Posts about physics

More Dark Matter Experiment Results

A dark-matter experiment deep in the Soudan mine of Minnesota now has detected a seasonal signal variation similar to one an Italian experiment has been reporting for more than a decade.

The new seasonal variation, recorded by the Coherent Germanium Neutrino Technology (CoGeNT) experiment, is exactly what theoreticians had predicted if dark matter turned out to be what physicists call Weakly Interacting Massive Particles (WIMPs).

“We cannot call this a WIMP signal. It’s just what you might expect from it,” said Juan Collar, associate professor in physics at the University of Chicago. Collar and John Orrell of Pacific Northwest National Laboratory, who lead the CoGeNT collaboration, are submitting their results in two papers to Physical Review Letters.

WIMPS might have caused the signal variation, but it also might be a random fluctuation, a false reading sparked by the experimental apparatus itself or even some exotic new phenomenon in atomic physics, Collar said.

Dark matter accounts for nearly 90 percent of all matter in the universe, yet its identity remains one of the biggest mysteries of modern science. Although dark matter is invisible to telescopes, astronomers know it is there from the gravitational influence it exerts over galaxies.

Theorists had predicted that dark matter experiments would detect an annual modulation because of the relative motion of the Earth and sun with respect to the plane of the Milky Way galaxy.
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5% of the Universe is Normal Matter, What About the Other 95%?

Dark Matters from PHD Comics on Vimeo.

Great discussion and illustration of the state of our understanding of physics, matter, dark matter and the rest of the stuff our universe has from PhD comics. What is the universe made of? 5% of it is normal matter (the stardust we are made of), 20% dark matter and the other 75% – we have no idea!

Dark Cosmos is a nice book on some of these ideas. It is 5 years old so missing some of the latest discoveries.

Related: Why do we Need Dark Energy to Explain the Observable Universe?The Mystery of Empty SpaceFriday Fun, CERN Version
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Gravity and the Scientific Method

One of the topics I return to repeatedly is the scientific method – theories must to tested. As evidence mounts that new ideas do a good job of explaining theories they become more accepted. But they continue to be tested in new ways as the ideas are extended and ramification are explored. And science progress means that old conventions can be overturned as new evidence is gathered.

Science is not about current beliefs. Science is about seeking knowledge. If the search for knowledge leads to evidence that old ideas were wrong those ideas are overturned. Since people are involved that process isn’t as clean as it sounds above. People get comfortable with beliefs. They build careers on expanding those beliefs. Most are uncomfortable when they are challenged and don’t accept new ideas even when the evidence mounts. But some do accept the new ideas. Some challenge the new ideas by running experiments. And some of those prove the new ideas faulty. Some become convinced of the new ideas as the results of their experiments make the new ideas seem more sensible (instead of getting the results they expected).

Building the body of scientific knowledge is not nearly as clean and simple as most people think. It isn’t a simple process, what is the underlying truth can be debatable. But the beauty of the scientific process is how it helps us overcome our biases and provide evidence to support the theories we support. The scientific method (combined with our human involvement) doesn’t mean new ideas are accepted easily but it does mean new ideas compete on the basis of evidence not just the power of those that hold the beliefs.

Is gravity not actually a force? Forcing theory to meet experiments
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Engineering Again Dominates The Highest Paying College Degree Programs

As usual most of the highest paying undergraduate college degrees in the USA are engineering. Based on data from payscale, all of the top 10 highest paying fields are in engineering. The highest non-engineering fields are applied mathematics and computer science. Petroleum Engineering salaries have exploded over the last few years to $93,000 for a starting median salary, more than $30,000 above the next highest paying degree.

Mid-career median salaries follow the same tendency for engineering degrees, though in this case, 3 of the top 10 salaries (15 years into a career) are for those with non-engineering degrees: applied mathematics, physics and economics.

