Is Einstein’s Theory in Danger?

Publish Date: Jan 02, 2014 | 35 Ratings | 4.66 out of 5 | Print | 14 Customer Reviews | Submit your review

Table of Contents

  1. The OPERA Experiment
  2. Challenges With Detector Production—50 Microns Accuracy
  3. Automation Using Robotics and Machine Vision
  4. Surpassing the Speed of Light?

Serendipity is the discovery of something fortunate. That’s what seems to have happened at the Gran Sasso National Laboratory (LNGS) near L’Acquila, Italy, the site of the OPERA (Oscillation Project with Emulsion-tRacking Apparatus) experiment. The OPERA experiment has measured neutrinos (subatomic particles) that have apparently traveled faster than light. Subsequent measurements and analysis are underway before the result is widely accepted by the scientific community; however, if validated, the result will alter the laws of physics. Light is the fastest thing in the universe and is the notion on which Einstein’s theory of relativity is based. If these neutrinos have traveled faster than light, things in science fiction movies such as time travel and existence of new dimensions may all become a reality. To get to the point of this serendipitous discovery, you must understand the OPERA experiment and its goals.

1. The OPERA Experiment

Neutrinos are some of the fundamental particles that make up the universe, and are very similar to electrons but are electrically neutral. There are three types, or “flavors,” of neutrinos that are each related to a charged particle: electron (associated with electrons) and two heavier versions, the tau and the muon. The OPERA experiment’s charter was to test the phenomenon of neutrino oscillations, where under the right conditions one flavor of neutrino transmutates into a different flavor. To verify this, the European Organization for Nuclear Research, known as CERN, collaborated with LNGS. Neutrino oscillation is an important study in particle physics that helps scientists better understand the nature of matter, the forces acting on them, and, in general, provides clarification about the fundamental nature of underlying physics.

Figure 1. CERN to Gran Sasso Neutrino Beam

To study the neutrino oscillations, researchers at CERN (in Geneva, Switzerland) produce a high-intensity, high-energy beam of muon neutrinos. This beam is pointed toward the OPERA detector in the LNGS underground laboratory some 700 kilometers away in Gran Sasso. The goal of the OPERA detector is to check for the tau neutrinos from the oscillation of muon neutrinos during the three millisecond travel some 11 kilometers underground and 730 kilometers in the earth’s crust from Geneva to Gran Sasso. Because neutrinos are electrically neutral, the electromagnetic forces that act on charged particles like electrons and protons do not affect them. Neutrinos are affected only by the weak subatomic force and therefore can travel great distances through matter without being affected. Because of this property, scientists can shoot the neutrinos toward Gran Sasso in the earth’s crust without having a dedicated tunnel or cable.

Figure 2. The OPERA detector at LNGS

To check for neutrino events, “bricks” of photographic emulsion films interleaved with lead plates are assembled to form walls that contain 3,328 bricks each. Every brick is made up of 57 emulsion films and lead plates. A plastic scintillator is placed behind each of the 62 walls to detect the occurrence of a neutrino event in real time. This target is complemented by trackers, spectrometers, and an ancillary infrastructure. The total weight of this massive detector is about 1,800 tons. This huge detector is necessitated by the fact that the neutrinos are not affected by electromagnetic forces and also have a very weak interaction with matter.

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2. Challenges With Detector Production—50 Microns Accuracy

The detector is a huge mass of different materials, so researchers must be careful when assembling the different components. The slightest misalignments of the thin photographic films and lead plates would result in detectors being unable to track the trajectory of the neutrinos and the neutrino interactions. To get accurate results, the alignments of the bricks and the walls had to be within 0.05 mm (50 µ).

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3. Automation Using Robotics and Machine Vision

A brick assembly machine used anthropomorphic robots to stack the films and lead plates to form the bricks. This initial setup did not involve any machine vision, so the robot was flying blind and early trials indicated that the 50 micron alignment accuracy was not reached. ImagingLab, a National Instruments Alliance Partner, was tasked with achieving the necessary accuracy.

ImagingLab chose to retrofit the brick assembly line with a machine vision system capable of providing corrective feedback to the robots during assembly, as well as recording the residual position error of each film. The imaging system had to be compact in size and mechanically very stable with a resolution in excess of 50 microns. Since they used photographic films, ImagingLab decided to use a near-infrared illumination well outside of the emulsion plates instead of regular light, which would spoil the films. They used two charge-coupled device (CCD) cameras for imaging.

