X-ray vision -Fishes

Paws off! Two brown bears get into vicious fight over perfect fishing spot as they try to catch dinner

Fishermen can be very protective over their favourite spot  as these brown bears showed when they got into a fight over salmon.

These images were taken by 15-year-old schoolgirl Elizaveta Tischenko as she watched the animals attempting to catch their dinner in Katmai National Park, in southern Alaska.

Elizaveta said one bear was catching a steady stream of fish when the other grew jealous after hardly catching any and tried to muscle his way in.

While the newcomer was tolerated for a while, eventually he began to treat on the claws of the other bear, which is when the fighting started. 

Elizaveta, who was watching from a grassy verge said: 'I had been watching the bear fish from a safe distance when I noticed another bear wander in.

'The first bear was not happy about the other bear being there and began to get more agitated as it began to try to catch fish in the water.

'It wasn't long before the two approached one another and began roaring ferociously to try and scare each other away. Neither one would back down for quite a while and they began to grapple with each other in the water.

'Eventually, the new bear on the scene decided to cut its loses and sulked off out of sight. When they are fishing they look quite cute and innocent but when they fight you get to see the true nature of the animals.'

Why Is Ice Slippery?

If you’ve ever shakily stepped onto the ice at your local skating rink, you are intimately familiar with the fear of falling on slippery ice. But what makes ice so slippery in the first place? Interestingly enough, scientists are still trying to figure that one out.

Physicists used to believe that ice became slippery when it was exposed to applied pressure. This pressure, they theorized, lowered the melting temperature of the top layer of ice. They believed that when a person went ice skating, the pressure from the blade caused the topmost layer of ice to melt. The thin layer of water allowed the ice skate to glide easily over the surface. After the blade passed, the top layer of water refroze.

However, most scientists today claim that this theory is wrong. “Ice is a very mysterious solid,” Robert M. Rosenberg, a chemistry professor at Lawrence University, said in an interview with The New York Times.

Scientists found that while pressure does lower the melting point of ice, it only does so by a fraction of a degree. Instead, they proposed that the friction from an ice skate causes the ice to melt beneath it.

Others believe that ice naturally possesses a fluid layer comprised of unstable water molecules. While these molecules search for stability, they move chaotically over the ice’s surface and create a slippery layer.

Read more : http://mentalfloss.com/article/53650/why-ice-slippery?ico=home^editors_choice

Why Nuclear Bombs Create Mushroom Clouds

This phenomenon all comes down to a little something called the Rayleigh-Taylor instability, and by extension, convection. I’ll begin with the somewhat longer, but less geeky explanation before descending once again into extreme nerdery.

It all starts with an explosion that creates a Pyrocumulus Cloud. This ball of burning hot gases is accelerated outwardly in all directions. Since the burning ball of accelerated gases is hotter, and therefore less dense, than the surrounding air, it will begin to rise- in the case of nuclear explosions, extremely rapidly. This ultimately forms the mushroom cap.

As the ball rises, it will leave behind air that is heated, creating a chimney-like effect that draws in any smoke and gases on the outer edge of the chimney- convection in action! Visually, this forms the stipe (stalk) of the mushroom.

The perception that the mushroom cap is curling down and around the stipe is primarily a result of the differences in temperature at the center of the cap and its outside. The center is hotter and therefore will rise faster, leaving the slower outer edges to be caught up in the stipe convection’s awesome attributes.

Once that cloud reaches a certain point in our atmosphere, where the density of the gas cloud is the same as the density of the surrounding air, it will spread out, creating a nice cap.

This brings me to the shorter, yet more geeky answer.

This entire process is something that describes the Rayleigh-Taylor instability. This instability is well known in physics and, in general, describes the merging between two different substances (mainly liquids and gases) that have different densities and are subjected to acceleration. In the case of an atomic bomb, the acceleration, and the hotter gases creating the differing densities of material, are caused by the explosion.

From this, you might have guessed you don’t necessarily need an atomic bomb to create a mushroom cloud. All you need is enough energy delivered rapidly (in this case an explosion) that creates a pocket of differing densities of material (in this case, heated gases).

There are numerous other examples in our world that create, and are described by, the same phenomenon that gives us this formation.  For instance, the magnetic fields of planets, the jet-stream of winds that help control our planet’s climate, the sound of snapping shrimp, even our understanding of certain different forms of fusion can all be attributed to Rayleigh-Taylor instability.

Now, you might have also noticed that nuclear explosions, besides producing this frightening fungal formation, also sometimes result in a cloud ring around the mushroom cap.  What’s going on here is that a low pressure area is created via the negative phase of the shockwave (the phase that follows the wave of compressed gases at the leading part of the shock wave).  This results in a drop in temperature, which along with the low pressure can potentially lower the dew point sufficiently for a temporary cloud to form. This cloud halo around the explosion is known as a “Wilson Cloud”, named after Scottish physicist Charles Wilson who invented the Wilson Cloud Chamber where similar sorts of things can be observed.

Thanks : http://www.todayifoundout.com/index.php/2013/11/nuclear-bombs-create-mushroom-cloud

FYI: What Is The Limit To How Fast A Human Can Run?

The limit to how fast a human can run is 9.48 seconds for the 100-meter race, 0.10 seconds faster than Usain Bolt’s current world record, according to Stanford biologist Mark Denny. That is, if you are talking about natural human beings.