Highest Paid Undergrad College Degrees
Degree Starting Median Salary Mid-Career Median Salary 2009 starting salary
Petroleum Engineering $93,000 $157,000
Chemical Engineering $64,800 $108,000 $65,700
Nuclear Engineering $63,900 $104,000
Computer Engineering $61,200 $99,500 $61,700
Electrical Engineering $60,800 $104,000 $60,200
Aerospace Engineering $59,400 $108,000 $59,600
Material Science and Engineering $59,400 $93,600
Industrial Engineering $58,200 $97,400 $57,100
Mechanical Engineering $58,300 $97,400 $58,900
Software Engineering $56,700 $91,300
Applied Mathematics $56,400 $101,000
Computer Science $56,200 $97,700 $56,400

Related: PayScale Survey Shows Engineering Degree Results in the Highest Pay (2009)Engineering Majors Hold 8 of Top 10 Highest Paid Majors (2010)Engineering Graduates Get Top Salary Offers in 2006Shortage of Petroleum Engineers (2006)10 Jobs That Provide a Great Return on Investment

More degrees are shown in the following table, but this table doesn’t include all the degree; it just shows a sample of the rest of the degrees.
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Amazing Webcast of the Aurora Borealis

The Aurora from Terje Sorgjerd on Vimeo.

Norwegian landscape photographer Terje Sorgjerd spent a week capturing one of the biggest aurora borealis shows in recent years. He shot the video in and around Kirkenes and Pas National Park bordering Russia at temperatures around -25 Celsius.

Aurora are caused by the collision of charged particles and the Earth’s magnetic field. Aurora Borealis is Latin for northern lights. An aurora is usually observed at night and typically occurs in the ionosphere. The lights are commonly visible between 60 and 72 degrees north and south latitudes, which place them in a ring just within the Arctic and Antarctic polar circles.

Auroras result from emissions of photons in the Earth’s upper atmosphere, above 80 km (50 miles), from ionized nitrogen atoms regaining an electron, and oxygen and nitrogen atoms returning from an excited state to ground state. They are ionized or excited by the collision of solar wind particles being funneled down and accelerated along the Earth’s magnetic field lines; excitation energy is lost by the emission of a photon of light, or by collision with another atom or molecule. Oxygen emissions give off a green or reddish hue, depending on the amount of energy. Nitrogen emissions give off a blue (if the atom regains and electron after it has been ionized) or red hue (if returning to the ground state from an excited state).

Auroras are associated with the solar wind, a flow of ions continuously flowing outward from the Sun. The Earth’s magnetic field traps these particles, many of which travel toward the poles where they are accelerated toward Earth. Collisions between these ions and atmospheric atoms and molecules cause energy releases in the form of auroras appearing in large circles around the poles. Auroras are more frequent and brighter during the intense phase of the solar cycle when coronal mass ejections increase the intensity of the solar wind.

Related: Magnetic MovieSolar EruptionMagnetic Portals Connect Sun and EarthThe Mystery of Empty SpaceLooking for Signs of Dark Matter Over Antarctica

Bronx High School of Nobel Prize for Physics Laureates

Bronx physics

Bronx Science owes its historic status to the fact that seven future Nobel-prize-winning physicists went through its doors – more than any other high school in the world and more than most countries have ever achieved. The school, which opened in 1938, was founded by the educator Morris Meister, who believed that if a school put bright students together, it would kindle ill-defined but valuable learning processes. The school seems to have proved him right: according to the Bronx laureates, their physics learning took place mainly outside the classroom.

Leon Cooper, who shared the 1972 prize for work on superconductivity, recalls physics lessons as boring, and was far more enchanted by his biology classes, which lured him to stay late after school designing and running experiments “until they threw me out”. Indeed, the school’s basic-physics textbook was written by a certain Charles E Dull, whose work, though widely used in US high schools, lived up to his name. The future particle physicist Melvin Schwartz, who shared the 1988 Nobel gong, once told me his classmates’ excited discussions – not his teacher – were what first awakened his interest in physics.

[today] the school’s most fearsome physics module – Advanced Placement Physics C – is tougher than most college-physics courses. Its dynamic instructor is Ghada Nehmeh, who was born in Lebanon and studied nuclear physics. Diminutive – smaller than most of her students – and scarf-clad, she jumps rapidly from lab table to lab table, helping piece together equipment and analyse results. Famous for being ruthlessly demanding, she tests the students on their first day by assigning them 40 calculus problems, due back the next day. “I’d never seen derivatives before,” says Kezi Cheng, a senior interested in theoretical physics. So Cheng did what most Bronx Science students do – she asked her classmates to give her a crash course on the subject. “They’re always willing to help.”

Sounds like a great place to go to school. The article also has some good anecdotes about how these students learned by seeking knowledge themselves not passively sitting and being lectured to.

