It is one of the more obscure ideas in physics, frequently misunderstood by students and experts alike, so researchers are trying to refine their understanding of the Heisenberg uncertainty principle.
Are you wondering what the heck the HUP actually means? I’ve had requests for a detailed layman’s explanation, so I’ll start working on something. Meanwhile, this MinutePhysics video pretty much explains it in a minute.
So says Tufts University physicist, Alexander Vilenkin, who made this statement at a meeting in January in honor of Stephen Hawking’s 70th birthday. (I’m a little late getting around to this, but it’s worth commenting on.)
To fully appreciate the magnitude of this statement, consider that the prevailing view of cosmology for more than two thousand years was that of an eternal universe. This view began to change in the 1920s, when astronomer Edwin Hubble discovered that the spectra of most galaxies are redshifted, and the further away a galaxy is from the Milky Way, the more its spectrum is redshifted. What this means in plain English is that almost all of the galaxies he observed are rushing away from each other, and those that were further away are rushing away faster. Incredibly, it appeared the universe was not only changing, but expanding. If you imagine running the expansion in reverse, so that galaxies rush toward one another as you go back in time, you end up with a point at which the expansion started — a beginning in time and space.
Belgian physicist and priest, Georges Lemaître, anticipated this discovery with what he called the “hypothesis of the primeval atom,” based on his solution to the Einstein field equations. The universe’s beginning was predicted to have been very energetic and violent, and was therefore dubbed as the “big bang.” Four decades later, physicists Arno Penzias and Robert Wilson discovered the predicted afterglow of this big bang, which eventually earned them Nobel prizes. By the late 1980s, sophisticated satellites were mapping the tiny fluctuations in the intensity of the big bang afterglow, which allowed physicists to calculate an age for the universe. By the end of the 20th century, there was near-consensus that the universe had a beginning that occurred some 11-17 billion years ago. (The cosmological model-based number is ~14 billion years.)
The big bang has had its detractors. It was astrophysicist Fred Hoyle, out of deep skepticism for the idea, who sarcastically applied the term “big bang” to this cosmological model. (Let it not be said that physicists are overly sensitive — the term stuck and has been used in all seriousness ever since.) Hoyle’s collaborator, astrophysicist Geoffrey Burbidge, famously ridiculed physicists who had hopped on the big bang bandwagon as “rushing off to join the First Church of Christ of the Big Bang.” There were two reasons scientists reacted this way. First, some scientists found the idea of a universe with a beginning uncomfortably close to the Genesis account of creation. Second, from the point of view of physics, mathematics, and philosophy, a universe with a beginning is far more messy to deal with than an eternal universe, which requires no explanation. Even still, the evidence for a beginning is now so overwhelming that most physicists have come to accept it, and the big bang has become the prevailing paradigm governing all of physics.
Nevertheless, some physicists had not given up on the idea of an eternal universe, but the focus changed to devising sophisticated models for an eternal universe that fit the observed data — in other words, an eternal universe that incorporated key features of the big bang model. Some of these features are explainable by invoking what’s called inflation, which refers to an early period of exceedingly rapid expansion. This idea was proposed by Alan Guth in the 1980s, and it can also be applied to an eternally inflating universe in which regions of the universe undergo localized inflation, creating “pocket universes.” This inflation continues forever, both in the past and into the future, and so in a sense it represents an eternal universe. Another idea was the cyclical universe, which posited that the universe is eternally expanding and contracting. In this way, the big bang that occurred 14 billion years ago would be just one of an infinite number of big bangs followed by ‘big crunches.’
All of the evidence indicates ours is a universe undergoing perpetual change. To replace Aristotle’s age-old idea of an eternal, unchanging universe, physicists came up with hypothetical eternal universes that were perpetually changing. This was an ingenius approach, but as Vilenkin announced last month, they just don’t work. Guth’s idea turns out to predict eternal inflation in the future, but not in the past. The cyclical model of the universe predicts that with each big bang, the universe becomes more and more chaotic. An eternity of big bangs and big crunches would lead to a universe of maximum disorder with no galaxies, stars, or planets — clearly at odds with what we observe.
