Pros and Cons of Various Methods of Interstellar Travel

It’s a staple of science fiction, and something many people have fantasized about at one time or another: the idea of sending out spaceships with colonists and transplanting the seed of humanity among the stars. Between discovering new worlds, becoming an interstellar species, and maybe even finding extra-terrestrial civilizations, the dream of  spreading beyond the Solar System is one that can’t become reality soon enough!

For decades, scientists have contemplated how humanity might one-day reach achieve this lofty goal. And the range of concepts they have come up with present a whole lot of pros and cons. These pros and cons were raised in a recent study by Martin Braddock, a member of the Mansfield and Sutton Astronomical Society, a Fellow of the Royal Society of Biology, and a Fellow of the Royal Astronomical Society.

The study, titled “Concepts for Deep Space Travel: From Warp Drives and Hibernation to World Ships and Cryogenics“, recently appeared in the scientific journal Current Trends in Biomedical Engineering and Biosciences (a Juniper Journals publication). As Braddock indicates in his study, the question of how human beings could explore neighboring star systems has become more relevant in recent years thanks to exoplanet discoveries.

A list of some of the recently-discovered potentially habitable exoplanets. Credit: hpcf.upr.edu

As we reviewed in a previous article, “How Long Would it Take to Travel to the Nearest Star?“, there are numerous proposed and theoretical ways to travel between our Solar System and other stars in the galaxy. However, beyond the technology involved, and the time it would take, there are also the biological and psychological implications for human crews that would need to be taken into account beforehand.

And thanks to the way public interest in space exploration has become renewed in recent years, cost-benefit analyses of all the possible methods is becoming increasingly necessary. As Dr. Braddock told Universe Today via email|:

“Interstellar travel has become more relevant because of the concerted effort to find ways across all of the space agencies to maintain human health in ‘short’ (2-3 yr) space travel. With Mars missions reasonably in sight, Stephen Hawking’s death highlighting one his many beliefs that we should colonize deep space and Elon Musk’s determination to minimize waste on space travel, together with reborn visions of ‘bolt-on’ accessories to the ISS (the Bigelow expandable module) conjures some imaginative concepts.”

All told, Dr. Braddock considers five principle means for mounting crewed missions to other star systems in his study. These include super-luminal (aka/ FTL) travel, hibernation or stasis regimes, negligible senescence (aka. anti-aging) engineering, world ships capable of supporting multiple generations of travellers (aka. generation ships), and cyogenic freezing technologies.

Artist’s concept of a spacecraft using an Alcubierre Warp Drive. Credit: NASA

For FTL travel, the advantages are obvious, and while it remains entirely theoretical at this point, there are concepts being investigated today. A notable FTL concept – known as the Alcubierre Warp Drive – is currently being researched by multiple organizations, which includes the Tau Zero Foundation and the Advanced Propulsion Physics Laboratory: Eagleworks (APPL:E) at NASA’s Johnson Space Center.

To break it down succinctly, this method of space travel involves stretching the fabric of space-time in a wave which would (in theory) cause the space ahead of a ship to contract and the space behind it to expand. The ship would then ride this region, known as a “warp bubble”, through space. Since the ship is not moving within the bubble, but is being carried along as the region itself moves, conventional relativistic effects such as time dilation would not apply.

As Dr. Brannock indicates, the advantages of such a propulsion system include being able to achieve “apparent” FTL travel without violating the laws of Relativity. In addition, a ship traveling in a warp bubble would not have to worry about colliding with space debris, and there would be no upper limit to the maximum speed attainable. Unfortunately, the downsides of this method of travel are equally obvious.

These include the fact that there is currently no known methods for creating a warp bubble in a region of space that does not already contain one. In addition, extremely high energies would be required to create this effect, and there is no known way for a ship to exit a warp bubble once it has entered. In short, FTL is a purely theoretical concept for the time being and there are no indications that it will move from theory to practice in the near future.

“The first [strategy] is FTL travel, but the other strategies accept that FTL travel is very theoretical and that one option is to extend human life or to engage in multiple-generational voyages,” said Dr. Braddock. “The latter could be achieved in the future, given the willingness to design a large enough craft and the propulsion technology development to achieve 0.1 x c.”

