Tachyon

Tachyon (pronounced tak-ee-on)

In theoretical physics, a hypothetical elementary particle capable of travelling faster than the speed of light

1967: The construct was tachy + on, a hypothetical Ancient Greek etymon derived from ταχυόν (takhuón) (a quick thing), from ταχύς (takhús) (swift, rapid).  The on suffix is used in physics to form nouns denoting subatomic particles (eg proton), quanta (eg photon), molecular units (eg codon), or substances (eg interferon). Tachyon is a noun and tachyonic is an adjective (the more attractive adjectival form in French is tachyonique); the noun plural is tachyons.

The universe’s universal speed limit

In the literature, the earliest reference to speculative discussions about faster-than-light particles appears to be work published in 1904 by German theoretical physicist Arnold Sommerfeld (1868–1951), others suggesting the possibility in 1962 used the term meta-particle.  In 1967, US physicist Gerald Feinberg (1933–1992) coined the word tachyon in a paper titled Possibility of Faster-Than-Light Particles, based on his study of how such particles would behave according to special relativity.

Tachyons probably can’t exist because they would conflict with many known laws of physics and speculative experiments have been designed to demonstrate the logical paradoxes their existence would create.  Despite this theoretical proof of their impossibility, experiments have been performed to look for them, but no evidence has been found.  They can be imagined because it’s a variation of the visual effect of watching an airplane travelling faster than the speed of sound.  There, the airplane is seen before being heard.  Because a tachyon must always be faster than light, it wouldn’t be possible to see it coming and after it passed, the observer would see two images of it, appearing and departing.  The meta-implication, were faster-than-light travel possible for some things or layers, is the universe being a space in which, at least in part, everything is happening at the same time.

The speed limit ultimately is always C.

However, just because tachyons can't exist hasn't stopped physicists pondering the possibilities offered by tachyonic devices.  The concept of the tachyonic antitelephone was in 1969 proposed by US physicist Gregory Benford (b 1941), his idea being that if a tachyon could be sent back in time, it could be used to transmit information faster than the speed of light, the hypothetical device thus able to send information back in time.  That of course would have the potential for both good and evil but would anyway violate the law of causality, as effect would occur before cause.