Tag Archives: theory

It’s Official — Big Rip Coming!

San_Sebastian-Cementerio_de_PolloeThe UK’s Daily Telegraph newspaper just published this article, so it must be true. After all, the broadsheet has been a stalwart of conservative British journalism since, well, the dawn of time, some 6,000 year ago.

Apparently our universe will end in a so-called Big Rip, and not in a Big Freeze. Nor will it end in a Big Crunch, which is like the Big Bang in reverse. The Big Rip seems to be a rather calm and quiet version of the impending cosmological apocalypse. So, I’m all for it. I can’t wait… 22 billion years and counting.

From the Daily Telegraph:

A group of scientists claim to have evidence supporting the Big Rip theory, explaining how the universe will end – in 22 billion years.

Researchers at Vanderbilt University in Nashville, Tennessee, have discovered a new mathematical formulation that supports the Big Rip theory – that as the universe expands, it will eventually be ripped apart.

“The idea of the Big Rip is that eventually even the constituents of matter would start separating from each other. You’d be seeing all the atoms being ripped apart … it’s fair to say that it’s a dramatic scenario,” Dr Marcelo Disconzi told the Guardian.

Scientists observed distant supernovae to examine whether the Big Rip theory, which was first suggested in 2003, was possible.

The theory relies on the assumption that the universe continues to expand faster and faster, eventually causing the Big Rip.

“Mathematically we know what this means. But what it actually means in physical terms is hard to fathom,” said Dr Disconzi.

Conflicting theories for how the universe will end include the Big Crunch, whereby the Big Bang reverses and everything contracts, and the Big Freeze, where as the universe slowly expands it eventually becomes too cold to sustain life.

Previous questions raised over the Big Rip theory include explaining how sticky fluids – that have high levels of viscosity – can travel faster than the speed of light, defying the laws of physics.

However, the Vanderbilt team combined a series of equations, including some dating back to 1955, to show that viscosity may not be a barrier to a rapidly expanding universe.

“My result by no means settles the question of what the correct formulation of relativistic viscous fluids is. What it shows is that, under some assumptions, the equations put forward by Lichnerowicz have solutions and the solutions do not predict faster-than-light signals. But we still don’t know if these results remain valid under the most general situations relevant to physics,” Dr Disconzi told the New Statesman.

Read the story here.

Image: Cementerio de Polloe, en Donostia-San Sebastián, 2014. Courtesy of Zarateman. Public domain.

Wolfgang Pauli’s Champagne

PauliAustrian theoretical physicist dreamed up neutrinos in 1930, and famously bet a case of fine champagne that these ghostly elementary particles would never be found. Pauli lost the bet in 1956. Since then researchers have made great progress both theoretically and experimentally in trying to delve into the neutrino’s secrets. Two new books describe the ongoing quest.

From the Economist:

Neutrinoa are weird. The wispy particles are far more abundant than the protons and electrons that make up atoms. Billions of them stream through every square centimetre of Earth’s surface each second, but they leave no trace and rarely interact with anything. Yet scientists increasingly agree that they could help unravel one of the biggest mysteries in physics: why the cosmos is made of matter.

Neutrinos’ scientific history is also odd, as two new books explain. The first is “Neutrino Hunters” by Ray Jayawardhana, a professor of astrophysics at the University of Toronto (and a former contributor to The Economist). The second, “The Perfect Wave”, is by Heinrich Päs, a neutrino theorist from Technical University in the German city of Dortmund.

The particles were dreamed up in 1930 by Wolfgang Pauli, an Austrian, to account for energy that appeared to go missing in a type of radioactivity known as beta decay. Pauli apologised for what was a bold idea at a time when physicists knew of just two subatomic particles (protons and electrons), explaining that the missing energy was carried away by a new, electrically neutral and, he believed, undetectable subatomic species. He bet a case of champagne that it would never be found.

Pauli lost the wager in 1956 to two Americans, Frederick Reines and Clyde Cowan. The original experiment they came up with to test the hypothesis was unorthodox. It involved dropping a detector down a shaft within 40 metres of an exploding nuclear bomb, which would act as a source of neutrinos. Though Los Alamos National Laboratory approved the experiment, the pair eventually chose a more practical approach and buried a detector near a powerful nuclear reactor at Savannah River, South Carolina, instead. (Most neutrino detectors are deep underground to shield them from cosmic rays, which can cause similar signals.)

However, as other experiments, in particular those looking for neutrinos in the physical reactions which power the sun, strove to replicate Reines’s and Cowan’s result, they hit a snag. The number of solar neutrinos they recorded was persistently just one third of what theory said the sun ought to produce. Either the theorists had made a mistake, the thinking went, or the experiments had gone awry.

