength

21. A rope is stretched horizontally between two students. One of the students shakes an end of the rope up and down. Which of the following terms best describes the type of wave that is produced?

A. electromagnetic
B. longitudinal
C. rotational
D. transverse

#26. MCAS 2012

mcas-2012-represent-an-em-wave

#29. Student X and student Y are receiving sound waves from a stationary source. The sound waves have a frequency of 10 kHz. Student X is stationary and student Y is traveling toward the source of the sound waves.
Which of the following statements describes what will happen as student Y moves?

A. Student X will receive sound waves with a frequency higher than 10 kHz.B. Student X will receive sound waves with a frequency lower than 10 kHz.
C. Student Y will receive sound waves with a frequency higher than 10 kHz.
D. Student Y will receive sound waves with a frequency lower than 10 kHz.

#37 Two waves traveling in the same medium are shown below.

mcas-2012-comparing-waves

Which of the following correctly compares the two waves?
A. Wave X has half the amplitude of wave Y.
B. Wave X has twice the amplitude of wave Y.
C. Wave X has a lower frequency and longer wavelength than wave Y.
D. Wave X has a higher frequency and shorter wavelength than wave Y

#42 In which of the following media do sound waves most likely travel the fastest?
A. crude oil
B. distilled water
C. solid steel
D. warm air

MCAS 2013

#2. A student is shaking one end of a small rug with a ball on top of it. The wave that is produced travels through the rug and moves the ball upward, as shown in the diagram below

shake-rug-waves-mcas-2013

#6. A person is driving north in a car at a constant speed. A police officer is
driving south toward him at a constant speed. The police officer uses a radar
unit to measure the speed of the person’s car. The radar unit sends out waves of
a certain frequency toward the person’s car. The waves reflect off the person’s car and travel back to the radar unit in the police car. What happens to the frequency of the waves detected by the radar unit?
A. The frequency is lower as the person’s car approaches.
B. The frequency is higher as the person’s car approaches.
C. The frequency remains the same but with increased energy as the person’s car approaches.
D. The frequency remains the same but with decreased energy as the person’s car approaches.

#22. Which of the following properties makes a light wave different from all mechanical waves?
A. A light wave slows down in a vacuum.
B. A light wave is able to transmit energy.
C. A light wave exists as a transverse wave.
D. A light wave can travel without a medium

#25. Which of the following observed properties of a wave is changed by the Doppler effect?
A. amplitude
B. direction
C. frequency
D. speed

#28. The diagram below shows two students making a wave with a coiled spring

mcas-2103-spring-waves-on-tabletop

MCAS 2014

#2. Waves rock a boat in the middle of a pond. The boat moves up and down 10 times in 20 seconds. What is the period of the waves?
A. 0.5 s       B. 2 s     C. 10 s     D. 20 s

#16. A sound wave with a frequency of 1,700 Hz is traveling through air at a speed of 340 m/s. What is the wavelength of this sound wave?
A. 0.2 m     B. 5.0 m    C. 2,040 m      D. 57,800 m

#19. Sunscreen protects skin by absorbing harmful ultraviolet radiation from the Sun. Ultraviolet radiation has which of the following properties?
A. a shorter wavelength than x-rays
B. a lower frequency than radio waves
C. a higher frequency than visible light
D. a longer wavelength than microwaves

#23. ESSAY. Waves can be classified as either electromagnetic or mechanical.
a. Describe two differences between electromagnetic and mechanical waves.
b. Give two examples of electromagnetic waves.
c. Give two examples of mechanical waves.

#26. A wave with a wavelength of 3.2 m is generated in a pond. The frequency of the wave is 0.60 Hz. What is the speed of this wave?
A. 0.19 m/s
B. 1.9 m/s
C. 3.8 m/s
D. 5.3 m/s

#30. The diagram below shows a representation of two different waves

2-spring-waves-transverse-longitudinal-mcas-2014

MCAS 2015

14. A train driver blows the train’s horn as it moves away from a station. Which of the following statements describes how the sound of the horn heard by an observer standing at the station platform differs from the sound heard by the train driver?
A. The observer hears the sound as having a greater velocity.
B. The observer hears the sound as having a lower frequency.
C. The observer hears the sound as having a greater amplitude.
D. The observer hears the sound as having a shorter wavelength

#17. A windsurfer moves at 5 m/s while staying on the crest of a wave, as shown below.

mcas-2015-windsurfer-waves

#29. A seismic wave called a P-wave travels through the solid part of Earth. In a P-wave, the solid particles of Earth move parallel to the direction the P-wave travels. P-waves are which of the following types of waves?
A. electromagnetic
B. longitudinal
C. torsional
D. transverse

#38.  At a given temperature, a longitudinal mechanical wave will travel fastest through which of the following?
A. a gas
B. a liquid
C. a solid
D. a vacuum

#45. Essay and Drawing! A floating object moves up and down 15 times in 60 s because of ocean waves.
a. Calculate the period of the ocean waves. Show your calculations and include units in
your answer.
b. Calculate the frequency of the ocean waves. Show your calculations and include units in
your answer.