In a 2008 study published in the Journal of Experimental Biology, Denny modeled the fastest human running speed using records of men’s 100-meter race results going back to the 1900s. Denny plotted the annual best times in the race into a graph and used computer programs to come up with an equation whose curve best models the behavior of the actual graph he obtained. The curve showed humanly achievable time for the 100-meter race would level off at 9.48 seconds. “They haven't plateaued yet, but you can definitely see the data are bending a little towards that plateau,” Denny says.

Denny, who also modeled the best times for racing thoroughbreds and greyhounds in the same study, found there’s a speed limit for these races as well, with little improvement in the Kentucky Derby since the 1950s and dogs’ performances leveling off in the 1970s.

“If you look at other species — ones that we're trying to breed to run faster and faster — it's not working,” he says. “There's no reason to think that human beings are any different from the other species, that somehow these things don't have limits.”

Statistical models do not explain the mechanics behind running. So Peter Weyand, a biomechanics professor at Southern Methodist University, has taken a different approach to the question.

A leading expert in human locomotion, Weyand says the primary factor influencing speed is how much force sprinters hit the ground with their feet.

When athletes run at a constant speed, they use their limbs like pogo sticks, Weyand says. Once a sprinter hits the ground, his limb compresses and gets him ready to rebound. When he’s in the air, the feet get ready to hit the ground again.

When a runner hits the ground, 90 percent of the force goes vertically to push him up again, while only 5 percent propels him horizontally. In that regard, sprinters behave a lot like a super ball, Weyand says. “What they do is they bounce a lot,” he says.

Our body naturally adjusts how fast we run by changing how hard we hit the ground. The harder we hit the ground, the faster we go.

So just how hard can humans hit the ground while they run?

In a 2010 study published in the Journal of Applied Physiology, Weyand and four other scientists had runners running on treadmills at a constant speed in different gaits –- running forward, backward, and hopping. Their study finds that when we hop, our limbs hit the ground with 30 percent more force than when we run, primarily because the foot stays much longer in the air. Based on that information, Weyand and his team calculated that in theory, human beings can run as fast as 19.3 meters per second — that is, if they hit the ground with the maximum force physiologically possible. If a sprinter were to run at that speed throughout the 100-meter race, he would finish in 5.18 seconds.

But that’s not the end of the story. In a new study to be published this year, Weyand and his team have found that maximizing running speed requires a tradeoff between hitting the ground hard and maintaining stride frequency. Hitting the ground with maximum force requires the sprinter to spend more time in the air, which slows down the strides he can make per second. The optimal combination of stride frequency and ground force varies with individuals depending on their size, leg length, and the speed they run, Weyand says. There is no golden ratio.

So what’s the fastest human running speed possible under this new model? Weyand is reluctant to give a definite number. “Science is not good at making predictions of extremes,” he says.
Nonetheless, he says he wouldn’t take 9 seconds for men’s 100-meter race off the table. “Something in the low 9s is definitely possible, perhaps faster,” he says.

That speed still won’t allow us to outrun an adult cheetah, the fastest land mammal, which can cover 100 meters in less than 6 seconds.

Science and technology are changing the limits to human running speed. Athletes nowadays can take hormone doses to change the mechanical properties of muscles, and scientists have succeeded in tweaking mice’s DNAs to alter their muscle fibers.

“We're sort of moving into a Brave New World in athletics where there are many many different types of performance enhancement avenues available,” Weyand says. “What's happening is that identifying what's natural and what's not natural is becoming increasingly blurry. To me, (to answer) what's the ultimate speed somebody can run, we now have to go through a list of 10 different conditions: are we talking about no gene doping, no special technology, no pharmaceutical agents … But as we go further and further along there's even potential for tracking shoe design to change speed. It starts to become a horribly complicated question.”

Thanks :http://www.popsci.com/science/article/2013-05/fyi-there-limit-how-fast-human-can-run

Recovering From Postdoc Mistakes

"The best thing you can do in a postdoc is to do things that you enjoy," urges Doon Gibbs, deputy director for science and technology at Brookhaven National Laboratory, who has overseen the supervision of many postdocs over 25 years. Ensure those tasks are noticeable, such as publishing papers and presenting at conferences, he adds. But possessing a passion and self-promotion prowess alone does not a successful scientist make. Too often postdocs end up making mistakes along the way that can sideline them from the vocation they desire. Whether it is spending too long in a postdoc appointment, relying too much on their advisor, or simply not taking ownership of their career, there are many possible ways that early-career scientists can blunder. But luckily, there are clever means and methods to remedy even the most serious of slip-ups. By Alaina G. Levine

Why Am I Here?

The postdoc appointment is meant to serve as the stepping-stone to victory in academic science and certain positions in industry, says Harold Myron, former director of education programs at Argonne National Laboratory. The job is designed as a training program to instill certain skills, techniques, tools, and tactics for pursuing advanced research. Ideally, a postdoc should sharpen their innovative problem-solving abilities and learn to manage research group resources, such as employees and grant money.