In other words, the most plausible concepts for interstellar space travel are not likely to achieve speeds of more than ten percent the speed of light about 29,979,245.8 m / s (~107,925,285 km/h; 67,061,663 mph). This is still a very tall order considering that the fastest mission to date was the Helios 2 mission, which achieved a a maximum velocity of over 66,000 m/s (240,000 km/h; 150,000 mph). Still, this provides a more realistic framework to work within.

Where hibernation and stasis regiments are concerned, the advantages (and disadvantages) are more immediate. For starters, the technology is realizable and has been extensively studies on shorter timescales for both humans and animals. In the latter case, natural hibernation cycles provide the most compelling evidence that hibernation can last for months without incident.

The downsides, however, come down to all the unknowns. For example, there are the likely risks of tissue atrophy resulting from extended periods of time spent in a microgravity environment. This could be mitigated by artificial gravity or other means (such as electrostimulation of muscles), but considerable clinical research is needed before this could be attempted. This raises a whole slew of ethical issues, since such tests would pose their own risks.

Strategies for Engineered Negligible Senescence (SENS) are another avenue, offering the potential for human beings to counter the effects of long-duration spaceflight by reversing the aging process. In addition to ensuring that the same generation that boarded the ship would be the one to make it to its destination, this technique also has the potential to drive stem cell therapy research here on Earth.

However, in the context of long-duration spaceflight, multiple treatments (or continuous ones throughout the travel process) would likely be necessary to achieve full rejuvenation. A considerable amount of research would also be needed beforehand in order to test the process and address the individual components of aging, once again leading to a number of ethical issues.

Then there’s worldships (aka. generation ships), where self-contained and self sustaining spacecraft large enough to accommodate several generations of space travelers would be used. These ships would rely on conventional propulsion and therefore take centuries (or millennia) to reach another star system. The immediate advantages of this concept is that it would fulfill two major goals of space exploration, which would be to maintain a human colony in space and to permit travel to a potentially-habitable exoplanet.

In addition, a generation ship would rely on propulsion concepts that are currently feasible, and a crew of thousands would multiply the chances of successfully colonizing another planet. Of course, the cost of constructing and maintaining such large spaceships would be prohibitive. There are also the moral and ethical challenges of sending human crews into deep space for such extended periods of time.

For instance, is there any guarantee that the crew wouldn’t all go insane and kill each other? And last, there is the fact that newer, more advanced ships would be developed on Earth in the meantime. This means that a faster ship, which would depart Earth later, would be able to overtake a generation ship before it reached another star system. Why spend so much on a ship when it’s likely to become obsolete before it even makes it to its destination?

A concept for a multi-generation ship being designed by the TU Delft Starship Team (DSTART), with support from the ESA. Credit and Copyright: Nils Faber & Angelo Vermeulen

Last, there is cryogenics, a concept that has been explored extensively in the past few decades as a possible means for life-extension and space travel. In many ways, this concept is an extension of hibernation technology, but benefits from a number of recent advancements. The immediate advantage of this method is that it accounts for all the current limitations imposed by technology and a relativistic Universe.

Basically, it doesn’t matter if FTL (or speeds beyond 0.10 c) are possible or how long a voyage will take since the crew will be asleep and perfectly preserved for the duration. On top of that, we already know the technology works, as demonstrated by recent advancements where organ tissues and even whole organisms were warmed and vitrified after being cryogenically frozen.

However, the risks also greater than with hibernation. For instance, the long-term effects of cryogenic freezing on the physiology and central nervous system of higher-order animals and humans is not yet known. This means that extensive testing and human trials would be needed before it was ever attempted, which once again raises a number of ethical challenges.

In the end, there are a lot of unknowns associated with any and all potential methods of interstellar travel. Similarly, much more research and development is necessary before we can safely say which of them is the most feasible. In the meantime, Dr. Braddock admits that it’s much more likely that any interstellar voyages will involve robotic explorers using telepresence technology to show us other worlds – though these don’t possess the same allure.

Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity’s first interstellar voyage. Credit: breakthroughinitiatives.org

“Almost certainly, and this revisits the early concept of von Neumann replication probes (minus the replication!),” he said. “Cube Sats or the like may well achieve this goal but will likely not engage the public imagination nearly as much as human space travel. I believe Sir Martin Rees has suggested the concept of a semi-human AI type device… also some way off.”

Currently, there is only one proposed mission for sending an interstellar space craft to a nearby star system. This would be Breakthrough Starshot, a proposal to send a laser sail-driven nanocraft to Alpha Centauri in just 20 years. After being accelerated to 4,4704,000 m/s (160,934,400 km/h; 100 million mph) 20% the speed of light, this craft would conduct a flyby of Alpha Centauri and also be able to beam home images of Proxima b.

Beyond that, all the missions that involve venturing to the outer Solar System consist of robotic orbiters and probes and all proposed crewed missions are directed at sending astronauts back to the Moon and on to Mars. Still, humanity is just getting started with space exploration and we certainly need to finish exploring our own Solar System before we can contemplate exploring beyond it.

In the end, a lot of time and patience will be needed before we can start to venture beyond the Kuiper Belt and Oort Cloud to see what’s out there.

Further Reading: ResearchGate

What is the Alcubierre “Warp” Drive?

It’s always a welcome thing to learn that ideas that are commonplace in science fiction have a basis in science fact. Cryogenic freezers, laser guns, robots, silicate implants… and let’s not forget the warp drive! Believe it or not, this concept – alternately known as FTL (Faster-Than-Light) travel, Hyperspace, Lightspeed, etc. – actually has one foot in the world of real science.

In physics, it is what is known as the Alcubierre Warp Drive. On paper, it is a highly speculative, but possibly valid, solution of the Einstein field equations, specifically how space, time and energy interact. In this particular mathematical model of spacetime, there are features that are apparently reminiscent of the fictional “warp drive” or “hyperspace” from notable science fiction franchises, hence the association.

Background:

Since Einstein first proposed the Special Theory of Relativity in 1905, scientists have been operating under the restrictions imposed by a relativistic universe. One of these restrictions is the belief that the speed of light is unbreakable and hence, that there will never be such a thing as FTL space travel or exploration.

Visualization of a warp field, according to the Alcubierre Drive. Credit: AllenMcC

Even though subsequent generations of scientists and engineers managed to break the sound barrier and defeat the pull of the Earth’s gravity, the speed of light appeared to be one barrier that was destined to hold. But then, in 1994, a Mexican physicist by the name of Miguel Alcubierre came along with proposed method for stretching the fabric of space-time in way which would, in theory, allow FTL travel to take pace.

Concept:

To put it simply, this method of space travel involves stretching the fabric of space-time in a wave which would (in theory) cause the space ahead of an object to contract while the space behind it would expand. An object inside this wave (i.e. a spaceship) would then be able to ride this region, known as a “warp bubble” of flat space.

This is what is known as the “Alcubierre Metric”. Interpreted in the context of General Relativity, the metric allows a warp bubble to appear in a previously flat region of spacetime and move away, effectively at speeds that exceed the speed of light. The interior of the bubble is the inertial reference frame for any object inhabiting it.

Since the ship is not moving within this bubble, but is being carried along as the region itself moves, conventional relativistic effects such as time dilation would not apply. Hence, the rules of space-time and the laws of relativity would not be violated in the conventional sense.

Artist’s concept of a spacecraft using an Alcubierre Warp Drive. Credit: NASA

One of the reasons for this is because this method would not rely on moving faster than light in the local sense, since a light beam within this bubble would still always move faster than the ship. It is only “faster than light” in the sense that the ship could reach its destination faster than a beam of light that was traveling outside the warp bubble.

Difficulties:

However, there is are few problems with this theory. For one, there are no known methods to create such a warp bubble in a region of space that would not already contain one. Second, assuming there was a way to create such a bubble, there is not yet any known way of leaving once inside it. As a result, the Alcubierre drive (or metric) remains in the category of theory at this time.

