A Relativistic speed is a speed which is a significant proportion of the speed of light

Speed of light

The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

. Therefore scientific analysis must take the consequences of special relativity

Consequences of special relativity

Special relativity has several consequences that struck many people as counterintuitive, among which are:* The time lapse between two events is not invariant from one observer to another, but is dependent on the relative speeds of the observers' reference frames...

 into account. A relativistic particle

Relativistic particle

A relativistic particle is a particle which moves with a relativistic speed; that is, a speed comparable to the speed of light. This is achieved by photons to the extent that effects described by special relativity are able to describe those of such particles themselves...

 is a subatomic particle

Subatomic particle

In physics or chemistry, subatomic particles are the smaller particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles...

 moving at relativistic speed.

The boundary for when a particle becomes relativistic is difficult to define, but a particle can generally be said to be relativistic when Newtonian Mechanics no longer provide an accurate description which, within a margin of error of 1%, is 10% of the speed of light.

See also

• Special relativity
  Special relativity
  Special relativity is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".It generalizes Galileo's...
  
  
• Relativistic wave equations
  Relativistic wave equations
  Before the creation of quantum field theory, physicists attempted to formulate versions of the Schrödinger equation which were compatible with special relativity...
  
  
• Lorentz factor
  Lorentz factor
  The Lorentz factor or Lorentz term appears in several equations in special relativity, including time dilation, length contraction, and the relativistic mass formula. Because of its ubiquity, physicists generally represent it with the shorthand symbol γ . It gets its name from its earlier...
  
  
• Relativistic jet
  Relativistic jet
  Relativistic jets are extremely powerful jets of plasma which emerge from presumed massive objects at the centers of some active galaxies, notably radio galaxies and quasars. Their lengths can reach several thousand or even hundreds of thousands of light years...
  
  
• Relativistic mass
• Relativistic plasma
  Relativistic plasma
  Relativistic plasmas in physics are plasmas for which relativistic corrections to a particle's mass and velocity are important. Such corrections typically become important when a significant number of electrons reach speeds greater than 0.86c .Such plasmas may be created either by heating a gas to...
  
  
• Relativistic beaming
  Relativistic beaming
  Relativistic beaming is the process by which relativistic effects modify the apparent luminosity of emitting matter that is moving at speeds close to the speed of light...