Tachyon

History:

The term tachyon was coined by Gerald Feinberg in a 1967 paper titled "Possibility of Faster-Than-Light Particles".[3] He had been inspired by the science-fiction story "Beep" by James Blish.[32] Feinberg studied the kinematics of such particles according to special relativity. In his paper he also introduced fields with imaginary mass (now also referred to as tachyons) in an attempt to understand the microphysical origin such particles might have.

The first hypothesis regarding faster-than-light particles is sometimes attributed to German physicist Arnold Sommerfeld in 1904,[33] and more recent discussions happened in 1962[21] and 1969.[34]

In September 2011, it was reported that a tau neutrino had traveled faster than the speed of light in a major release by CERN; however, later updates from CERN on the OPERA project indicate that the faster-than-light readings were due to a faulty element of the experiment's fibre optic timing system.[35

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Portions of this entry contributed by Waldyr A. Rodrigues, Jr. Tachyons are a putative class of particles which able to travel faster than the speed of light. Tachyons were first proposed by physicist Arnold Sommerfeld, and named by Gerald Feinberg. The word tachyon derives from the Greek (tachus), meaning "speedy.

A tachyon (/ˈtækiɒn/) or tachyonic particle is a hypothetical particle that always travels faster than light. Most physicists believe that faster-than-light particles cannot exist because they are not consistent with the known laws of physics.[1][2] If such particles did exist, they could be used to build a tachyonic antitelephone and send signals faster than light, which (according to special relativity) would lead to violations of causality.[2] No experimental evidence for the existence of such particles has been found.

The possibility of particles moving faster than light was first proposed by Robert Ehrilch and Arnold Sommerfeld, independently of each other. In the 1967 paper that coined the term,[3] Gerald Feinberg proposed that tachyonic particles could be quanta of a quantum field with imaginary mass. However, it was soon realized that excitations of such imaginary mass fields do not under any circumstances propagate faster than light,[4] and instead the imaginary mass gives rise to an instability known as tachyon condensation.[1] Nevertheless, in modern physics the term tachyon often refers to imaginary mass fields rather than to faster-than-light particles.[1][5] Such fields have come to play a significant role in modern physics.

The term comes from the Greek: ταχύ, tachy, meaning rapid. The complementary particle types are called luxons (which always move at the speed of light) and bradyons (which always move slower than light); both of these particle types are known to exist.

In special relativity, a faster-than-light particle would have space-like four-momentum,[3] in contrast to ordinary particles that have time-like four-momentum. Although in some theories the mass of tachyons is regarded as imaginary, in some modern formulations the mass is considered real,[6][7][8] the formulas for the momentum and energy being redefined to this end. Moreover, since tachyons are constrained to the spacelike portion of the energy–momentum graph, they could not slow down to subluminal speeds.[3]