Mathematically, it can be represented by the following equation: ds2= – (a2 – BiBi) dt2 + 2Bi dxi dt + gijdxi dxj, where a is the lapse function that gives the interval of proper time between nearby hypersurfaces, Bi is the shift vector that relates the spatial coordinate systems on different hypersurfaces and gij is a positive definite metric on each of the hypersurfaces.

Attempts at Development:

In 1996, NASA founded a research project known as the Breakthrough Propulsion Physics Project (BPP) to study various spacecraft proposals and technologies. In 2002, the project’s funding was discontinued, which prompted the founder – Marc G. Millis – and several members to create the Tau Zero Foundation. Named after the famous novel of the same name by Poul Anderson, this organization is dedicated to researching interstellar travel.

In 2012, NASA’s Advanced Propulsion Physics Laboratory (aka. Eagleworks) announced that they had began conducting experiments to see if a “warp drive” was in fact possible. This included developing an interferometer to detect the spatial distortions produced by the expanding and contracting space-time of the Alcubierre metric.

The team lead – Dr. Harold Sonny White – described their work in a NASA paper titled Warp Field Mechanics 101. He also explained their work in NASA’s 2012 Roundup publication:

“We’ve initiated an interferometer test bed in this lab, where we’re going to go through and try and generate a microscopic instance of a little warp bubble. And although this is just a microscopic instance of the phenomena, we’re perturbing space time, one part in 10 million, a very tiny amount… The math would allow you to go to Alpha Centauri in two weeks as measured by clocks here on Earth. So somebody’s clock onboard the spacecraft has the same rate of time as somebody in mission control here in Houston might have. There are no tidal forces, no undue issues, and the proper acceleration is zero. When you turn the field on, everybody doesn’t go slamming against the bulkhead, (which) would be a very short and sad trip.”

In 2013, Dr. White and members of Eagleworks published the results of their 19.6-second warp field test under vacuum conditions. These results, which were deemed to be inconclusive, were presented at the 2013 Icarus Interstellar Starship Congress held in Dallas, Texas.

When it comes to the future of space exploration, some very tough questions seem unavoidable. And questions like “how long will it take us to get the nearest star?” seem rather troubling when we don’t make allowances for some kind of hypervelocity or faster-than-light transit method. How can we expect to become an interstellar species when all available methods with either take centuries (or longer), or will involve sending a nanocraft instead?

At present, such a thing just doesn’t seem to be entirely within the realm of possibility. And attempts to prove otherwise remain unsuccessful or inconclusive. But as history has taught us, what is considered to be impossible changes over time. Someday, who knows what we might be able to accomplish? But until then, we’ll just have to be patient and wait on future research.

We have written many articles about the Alcubierre “Warp” Drive for Universe Today. Here’s Warp Drives Probably Impossible After All, Warp Drives and Cloaking Devices not just Science Fiction Anymore, Warp Drive May Come with a Killer Downside, Astronomy Without a Telescope – Warp Drive on Paper, and Zoom, Zoom, Zoom: Gorgeous Warp Ship Design Delights The Internet.

If you’d like more info on the Alcubierre “Warp” Drive, check out an article from Wikipedia. Also, check out another article about the warp drive spaceship engine.

We’ve also recorded an entire episode of Astronomy Cast all about Light Echoes. Listen here, Episode 215: Light Echoes.

Sources:

Neutrinos Obey The Speed Limit, After All

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Neutrinos have been cleared of allegations of speeding, according to an announcement issued today by CERN and the ICARUS experiment at Italy’s Gran Sasso National Laboratory. Turns out they travel exactly as fast as they should, and not a nanosecond more.

The initial announcement in September 2011 from the OPERA experiment noted a discrepancy in the measured speed of neutrinos traveling in a beam sent to the detectors at Gran Sasso from CERN in Geneva. If their measurements were correct, it would have meant that the neutrinos had arrived 60 nanoseconds faster than the speed of light allows. This, understandably, set the world of physics a bit on edge as it would effectually crumble the foundations of the Standard Model of physics.