As the journal New Scientist reports, physicists can’t avoid a creation event. Vilenkin’s admission exemplifies the reason physics is the king of all the sciences — physicists are generally willing to admit when their cherished ideas don’t work, and they eventually go where the data and logic lead them. Whether this particular realization will pave the way to serious discussion of God and consistency with the Genesis account of creation remains to be seen. Physicists can be a stubborn bunch. As Nobel laureate George P. Thomson observed, “Probably every physicist would believe in a creation if the Bible had not unfortunately said something about it many years ago and made it seem old-fashioned.” Still, some physicists are open to the idea. Gerald Schroeder, who is also an applied theologian, has written profoundly on the subject. His book, The Science of God, is an illuminating discussion of how the Bible and biblical commentary relate to the creation of the universe.
Crab is emitting super-energetic gamma rays
Here’s another chapter for the books of “Persistence Pays Off” and “Who Woulda Thought?” A team of astronomers has discovered very energetic gamma-ray pulses emanating from the core of the Crab Nebula, in defiance of current theory. The nebula, a remnant of a 1,000 year-old supernova, is a semi-chaotic mass of gas surrounding a type of neutron star called a pulsar, the source of the gamma rays. Like all neutron stars, a pulsar is the tiny, extremely dense, collapsed core of a progenitor star; what makes these objects special is that the axis of rotation is offset from the bright magnetic poles, so that every time they spin they are observed to emit a pulse, like a lighthouse. Given its relative young age and close proximity to Earth — a mere 6,500 light-years — the Crab pulsar has been well-studied by astronomers. Theorists thought it was not possible for a pulsar to emit such energetic gamma-ray pulses, leading some of their colleagues to tell members of the team they were “crazy” for even trying to observe them. But the astronomers’ persistence paid off, and the new discovery is already changing how theorists think about these objects.
“We thought we understood the gamma-ray emission, and this was really becoming a foundational feature of our models, but that’s now thrown out,” [one of the authors of the study, Andrew] McCann explained. “The reason why this is so exciting is that it’s turning things around in the field.”
You gotta love how astronomers and physicists get excited every time a new discovery shoots down current theory. That’s exactly the kind of attitude that moves science forward.
Uranus pummeled by other planets?
The distant gaseous planet has long been a puzzle to astronomers, who have been trying to explain its peculiar axis tilt ever since it was discovered.
Most of the planets in the solar system exhibit axis tilt — this is where the axis of a planet’s rotation is at an angle to an imaginary line that runs perpendicular to the planet’s orbital plane. Mercury is alone in that it has virtually zero axis tilt, though Jupiter’s is also diminutive at just 3 degrees. The Earth’s axis tilt is 23.5 degrees, and Venus is nearly upside down with its rotation axis pointing almost completely downward (this is also somewhat of a mystery to astronomers).
Uranus is the strangest of all, as it rotates flopped over on its side. Some astronomers have hypothesized that Uranus was pummeled by another planet in the early history of the solar system, and this collision resulted in Uranus’ 98-degree axis tilt. However, another collision might be required to explain the spin of Uranus’ moons, which should otherwise spin backwards. A new simulation created by astronomers indicates that collisions with two Earth-sized planets could explain Uranus’ observed configuration. The main problem with this idea, however, is to explain where the two Earth-sized planets came from.
Evidence for water on Mars?
Astronomers have discovered seasonal dark streaks on the surface of Mars that could be signs of melted water running across the surface. Meanwhile, NASA’s Curiosity rover is slated to visit Mars next year to look for signs of water in the Gale crater. The discovery of liquid water on Mars will greatly facilitate any plans to establish future colonies there.
Physics
Three American scientists have been awarded the Nobel Prize in physics for their discovery that the universe is expanding at an accelerating rate. Saul Perlmutter will share the prize with Brian Schmidt and Adam Riess.
The discovery of the accelerating expansion of the universe followed an unexpected observational discovery in 1998. Astronomers in two different groups — the Supernova Cosmology Project (Perlmutter) and the High-z Supernova Search Team (Schmidt and Riess) — were observing the characteristic light signature of a certain type of supernova, called a Type 1a supernova, to probe the expansion history of the universe.
Let’s pause the story for a moment to explore the significance of these objects. Type 1a supernovae are a special subclass of exploding stars. Other types of supernovae occur when a massive star runs out of fuel, causing the core to collapse; their intrinsic brightness depends on a variety of factors, including the mass of the progenitor star. Type 1a supernovae occur when a white dwarf — the exposed core of a dead less-massive star — reaches a mass limit, called the Chandrasekhar limit. The mass limit can be reached if a white dwarf siphons matter from a companion star (see the header image above) or if two white dwarfs in a binary system collide. Since the resulting explosion always occurs at roughly the same mass, these supernovae always have roughly the same intrinsic brightness. This predictable brightness makes Type 1a supernovae excellent probes of distance and cosmic history.