Too often graduate students take a postdoc appointment for the wrong reasons, which of course, can be a mistake in and of itself. There is a decades-old tradition that "the postdoc is a training ground for a tenure-track position, that this is the metric for success for young scientists," saysCathee Phillips, executive director of the National Postdoctoral Association (NPA). "Postdocs have heard this for years, which causes them not to think about their own strategic career plan, because they think the postdoc will naturally flow into a tenure-track position." But with only 20 percent of postdocs advancing to tenure-track employment, many find themselves realizing too late, or waiting too long, to make a career plan with tangible contingency options.

Sebastian (not his real name), who works as an administrator at a medical school in the southern United States, admits he made a number of mistakes in his two postdocs, not the least of which were going in naively and staying too long without a concrete career plan. "If you don't want a tenure-track position, then there's no reason to do a postdoc," he declares, and reveals that his lack of planning led to miscommunication with his bosses and wasted time.

In his first appointment, which only lasted a year, Sebastian's principal investigator (PI) needed someone experienced in a particular biomedical technique, which he did not have. The mentor did not have time to train his protégé, which led to arguments. "It was the wrong lab for me, and my naivety led me to accept bullying [from my advisor]," he says. "My mistake was that I stayed as long as I did."

Ultimately, Sebastian recovered from what could have been a costly career blunder by forging his own path into academic program management. "It is vitally important for postdocs to be aggressive and take charge of their careers," he cautions.

All The Doctorates Are Doing It…

When deciding whether to accept a particular postdoc, it is paramount to confirm that you are proceeding with the appointment for the right reasons.

However, frequently, graduate students venture into a postdoc out of a feeling of desperation for a job, resulting in a lack of inquiry about basic elements of the appointment and little or no negotiation for benefits. "When you're finished with your Ph.D., people look into what postdocs they want," confesses Jimmy Weterings, whose appointment took place at Vrije Universiteit Amsterdam in the Netherlands, and who is currently seeking an academic position. "There are some people, and I count myself among them, who will take anything—it's a safety feeling. You finished your Ph.D., you know you will have income, but I didn't think beyond the two years."

Weterings, who did not possess a strategic plan, neglected to bargain for essentials that would have bolstered his career progression, such as teaching his own course. "In hindsight, I learned a lot about negotiation and talking with people," he says. Weterings advises you can prevent this common mistake by relinquishing the feeling of desperation that you have to take a job without asking vital questions about it from the start. And "don't take the first one that comes along," he adds. "Think if it's the right opportunity, ask yourself 'what will I accomplish'?"

Fiona (not her real name), who recently finished a two-year biology postdoc at a state university in the western U.S., had been thinking of leaving academia after earning her Doctorate. She decided to pursue the postdoc anyway because finishing her thesis left her "on a high," and she thought "it might be rash" to depart the tenure-track too soon. Her gaffe was that she did "not question people enough" about what she would be doing day-to-day. "I was so excited about getting a job,…I didn't think to ask how people in the lab generally felt," she says.

Within the first year of her appointment, her project lost funding. There was no financial support to attend conferences. And with a PI who was close to retirement and on sabbatical, Fiona discovered difficulty maintaining motivation.

But Fiona was lucky in one respect: Although she did not have a crystallized career plan when she entered her postdoc, she did have ideas about where she wanted to go next. She leveraged her postdoc experience to launch a fulfilling career in medical writing.

Help! I'm In a Postdoc And Can't Get Out!

Although the number of years one spends in a postdoc differs depending on the chosen field, specialty, and career choice, most advisors agree that three to five years should be the cut-off point. Yet, some postdocs stay much longer, languishing with seemingly no end in sight—a big mistake, stress some experts. "The postdoc experience is not meant to be limitless," saysTrevor Penning, who served as associate dean for postdoctoral research and training at the University of Pennsylvania School of Medicine from 1997 to 2005.

Some stay because they don't know what else to do. "Knowing you have x years, a postdoc must develop a timeline and goals," continues Penning. "Go home every night and ask yourself 'what did I accomplish today that furthered my career?' If every day you accomplish nothing, you need to take action…it's a warning sign of bad things." With improper planning and a lack of assertiveness, early-career scientists can get stuck in a seemingly endless hamster wheel of postdoc appointment after appointment. After not landing a tenure-track position the first or second time around, some postdocs simply stay put where they are while others pursue another postdoc.

Gibbs is concerned that a postdoc who stays too long could be taken advantage of by their supervisor. Sebastian for example, feels he was treated as a technician during his postdoc. According to other associates and even PIs, it is not uncommon for some postdocs to be looked upon as an extra pair of hands and be charged with less complex routine tasks, as opposed to more creative, scientifically driven endeavors.

"If you find yourself in a situation that is untenable, [ask yourself] 'is it in my best interest to stay in the lab?'" suggests Penning. Identifying the problem early is critical. "It's much better to lose one year than five."

The Medium Is Me (And My Mentor)

Your mentor has the potential to heavily influence your career. But it is your career. Mary (not her real name), who received her Ph.D. in the biological sciences, proffers serious counsel regarding the all-to-frequent misstep of allocating complete control of your livelihood to another person, especially your supervisor. "Never expect your mentor to only be looking out for you. You have to look out for yourself," she says. After all, "your boss's priority is their own career."

There is so much riding on your relationship with your PI, so "choose your postdoc mentor carefully," warns Mary. In addition to serving as your advisor, and ideally as a coach and champion, a good mentor should help orchestrate pathways for you to advance to the next stage of your career. So examine his or her track record of training associates, and pick "someone who moves people on to successful positions," she says.