As other facilities set out to duplicate the results, further investigations by the OPERA team indicated that the speed anomaly may have been the result of bad fiberoptic wiring between the detectors and the GPS computers, although this was never officially confirmed to be the exact cause.

Now, a a statement from CERN reports the results of the ICARUS experiment — Imaging Cosmic and Rare Underground Signals — which is stationed at the same facilities as OPERA. The ICARUS data, in measuring neutrinos from last year’s beams, show no speed anomaly — further evidence that OPERA’s measurement was very likely a result of error.

The full release states:

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The ICARUS experiment at the Italian Gran Sasso laboratory has today reported a new measurement of the time of flight of neutrinos from CERN to Gran Sasso. The ICARUS measurement, using last year’s short pulsed beam from CERN, indicates that the neutrinos do not exceed the speed of light on their journey between the two laboratories. This is at odds with the initial measurement reported by OPERA last September.

What neutrinos look like to ICARUS. (LNGS)

“The evidence is beginning to point towards the OPERA result being an artefact of the measurement,” said CERN Research Director Sergio Bertolucci, “but it’s important to be rigorous, and the Gran Sasso experiments, BOREXINO, ICARUS, LVD and OPERA will be making new measurements with pulsed beams from CERN in May to give us the final verdict. In addition, cross-checks are underway at Gran Sasso to compare the timings of cosmic ray particles between the two experiments, OPERA and LVD. Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements. This is how science works.” 

The ICARUS experiment has independent timing from OPERA and measured seven neutrinos in the beam from CERN last year. These all arrived in a time consistent with the speed of light.

“The ICARUS experiment has provided an important cross check of the anomalous result reports from OPERA last year,” said Carlo Rubbia, Nobel Prize winner and spokesperson of the ICARUS experiment. “ICARUS measures the neutrino’s velocity to be no faster than the speed of light. These are difficult and sensitive measurements to make and they underline the importance of the scientific process. The ICARUS Liquid Argon Time Projection Chamber is a novel detector which allows an accurate reconstruction of the neutrino interactions comparable with the old bubble chambers with fully electronics acquisition systems. The fast associated scintillation pulse provides the precise  timing of each event, and has been exploited for the neutrino time-of-flight measurement. This technique is now recognized world wide as the most appropriate for future large volume neutrino detectors”.

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An important note is that, although further research points more and more to neutrinos behaving as expected, the OPERA team had proceeded in a scientific manner right up to and including the announcement of their findings.

“Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements,” the ICARUS team reported. “This is how science works.”

See more news from CERN here.

Warp Drives May Come With a Killer Downside

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Planning a little space travel to see some friends on Kepler 22b? Thinking of trying out your newly-installed FTL3000 Alcubierre Warp Drive to get you there in no time? Better not make it a surprise visit — your arrival may end up disintegrating anyone there when you show up.

“Warp” technology and faster-than-light (FTL) space travel has been a staple of science fiction for decades. The distances in space are just so vast and planetary systems — even within a single galaxy — are spaced so far apart, such a concept is needed to make casual human exploration feasible (and fit within the comforts of people’s imagination as well… nobody wants to think about Kirk and Spock bravely going to some alien planet while everyone they’ve ever known dies of old age!)

While many factors involving FTL travel are purely theoretical — and may remain in the realm of imagination for a very long time, if not ever — there are some concepts that play well with currently-accepted physics.

Warp field according to the Alcubierre drive. (AllenMcC.)

The Alcubierre warp drive is one of those concepts.

Proposed by Mexican theoretical physicist Miguel Alcubierre in 1994, the drive would propel a ship at superluminal speeds by creating a bubble of negative energy around it, expanding space (and time) behind the ship while compressing space in front of it. In much the same way that a surfer rides a wave, the bubble of space containing the ship and its passengers would be pushed at velocities not limited to the speed of light toward a destination.

Of course, when the ship reaches its destination it has to stop. And that’s when all hell breaks loose.