Related: Science Education in the 21st CenturyFeynman “is a second Dirac, only this time human”The Nobel Prize in Physics 2009Letting Children Learn, Hole in the Wall Computers

Friday Fun: Aerodynamics for Sports

“Impossible” Soccer Kick Leads to New Physics Equation

The amazing goal — which left French goalkeeper Fabien Barthez too stunned to react — was scored during a friendly match in the run up to the 1998 World Cup. A group of French scientists, perhaps desperate to prove that at least the laws of physics weren’t actively rooting against their national team, have been able to figure out the trajectory of the ball and, with it, an equation to describe its unusual path.

It all comes down to the fact that, when a sphere spins, its trajectory is a spiral. Usually, gravity and the relatively short distance the ball travels cover up this spiral trajectory, but Carlos was a mere 115 feet away and kicked the ball hard enough to reveal its true spiral-like path.

In this open access paper, the spinning ball spiral, the authors explore the science behind ball paths in different situations.

one can identify sports dominated by aerodynamics (table tennis, golf and tennis) and sports dominated by gravity (basketball and handball). In between, we find sports where both gravity and aerodynamics play a comparable role (soccer, volleyball and baseball). Indeed, in the first category of sports, the spin is systematically used, while it is not relevant in the second category, and it only appears occasionally in the third one, in order to produce surprising trajectories.

Related: Friday Fun: Amazing GoalThe Science of the Football SwerveEngineering a Better Football

The Mystery of Empty Space

Get ready to re-think your ideas of reality. Join UCSD physicist Kim Griest as he takes you on a fascinating excursion, addressing some of the massive efforts and tantalizing bits of evidence which suggest that what goes on in empty space determines the properties of the three-dimensional existence we know and love, and discusses how that reality may be but the wiggling of strings from other dimensions.

Related: HiggsLooking for Signs of Dark Matter Over AntarcticaFeynman “is a second Dirac, only this time human”

Big Bangless and Endless Universe

A new the theory does away with the big bang and dark energy by having space, time and energy and no beginning and no ending.

Big Bang Abandoned in New Model of the Universe

Wun-Yi Shu at the National Tsing Hua University in Taiwan has developed an innovative new description of the Universe in which the roles of time space and mass are related in new kind of relativity.

Shu’s idea is that time and space are not independent entities but can be converted back and forth between each other. In his formulation of the geometry of spacetime, the speed of light is simply the conversion factor between the two. Similarly, mass and length are interchangeable in a relationship in which the conversion factor depends on both the gravitational constant G and the speed of light, neither of which need be constant.

So as the Universe expands, mass and time are converted to length and space and vice versa as it contracts. This universe has no beginning or end, just alternating periods of expansion and contraction. In fact, Shu shows that singularities cannot exist in this cosmos.

It’s easy to dismiss this idea as just another amusing and unrealistic model dreamed up by those whacky comsologists.

That is until you look at the predictions it makes. During a period of expansion, an observer in this universe would see an odd kind of change in the red-shift of bright objects such as Type-I supernovas, as they accelerate away. It turns out, says Shu, that his data exactly matches the observations that astronomers have made on Earth.

That’s not to say Shu’s theory is perfect. Far from it. One of the biggest problems he faces is explaining the existence and structure of the cosmic microwave background, something that many astrophysicists believe to be the the strongest evidence that the Big Bang really did happen. The CMB, they say, is the echo of the Big bang.

How it might arise in Shu’s cosmology isn’t yet clear but I imagine he’s working on it.

Science is useful in letting us understand the world better. But it also is an evolving understanding as we learn more and search for answers to more questions. Many attempts to put forth new ideas and have them gain acceptance are made. Most fail to gain traction. But even many of the ideas that are not accepted are interesting.

Read Cosmological Models with No Big Bang by Wun-Yi Shu (on the wonderful open access arXiv).

Related: Why Wasn’t the Earth Covered in Ice 4 Billion Years Ago, When the Sun was DimmerWhy do we Need Dark Energy to Explain the Observable Universe?The State of Physics

All About Circuits

All About Circuits is an online textbook covering electricity and electronics. Topics covered include: Basic Concepts of Electricity’ OHM’s Law; Electrical Safety; Series and Parallel Circuits; Physics of Conductors and Insulators; Solid-State Device Theory; Binary Arithmetic; Logic Gates; Switches; Digital Storage? It is a great resource. Enjoy.

Related: Textbook RevolutionOpen Access Education MaterialsHigh-quality Curricula and Education Resources for TeachersOnline Mathematics Textbooks

Friday Fun: Amazing Goal

This amazing goal illustrates what is possible with an amazing football (soccer) player and some physics.

Related: The Science of the Football SwerveEngineering a Better Football
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