An additional wave property must be known in order to calculate the velocity of the ocean
waves.
c. In your Student Answer Booklet, identify this additional wave property and draw a wave
diagram showing how the property can be measured.
d. Describe what will happen to the object if the amplitude of the ocean waves increases and all other wave characteristics stay the same

**

Textbook p.393, #18.

How does increasing the wavelength of a rope by 50 % decreases its frequency by 33 %.

The relation between frequency and wavelength is

fλ=v

Then

f1λf2λ2

If ff, then f1.50f

λλ× f1fλ× f1.500.67λ1

The new wavelength is 67 % of the original (33 % less than the original).

Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

HS-PS4-1. Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling within various media. Recognize that electromagnetic waves can travel through empty space (without a medium) as compared to mechanical waves that require a medium

SAT subject test in Physics: Waves and optics

• General wave properties, such as wave speed, frequency, wavelength, superposition, standing wave diffraction, and Doppler effect
• Reflection and refraction, such as Snell’s law and changes in wavelength and speed
• Ray optics, such as image formation using pinholes, mirrors, and lenses
• Physical optics, such as single-slit diffraction, double-slit interference, polarization, and color

Peer review

This resource contains 2 lessons

peer-review-san-diego

Enter a caption

Image courtesy of the UC San Diego Library

(1) Scrutinizing science: Peer review. UC Museum of Paleontology of the University of California at Berkeley.

(2) In search of quality: The scientific peer review process.  EUFIC – The European Food Information Council. A non-profit organisation for science-based information on food and health.

______________________________________________

Scrutinizing Science: Peer Review

Peer review does the same thing for science that the “inspected by #7” sticker does for your t-shirt: provides assurance that someone who knows what they’re doing has double-checked it. In science, peer review typically works something like this:

  • A group of scientists completes a study and writes it up in the form of an article. They submit it to a journal for publication.

  • The journal’s editors send the article to several other scientists who work in the same field (i.e., the “peers” of peer review).

  • Those reviewers provide feedback on the article and tell the editor whether or not they think the study is of high enough quality to be published.

  • The authors may then revise their article and resubmit it for consideration.

  • Only articles that meet good scientific standards (e.g., acknowledge and build upon other work in the field, rely on logical reasoning and well-designed studies, back up claims with evidence, etc.) are accepted for publication.

peer-review

Peer review and publication are time-consuming, frequently involving more than a year between submission and publication. The process is also highly competitive. For example, the highly-regarded journal Science accepts less than 8% of the articles it receives, and The New England Journal of Medicine publishes just 6% of its submissions.

Peer-reviewed articles provide a trusted form of scientific communication. Even if you are unfamiliar with the topic or the scientists who authored a particular study, you can trust peer-reviewed work to meet certain standards of scientific quality.

Since scientific knowledge is cumulative and builds on itself, this trust is particularly important. No scientist would want to base their own work on someone else’s unreliable study!

Peer-reviewed work isn’t necessarily correct or conclusive, but it does meet the standards of science. And that means that once a piece of scientific research passes through peer review and is published, science must deal with it somehow — perhaps by incorporating it into the established body of scientific knowledge, building on it further, figuring out why it is wrong, or trying to replicate its results.

– Scrutinizing science: Peer review. UC Museum of Paleontology of the University of California at Berkeley.

______________

In search of quality: The scientific peer review process

Before a scientific assertion is made public it should be scrutinised for its credibility. Has the scientist drawn justifiable conclusions, based on the data available from sound scientific research?

The peer review process is a form of scientific quality control, where scientists open their research to the scrutiny of other experts in the field (peers).1

By reviewing and criticising each others’ work, scientists aim to ensure that only original and sound research is published and recognised.

How does it work?

When research is submitted for publication in a peer-reviewed journal, the journal invites several (usually two or more) independent experts to assess the credibility of the research.1

These experts consider the scientific methods, results and conclusions presented by the authors, asking themselves, if the science is technically sound, if the interpretation is consistent with the data, and if it is new, important or ground-breaking.2

Reviewers usually remain anonymous, are not paid for their assessment, and should not have any conflicts of interest in relation to the research. If a paper does not meet the requirements, based on the peer reviews, the editor can either reject it or deem it acceptable subject to adequate changes, allowing authors to react and revise their paper.

Why is it important?