Back to our story. The astronomers were using Type 1a supernovae to test the idea that the universe was slowing down in its expansion. If their idea was right, then the supernovae would appear to be brighter than expected, meaning they would be closer to the Earth than they would be if the universe had been expanding at a uniform rate. But they found the opposite: the supernovae appeared significantly dimmer than expected, meaning these exploding stars were further away than they would be for a uniform expansion. The astronomers concluded that the expansion of the universe was not slowing down, but rather speeding up. This conclusion was further supported by discoveries from other cosmological experiments, including mapping of the cosmic microwave background.
These discoveries led to the hypothesis that a mysterious force, called dark energy, is driving the accelerated expansion. Very little is currently known about this force, but several experiments, including HETDEX, Destiny, and SNAP, are underway to hopefully shed some light (as it were) on the subject.
Chemistry
Israeli scientist, Dan Schechtman, has been awarded the Nobel Prize in chemistry for his discovery of quasicrystals. What makes this award particularly interesting is the degree to which Schechtman persisted to make his discovery known. He worked for years in the face of skepticism and ridicule — two-time Nobel laureate, Linus Pauling, evidently referred to Schechtman as a “quasi-scientist” — before he managed to convince the scientific community that his observations overturned the prevailing model for how atoms and molecules can be arranged in solids.
A crystal is a type of material in which the arrangement of atoms is ordered and periodic. Scientists have probed crystalline structures using electron diffraction experiments in which beams of electrons are passed through crystal layers, producing an interference pattern. When Schechtman performed similar experiments on a different type of material, he found a peculiar interference pattern that seemed to defy the known laws of nature, since it indicated an ordered but non-periodic pattern in the arrangement of atoms. This is similar to the mosaic tile patterns found in medieval Islamic shrines.
Since Schechtman’s discovery, many quasicrystals have been synthesized and studied, and a naturally-occurring quasicrystal was discovered in Russia in 2009. Quasicrystals possess some useful properties, including a non-stick surface, low heat conduction, and hardness, that make them useful material for many products, from frying pans to surgical instruments.
In spite of his vindication and receiving the highest of accolades, Schechtman remains endearingly modest:
“The main lesson that I have learned over time is that a good scientist is a humble and listening scientist and not one that is sure 100 percent in what he read in the textbooks.”
Just as it’s difficult to be a devoted Christian in the face of skepticism, mockery, and exclusion, it’s difficult to be a devoted scientist under such conditions, as well. Schechtman deserves his award all the more for his determination and perseverance.
The big news coming out of CERN is that scientists there have apparently exceeded the speed of light. The experiment, carried out repeatedly over a period of three years, involved the acceleration of neutrinos — tiny, neutrally-charged particles — over a distance of nearly 500 miles and timing their travel. Surprisingly, the neutrinos arrived 60 billionths of a second faster than light would have. It may sound like a miniscule difference, but considering that light travels over 186,000 miles per second, it’s actually quite significant.
If confirmed, the discovery would undermine Albert Einstein’s 1905 theory of special relativity, which says that the speed of light is a “cosmic constant” and that nothing in the universe can travel faster.
To be specific, Einstein’s theory says that particles with mass can be accelerated to speeds arbitrarily close to the speed of light in a vacuum — say, 99.9999999999% of the speed of light — but never at the speed of light in a vacuum, and certainly not exceeding it. In some cases, particles with mass can exceed the speed of light in certain types of material, for example high-energy electrons traveling through water in pool-type nuclear reactors. When this happens, the particles emit an eerie glow called Cherenkov radiation. (Fun fact: As you can see below, this glow is blue in color, not neon-green as seen on The Simpsons.)
As for the implications of breaking the speed of light, some physicists are holding off on scrapping the theory of relativity until the results are confirmed at other facilities.
Alvaro De Rujula, a theoretical physicist at CERN, the European Organization for Nuclear Research outside Geneva from where the neutron beam was fired, said he blamed the readings on a so-far undetected human error.
If not, and it’s a big if, the door would be opened to some wild possibilities.
The average person, said De Rujula, “could, in principle, travel to the past and kill their mother before they were born.”