In fact, both were right all along. It was the neutrinos that, true to form, behaved oddly. As early as 1957 Bruno Pontecorvo, an Italian physicist who had defected to the Soviet Union seven years earlier, suggested that neutrinos could come in different types, known to physicists as “flavours”, and that they morph from one type to another on their way from the sun to Earth. Other scientists were sceptical. Their blueprint for how nature works at the subatomic level, called the Standard Model, assumed that neutrinos have no mass. This, as Albert Einstein showed, is the same as saying they travel at the speed of light. On reaching that speed time stops. If neutrinos switch flavours they would have to experience change, and thus time. That means they would have to be slower than light. In other words, they would have mass. (A claim in 2011 by Italian physicists working with CERN, Europe’s main physics laboratory, that neutrinos broke Einstein’s speed limit turned out to be the result of a loose cable.)

Pontecorvo’s hypothesis was proved only in 1998, in Japan. Others have since confirmed the phenomenon known as “oscillation”. The Standard Model had to be tweaked to make room for neutrino mass. But scientists still have little idea about how much any of the neutrinos actually weigh, besides being at least 1m times lighter than an electron.

The answer to the weight question, as well as a better understanding of neutrino oscillations, may help solve the puzzle of why the universe is full of matter. One explanation boffins like a lot because of its elegant maths invokes a whole new category of “heavy” neutrino decaying more readily into matter than antimatter. If that happened a lot when the universe began, then there would have been more matter around than antimatter, and when the matter and antimatter annihilated each other, as they are wont to do, some matter (ie, everything now visible) would be left over. The lighter the known neutrinos, according to this “seesaw” theory, the heftier the heavy sort would have to be. A heavy neutrino has yet to be observed, and may well, as Pauli described it, be unobservable. But a better handle on the light variety, Messrs Jayawardhana and Päs both agree, may offer important clues.

These two books complement each other. Mr Jayawardhana’s is stronger on the history (though his accounts of the neutrino hunters’ personal lives can read a little too much like a professional CV). It is also more comprehensive on the potential use of neutrinos in examining the innards of the sun, of distant exploding stars or of Earth, as well as more practical uses such as fingering illicit nuclear-enrichment programmes (since they spew out a telltale pattern of the particles).

Read the entire article here.

Image: Wolfgang Pauli, c1945. Courtesy of Wikipedia.

Old Concepts Die Hard

Regardless of how flawed old scientific concepts may be researchers have found that it is remarkably difficult for people to give these up and accept sound, new reasoning. Even scientists are creatures of habit.

[div class=attrib]From Scientific American:[end-div]

In one sense, science educators have it easy. The things they describe are so intrinsically odd and interesting — invisible fields, molecular machines, principles explaining the unity of life and origins of the cosmos — that much of the pedagogical attention-getting is built right in.  Where they have it tough, though, is in having to combat an especially resilient form of higher ed’s nemesis: the aptly named (if irredeemably clichéd) ‘preconceived idea.’ Worse than simple ignorance, naïve ideas about science lead people to make bad decisions with confidence. And in a world where many high-stakes issues fundamentally boil down to science, this is clearly a problem.

Naturally, the solution to the problem lies in good schooling — emptying minds of their youthful hunches and intuitions about how the world works, and repopulating them with sound scientific principles that have been repeatedly tested and verified. Wipe out the old operating system, and install the new. According to a recent paper by Andrew Shtulman and Joshua Valcarcel, however, we may not be able to replace old ideas with new ones so cleanly. Although science as a field discards theories that are wrong or lacking, Shtulman and Valcarcel’s work suggests that individuals —even scientifically literate ones — tend to hang on to their early, unschooled, and often wrong theories about the natural world. Even long after we learn that these intuitions have no scientific support, they can still subtly persist and influence our thought process. Like old habits, old concepts seem to die hard.

Testing for the persistence of old concepts can’t be done directly. Instead, one has to set up a situation in which old concepts, if present, measurably interfere with mental performance. To do this, Shtulman and Valcarcel designed a task that tested how quickly and accurately subjects verified short scientific statements (for example: “air is composed of matter.”). In a clever twist, the authors interleaved two kinds of statements — “consistent” ones that had the same truth-value under a naive theory and a proper scientific theory, and “inconsistent” ones. For example, the statement “air is composed of matter”  is inconsistent: it’s false under a naive theory (air just seems like empty space, right?), but is scientifically true. By contrast, the statement “people turn food into energy” is consistent: anyone who’s ever eaten a meal knows it’s true, and science affirms this by filling in the details about digestion, respiration and metabolism.