The peer review process checks that a paper explains clearly how the research was carried out, so that it can be reproduced by others. It also verifies that the methodology is appropriate for the specific field and set of objectives.

Another crucial part of the review process is assessing the originality of new research and the accurate referencing of related published research, particularly if these contrast with the research at hand. The review is also useful for those whose work is being scrutinised; it allows them to fine-tune their manuscript before public release.2

A manuscript is seldom accepted for publication without at least a minor revision.

The review process essentially strives to separate fact from speculation and personal opinion.2

Peer-reviewed research is never beyond criticism however, and any conclusions drawn must be considered in the context of other studies. Ideally, experiments should be repeated to assess whether results can be reproduced; this is how findings are truly substantiated. The real validation, therefore, comes after publication.

Non-peer-reviewed research

Unfortunately, research results often find their way into the public domain without being peer reviewed, and are spread via newspapers, magazines, the internet, television and radio. They may be unpublished findings presented at press conferences, or published findings from a journal that does not use peer review.

Even journals that do use peer review contain some non-peer-reviewed content, such as editorials and letters to the editor. Both scientists and journalists should understand the meaning and importance of peer review and clarify whether or not research they discuss has been peer-reviewed. There are potentially enormous costs to both science and society from the promotion of scientifically weak or flawed research findings.

An imperfect process

The peer review process does not protect against misconduct. It can identify mistakes, but relies on honesty and, as a result, can fail to recognise deliberately fraudulent research. Various organisations have produced integrity guidelines on good research practice aiming to reduce such occurrences.3

On the other side, financial or personal concerns may bias a reviewer’s professional judgement and objectivity. It is vital to consider in advance any factors, which could lead to bias.3

According to the European Science Foundation, preventing and managing such conflicts of interest is crucial in ensuring equity and integrity.3

Sometimes concerns are raised about the influence of the funding body on the design of the study, or the interpretation or reporting of the research outcomes. The peer review process gives credence to research, because the paper has been independently checked and critically evaluated, including the correct scientific interpretation of the results on the basis of other existing evidence – no matter who funded the research.2

Inevitably, there are variations in standards between journals. A journal’s “Impact Factor” reflects how often its papers are cited in other peer-reviewed journals, and gives some indication of importance of the journal in its field – the higher the number, the greater the impact or influence.

The process and culture of checking each other’s work is ongoing in the scientific world. Once a paper has been published, further criticism can be made by the scientific community via letters to the journal editor, discussions at conferences, or direct exchange with the research team behind the study in question. Authors can justify their findings and flaws uncovered can be corrected or retracted.1,2

This is the nature of science; all work is open to critique by other scientists.

References

  1. Science Media Centre (2012). Peer review in a nutshell: http://www.sciencemediacentre.org/wp-content/uploads/2012/09/Peer-Review-in-a-Nutshell.pdf
  2. Sense About Science (2004). Peer Review and the acceptance of new scientific ideas. London: Sense About Science. http://www.senseaboutscience.org/data/files/resources/17/peerReview.pdf
  3. European Science Foundation (2011). European peer review guide integrating policies and practices into coherent procedures. Strasbourg: European Science Foundation. http://www.vr.se/download/18.2ab49299132224ae10680001647/European+Peer+Review+Guide.pdf

 

Related ideas

Welcome to the Journal of Alternative Facts 🙂

 

Waves in 2 dimensions

Let’s throw a stone into water and then observe the circular crests and troughs

We see waves propagate in 2 dimensions: along the X-axis, and Y-axis, simultaneously.

Awavefront represents the crest of a wave in 2 dimensions

2-dimensional waves always travel perpendicular to their wavefronts

A wave’s direction is represented by a ray

Here, water waves, or light waves, hit a curved surface

The wavefronts reflect to a point, called the focus.

Refraction of 2-D waves

Refraction is the change in direction of wave propagation due to a change in its transmission medium.

Often seen with light.

Seen with water waves, when they move from deep water into shallow water.

Here light waves refrac as they move from one medium into another (from air into diamond)

In this simplified case, the light waves (or water waves) are all parallel to each other.

Here we see the same thing, but now the rays of light are more realistic.

They emanate from a source, so they are circular, not parallel.

Yet when the rays hit the water, they are approximately parallel, so the result is the same.

snells-law-wavefronts

Snell’s law at PhysicsClassroom.com

Water waves can be refracted

Animation: Wiley Refraction

Animation GCSE Light and water refraction

Here we see water waves changing direction, as they enter shallower waters.

water-wave-refraction-into-a-bay

From a presentation by Luo Yanjie.

From a presentation by Luo Yanjie.