Mary made the mistake of not checking on this before securing her appointment. Her PI had never gotten anyone through a Ph.D., let alone on to a good job, she claims. As such, her career has progressed at a very slow pace. She is now in her second postdoc at the same institution where she received her Doctorate.

"Postdocs have to be realistic about what to expect from their mentors," says Phillips. "These are busy people, and just because they hired postdocs doesn't mean they will automatically be good mentors, particularly if you are looking at a career outside of academia." Moreover, "the [appointment] is a two-way street with the mentor," notes Penning, "but the postdoc has to take ultimate responsibility for their own career success or failure."

Pedigree Is Not Always Key

Another classic conundrum is the sometimes misguided conviction that in order to progress in academe, you must spend your postdoc in a big, well-funded research group, says Carla (not her real name), a biologist who completed a five-year postdoc at a prestigious private university. But a large lab run by a famous scientist doesn't guarantee direct value for the postdoc, as she found out the hard way.

Carla, who is an assistant professor at a medical school in the eastern U.S., divulges that her postdoc was complicated by lack of face time with her PI. The supervisor was well-known and traveled extensively. He directed an enormous lab, consisting of a score of postdocs who were all jockeying for time with their advisor. Upon returning from his trips, the PI "would only talk to those whose projects meant the most to him or to people close to submitting a paper," she says.

But her research was not the group's main focus, so she did not receive substantial opportunity to meet with her mentor. Carla recommends staying on the supervisor's "radar screen" by making a careful decision to work on a project that is the highlight of the lab, she says.

"The largest labs may not give you the skills to be a professional scientist," warns Penning. And selecting your mentor "is not just about the lab's pedigree," he adds. "Choosing the wrong person to be a mentor can make an experience go south from the beginning."

But by networking and seeking out other mentors besides their PI, a postdoc can remedy a difficult situation. "They can't depend only on the PI for points of contact," says Philip S. Clifford, associate dean of the Graduate School of Biomedical Sciences at the Medical College of Wisconsin.

If there is confusion as to whether your supervisor is actively participating in your professional advancement, "it boils down to good communication between the mentor and the postdoc," states Penning. "When you ask for help, if help is not forthcoming, your decision is easy: you find another mentor."

When Another Postdoc Takes Over

There is great internal competition among postdocs that is often not acknowledged, admits Carla. She describes how another person in her lab "liked my project and usurped it," and the PI, whose management skills were subpar, did nothing. Carla was then faced with the decision of whether to leave the lab, start something fresh, or partner with someone who seemed like the enemy. "I decided to collaborate," she recalls, "but I ended up suffering because the other person ended up talking about it on job talks," which she felt limited her ability to use it in presentations for academic positions.

Carla's solution was to recognize that there was enough room in the job market and in the research field for her to differentiate herself from the other party. But "the onus was on me to distinguish myself," she says. "I took the hard road, but in the end, this gives the most meaning in science."

If you find yourself in a situation where you are faced with an internal rivalry that could backfire, Carla suggests speaking with the PI and the other person to find ways to partner together. For example, there might be an angle that allows both people to co-first-author a manuscript. Communication is crucial, she says, "so everyone maxes out the benefits." The bottom line is you don't want to burn any bridges.

There is great internal competition among postdocs that is often not acknowledged, admits Carla. She describes how another person in her lab "liked my project and usurped it," and the PI, whose management skills were subpar, did nothing. Carla was then faced with the decision of whether to leave the lab, start something fresh, or partner with someone who seemed like the enemy. "I decided to collaborate," she recalls, "but I ended up suffering because the other person ended up talking about it on job talks," which she felt limited her ability to use it in presentations for academic positions.

Carla's solution was to recognize that there was enough room in the job market and in the research field for her to differentiate herself from the other party. But "the onus was on me to distinguish myself," she says. "I took the hard road, but in the end, this gives the most meaning in science."

If you find yourself in a situation where you are faced with an internal rivalry that could backfire, Carla suggests speaking with the PI and the other person to find ways to partner together. For example, there might be an angle that allows both people to co-first-author a manuscript. Communication is crucial, she says, "so everyone maxes out the benefits." The bottom line is you don't want to burn any bridges.

The Portal To Success

Every vocation has potential pitfalls and every professional has made their share of mistakes. Whether it's spending too much time in "PostdocLand," choosing the wrong mentor or lab, or not having a targeted career plan with flexibility for unforeseen twists, there will always be opportunity to err in academic science. Fortunately, as sources say, if you recognize that you are in the driver's seat, acknowledge a problem's existence early on, and focus on finding a resolution, you can recover and discover success. There are plenty of resources to aid you on your adventure, (see " It Pays to Plan: Why You Need a Career Map," DOI:10.1126/science.opms.r1000098), and best of all, if you learn from your mistakes, some might argue they were never mistakes in the first place. As James Joyce wrote, "A man of genius makes no mistakes. His errors are volitional and are portals of discovery."

This article was published as an advertising feature in the March 18, 2011, issue of Science.

http://sciencecareers.sciencemag.org/career_magazine/previous_issues/articles/2011_03_18/science.opms.r1100101

Top 10 Science Mistakes

1: The Circulatory System

You don't have to be a doctor to know how important the heart is...but back in ancient Greece, you could be a doctor and STILL have no idea how important the heart is.

