Physics Archives

November 2, 2011December 24, 2015 by Ray Sanders

Absorption Lines Shed New Light on 90 Year Old Puzzle

Gemini North Observatory, Maunakea Hawaii. Image Credit: Gemini Observatory/AURA

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Using the Gemini North Telescope, astronomers studying the central region of the Milky Way have discovered 13 diffuse interstellar bands with the longest wavelengths to date. The team’s discovery could someday solve a 90-year-old mystery about the existence of these bands.

“These diffuse interstellar bands—or DIBs—have never been seen before,” says Donald Figer, director of the Center for Detectors at Rochester Institute of Technology and one of the authors of a study appearing in the journal Nature.

What phenomenon are responsible for these absorption lines, and what impact do they have on our studies of our galaxy?

Figer offers his explanation of absorption lines, stating, “Spectra of stars have absorption lines because gas and dust along the line of sight to the stars absorb some of the light.”

Figer adds, “The most recent ideas are that diffuse interstellar bands are relatively simple carbon bearing molecules, similar to amino acids. Maybe these are amino acid chains in space, which supports the theory that the seeds of life originated in space and rained down on planets.”

“Observations in different Galactic sight lines indicate that the material responsible for these DIBs ‘survives’ under different physical conditions of temperature and density,” adds team member Paco Najarro (Center of Astrobiology, Madrid).

The discovery of low energy absorption lines by Figer and his team helps to determine the nature of diffuse interstellar bands. Figer believes that any future models that predict which wavelengths the particles absorb will have to include the newly discovered lower energies, stating, “We saw the same absorption lines in the spectra of every star. If we look at the exact wavelength of the features, we can figure out the kind of gas and dust between us and the stars that is absorbing the light.”

nature10527-f2.2 — Spectra of the newly discovered Diffuse Interstellar Bands (DIB's).
Image Credit: Geballe, Najarro, Figer, Schlegelmilch, and de la Fuente.

Since their discovery 90 years ago, diffuse interstellar bands have been a mystery. To date, the known bands that have been identified before the team’s study occur mostly in visible wavelengths. Part of the puzzle is that the observed lines don’t match the predicted lines of simple molecules and can’t be traced to a single source.

“None of the diffuse interstellar bands has been convincingly identified with a specific element or molecule, and indeed their identification, individually and collectively, is one of the greatest challenges in astronomical spectroscopy, recent studies have suggested that DIB carriers are large carbon-containing molecules.” states lead author Thomas Geballe (Gemini Observatory).

One other benefit the newly discovered infrared bands offer is that they can be used to better understand the diffuse interstellar medium, where thick dust and gas normally block observations in visible light. By studying the stronger emissions, scientists may gain a better understanding of their molecular origin. So far, no research teams have been able to re-create the interstellar bands in a laboratory setting, mostly due to the difficulty of reproducing temperatures and pressure conditions the gas would experience in space.

If you’d like to learn more about the Gemini Observatory, visit: http://www.gemini.edu/
Read more about RIT’s Center for Detectors at: http://ridl.cis.rit.edu/

Source: Rochester Institute of Technology Press Release

November 2, 2011January 14, 2016 by Nancy Atkinson

TV Viewing Alert: New Mini-Series: Fabric of the Cosmos

A new 4-part mini-series debuts tonight on PBS station in the US, featuring theoretical physicist Brian Greene. The series is called “Fabric of the Cosmos” and is based on Greene’s 2004 book of the same name. It premieres tonight (Nov. 2, 2011) on NOVA, with subsequent episodes airing November 9, 16 and 23. The series will probe the most extreme realms of the cosmos, from black holes to dark matter, to time bending and parallel realities.

Check your local listings for time.

November 1, 2011April 26, 2016 by Tammy Plotner

Large Hadron Collider Finishes 2011 Proton Run

A new loop will be added to CERN's Antiproton Decelerator in 2016 to increase antiproton production at low energies. Credit: CERN

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The world’s largest and highest-energy particle accelerator has been busy. At 5:15 p.m. on October 30, 2011, the Large Hadron Collider in Geneva, Switzerland reached the end of its current proton run. It came after 180 consecutive days of operation and four hundred trillion proton collisions. For the second year, the LHC team has gone beyond its operational objectives – sending more experimental data at a higher rate. But just what has it done?

