It is a well-known fact that nothing can travel faster than the speed of light. The universal
speed of light is 300,000 km/sec. In Einstein’s theory of special relativity, only massless
particles like the photon travel at the speed of light; all other particles travel slower.
Theoretically, most physicists believe that faster-than-light particles cannot exist because
they violate known laws of physics. If such particles existed and could carry signals
faster than light, then according to Einstein's theory of relativity, they would break causality,
leading to logical dilemmas like the grandfather paradox. So, does this mysterious particle
really exist? Well, let’s find out. You might have come across the term tachyons
in science fiction and faster-than-light travel or communication. The term 'tachyon', which
comes from the Greek word 'tachys', which means fast, was coined by the late Gerald
Feinberg of Columbia University. According to physical theory, tachyons are hypothetical
particles that travel faster than light and have 'imaginary' masses. They are merely hypothetical
since they break several established physics laws (such as the general theory of relativity),
and their existence indicates that the theory that contains them is unstable. Let's look
more closely at what hypothetical tachyons are, what they mean, and how they relate to
other physical theories. The existence of tachyons can lead to paradoxes
involving "time travel." Normally, events are determined solely by what has occurred
in the past, however, features of Einstein's theory suggest that a tachyon could be identified
before it formed. Because the presence of a tachyon would contradict Einstein's extraordinarily
successful theory, a claim of tachyon detection would necessitate extraordinary evidence.
The mass of tachyon particles is fictitious. Any particles with an imaginary mass will
spontaneously decay, indicating that they do not include tachyonic particles or have
an imaginary mass. This is known as "tachyon condensation", in which a system can lower
its energy by producing particles spontaneously. It was once thought that tachyonic particles
might move faster than light. In addition, in a 1967 publication, it was postulated that
tachyonic particles might be quanta of fields with an imaginary mass that propagate more
quickly than light, which was the first time such a particle was stated and named a tachyon.
Something to note is that we often speak of tachyonic fields instead of tachyonic particles.
In modern physics, all fundamental particles are regarded as fields with excitations. The
consequence of a tachyonic field in known reality is that it is unstable and will undergo
tachyonic condensation, resulting in symmetry breaking and the creation of new particles.
Does Einstein's theory of relativity state that nothing can travel faster than light?
It simply argues that nothing with a mass greater than zero can travel to the speed
of light (or higher) because this would demand infinite energy and result in an infinite
mass. Only massless particles, like photons and gluons, can travel at the speed of light.
As a result, according to relativity theory, a particle will not be able to accelerate
faster than the speed of light. But what if it was always that fast, from the beginning
of time? What if it was created in this manner during the Big Bang?
If such a particle existed, it would be unable to slow down to slower than the speed of light.
It would have the strange property of requiring less energy as its velocity increased, hence
approaching its lowest energy state as it reached infinity's speed. To slow down to
the speed of light, on the other hand, would require infinite energy, and hence would never
be able to cross that speed barrier. As a result, particles traveling at different speeds
on either side of the speed of light encounter a two-way barrier.
That would not violate the laws of relativity, but it would have some strange properties.
One peculiar property is that tachyons would have an imaginary rest mass (assuming that
energy must be a real and positive value, as the equation on the screen shows). If the
denominator is an imaginary number, the numerator must also be an imaginary number for the result
to be an actual number. The other strange property is that depending
on the relative arrangements between the frames in spacetime, an observer could see tachyons
travel the other way through time, thereby seeing them before they are produced (in the
observer's frame). Fun fact, while particles with imaginary mass
are called tachyons, ordinary particles with a non-zero mass that travel slower than light
are called bradyons or tardyons, and massless particles are called luxons.
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