Back then, doctors like second-century Greek physician Galen believed (no kidding) that the liver (not the heart) circulated blood (along with some bile and phlegm), while the heart (really) circulated "vital spirit"(whatever that is).

How could they be so wrong? It gets worse.

Galen hypothesized that the blood moved in a back-and-forth motion and was consumed by the organs as fuel. What's more, these ideas stuck around for a very long time. How long?

It wasn't until 1628 that English physician William Harvey let us in on our heart's big secret. His "An Anatomical Study of the Motion of the Heart and of the Blood in Animals" took a while to catch on, but a few hundred years later, it seems beyond common sense -- perhaps the ultimate compliment for a scientific idea.

2: The Earth Is the Center of the Universe

Chalk it up to humanity's collectively huge ego. Second-century astronomer Ptolemy's (blatantly wrong) Earth-centered model of the solar system didn't just stay in vogue for 20 or 30 years; it stuck around for a millennium and then some.

It wasn't until almost 1,400 years later that Copernicus published his heliocentric (sun-centered) model in 1543. Copernicus wasn't the first to suggest that the we orbited the sun, but his theory was the first to gain traction.

Ninety years after its publication, the Catholic Church was still clinging to the idea that we were at the center of it all and duking it out with Galileo over his defense of the Copernican view. Old habits die hard.

3: Germs in Surgery

Laugh or cry (take your pick), but up until the late 19th century, doctors didn't really see the need to wash their hands before picking up a scalpel.

The result? A lot of gangrene. Most early-19th century doctors tended to attribute contagion to "bad air" and blamed disease on imbalances of the "four humors" (that's blood, phlegm, yellow bile and black bile, in case you weren't familiar).

"Germ theory" (the revolutionary idea that germs cause disease) had been around for a while, but it wasn't till Louis Pasteur got behind it in the 1860s that people started listening. It took a while, but doctors like Joseph Lister eventually connected the dots and realized that hospitals and doctors had the potential to pass on life-threatening germs to patients.

Lister went on to pioneer the idea of actually cleaning wounds and using disinfectant. Remember him next time you reach for the Purell.

4: DNA: Not So Important

DNA was discovered in 1869, but for a long time, it was kind of the unappreciated assistant: doing all the work with none of the credit, always overshadowed by its flashier protein counterparts.

Even after experiments in the middle part of the 20th century offered proof that DNA was indeed the genetic material, many scientists held firmly that proteins, not DNA, were the key to heredity. DNA, they thought, was just too simple to carry so much information.

It wasn't until Watson and Crick published their all-important double-helical model of the structure of DNA in 1953 that biologists finally started to understand how such a simple molecule could do so much. Perhaps they were confusing simplicity with elegance.

5: The Atom Is the Smallest Particle in Existence

Believe it or not, we weren't actually all that stupid in ancient times. The idea that matter was composed of smaller, individual units (atoms) has been around for thousands of years -- but the idea that there was something smaller than that was a bit harder to come by.

It wasn't until the early 20th century, when physicists like J.J. Thompson, Ernest Rutherford, James Chadwick and Neils Bohr came along, that we started to sort out the basics of particle physics: protons, neutrons and electrons and how they make an atom what it is. Since then, we've come a long way: on to charmed quarks and Higgs bosons, anti-electrons and muon neutrinos. Let's hope it doesn't get too much more complicated than that.

6: The Earth Is Only 6,000 Years Old

Once upon a time, the Bible was considered a scientific work. Really. People just kind of assumed it was accurate, even when it didn't make much sense.

Take the age of the planet, for example.

Back in the 17th century, a religious scholar took a hard look at the Bible and estimated that creation happened around 4004 B.C. (you know, approximately). Add in nearly 2,000 more years to get to the 18th century, when Western, Bible-reading geologists started to realize that the Earth was constantly shifting and changing, and you get about 6,000 years.

Hmm ... those biblical scholars may have been a bit off. Current estimates, based on radioactive dating, place the age of the planet at around, oh, 4.5 BILLION years.

By the 19th century, geologists started putting the pieces together to realize that if geologic change was happening as slowly as they thought it was, and if this Darwin guy was at all right about evolution (which was also a slow process), the Earth had to be WAY older than they had thought. The emergence of radioactive dating in the early 20th century would eventually prove them right.

7: The Rain Follows the Plow

If only it were so easy. It's actually kind of shocking that humanity held on to the idea that land would become fertile through farming for so long. Didn't anyone look around and see that all this farming of arid land wasn't doing much?

So much for observation.

In reality, this quite erroneous theory (popular during the American and Australian expansions) may have stayed alive in part because it did sometimes work -- or at least it seemed to work.

What we know now is that the plow wasn't actually bringing the rain; long-term weather patterns were. Arid regions (like the American West, for example) go through long-term cyclical droughts, followed by cycles of wetter years. Wait long enough and you'll get a few wet ones.

There's just one problem: wait a few more years and all the rain just goes away - only now, you've got a civilization to support.

8: Phlogiston

What? You've never heard of phlogiston? Well, don't beat yourself up about it, because it's not real.