When this year’s project started, its goal was to produce a surplus of data known to physicists as one inverse femtobarn. While that might seem like a science fiction term, it’s a science fact. An inverse femtobarn is a measurement of particle collision events per femtobarn – which is equal to about 70 million million collisions. The first inverse femtobarn came on June 17th, and just in time to prepare the stage for major physics conferences requiring the data be moved up to five inverse femtobarns. The incredible number of collisions was reached on October 18, 2011 and then surpassed as almost six inverse femtobarns were delivered to each of the two general-purpose experiments – ATLAS and CMS.

“At the end of this year’s proton running, the LHC is reaching cruising speed,” said CERN’s Director for Accelerators and Technology, Steve Myers. “To put things in context, the present data production rate is a factor of 4 million higher than in the first run in 2010 and a factor of 30 higher than at the beginning of 2011.”

But that’s not all the LHC delivered this year. This year’s proton run also shut out the accessible hiding space for the highly prized Higgs boson and supersymmetric particles. This certainly put the Standard Model of particle physics and our understanding of the primordial Universe to the test!

“It has been a remarkable and exciting year for the whole LHC scientific community, in particular for our students and post-docs from all over the world. We have made a huge number of measurements of the Standard Model and accessed unexplored territory in searches for new physics. In particular, we have constrained the Higgs particle to the light end of its possible mass range, if it exists at all,” said ATLAS Spokesperson Fabiola Gianotti. “This is where both theory and experimental data expected it would be, but it’s the hardest mass range to study.”

“Looking back at this fantastic year I have the impression of living in a sort of a dream,” said CMS Spokesperson Guido Tonelli. “We have produced tens of new measurements and constrained significantly the space available for models of new physics and the best is still to come. As we speak hundreds of young scientists are still analysing the huge amount of data accumulated so far; we’ll soon have new results and, maybe, something important to say on the Standard Model Higgs Boson.”

“We’ve got from the LHC the amount of data we dreamt of at the beginning of the year and our results are putting the Standard Model of particle physics through a very tough test ” said LHCb Spokesperson Pierluigi Campana. “So far, it has come through with flying colours, but thanks to the great performance of the LHC, we are reaching levels of sensitivity where we can see beyond the Standard Model. The researchers, especially the young ones, are experiencing great excitement, looking forward to new physics.”

Over the next few weeks, the LHC will be further refining the 2011 data set with an eye to improving our understanding of physics. And, while it’s possible we’ll learn more from current findings, look for a leap to a full 10 inverse femtobarns which may yet be possible in 2011 and projected for 2012. Right now the LHC is being prepared for four weeks of lead-ion running… an “attempt to demonstrate that large can also be agile by colliding protons with lead ions in two dedicated periods of machine development.” If this new strand of LHC operation happens, science will soon be using protons to check out the internal machinations of much heftier structures – like lead ions. This directly relates to quark-gluon plasma, the surmised primordial conglomeration of ordinary matter particles from which the Universe evolved.

“Smashing lead ions together allows us to produce and study tiny pieces of primordial soup,” said ALICE Spokesperson Paolo Giubellino, “but as any good cook will tell you, to understand a recipe fully, it’s vital to understand the ingredients, and in the case of quark-gluon plasma, this is what proton-lead ion collisions could bring.”

Original Story Source: CERN Press Release.

October 22, 2011January 14, 2016 by Tammy Plotner

Quantum Levitation And The Superconductor

Superconductivity and magnetic fields are like oil and water… they don’t mix. When it can, the superconductor will push out any magnetic fields from the interior in a process called the Meissner effect. It happens when a sample is cooled below its superconducting transition temperature, where it then cancels out its magnetic flux. What’s next? A superconductor. Now the fun really begins… Continue reading “Quantum Levitation And The Superconductor”

October 15, 2011December 24, 2015 by Tammy Plotner

Special Relativity May Answer Faster-than-Light Neutrino Mystery

The relativistic motion of clocks on board GPS satellites exactly accounts for the superluminal effect, says physicist. Credit: axirv

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Oh, yeah. Moving faster than the speed of light has been the hot topic in the news and OPERA has been the key player. In case you didn’t know, the experiment unleashed some particles at CERN, close to Geneva. It wasn’t the production that caused the buzz, it was the revelation they arrived at the Gran Sasso Laboratory in Italy around 60 nanoseconds sooner than they should have. Sooner than the speed of light allows!