Researchers from the University of Sydney have done some advanced crunching of numbers regarding the effects of FTL space travel via Alcubierre drive, taking into consideration the many types of cosmic particles that would be encountered along the way. Space is not just an empty void between point A and point B… rather, it’s full of particles that have mass (as well as some that do not.) What the research team — led by Brendan McMonigal, Geraint Lewis, and Philip O’Byrne — has found is that these particles can get “swept up” into the warp bubble and focused into regions before and behind the ship, as well as within the warp bubble itself.

When the Alcubierre-driven ship decelerates from superluminal speed, the particles its bubble has gathered are released in energetic outbursts. In the case of forward-facing particles the outburst can be very energetic — enough to destroy anyone at the destination directly in front of the ship.

“Any people at the destination,” the team’s paper concludes, “would be gamma ray and high energy particle blasted into oblivion due to the extreme blueshifts for [forward] region particles.”

In other words, don’t expect much of a welcome party.

Another thing the team found is that the amount of energy released is dependent on the length of the superluminal journey, but there is potentially no limit on its intensity.

“Interestingly, the energy burst released upon arriving at the destination does not have an upper limit,” McMonigal told Universe Today in an email. “You can just keep on traveling for longer and longer distances to increase the energy that will be released as much as you like, one of the odd effects of General Relativity. Unfortunately, even for very short journeys the energy released is so large that you would completely obliterate anything in front of you.”

So how to avoid disintegrating your port of call? It may be as simple as just aiming your vessel a bit off to the side… or, it may not. The research only focused on the planar space in front of and behind the warp bubble; deadly postwarp particle beams could end up blown in all directions!

Luckily for Vulcans, Tatooinians and any acquaintances on Kepler 22b, the Alcubierre warp drive is still very much theoretical. While the mechanics work with Einstein’s General Theory of Relativity, the creation of negative energy densities is an as-of-yet unknown technology — and may be impossible.

Which could be a very good thing for us, should someone out there be planning a surprise visit our way!

 

Read more about Alcubierre warp drives here, and you can download the full University of Sydney team’s research paper here.

Thanks to Brendan McMonigal and Geraint Lewis for the extra information!

Main image © Paramount Pictures and CBS Studios. All rights reserved.

 

Faster Than Light? More Like Faulty Wiring.

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You can shelf your designs for a warp drive engine (for now) and put the DeLorean back in the garage; it turns out neutrinos may not have broken any cosmic speed limits after all.

Ever since the news came out on September 22 of last year that a team of researchers in Italy had clocked neutrinos traveling faster than the speed of light, the physics world has been resounding with the potential implications of such a discovery — that is, if it were true. The speed of light has been a key component of the standard model of physics for over a century, an Einstein-established limit that particles (even tricky neutrinos) weren’t supposed to be able to break, not even a little.

Now, according to a breaking news article by Edwin Cartlidge on AAAS’ ScienceInsider, the neutrinos may be cleared of any speed violations.

“According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos’ flight and an electronic card in a computer,” Cartlidge reported.

The original OPERA (Oscillation Project with Emulsion-tRacking Apparatus) experiment had a beam of neutrinos fired from CERN in Geneva, Switzerland, aimed at an underground detector array located 730 km away at the Gran Sasso facility, near L’Aquila, Italy. Researchers were surprised to discover the neutrinos arriving earlier than expected, by a difference of 60 nanoseconds. This would have meant the neutrinos had traveled faster than light speed to get there.

Repeated experiments at the facility revealed the same results. When the news was released, the findings seemed to be solid — from a methodological standpoint, anyway.

Shocked at their own results, the OPERA researchers were more than happy to have colleagues check their results, and welcomed other facilities to attempt the same experiment.

Repeated attempts may no longer be needed.

Once the aforementioned fiber optic cable was readjusted, it was found that the speed of data traveling through it matched the 60 nanosecond discrepancy initially attributed to the neutrinos. This could very well explain the subatomic particles’ apparent speed burst.

Case closed? Well… it is science, after all.

“New data,” Cartlidge added, “will be needed to confirm this hypothesis.”

See the original OPERA team paper here.

