Sunday, September 25, 2011

CERN: ‘Speed of Light Exceeded’ (Maybe)

Sunlight to Earth, travel time

Sunlight (composed of photons) takes about 8 minutes, 19 seconds to reach Earth - Could a neutrino reach Earth faster?

The news from CERN physicists that the speed of light “may have been exceeded” sent a lightning bolt of excitement and disbelief (not quite surpassing the speed of light) throughout the world’s physics community.  Fully accepting that their results would be met with great skepticism, the same physicists are inviting other particle physicists and labs to verify — or disprove — their results, which, if validated, will overturn one of the principle tenets of modern physics: that nothing travels faster than the speed of light (notated as ‘c‘ in physical equations).

Based in Switzerland, CERN physicists were experimenting with neutrinos (a mysterious class of virtually massless particles) by shooting them to an underground detector located over 450 miles (730 km) away in Italy. According to the detector results, the quantum particle reached its destination 60 nanoseconds faster than would a particle of light — that’s 60 billionths of a second — with a margin of error of just 10 nanoseconds. That tiny amount of difference in timing is a huge deal.

According to Einstein’s Special Theory of Relativity (from 1906), the speed at which light travels (whether as a wave form, or as a particle, known as a photon) is constant; no signal or flow of energy can surpass this cosmically limiting speed, which is rounded off to 186, 282 miles per second (decimal places excluded from that figure).

Some theoretical physicists (Feinberg, Sundarshan, etc.) had previously postulated a faster-than-light-speed particle — termed a tachyon — to explain bizarre phenomena such as bosonic ‘string’ theory and quantum entanglement (in which two coupled particles, widely separated, appear to “communicate” instantaneously). But modern quantum theory views such “particles” as representing or indicating an instability in the system (i.e., the tachyon field) and not “real” particles, thus incapable of faster than light transmission.

light cone

In the diagram, the interval AB is 'time-like'; i.e., there is a frame of reference in which events A and B occur at the same location in space, separated only by occurring at different times. If A precedes B in that frame, then A precedes B in all frames. It is hypothetically possible for matter (or information) to travel from A to B, so there can be a causal relationship (with A the cause and B the effect). The interval AC in the diagram is 'space-like'; i.e., there is a frame of reference in which events A and C occur simultaneously, separated only in space. However there are also frames in which A precedes C (as shown) and frames in which C precedes A. If it were possible for a cause-and-effect relationship to exist between events A and C, then paradoxes of causality would result.

No, the limiting nature of the speed of light (and its mediating particle) seems necessary for any cosmic, causal sense-making.

For physicist, the finite/constant speed of light (in a vacuum) is necessary to preserve “causality” in the normal sense of the word, wherein a ’cause’ precedes an ‘effect’. But, there is a theoretical paradox in which an effect precedes its cause (see the light cone diagram, left), and  in which “faster than light signals” can be sent back into one’s own past, creating a causal paradox (if, and only if, no previous signal was received).

There is also the odd phenomena in which the spot where the beam of a search light hits the bottom of a cloud can move faster than light when the search light is moved quickly (note: this effect/speed is not achieved in a vacuum).*

However, under controlled laboratory conditions, there has been only one serious, experimental challenge to this physical constant: in 2007, physicists working with Fermilab’s Tevatron collider (located in the U.S.), achieved a similar feat with neutrinos, but the margin of error was quite large, and consequently, the results were dismissed by the physics community (too much “noise” in the detectors’ data).

But CERN’s margin of error is much smaller. Currently, physicist the world over are either analyzing the results (for  errors), or trying to duplicate the results in other particle accelerators (such as the J-PARC neutrino collider system in Japan, which is conducting its own neutrino and antimatter experiment called T2K).

CERN (the European Organization for Nuclear Research) is located outside Geneva, Switxerland, and is the world’s largest particle physics research laboratory and home to the Large Hadron Collider (LHC), the world’s most powerful particle accelerator (note: the LHC was not used in this experiment).

If verified, these experimental results would be “revolutionary” say scientists. Proving the existence of a faster-than-light-speed particle will not change how the Universe works, of course, but it will change our understanding of some of its fundamental features, the most fundamental of which (apart from the three Laws of Thermodynamics) is the speed of light, the square of which was introduced to the world’s consciousness through Einstein’s famous equation E = mc².

For more information and to see a video from CERN, check out the Huff Post article ‘CERN: Light Speed May Have Been Exceeded By Subatomic Particle’

* [source]: Salmon, Wesley, Four Decades of Scientific Explanation; referenced on, ‘speed of light’]

top diagram: (sunlight time to Earth) Brews ohare ; CC – BY – SA 3.0

bottom diagram: (light cone) r Sakurambo

Source: Planetsave (

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