Figure 3. The prototype of the machine vision system shows an NI PXI system and an NI frame grabber.

The imaging analysis software performs a series of measurements such as taking the position of the film edge, the alignment and verticality of the stack, and gross assembly errors. The position data are fed back to the robot controller (the individual plates are held by vacuum). Residual errors are recorded and used to automatically compensate the scan sequence of a multiplate exposure analysis of a neutrino event.

The system uses five 1454 Compact Vision Systems from National Instruments and 10 IEEE 1394 CCD cameras. Its software development is based on NI LabVIEW software and the IMAQ library. Early tests have used the NI Vision Assistant and NI Vision Builder for Automated Inspection. The automated assembly system has been deployed in the assembly of the OPERA detector and has successfully met the goal of 50 micron alignment accuracy.

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4. Surpassing the Speed of Light?

To generate the neutrino pulse that is shot toward OPERA, researchers used a proton pulse. They measured the exact time the neutrinos were launched by using a high-speed digitizer from National Instruments. The system uses a GPS signal to synchronize the timing of the neutrino pulse generator at CERN and the OPERA detector at LNGS. When the scientists measured the time it took for the neutrinos to travel from CERN to LNGS, they found that it took the neutrinos 60 nanoseconds less than it would take a beam of light to travel the same distance. Although 60 nanoseconds may not sound like much, it is so statistically significant that it prompted scientists to conduct this experiment multiple times. Later experiments have continued to yield similar results and the focus is now on finding any extraneous inaccuracies, such as the accuracy of the GPS signal, before the results can be validated. Furthermore, Fermilab in Illinois, USA has been tasked with conducting a similar experiment with existing infrastructure to verify the measurements.

These are exciting times for both the physics community and National Instruments. In addition to the OPERA experiment, several promising projects, such as the Higgs boson search at the Large Hadron Collider (LHC) in CERN and the research of energy from fusion at ITER, are currently happening. National Instruments is actively involved in these projects and in helping the scientists and engineers in the areas of measurement, analysis, diagnostics, and control. So, is Einstein’s theory of relativity in danger? The OPERA experiment that was intended to study neutrino oscillations seems to have serendipitously broken the fundamental laws of physics. Further validation in the coming days will shed some light on this new discovery.

Learn more about commercial off-the-shelf technologies for particle accelerators.

Arun Veeramani

Arun Veeramani is the senior market development manager for the science and big physics segment at National Instruments. He holds a master’s degree in electrical engineering from Arizona State University.


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Customer Reviews
14 Reviews | Submit your review

Measurement errors found - Jan 8, 2013

Oops. The guys at CERN later found 2 errors. Repeat tests confirmed that neutrinos are not faster than light. "Now we are 100% sure that the speed of light is the speed of neutrinos." - Sandro Centro, co-spokesman for the Icarus collaboration light_neutrino_anomaly environment-17560379

Nope - Jan 8, 2013

Fascinating story but the conclusion is a bit premature. From the CERN press office dated 8 June 2012: Neutrinos sent from CERN to Gran Sasso respect the cosmic speed limit At the 25th International Conference on Neutrino Physics and Astrophysics in Kyoto today, CERN Research Director Sergio Bertolucci presented results on the time of flight of neutrinos from CERN to the INFN Gran Sasso Laboratory on behalf of four experiments situated at Gran Sasso. The four, Borexino, ICARUS, LVD and OPERA all measure a neutrino time of flight consistent with the speed of light. This is at odds with a measurement that the OPERA collaboration put up for scrutiny last September, indicating that the original OPERA measurement can be attributed to a faulty element of the experiment’s fibre optic timing system.

60nS is only 60 feet at C - May 17, 2012

I doubt that they know the distance between the source and the detector to 60 feet accuracy. How would they measure that? Moreover, measuring the time of arrival of the neutrino and the tiime of emission of the same neutrino to 60nS seems fraught. Since neutrinos cannot be numbered, the neuttino beam would have to be modulated. e.g. chopped on and off.I wonder how this was done? Then there is the issue that both the source and detector are moving. Now Einstein disounts a linear motion, but the earth's rotation is not acceleration free. Then we have the fact that the neutrino beam is propagating perpendicular to a grabvitational field - it's not free space. Moreover, the metric of spacetime inside the dense matter of the earth is not the same as the metric of empty space. I would recommend addressing all those issues before concluding that Relativity was violated.

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