Since the announcement, the physics world has been on fire, producing more than 80 papers – each with their own opinion. While some tried to explain the effect, others discredited it. The overpowering concensus was the OPERA team simply must have forgotten one critical element. On October 14, 2011, Ronald van Elburg at the University of Groningen in the Netherlands put forth his own statement – one that provides a persuasive point that he may have found the error in the calculations.

To get a clearer picture, the distance the neutrinos traveled is straightforward. They began in CERN and were measured via global positioning systems. However, the Gran Sasso Laboratory is located beneath the Earth under a kilometre-high mountain. Regardless, the OPERA team took this into account and provided an accurate distance measurement of 730 km to within tolerances of 20 cm. The neutrino flight time is then measured by using clocks at the opposing ends, with the team knowing exactly when the particles left and when they landed.

But were the clocks perfectly synchronized?

Keeping time is again the domain of the GPS satellites which each broadcasting a highly accurate time signal from orbit some 20,000km overhead. But is it possible the team overlooked the amount of time it took for the satellite signals to return to Earth? In his statement, van Elburg says there is one effect that the OPERA team seems to have overlooked: the relativistic motion of the GPS clocks.

Sure, radio waves travel at the speed of light, so what difference does the satellite position make? The truth is, it doesn’t.. but the time of flight does. Here we have a scenario where one clock is on the ground while the other is orbiting. If they are moving relative to one another, this calculation needs to be included in the findings. The orbiting probes are positioned from West to East in a plane inclined at 55 degrees to the equator… almost directly in line with the neutrino flight path. This means the clock on the GPS is seeing the neutrino source and detector as changing.

“From the perspective of the clock, the detector is moving towards the source and consequently the distance travelled by the particles as observed from the clock is shorter,” says van Elburg.

According to the news source, he means shorter than the distance measured in the reference frame on the ground and the OPERA team overlooks this because it thinks of the clocks as on the ground not in orbit. Van Elburg calculates that it should cause the neutrinos to arrive 32 nanoseconds early. But this must be doubled because the same error occurs at each end of the experiment. So the total correction is 64 nanoseconds, almost exactly what the OPERA team observes.

Is this the final answer for traveling faster than the speed of light? No. It’s just another possible answer to explain a new riddle… and a confirmation of a new revelation.

Original Story Source: Technology Review News Release. For Further Reading: Can apparent superluminal neutrino speeds be explained as a quantum weak measurement?.

October 8, 2011December 24, 2015 by Steve Nerlich

Astronomy Without A Telescope – Light Speed

The effect of time dilation is negligible for common speeds, such as that of a car or even a jet plane, but it increases dramatically when one gets close to the speed of light.

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The recent news of neutrinos moving faster than light might have got everyone thinking about warp drive and all that, but really there is no need to imagine something that can move faster than 300,000 kilometres a second.

Light speed, or 300,000 kilometres a second, might seem like a speed limit, but this is just an example of 3 + 1 thinking – where we still haven’t got our heads around the concept of four dimensional space-time and hence we think in terms of space having three dimensions and think of time as something different.

For example, while it seems to us that it takes a light beam 4.3 years to go from Earth to the Alpha Centauri system, if you were to hop on a spacecraft going at 99.999 per cent of the speed of light you would get there in a matter of days, hours or even minutes – depending on just how many .99s you add on to that proportion of light speed.

This is because, as you keep pumping the accelerator of your imaginary star drive system, time dilation will become increasingly more pronounced and you will keep getting to your destination that much quicker. With enough .999s you could cross the universe within your lifetime – even though someone you left behind would still only see you moving away at a tiny bit less than 300,000 kilometres a second. So, what might seem like a speed limit at first glance isn’t really a limit at all.

The effect of time dilation is negligible for common speeds we are familiar with on Earth, but it increases dramatically and asymptotically as you approach the speed of light.