Phlogiston, proposed in 1667 by Johann Joachim Becher, was another element to add to the list (earth, water, air, fire and sometimes ether); it wasn't fire itself, but the stuff fire was made of. All combustible objects contained this stuff, Becher insisted, and they released it when they burned.

Scientists bought into the theory and used it to explain a few things about fire and burning: why things burned out (must have run out of phlogiston), why fire needed air to burn (air must absorb phlogiston), why we breathe (to get rid of phlogiston in the body).

Today, we know that we breathe to get oxygen to support cellular respiration, that objects need oxygen (or an oxidizing agent) to burn and that phlogiston just doesn't exist.

9: Heavier Objects Fall Faster

OK, trick question: do heavier objects fall faster than lighter ones? Today, we all know that they don't, but it's understandable how Aristotle could've gotten this one wrong.

It wasn't until Galileo came along in the late 16th century that anyone really tested this out. Though he most likely did not, as legend holds, drop weights from the tower of Pisa, Galileo did perform experiments to back up his theory that gravity accelerated all objects at the same rate. In the 17th century, Isaac Newton took us a step further, describing gravity as the attraction between two objects: on Earth, the most important being the attraction between one very massive object (our planet) and everything on it.

A couple of hundred years later, Albert Einstein's work would take us in a whole new direction, viewing gravity as the curvature that objects cause in space-time. And it's not over. To this day, physicists are ironing out the kinks and trying to find a theory that works equally well for the macroscopic, microscopic and even subatomic. Good luck with that.

10: Alchemy

The idea of morphing lead into gold may seem a little crazy these days, but take a step back and pretend you live in ancient or medieval times.

Pretend you never took high-school chemistry and know nothing about elements or atomic numbers or the periodic table. What you do know is that you've seen chemical reactions that seemed pretty impressive: substances change colors, spark, explode, evaporate, grow, shrink, make strange smells - all before your eyes.

Now, if chemistry can do all that, it seems pretty reasonable that it might be able to turn a dull, drab, gray metal into a bright, shiny yellow one, right? In the hopes of getting that job done, alchemists sought out the mythical "philosopher's stone," a substance that they believed would amplify their alchemical powers.

They also spent a lot of time looking for the "elixir of life." Never found that, either. 

http://science.discovery.com/top-ten/2009/science-mistakes/science-mistakes.html

The Worst Mistake in the History of the Human Race

To science we owe dramatic changes in our smug self-image. Astronomy taught us that our earth isn't the center of the universe but merely one of billions of heavenly bodies. From biology we learned that we weren't specially created by God but evolved along with millions of other species. Now archaeology is demolishing another sacred belief: that human history over the past million years has been a long tale of progress. In particular, recent discoveries suggest that the adoption of agriculture, supposedly our most decisive step toward a better life, was in many ways a catastrophe from which we have never recovered. With agriculture came the gross social and sexual inequality, the disease and despotism, that curse our existence.

