Sections
Glossary
Glossary
- classical velocity addition
- the method of adding velocities when ; velocities add like regular numbers in one-dimensional motion: , where is the velocity between two observers, is the velocity of an object relative to one observer, and is the velocity relative to the other observer
- first postulate of special relativity
- the idea that the laws of physics are the same and can be stated in their simplest form in all inertial frames of reference
- inertial frame of reference
- a reference frame in which a body at rest remains at rest and a body in motion moves at a constant speed in a straight line unless acted on by an outside force
- length contraction
- , the shortening of the measured length of an object moving relative to the observer’s frame:
- Michelson-Morley experiment
- an investigation performed in 1887 that proved that the speed of light in a vacuum is the same in all frames of reference from which it is viewed
- proper length
- ; the distance between two points measured by an observer who is at rest relative to both of the points; Earth-bound observers measure proper length when measuring the distance between two points that are stationary relative to Earth
- proper time
- the time measured by an observer at rest relative to the event being observed: , where
- relativistic Doppler effects
- a change in wavelength of radiation that is moving relative to the observer; the wavelength of the radiation is longer (called a red shift) than that emitted by the source when the source moves away from the observer and shorter (called a blue shift) when the source moves toward the observer; the shifted wavelength is described by the equation
11.80where is the observed wavelength, is the source wavelength, and is the velocity of the source to the observer
- relativistic kinetic energy
- the kinetic energy of an object moving at relativistic speeds: where
- relativistic momentum
- , the momentum of an object moving at relativistic velocity; , where is the rest mass of the object, is its velocity relative to an observer, and the relativistic factor
- relativistic velocity addition
- the method of adding velocities of an object moving at a relativistic speed: , where is the relative velocity between two observers, is the velocity of an object relative to one observer, and is the velocity relative to the other observer
- relativity
- the study of how different observers measure the same event
- rest energy
- the energy stored in an object at rest:
- rest mass
- the mass of an object as measured by a person at rest relative to the object
- second postulate of special relativity
- the idea that the speed of light is a constant, independent of the source
- special relativity
- the theory that, in an inertial frame of reference, the motion of an object is relative to the frame from which it is viewed or measured
- time dilation
- the phenomenon of time passing slower to an observer who is moving relative to another observer
- total energy
- defined as , where
- twin paradox
- this asks why a twin traveling at a relativistic speed away and then back toward Earth ages less than the Earth-bound twin. The premise to the paradox is faulty because the traveling twin is accelerating, and special relativity does not apply to accelerating frames of reference