Even in the face of such wild possibilities, I admire the restraint and humility of the CERN research group that conducted the experiment:
But Ereditato [spokesman for the CERN research group] and his team are wary of letting such science fiction story lines keep them up at night.
“We will continue our studies and we will wait patiently for the confirmation,” he told the AP. “Everybody is free to do what they want: to think, to claim, to dream.”
He added: “I’m not going to tell you my dreams.”
Compared with the wild speculation of some other scientists over similarly startling results in the recent past, this is refreshing.
Want to know the most efficient way to board a plane? Ask an astrophysicist. (Hint: boarding back-to-front is one of the least efficient ways.)
Astrophysicists working in California and Zurich have created a virtual Milky Way galaxy using a sophisticated supercomputer simulation that took an astonishing eight months to run.
Even without the need for all that computing time, it’s not easy to create a spiral galaxy. Previous attempts yielded awkward results, but the astrophysicists working on this simulation were able to account for important processes — like supernova winds that push hydrogen gas out of a galaxy and shut down star formation — to produce a galaxy that has the right proportions.
The main challenge was to create the galaxy in the context of current cosmology, which says that the universe is mostly made up of stuff we can’t even see — dark matter and dark energy. Cosmologists (physicists who study the overall structure and evolution of the universe) have calculated what percent of the total ‘stuff’ of the universe is comprised of each major component — visible matter, dark matter, and dark energy. Astrophysicists who study galaxy formation were then tasked with figuring out how to create a Milky Way-like galaxy given these proportions. Here is the model of the universe they were given:
Data from sky surveys, such as the Sloan Digital Sky Survey, show that the universe appears on large scales to be comprised of giant sheets and chains surrounding enormous voids. Galaxies are the visible building blocks of this cosmic web-like structure. Dark matter is posited to be the main gravitational component in creating these sheets and chains, drawing hydrogen gas in to eventually create galaxies. Notice in the simulation how big globs slammed into the galaxy from all directions as it was forming — those were flows of cold hydrogen gas and smaller galaxies crashing into the nascent spiral galaxy.
The following is an excellent (and incredibly beautiful) series of simulations showing the large-scale structure of the universe and how this cosmic web likely formed:
Note: Gpc = gigaparsecs (a billion parsecs); Mpc = megaparsecs (a million parsecs); one parsec = approximately three light-years. (The ‘h’ is a parameter for the Hubble constant, which basically says how fast the universe is expanding. Its value is approximately 1.) The Milky Way is about 100,000 light-years across. The initial scale of the Millenium simulation is therefore HUGE. It’s not until the sim zooms in to the smallest scales that you can discern individual galaxies.
This most recent supercomputer simulation of the Milky Way-like spiral galaxy is a step forward, because it demonstrates that it’s possible to create such a galaxy given the known laws of physics and what we understand about the overall structure of the universe.
I’m starting to get whiplash from all this back-and-forth on the Higgs boson (aka the “God particle”), but now its existence is really looking doubtful:
Scientists chasing a particle they believe may have played a vital role in [the] creation of the universe indicated on Monday they were coming to accept it might not exist after all.
But they stressed that if the so-called Higgs boson turns out to have been a mirage, the way would be open for advances into territory dubbed “new physics” to try to answer one of the great mysteries of the cosmos. …
“Whatever the final verdict on Higgs, we are now living in very exciting times for all involved in the quest for new physics,” Guido Tonelli, from one of the two LHC detectors chasing the Higgs, said as the new observations were announced.
You have to admire their willingness to drop the Higgs hypothesis if it doesn’t work out. The idea has been around for decades, and a lot of hopes were pinned on it being right. But the willingness to go where the data take you is what moves science forward.
New results from the Large Hadron Collider have physicists wondering if they have actually, for reals now, detected the signal of a Higgs boson, aka the “God particle.” Earlier this year, scientists at Tevatron (an accelerator at Fermilab) thought they might have picked up the signal of a Higgs boson, but excitement turned to disappointment as it was revealed last month that the result could not be replicated with Tevatron’s other detector.
The Higgs boson is the lynchpin of the Standard Model of particle physics, explaining as it does why particles have mass, so physicists are trying like all get-out to find it. This latest hint at its existence is interesting, but nobody at LHC will be making any definitive statements about the result until they’ve analyzed the data and determined whether these fluctuations are statistically important.
Remember a couple of years ago when physicists thought the universe might be a hologram? No? Well, anyway, it turns out the universe is (almost certainly) not a hologram.
SixDay Science 