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UPDATE 2/22/12 11:48 pm EST: According to a more recent article on Nature’s newsblog, the Science Insider report erroneously attributed the 60 nanosecond discrepancy to loose fiber optic wiring from the GPS unit, based on inside “sources”. OPERA’s statement doesn’t specify as such, “saying instead that its two possible sources of error point in opposite directions and it is still working things out.”

OPERA’s official statement released today is as follows:

“The OPERA Collaboration, by continuing its campaign of verifications on the neutrino velocity measurement, has identified two issues that could significantly affect the reported result. The first one is linked to the oscillator used to produce the events time-stamps in between the GPS synchronizations. The second point is related to the connection of the optical fiber bringing the external GPS signal to the OPERA master clock.

These two issues can modify the neutrino time of flight in opposite directions. While continuing our investigations, in order to unambiguously quantify the effect on the observed result, the Collaboration is looking forward to performing a new measurement of the neutrino velocity as soon as a new bunched beam will be available in 2012. An extensive report on the above mentioned verifications and results will be shortly made available to the scientific committees and agencies.” (via Nature newsblog.)

Neutrinos Still Breaking Speed Limits

Particle Collider

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New test results are in from OPERA and it seems those darn neutrinos, they just can’t keep their speed down… to within the speed of light, that is!

report released in September by scientists working on the OPERA project (Oscillation Project with Emulsion-tracking Apparatus) at Italy’s Gran Sasso research lab claimed that neutrinos emitted from CERN 500 miles away in Geneva arrived at their detectors 60 nanoseconds earlier than expected, thus traveling faster than light. This caused no small amount of contention in the scientific community and made news headlines worldwide – and rightfully so, as it basically slaps one of the main tenets of modern physics across the face.

Of course the scientists at OPERA were well aware of this, and didn’t make such a proclamation lightly; over two years of repeated research was undergone to make sure that the numbers were accurate… as well as could be determined, at least. And they were more than open to having their tests replicated and the results reviewed by their peers. In all regards their methods were scientific yet skepticism was widespread… even within OPERA’s own ranks.

One of the concerns that arose regarding the discovery was in regards to the length of the neutrino beam itself, emitted from CERN and received by special detector plates at Gran Sasso. Researchers couldn’t say for sure that any neutrinos detected were closer to the beginning of the beam versus the end, a disparity (on a neutrino-sized scale anyway) of 10.5 microseconds… that’s 10.5 millionths of a second! And so in October, OPERA requested that proton pulses be resent – this time lasting only 3 nanoseconds each.

The OPERA Neutrino Detector

The results were the same. The neutrinos arrived at Gran Sasso 60 nanoseconds earlier than anticipated: faster than light.

The test was repeated – by different teams, no less – and so far 20 such events have been recorded. Each time, the same.

Faster. Than light.

What does this mean? Do we start tearing pages out of physics textbooks? Should we draw up plans for those neutrino-powered warp engines? Does Einstein’s theory of relativity become a quaint memento of what we used to believe?

Hardly. Or, at least, not anytime soon.

OPERA’s latest tests have managed to allay one uncertainty regarding the results, but plenty more remain. One in particular is the use of GPS to align the clocks at the beginning and end of the neutrino beam. Since the same clock alignment system was used in all the experiments, it stands that there may be some as-of-yet unknown factor concerning the GPS – especially since it hasn’t been extensively used in the field of high-energy particle physics.

In addition, some scientists would like to see more results using other parts of the neutrino detector array.

Of course, like any good science, replication of results is a key factor for peer acceptance. And thus Fermilab in Batavia, Illinois will attempt to perform the same experiment with its MINOS (Main Injector Neutrino Oscillation Search) facility, using a precision matching OPERA’s.

MINOS hopes to have its independent results as early as next year.

No tearing up any textbooks just yet…

 

Read more in the Nature.com news article by Eugenie Samuel Reich. The new result was released on the arXiv preprint server on November 17. (The original September 2011 OPERA team paper can be found here.)

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.

Astronomy Without A Telescope – FTL Neutrinos (Or Not)

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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.