Shtulman and Valcarcel tested 150 college students on a battery of 200 such statements that included an equal and random mix of consistent and inconsistent statements from several domains, including astronomy, evolution, physiology, genetics, waves, and others. The scientists measured participants’ response speed and accuracy, and looked for systematic differences in how consistent vs. inconsistent statements were evaluated.

If scientific concepts, once learned, are fully internalized and don’t conflict with our earlier naive concepts, one would expect consistent and inconsistent statements to be processed similarly. On the other hand, if naive concepts are never fully supplanted, and are quietly threaded into our thought process, it should take take longer to evaluate inconsistent statements. In other words, it should take a bit of extra mental work (and time) to go against the grain of a naive theory we once held.

This is exactly what Shtulman and Valcarcel found. While there was some variability between the different domains tested, inconsistent statements took almost a half second longer to verify, on average. Granted, there’s a significant wrinkle in interpreting this result. Specifically, it may simply be the case that scientific concepts that conflict with naive intuition are simply learned more tenuously than concepts that are consistent with our intuition. Under this view, differences in response times aren’t necessarily evidence of ongoing inner conflict between old and new concepts in our brains — it’s just a matter of some concepts being more accessible than others, depending on how well they were learned.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]Image courtesy of New Scientist.[end-div]

Have Wormhole, Will Travel

Intergalactic travel just became a lot easier, well, if only theoretically at the moment.

[div class=attrib]From New Scientist:[end-div]

IT IS not every day that a piece of science fiction takes a step closer to nuts-and-bolts reality. But that is what seems to be happening to wormholes. Enter one of these tunnels through space-time, and a few short steps later you may emerge near Pluto or even in the Andromeda galaxy millions of light years away.

You probably won’t be surprised to learn that no one has yet come close to constructing such a wormhole. One reason is that they are notoriously unstable. Even on paper, they have a tendency to snap shut in the blink of an eye unless they are propped open by an exotic form of matter with negative energy, whose existence is itself in doubt.

Now, all that has changed. A team of physicists from Germany and Greece has shown that building wormholes may be possible without any input from negative energy at all. “You don’t even need normal matter with positive energy,” says Burkhard Kleihaus of the University of Oldenburg in Germany. “Wormholes can be propped open with nothing.”

The findings raise the tantalising possibility that we might finally be able to detect a wormhole in space. Civilisations far more advanced than ours may already be shuttling back and forth through a galactic-wide subway system constructed from wormholes. And eventually we might even be able to use them ourselves as portals to other universes.

Wormholes first emerged in Einstein’s general theory of relativity, which famously shows that gravity is nothing more than the hidden warping of space-time by energy, usually the mass-energy of stars and galaxies. Soon after Einstein published his equations in 1916, Austrian physicist Ludwig Flamm discovered that they also predicted conduits through space and time.

But it was Einstein himself who made detailed investigations of wormholes with Nathan Rosen. In 1935, they concocted one consisting of two black holes, connected by a tunnel through space-time. Travelling through their wormhole was only possible if the black holes at either end were of a special kind. A conventional black hole has such a powerful gravitational field that material sucked in can never escape once it has crossed what is called the event horizon. The black holes at the end of an Einstein-Rosen wormhole would be unencumbered by such points of no return.

Einstein and Rosen’s wormholes seemed a mere curiosity for another reason: their destination was inconceivable. The only connection the wormholes offered from our universe was to a region of space in a parallel universe, perhaps with its own stars, galaxies and planets. While today’s theorists are comfortable with the idea of our universe being just one of many, in Einstein and Rosen’s day such a multiverse was unthinkable.

Fortunately, it turned out that general relativity permitted the existence of another type of wormhole. In 1955, American physicist John Wheeler showed that it was possible to connect two regions of space in our universe, which would be far more useful for fast intergalactic travel. He coined the catchy name wormhole to add to black holes, which he can also take credit for.

The trouble is the wormholes of Wheeler and Einstein and Rosen all have the same flaw. They are unstable. Send even a single photon of light zooming through and it instantly triggers the formation of an event horizon, which effectively snaps shut the wormhole.