To try and comprehend the four dimensional perspective on this, consider that it’s impossible to move across any distance without also moving through time. For example, walking a kilometer may be a duration of thirty minutes – but if you run, it might only take fifteen minutes.

Speed is just a measure of how long it takes you reach a distant point. Relativity physics lets you pick any destination you like in the universe – and with the right technology you can reduce your travel time to that destination to any extent you like – as long as your travel time stays above zero.

That is the only limit the universe really imposes on us – and it’s as much about logic and causality as it is about physics. You can travel through space-time in various ways to reduce your travel time between points A and B – and you can do this up until you almost move between those points instantaneously. But you can’t do it faster than instantaneously because you would arrive at B before you had even left A.

If you could do that, it would create impossible causality problems – for example you might decide not to depart from point A, even though you’d already reached point B. The idea is both illogical and a breach of the laws of thermodynamics, since the universe would suddenly contain two of you.

So, you can’t move faster than light – not because of anything special about light, but because you can’t move faster than instantaneously between distant points. Light essentially does move instantaneously, as does gravity and perhaps other phenomena that we are yet to discover – but we will never discover anything that moves faster than instantaneously, as the idea makes no sense.

We mass-laden beings experience duration when moving between distant points – and so we are able to also measure how long it takes an instantaneous signal to move between distant points, even though we could never hope to attain such a state of motion ourselves.

We are stuck on the idea that 300,000 kilometres a second is a speed limit, because we intuitively believe that time runs at a constant universal rate. However, we have proven in many different experimental tests that time clearly does not run at a constant rate between different frames of reference. So with the right technology, you can sit in your star-drive spacecraft and make a quick cup of tea while eons pass by outside. It’s not about speed, it’s about reducing your personal travel time between two distant points.

As Woody Allen once said: Time is nature’s way of keeping everything from happening at once. Space-time is nature’s way of keeping everything from happening in the same place at once.

October 7, 2011December 24, 2015 by Tammy Plotner

The Crab Gets Cooked With Gamma Rays

X-ray: NASA/CXC/ASU/J. Hester et al.; Optical: NASA/HST/ASU/J. Hester et al.; Radio: NRAO/AUI/NSF Image of the Crab Nebula combines visible light (green) and radio waves (red) emitted by the remnants of a cataclysmic supernova explosion in the year 1054. and the x-ray nebula (blue) created inside the optical nebula by a pulsar (the collapsed core of the massive star destroyed in the explosion). The pulsar, which is the size of a small city, was discovered only in 1969. The optical data are from the Hubble Space Telescope, and the radio emission from the National Radio Astronomy Observatory, and the X-ray data from the Chandra Observatory.

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It’s one of the most famous sights in the night sky… and 957 years ago it was bright enough to be seen during the day. This supernova event was one of the most spectacular of its kind and it still delights, amazes and even surprises astronomers to this day. Think there’s nothing new to know about M1? Then think again…

An international collaboration of astrophysicists, including a group from the Department of Physics in Arts & Sciences at Washington University in St. Louis, has detected pulsed gamma rays coming from the heart of the “Crab”. Apparently the central neutron star is putting off energies that can’t quite be explained. These pulses between range 100 and 400 billion electronvolts (Gigaelectronvolts, or GeV), far higher than 25 GeV, the most energetic radiation recorded. To give you an example, a 400 GeV photon is almost a trillion times more energetic than a light photon.

“This is the first time very-high-energy gamma rays have been detected from a pulsar – a rapidly spinning neutron star about the size of the city of Ames but with a mass greater than that of the Sun,” said Frank Krennrich, an Iowa State professor of physics and astronomy and a co-author of the paper.

We can thank the Arizona based Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of four 12-meter Cherenkov telescopes covered in 350 mirrors for the findings. It is continually monitoring Earth’s atmosphere for the fleeting signals of gamma-ray radiation. However, findings like these on such a well-known object is nearly unprecedented.

