When the United Kingdom voted to leave the European Union last month, the seaside town of Port Talbot in Wales eagerly went along with the move. Brexit was approved by some 57 percent of the town's residents.

Now some of them are wondering if they made the wrong decision.

The June 23 Brexit vote has raised questions about the fate of the troubled Port Talbot Works, Britain's largest surviving steel plant — a huge, steam-belching facility that has long been the town's biggest employer.

Solar Impulse 2 has landed in Cairo, completing the penultimate leg of its attempt to circumnavigate the globe using only the power of the sun.

The trip over the Mediterranean included a breathtaking flyover of the Pyramids. Check it out:

President Obama is challenging Americans to have an honest and open-hearted conversation about race and law enforcement. But even as he sits down at the White House with police and civil rights activists, Obama is mindful of the limits of that approach.

"I've seen how inadequate words can be in bringing about lasting change," the president said Tuesday at a memorial service for five law officers killed last week in Dallas. "I've seen how inadequate my own words have been."

Mice watching Orson Welles movies may help scientists explain human consciousness.

At least that's one premise of the Allen Brain Observatory, which launched Wednesday and lets anyone with an Internet connection study a mouse brain as it responds to visual information.

The FBI says it is giving up on the D.B. Cooper investigation, 45 years after the mysterious hijacker parachuted into the night with $200,000 in a briefcase, becoming an instant folk figure.

"Following one of the longest and most exhaustive investigations in our history," the FBI's Ayn Dietrich-Williams said in a statement, "the FBI redirected resources allocated to the D.B. Cooper case in order to focus on other investigative priorities."

This is the first in a series of essays concerning our collective future. The goal is to bring forth some of the main issues humanity faces today, as we move forward to uncertain times. In an effort to be as thorough as possible, we will consider two kinds of threats: those due to natural disasters and those that are man-made. The idea is to expose some of the dangers and possible mechanisms that have been proposed to deal with these issues. My intention is not to offer a detailed analysis for each threat — but to invite reflection and, hopefully, action.

Alabama authorities say a home burglary suspect has died after police used a stun gun on the man.  Birmingham police say he resisted officers who found him in a house wrapped in what looked like material from the air conditioner duct work.  The Lewisburg Road homeowner called police Tuesday about glass breaking and someone yelling and growling in his basement.  Police reportedly entered the dwelling and used a stun gun several times on a white suspect before handcuffing him.  Investigators say the man was "extremely irritated" throughout and didn't obey verbal commands.

It can be hard to distinguish among the men wearing grey suits and regulation haircuts on Pennsylvania Avenue in Washington. But David Margolis always brought a splash of color.

It wasn't his lovably disheveled wardrobe, or his Elvis ring, but something else: the force of his flamboyant personality. Margolis, a graduate of Harvard Law School, didn't want to fit in with the crowd. He wanted to stand out.

Montgomery Education Foundation's Brain Forest Summer Learning Academy was spotlighted Wednesday at Carver High School.  The academic-enrichment program is for rising 4th, 5th, and 6th graders in the Montgomery Public School system.  Community Program Director Dillion Nettles, says the program aims to prevent learning loss during summer months.  To find out how your child can participate in next summer's program visit Montgomery-ed.org

A police officer is free on bond after being arrested following a rash of road-sign thefts in southeast Alabama.  Brantley Police Chief Titus Averett says officer Jeremy Ray Walker of Glenwood is on paid leave following his arrest in Pike County.  The 30-year-old Walker is charged with receiving stolen property.  Lt. Troy Johnson of the Pike County Sheriff's Office says an investigation began after someone reported that Walker was selling road signs from Crenshaw County.  Investigators contacted the county engineer and learned signs had been reported stolen from several roads.

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When Is A Theory Wrong?

Nov 21, 2012
Originally published on November 21, 2012 11:26 am

"Simple," you may say. "All you have to do is test the theory against experimental data and, if predictions don't work, toss the theory in the garbage can." In practice, however, things are way more complicated.

Take it from the start: a hypothesis is proposed to explain a known phenomenon, say, the orbit of the moon or the cause of a disease. The hypothesis can also propose the existence of something new, for example, the existence of a particle or global warming. The first case, a hypothesis that explains what's out there, is easier to deal with. Experiments are set up to test the hypothesis. Does it explain what it's supposed to explain? Are there rival hypotheses that do a better job, that is, explain more with less? Assuming the hypothesis passes the tests, it is then accepted until something better comes along.