 

Details on the cause of refraction (PhysicsClassroom.Com)

 

Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

HS-PS4-1. Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling within various media. Recognize that electromagnetic waves can travel through empty space (without a medium) as compared to mechanical waves that require a medium

SAT subject test in Physics: Waves and optics

• General wave properties, such as wave speed, frequency, wavelength, superposition, standing wave diffraction, and Doppler effect
• Reflection and refraction, such as Snell’s law and changes in wavelength and speed
• Ray optics, such as image formation using pinholes, mirrors, and lenses
• Physical optics, such as single-slit diffraction, double-slit interference, polarization, and color

How a computer interprets instructions

How does a computer understand (interpret and execute) a high level programming language?

high-level-vs-low-level-language

 

What’s the difference between a high-level computer language and a low-level language? How does a computer interpret these languages, so the program can run?  What is computer programming?

How does a computer understand a computer program  http://guyhaas.com/bfoit/itp/Programming.html

BBC Bitesize Revision: Running a program, the CPU, etc. (a 5 page step-by-step resource)  http://www.bbc.co.uk/education/guides/z2342hv/revision/1

How do you communicate with computers? Through a programming language.  Source code and language differences: Learntocodewith.me

Break down how code gets translated from the code programmers write, to the code computers read, the difference between compiled and interpreted code, and what makes “just-in-time” compilers so fast and efficient.  The Basics of Compiled Languages, Interpreted Languages, and Just-in-Time Compilers

How do computers understand programming languages? How do you “teach” a computer a language?  Explanation by Christian Benesch, software engineer and architect (among other explanations) here

How does a computer understand a computer program?  Codeconquest.com How does coding work?

What is a program? What is a programming language? Depending on the language used, and the particular implementation of the language used, the process to translate high-level language statements to actions may involve compilation and interpretation.  Introduction to Programming (Wikiversity)

Subtractive color

There are 2 ways to create color:

additive model/RGB:

Make new colors by adding beams of light

RGB: red, green, blue

subtractive model/CMYK:

Making new colors by adding pigments (dyes, inks, paints)

CMYK: Cyan, Magenta, Yellow, Black

This lesson is on the subtractive color model.

Additive and Subtractive primary colors

Paints/inks/dyes contain pigments, molecules that absorb some frequencies of light, but not others.

When paints/inks/dyes are mixed, the mixture absorbs all the frequencies that each individual one absorbs.

Examples:

Blue paint absorbs red, orange, and yellow light. It reflects the rest (blue, violet, some green)

Yellow paint absorbs blue & violent. It reflects mostly yellow, and some red, orange, and green.

Images by Paul Hewitt

Subtractive When blue and yellow paints are mixed Hewitt

Mixing colored light is called color mixing by addition.
When you cast lights on a stage, you use the rules of color addition, but when you mix paint, you use the rules of color subtraction.

The three colors most useful in color mixing by subtraction are:
• magenta (bluish red)
• yellow
• cyan (greenish blue)

Magenta, yellow, and cyan are the subtractive primary colors, used in printing illustrations in full color.

mixing-colored-pigments

Color printing is done on a press that prints each page with four differently colored inks (magenta, yellow, cyan, and black).

• Each color of ink comes from a different plate, which transfers the ink to the paper.

• The ink deposits are regulated on different parts of the plate by tiny dots.

• The overlapping dots of three colors plus black give the appearance of many colors.

colors-of-ink-used-for-color-illustrations

SlideShare on Color and Light

Learning Standards

Massachusetts Arts Curriculum Framework: The Practice Of Creating

PreK- 4 Visual Arts Standards – Identify primary and secondary colors; predict and demonstrate the effects of blending or overlapping primary colors; demonstrate knowledge of making dark to light values of colors. Identify and use basic two-dimensional hollow and solid geometric shapes (circle, triangle, square, rectangle) and three-dimensional forms (sphere, pyramid, cube).

Grades 5-8 Visual Arts Standards – Create compositions that reflect knowledge of the elements and principles of art, i.e., line, color, form, texture; balance, repetition, rhythm, scale, and proportion. Demonstrate the ability to apply elements and principles of art to graphic, textile, product, and architectural design.

Massachusetts Arts Curriculum Framework, The Arts Disciplines: Visual Arts, PreK–12 STANDARD 2: Elements and Principles of Design

By the end of Grade 4: 2.1 Students will, for color, explore and experiment with the use of color in dry and wet media Identify primary and secondary colors and gradations of black, white and gray in the environment and artwork.
By the end of Grade 8: 2.7 Students will, for color, use and be able to identify hues, values, intermediate shades, tints, tones, complementary, analogous, and monochromatic colors. Demonstrate awareness of color by painting objective studies from life and freeform abstractions that employ relative properties of color.

Design a site like this with WordPress.com
Get started