“We presented the results at a conference and the entire community was stunned,” says Henric Krawczynski, PhD, professor of physics at Washington University. The WUSTL group led by James H. Buckley, PhD, professor of physics, and Krawczynski is one of six founding members of the VERITAS consortium.

crabpulsar — An X-ray image of the Crab Nebula and pulsar. Image by the Chandra X-ray Observatory, NASA/CXC/SAO/F. Seward.

We know the Crab’s story and how its pulsar sweeps around like a lighthouse… But Krennrich said such high energies can’t be explained by the current understanding of pulsars. Not even curvature radiation can be at the root of these gamma-ray emissions.

“The pulsar in the center of the nebula had been seen in radio, optical, X-ray and soft gamma-ray wavelengths,” says Matthias Beilicke, PhD, research assistant professor of physics at Washington University. “But we didn’t think it was radiating pulsed emissions above 100 GeV. VERITAS can observe gamma-rays between100 GeV and 30 trillion electronvolts (Teraelectronvolts or TeV).”

Just enough to cook one crab… well done!

Original Story Source: Iowa State University News Release. For Further Reading: Washington University in St. Louis News Release.

October 3, 2011January 14, 2016 by Jason Major

Particle Physics and Faster-Than-Light Neutrinos…Discuss.

On September 22, an international team of researchers working on the OPERA project at the Gran Sasso research facility released a paper on some potentially physics-shattering findings: beams of neutrinos that had traveled from the CERN facility near Geneva to their detector array outside of Rome at a speed faster than light. (Read more about this here and here.) Not a great deal faster, to be sure – only 60 nanoseconds faster than expected – but still faster. There’s been a lot of recoil from the scientific community about this announcement, and rightly so, since if it does end up being a legitimate finding then it would force us to rework much of what we have come to know about physics ever since Einstein’s theory of relativity.

Of course, to those of us not so well-versed in particle physics *raises hand* a lot of this information can quickly become overwhelming, to say the least. Thankfully the folks at Sixty Symbols have recorded this interview with two astrophysicists at the UK’s University of Nottingham. It helps explain some of the finer points of the discovery, what it means and what the science community in general thinks about it. Check it out!

Thanks to Dan Satterfield for posting this at his Wild Wild Science blog.

October 1, 2011December 24, 2015 by Steve Nerlich

Astronomy Without A Telescope – FTL Neutrinos (Or Not)

Location of the Grand Sasso OPERA neutrino experiment in Italy - which receives a beam of neutrinos from CERN - and at faster than the speed of light if you can believe it. Credit: CERN.

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The recent news from the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) neutrino experiment, that neutrinos have been clocked travelling faster than light, made the headlines over the last week – and rightly so. There are some very robust infrastructure and measurement devices involved that give the data a certain gravitas.

The researchers had appropriate cause to put their findings up for public scrutiny and peer review – and to their credit have produced a detailed paper on the subject, beyond just the media releases we have seen. Nonetheless, it has been reported that some senior members of the OPERA research team declined to be associated with this paper, considering that it was all a bit preliminary.

After all, the reported results indicate that the neutrinos crossed a distance of 730 kilometres in 60 nanoseconds less time than light would have taken. But given that light would have taken 2.4 million nanoseconds to cross the same distance – there is a lot hanging on such a proportionally tiny difference.

It would have been a different story if the neutrinos had been clocked at 1.5x or 2x light speed, but this is more like 1.0025x light speed. And it would have been no surprise to anyone to have found the neutrinos travelling at 99.99% of light speed, given their association with the Large Hadron Collider. So, confirming that they really are exceeding light speed, but only by a tiny amount, requires supreme confidence in the measuring systems used. And there are reasons to doubt that there are grounds for such confidence.

The distance component of the speed calculation had an error of less than 20 cm out of the 730 kilometres path, or 0.00003% if you like, over the data collection period. That’s not much error, but then the degree to which the neutrinos are claimed to have moved faster than light isn’t that much either.

But the travel time component of the speed calculation is the real question mark here. The release time of neutrinos from the source could only be inferred as arising from a 10.5 microsecond burst of protons from the CERN Super Proton Synchrotron (SPS) – fired at a graphite target, which then releases neutrinos towards OPERA.