At first, the evidence against this revisionist interpretation will strike twentieth century Americans as irrefutable. We're better off in almost every respect than people of the Middle Ages, who in turn had it easier than cavemen, who in turn were better off than apes. Just count our advantages. We enjoy the most abundant and varied foods, the best tools and material goods, some of the longest and healthiest lives, in history. Most of us are safe from starvation and predators. We get our energy from oil and machines, not from our sweat. What neo-Luddite among us would trade his life for that of a medieval peasant, a caveman, or an ape?
For most of our history we supported ourselves by hunting and gathering: we hunted wild animals and foraged for wild plants. It's a life that philosophers have traditionally regarded as nasty, brutish, and short. Since no food is grown and little is stored, there is (in this view) no respite from the struggle that starts anew each day to find wild foods and avoid starving. Our escape from this misery was facilitated only 10,000 years ago, when in different parts of the world people began to domesticate plants and animals. The agricultural revolution spread until today it's nearly universal and few tribes of hunter-gatherers survive.
From the progressivist perspective on which I was brought up, to ask "Why did almost all our hunter-gatherer ancestors adopt agriculture?" is silly. Of course they adopted it because agriculture is an efficient way to get more food for less work. Planted crops yield far more tons per acre than roots and berries. Just imagine a band of savages, exhausted from searching for nuts or chasing wild animals, suddenly grazing for the first time at a fruit-laden orchard or a pasture full of sheep. How many milliseconds do you think it would take them to appreciate the advantages of agriculture?
The progressivist party line sometimes even goes so far as to credit agriculture with the remarkable flowering of art that has taken place over the past few thousand years. Since crops can be stored, and since it takes less time to pick food from a garden than to find it in the wild, agriculture gave us free time that hunter-gatherers never had. Thus it was agriculture that enabled us to build the Parthenon and compose the B-minor Mass.
While the case for the progressivist view seems overwhelming, it's hard to prove. How do you show that the lives of people 10,000 years ago got better when they abandoned hunting and gathering for farming? Until recently, archaeologists had to resort to indirect tests, whose results (surprisingly) failed to support the progressivist view. Here's one example of an indirect test: Are twentieth century hunter-gatherers really worse off than farmers? Scattered throughout the world, several dozen groups of so-called primitive people, like the Kalahari bushmen, continue to support themselves that way. It turns out that these people have plenty of leisure time, sleep a good deal, and work less hard than their farming neighbors. For instance, the average time devoted each week to obtaining food is only 12 to 19 hours for one group of Bushmen, 14 hours or less for the Hadza nomads of Tanzania. One Bushman, when asked why he hadn't emulated neighboring tribes by adopting agriculture, replied, "Why should we, when there are so many mongongo nuts in the world?"
While farmers concentrate on high-carbohydrate crops like rice and potatoes, the mix of wild plants and animals in the diets of surviving hunter-gatherers provides more protein and a bettter balance of other nutrients. In one study, the Bushmen's average daily food intake (during a month when food was plentiful) was 2,140 calories and 93 grams of protein, considerably greater than the recommended daily allowance for people of their size. It's almost inconceivable that Bushmen, who eat 75 or so wild plants, could die of starvation the way hundreds of thousands of Irish farmers and their families did during the potato famine of the 1840s.
So the lives of at least the surviving hunter-gatherers aren't nasty and brutish, even though farmes have pushed them into some of the world's worst real estate. But modern hunter-gatherer societies that have rubbed shoulders with farming societies for thousands of years don't tell us about conditions before the agricultural revolution. The progressivist view is really making a claim about the distant past: that the lives of primitive people improved when they switched from gathering to farming. Archaeologists can date that switch by distinguishing remains of wild plants and animals from those of domesticated ones in prehistoric garbage dumps.
How can one deduce the health of the prehistoric garbage makers, and thereby directly test the progressivist view? That question has become answerable only in recent years, in part through the newly emerging techniques of paleopathology, the study of signs of disease in the remains of ancient peoples.
In some lucky situations, the paleopathologist has almost as much material to study as a pathologist today. For example, archaeologists in the Chilean deserts found well preserved mummies whose medical conditions at time of death could be determined by autopsy (Discover, October). And feces of long-dead Indians who lived in dry caves in Nevada remain sufficiently well preserved to be examined for hookworm and other parasites.
Usually the only human remains available for study are skeletons, but they permit a surprising number of deductions. To begin with, a skeleton reveals its owner's sex, weight, and approximate age. In the few cases where there are many skeletons, one can construct mortality tables like the ones life insurance companies use to calculate expected life span and risk of death at any given age. Paleopathologists can also calculate growth rates by measuring bones of people of different ages, examine teeth for enamel defects (signs of childhood malnutrition), and recognize scars left on bones by anemia, tuberculosis, leprosy, and other diseases.
One straight forward example of what paleopathologists have learned from skeletons concerns historical changes in height. Skeletons from Greece and Turkey show that the average height of hunger-gatherers toward the end of the ice ages was a generous 5' 9'' for men, 5' 5'' for women. With the adoption of agriculture, height crashed, and by 3000 B. C. had reached a low of only 5' 3'' for men, 5' for women. By classical times heights were very slowly on the rise again, but modern Greeks and Turks have still not regained the average height of their distant ancestors.
Another example of paleopathology at work is the study of Indian skeletons from burial mounds in the Illinois and Ohio river valleys. At Dickson Mounds, located near the confluence of the Spoon and Illinois rivers, archaeologists have excavated some 800 skeletons that paint a picture of the health changes that occurred when a hunter-gatherer culture gave way to intensive maize farming around A. D. 1150. Studies by George Armelagos and his colleagues then at the University of Massachusetts show these early farmers paid a price for their new-found livelihood. Compared to the hunter-gatherers who preceded them, the farmers had a nearly 50 per cent increase in enamel defects indicative of malnutrition, a fourfold increase in iron-deficiency anemia (evidenced by a bone condition called porotic hyperostosis), a theefold rise in bone lesions reflecting infectious disease in general, and an increase in degenerative conditions of the spine, probably reflecting a lot of hard physical labor. "Life expectancy at birth in the pre-agricultural community was bout twenty-six years," says Armelagos, "but in the post-agricultural community it was nineteen years. So these episodes of nutritional stress and infectious disease were seriously affecting their ability to survive."