Bizarrely, it is the American planetary astronomer Carl Sagan who is credited with moving the field on. In his science fiction novel, Contact, he needed a quick and scientifically sound method of galactic transport for his heroine – played by Jodie Foster in the movie. Sagan asked theorist Kip Thorne at the California Institute of Technology in Pasadena for help, and Thorne realised a wormhole would do the trick. In 1987, he and his graduate students Michael Morris and Uri Yertsever worked out the recipe to create a traversable wormhole. It turned out that the mouths could be kept open by hypothetical material possessing a negative energy. Given enough negative energy, such a material has a repulsive form of gravity, which physically pushes open the wormhole mouth.

Negative energy is not such a ridiculous idea. Imagine two parallel metal plates sitting in a vacuum. If you place them close together the vacuum between them has negative energy – that is, less energy than the vacuum outside. This is because a normal vacuum is like a roiling sea of waves, and the waves that are too big to fit between the plates are naturally excluded. This leaves less energy inside the plates than outside.

Unfortunately, this kind of negative energy exists in quantities far too feeble to prop open a wormhole mouth. Not only that but a Thorne-Morris-Yertsever wormhole that is big enough for someone to crawl through requires a tremendous amount of energy – equivalent to the energy pumped out in a year by an appreciable fraction of the stars in the galaxy.

Back to the drawing board then? Not quite. There may be a way to bypass those difficulties. All the wormholes envisioned until recently assume that Einstein’s theory of gravity is correct. In fact, this is unlikely to be the case. For a start, the theory breaks down at the heart of a black hole, as well as at the beginning of time in the big bang. Also, quantum theory, which describes the microscopic world of atoms, is incompatible with general relativity. Since quantum theory is supremely successful – explaining everything from why the ground is solid to how the sun shines – many researchers believe that Einstein’s theory of gravity must be an approximation of a deeper theory.

[div class=attrib]Read the entire article here.[end-div]

[div class=attrib]Image of a traversable wormhole which connects the place in front of the physical institutes of Tübingen University with the sand dunes near Boulogne sur Mer in the north of France. Courtesy of Wikipedia.[end-div]

Once Not So Crazy Ideas About Our Sun

Some wacky ideas about our sun from not so long ago help us realize the importance of a healthy dose of skepticism combined with good science. In fact, as you’ll see from the timestamp on the image from NASA’s Solar and Heliospheric Observatory (SOHO) science can now bring us – the public – near realtime images of our nearest star.

[div class=attrib]From Slate:[end-div]

The sun is hell.

The18th-century English clergyman Tobias Swinden argued that hell couldn’t lie below Earth’s surface: The fires would soon go out, he reasoned, due to lack of air. Not to mention that the Earth’s interior would be too small to accommodate all the damned, especially after making allowances for future generations of the damned-to-be. Instead, wrote Swinden, it’s obvious that hell stares us in the face every day: It’s the sun.

The sun is made of ice.

In 1798, Charles Palmer—who was not an astronomer, but an accountant—argued that the sun can’t be a source of heat, since Genesis says that light already existed before the day that God created the sun. Therefore, he reasoned, the sun must merely focus light upon Earth—light that exists elsewhere in the universe. Isn’t the sun even shaped like a giant lens? The only natural, transparent substance that it could be made of, Palmer figured, is ice. Palmer’s theory was published in a widely read treatise that, its title crowed, “overturn[ed] all the received systems of the universe hitherto extant, proving the celebrated and indefatigable Sir Isaac Newton, in his theory of the solar system, to be as far distant from the truth, as any of the heathen authors of Greece or Rome.”

Earth is a sunspot.

Sunspots are magnetic regions on the sun’s surface. But in 1775, mathematician and theologian J. Wiedeberg said that the sun’s spots are created by the clumping together of countless solid “heat particles,” which he speculated were constantly being emitted by the sun. Sometimes, he theorized, these heat particles stick together even at vast distances from the sun—and this is how planets form. In other words, he believed that Earth is a sunspot.

The sun’s surface is liquid.

Throughout the 18th and 19th centuries, textbooks and astronomers were torn between two competing ideas about the sun’s nature. Some believed that its dazzling brightness was caused by luminous clouds and that small holes in the clouds, which revealed the cool, dark solar surface below, were the sunspots. But the majority view was that the sun’s body was a hot, glowing liquid, and that the sunspots were solar mountains sticking up through this lava-like substance.

The sun is inhabited.

No less a distinguished astronomer than William Herschel, who discovered the planet Uranus in 1781, often stated that the sun has a cool, solid surface on which human-like creatures live and play. According to him, these solar citizens are shielded from the heat given off by the sun’s “dazzling outer clouds” by an inner protective cloud layer—like a layer of haz-mat material—that perfectly blocks the solar emissions and allows for pleasant grassy solar meadows and idyllic lakes.