The researchers substantially restrained the potential error (i.e. 10.5 microseconds) by comparing the time distributions of SPS proton release and neutrino detection at OPERA over repeated trials, to give a probability density function of the time of emission of the neutrinos. But this is really just a long-winded way of saying they could only estimate the likely travel time, more or less. And the dependence on GPS satellite links to time stamp the release and detection steps represents a further source of potential measurement error.

Some of the complex infrastructure required to infer the travel time of neutrinos across the OPERA experiment. Credit Adam et al.

It’s also important to note that this was not a race. The 730 kilometre straight-line pathway to OPERA is through the Earth’s crust – which is virtually transparent to neutrinos, but opaque to light. The travel time of light is hence inferred from measuring the path distance. So it was never the case that the neutrinos were seen to beat a light beam across the path distance.

The real problem with the OPERA experiment is that the calculated bettering of light speed is a very tiny margin that has been measured over a relatively short path distance. If the experiment could be repeated by firing at a neutrino detector on the Moon say, that longer path distance would deliver more robust and more convincing data – since, if the OPERA effect is real, the neutrinos should very obviously reach the Moon quicker than a light beam could.

Until then, it all seems a bit premature to start throwing out the physics textbooks.

Further reading:
Adam et al Measurement of the neutrino velocity with the OPERA detector in the CNGS beam.

A contrary view – including reports than not all the Gran Sasso team are on board with the FTL neutrino idea.

September 28, 2011December 24, 2015 by Tammy Plotner

Bending The Rules – Exploring Gravitational Redshift

A cluster of galaxies as seen from the Hubble Space Telescope

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Hey. We’re all aware of Einstein’s theories and how gravity affects light. We know it was proved during a total solar eclipse, but what we’ve never realized in observational astronomy is that light just might get bent by other gravitational influences. If it can happen from something as small as a star, then what might occur if you had a huge group of stars? Like a galaxy… Or a group of galaxies!

What’s new in the world of light? Astrophysicists at the Dark Cosmology Centre at the Niels Bohr Institute have now gone around the bend and came up with a method of measuring how outgoing light is affected by the gravity of galaxy clusters. Not only does each individual star and each individual galaxy possess its own gravity, but a galaxy group is held together by gravitational attraction as well. Sure, it stands to reason that gravity is affecting what we see – but there’s even more to it. Redshift…

“It is really wonderful. We live in an era with the technological ability to actually measure such phenomena as cosmological gravitational redshift”, says astrophysicist Radek Wojtak, Dark Cosmology Centre under the Niels Bohr Institute at the University of Copenhagen.

Together with team members Steen Hansen and Jens Hjorth, Wojtak has been collecting light data and measurements from 8,000 galaxy clusters. Their studies have included calculations from mid-placed members to calibrations on those that reside at the periphery.

“We could measure small differences in the redshift of the galaxies and see that the light from galaxies in the middle of a cluster had to ‘crawl’ out through the gravitational field, while it was easier for the light from the outlying galaxies to emerge”, explains Radek Wojtak.

The next step in the equation is to measure the entire galaxy cluster’s total mass to arrive at its gravitational potential. Then, using the general theory of relativity, the gravitational redshift could be determined by galaxy location.

“It turned out that the theoretical calculations of the gravitational redshift based on the general theory of relativity was in complete agreement with the astronomical observations.” explains Wojtak. “Our analysis of observations of galaxy clusters show that the redshift of the light is proportionally offset in relation to the gravitational influence from the galaxy cluster’s gravity. In that way our observations confirm the theory of relativity.”

Of course, this kind of revelation also has other implications… theoretical dark matter just might play a role in gravitational redshift, too. And don’t forget dark energy. All these hypothetical models need to be taken into account. But, for now, we’re looking at the big picture in a different way.

“Now the general theory of relativity has been tested on a cosmological scale and this confirms that the general theory of relativity works and that means that there is a strong indication for the presence of dark energy”, explains Radek Wojtak.

As Walt Whitman once said, “I open the scuttle at night and see the far-sprinkled systems, And all I see multiplied as high as I can cypher edge but the rim of the farther systems. Wider and wider they spread, expanding, always expanding,Outward and outward and forever outward.”

Original Story Source: EurekAlert News Release. Link to Gravitational redshift of galaxies in clusters as predicted by general relativity.