Lessons learned (so far) from the superluminal neutrino episode April 7, 2012
Posted by admin in : Astronomy and Astrophysics (ASTRO), Cosmology, Gravitation, and Relativity (CGR), Nuclear and Particle Physics (NPP) , add a commentReprinted from Waves and Packets, April 7,2012 edition
With the March 15 paper of the ICARUS group claiming no advance effect for their (seven) neutrino events, it seems the urgency and interest in this matter is dwindling. OPERA spokesperson Antonio Ereditato and experimental coordinator Dario Autiero have announced their resignations, following a controversial vote of “no confidence” from the collaboration’s other leaders. Waves and Packets has asked three distinguished physicists what they think the lessons learned are from the entire episode.
“It is misconception that Einstein’s special theory of relativity says that nothing can travel faster than the speed of light. For example, electrons can travel faster than the speed of light in water. This leads to a phenomena known as Cherenkov radiation which is seen as a blue glow in nuclear reactors. In addition, for a long time it’s been speculated that subatomic particles known as a tachyons might exist. Tachyons are theoretically predicted particles that travel faster than the speed of light in a vacuum and are consistent with Einstein’s theory of relativity. For ordinary subliminal particles light acts as a barrier from above. That is ordinary matter cannot be accelerated to the speed of light. For superluminal tachyons light acts as a barrier from below. That is to say that tachyons cannot be decelerated to the speed of light. It has been conjectured that tachyons could be used to send signals back in time. To date tachyons have not been observed experimentally.” Ronald Mallett, University of Connecticut-Storrs
“I think the first thing the whole episode indicates is that there is still enormous public interest in our field. The need to explore is still felt keenly so we need to be clear that announcing results, even controversial ones, should be respected by scientists if proper peer review of those results has been performed. It also points out the absolute necessity of following through on external checks. Public review of the scientific process is not a bad thing nor is showing some humility and skepticism even about ‘sacred’ principles like special relativity. Episodes like this one give us the opportunity to address misconceptions like those surrounding the connection between special relativity and the speed of light. Showing fallibility doesn’t weaken us as long as we remain appropriate demanding of ‘extraordinary proof’ for “extraordinary results.” Larry Gladney, University of Pennsylvania
“I can think of two positive remarks to be made. The first is that, given an information leak from someone familiar with the OPERA experiment to Science magazine, the OPERA Collaboration did the right thing in going public with the information they had at hand. In the spirit of good science, they nearly begged other experiments to validate or invalidate their working hypothesis of superluminal neutrinos. It now appears that invalidation was in order, as reported by the ICARUS experiment. Over the next several months, we may anticipate half a dozen experiments on three continents providing further measurements of neutrino speed; new data will also be forthcoming from the OPERA and ICARUS experiments. My second positive remark is that many of us have been pushed by the OPERA claim to examine the deeper meaning of Special and General Relativity. While paradoxes, such as superluminal travel with inherent negation of cause and effect, are mathematically consistent with Einstein’s equations, they generally are hidden behind horizons, or require invocation of new physics such as negative energy, extra dimensions, sterile neutrinos, etc. It has been fun and educational to think about the possibilities. Any opportunity to explore a guarded secret of Nature must be seized upon. It unfortunately appears now that superluminal neutrino travel may not be one of Her guarded secrets.” Thomas Weiler, Vanderbilt University
What’s your view? Contact Waves and Packets at editors@wavesandpackets.org.
News From The Front, VII: What is Fundamental, Anyway? July 4, 2009
Posted by CGrBlogs in : Cosmology, Gravitation, and Relativity (CGR), Nuclear and Particle Physics (NPP) , add a commentEditor’s note: The following excerpt comes to us from theoretical physicist Clifford Johnson, a professor in the University of Southern California Department of Physics and Astronomy. Professor Johnson’s work primarily focuses on (super)string theory, gravity, gauge theory and M-theory. — CPW
One of the words I dislike most in my field – or more accurately, a common usage thereof – is “fundamental”. This is because it is usually used as a weapon, very often by people in my area of physics (largely concerned with particle physics, high energy physics, origins questions and so forth), to dismiss the work of others as somehow uninteresting or irrelevant. I don’t like this. Never have. Not only is it often allied to a great deal of arrogance and misplaced swagger, it is often just plain short-sighted, since you never know where good ideas and techniques will come from. A glance at the history of physics shows just how much cross-pollination there is between fields in terms of ideas and techniques. You never know for sure where valuable insights into certain kinds of problems may come from.
Fundamental physics is a term I used to hear used a lot to refer to particle physics (also called high energy physics a lot more these days). This was especially true some years back when I was an undergraduate in the UK, and it persisted in graduate school too, and is still in use today, although I think it is declining a bit in favour of less loaded terms. Somehow, a lot of particle physics is regarded as being all about the “what is everything made of at the very smallest scales” sort of question, first discussing atoms, and then atoms being made of electrons surrounding a nucleus, and the nucleus being made of protons and neutrons, and those in turn being made of quarks, and so on, in this was arriving at a list of “fundamental” particles. There’s the parallel discussion about the “fundamental” forces (e.g., electromagnetism and the nuclear forces) being described in terms of exchanges of particles like photons, gluons, and W and Z particles and so forth. There’s no real harm in the use of the term fundamental in this context, but this is about where the word gets elevated beyond its usefulness and starts becoming a hurdle to progress, and then a barrier. Somehow, “fundamental”, meaning “building block” gets turned, oddly, into “most important”. The issue of what the smallest building blocks are gets elevated to the most important quest, when it is in reality only a component of the story. It is rather like saying that the most important things about the Taj Mahal are the beautiful stones, tiles, and other components from which it is constructed.
Perspectives have evolved a bit since my salad days, with the rise of wider recognition of the connection between particle physics, and astrophysics and cosmology. I think that things are (these days) more widely seen to be the more rich interconnected and beautiful landscape of phenomena that they are, but I still find, especially among younger people, the “building block” attitude to be prevalent.
I raise this since sometimes I find that people don’t understand that there are fundamental and vital questions in other areas that connect to so many interesting areas of physics. [...]
Read the rest of the article on Asymptotia here.