The evidence suggests that the Indians at Dickson Mounds, like many other primitive peoples, took up farming not by choice but from necessity in order to feed their constantly growing numbers. "I don't think most hunger-gatherers farmed until they had to, and when they switched to farming they traded quality for quantity," says Mark Cohen of the State University of New York at Plattsburgh, co-editor with Armelagos, of one of the seminal books in the field, Paleopathology at the Origins of Agriculture. "When I first started making that argument ten years ago, not many people agreed with me. Now it's become a respectable, albeit controversial, side of the debate."
There are at least three sets of reasons to explain the findings that agriculture was bad for health. First, hunter-gatherers enjoyed a varied diet, while early fanners obtained most of their food from one or a few starchy crops. The farmers gained cheap calories at the cost of poor nutrition, (today just three high-carbohydrate plants -- wheat, rice, and corn -- provide the bulk of the calories consumed by the human species, yet each one is deficient in certain vitamins or amino acids essential to life.) Second, because of dependence on a limited number of crops, farmers ran the risk of starvation if one crop failed. Finally, the mere fact that agriculture encouraged people to clump together in crowded societies, many of which then carried on trade with other crowded societies, led to the spread of parasites and infectious disease. (Some archaeologists think it was the crowding, rather than agriculture, that promoted disease, but this is a chicken-and-egg argument, because crowding encourages agriculture and vice versa.) Epidemics couldn't take hold when populations were scattered in small bands that constantly shifted camp. Tuberculosis and diarrheal disease had to await the rise of farming, measles and bubonic plague the appearnce of large cities.
Besides malnutrition, starvation, and epidemic diseases, farming helped bring another curse upon humanity: deep class divisions. Hunter-gatherers have little or no stored food, and no concentrated food sources, like an orchard or a herd of cows: they live off the wild plants and animals they obtain each day. Therefore, there can be no kings, no class of social parasites who grow fat on food seized from others. Only in a farming population could a healthy, non-producing elite set itself above the disease-ridden masses. Skeletons from Greek tombs at Mycenae c. 1500 B. C. suggest that royals enjoyed a better diet than commoners, since the royal skeletons were two or three inches taller and had better teeth (on the average, one instead of six cavities or missing teeth). Among Chilean mummies from c. A. D. 1000, the elite were distinguished not only by ornaments and gold hair clips but also by a fourfold lower rate of bone lesions caused by disease.
Similar contrasts in nutrition and health persist on a global scale today. To people in rich countries like the U. S., it sounds ridiculous to extol the virtues of hunting and gathering. But Americans are an elite, dependent on oil and minerals that must often be imported from countries with poorer health and nutrition. If one could choose between being a peasant farmer in Ethiopia or a bushman gatherer in the Kalahari, which do you think would be the better choice?
Farming may have encouraged inequality between the sexes, as well. Freed from the need to transport their babies during a nomadic existence, and under pressure to produce more hands to till the fields, farming women tended to have more frequent pregnancies than their hunter-gatherer counterparts -- with consequent drains on their health. Among the Chilean mummies for example, more women than men had bone lesions from infectious disease.
Women in agricultural societies were sometimes made beasts of burden. In New Guinea farming communities today I often see women staggering under loads of vegetables and firewood while the men walk empty-handed. Once while on a field trip there studying birds, I offered to pay some villagers to carry supplies from an airstrip to my mountain camp. The heaviest item was a 110-pound bag of rice, which I lashed to a pole and assigned to a team of four men to shoulder together. When I eventually caught up with the villagers, the men were carrying light loads, while one small woman weighing less than the bag of rice was bent under it, supporting its weight by a cord across her temples.
As for the claim that agriculture encouraged the flowering of art by providing us with leisure time, modern hunter-gatherers have at least as much free time as do farmers. The whole emphasis on leisure time as a critical factor seems to me misguided. Gorillas have had ample free time to build their own Parthenon, had they wanted to. While post-agricultural technological advances did make new art forms possible and preservation of art easier, great paintings and sculptures were already being produced by hunter-gatherers 15,000 years ago, and were still being produced as recently as the last century by such hunter-gatherers as some Eskimos and the Indians of the Pacific Northwest.
Thus with the advent of agriculture and elite became better off, but most people became worse off. Instead of swallowing the progressivist party line that we chose agriculture because it was good for us, we must ask how we got trapped by it despite its pitfalls.
One answer boils down to the adage "Might makes right." Farming could support many more people than hunting, albeit with a poorer quality of life. (Population densities of hunter-gatherers are rarely over on person per ten square miles, while farmers average 100 times that.) Partly, this is because a field planted entirely in edible crops lets one feed far more mouths than a forest with scattered edible plants. Partly, too, it's because nomadic hunter-gatherers have to keep their children spaced at four-year intervals by infanticide and other means, since a mother must carry her toddler until it's old enough to keep up with the adults. Because farm women don't have that burden, they can and often do bear a child every two years.
As population densities of hunter-gatherers slowly rose at the end of the ice ages, bands had to choose between feeding more mouths by taking the first steps toward agriculture, or else finding ways to limit growth. Some bands chose the former solution, unable to anticipate the evils of farming, and seduced by the transient abundance they enjoyed until population growth caught up with increased food production. Such bands outbred and then drove off or killed the bands that chose to remain hunter-gatherers, because a hundred malnourished farmers can still outfight one healthy hunter. It's not that hunter-gatherers abandoned their life style, but that those sensible enough not to abandon it were forced out of all areas except the ones farmers didn't want.
At this point it's instructive to recall the common complaint that archaeology is a luxury, concerned with the remote past, and offering no lessons for the present. Archaeologists studying the rise of farming have reconstructed a crucial stage at which we made the worst mistake in human history. Forced to choose between limiting population or trying to increase food production, we chose the latter and ended up with starvation, warfare, and tyranny.
Hunter-gatherers practiced the most successful and longest-lasting life style in human history. In contrast, we're still struggling with the mess into which agriculture has tumbled us, and it's unclear whether we can solve it. Suppose that an archaeologist who had visited from outer space were trying to explain human history to his fellow spacelings. He might illustrate the results of his digs by a 24-hour clock on which one hour represents 100,000 years of real past time. If the history of the human race began at midnight, then we would now be almost at the end of our first day. We lived as hunter-gatherers for nearly the whole of that day, from midnight through dawn, noon, and sunset. Finally, at 11:54 p. m. we adopted agriculture. As our second midnight approaches, will the plight of famine-stricken peasants gradually spread to engulf us all? Or will we somehow achieve those seductive blessings that we imagine behind agriculture's glittering facade, and that have so far eluded us?