It's the second case, a hypothesis that predicts new phenomena, that is more challenging. What if the particle isn't found? Or global warming is deceptively subtle?

The complication, at least in the physical sciences, comes from the way predictive hypotheses are built. In general, and especially in physics, chemistry, and astronomy, hypotheses are based on mathematical models, descriptions that attempt to approximate the workings of Nature. Every model is thus an incomplete replica of what's really trying to explain. As a consequence, no model is complete or perfect.

In particle physics, the branch of physics that tries to find the most basic constituents of matter and studies how they interact with one another, all that we know up to now is condensed in the so-called Standard Model. According to the model, there are 12 fundamental particles of matter arranged into three "families" with four members each.

For example, the matter we are made of, atoms, is composed of electrons, protons, and neutrons. Protons and neutrons are, in turn, composed of two types of a different particle called a "quark." So, the family of particles that dominates the world around us is composed of the electron and the up and down quarks. In addition, there is the electron-neutrino, an elusive particle that shows up in radioactive decays and at the core of the Sun.

The other two families have a similar structure, but the particles are heavier. Their members are found mostly (but not exclusively) through high-energy collisions in particle accelerators such as the Large Hadron Collider (LHC), famous for the discovery of the Higgs boson this past July. By the way, the Higgs is the newest member of the Standard Model, although we still need to understand a few of its properties to know exactly where it sits. (Sean Carroll just published a book on the Higgs, which I highly recommend, The Particle at the End of the Universe.)

Since every model is incomplete, there are gaps in the Standard Model. To fill them, physicists propose extensions, new models with new particles. The main test of these extensions is to find out if the particles they predict exist. Of the extensions, the most popular by far is called supersymmetry.

Proposed in 1974, supersymmetry is indeed super: if the world is supersymmetric there should be twice as many particles out there. The reason is that supersymmetry transforms every particle into a new one by changing a fixed amount of its internal rotation, or spin. (For the experts, by ½ of Planck's constant, equivalent to the spin of the electron.)

There are many possible extensions of the Standard Model that invoke supersymmetry; they make different predictions for what kinds of particles experiments should find. The simplest predict that all supersymmetric particles (the extra ones that double the count) should be unstable but for the lightest of them all. This fellow should be around if these models are correct. Supersymmetry has also been proposed as an explanation to the cosmological dark matter problem, or why galaxies seem to rotate faster than what simple Newtonian gravity predicts. The lightest supersymmetric particle would gather on the outskirts of galaxies, creating an invisible dark cloak that changes its rotation speed.

Physicists at the LHC and dozens of other experiments have been avidly hunting for supersymmetric particles. Up to now, they found no trace of any. Recently, LHC physicists looked at the decay of a particle called the B-meson, further complicating things for supersymmetry. (Particles are usually unstable and decay, or disintegrate, into lighter ones.) Different models predict different types of decay. Of these, the B-meson has a particularly rare one, at least according to the Standard Model, where it decays into two muons, heavier cousins of the electron. For every billion times the B-meson decays, it only follows this path three or four times. Observations of B-meson decay at the LHC have fallen in line with Standard Model predictions, not with the decay predictions of most supersymmetric models.

Given the lack of data in support of supersymmetry after all these years, why is the theory still considered viable?

The complication comes from the way mathematical models depend on various adjustable parameters. For example, the decay rate of a particle may depend on its mass and the way it interacts with other particles; if certain types of decays aren't seen, parameters can be changed to reflect that. The model may be made to hide from available experiments. And given that technology has more concrete limits than the imagination of theorists, a model may always be beyond the detectable.

How, then, can such types of models be ruled out? Well, simpler versions may be ruled out when the tweaking of parameters becomes so extreme that the model loses its original motivation: it explains nothing and becomes too cumbersome. Or a forbidden particle is discovered. Then there are always the more complicated versions, with more parameters that are harder to rule out.

The point is that there isn't a clear-cut answer. The physicist Max Planck used to say that wrong ideas don't die out, their proponents do. It will be interesting to watch what will happen in the next few years with supersymmetry and its proponents if tests keep producing negative answers.


You can keep up with more of what Marcelo is thinking on Facebook and Twitter: @mgleiser

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