Relativity

Home > Physics > Classical Physics > Relativity

The study of the laws of physics that apply to objects moving at high speeds or in the presence of strong gravitational fields.

Frame of reference: A specific point of view from which physical measurements are taken. This is important in relativity because different frames of reference can experience time and space differently.
Inertial reference frame: A frame of reference in which an object at rest remains at rest and an object in motion continues to move at a constant velocity, with no acceleration.
Lorentz transformation: The mathematical equations that describe how measurements of time and space vary between different frames of reference in special relativity.
Time dilation: The phenomenon in which time appears to run differently for different observers, depending on their relative motion.
Length contraction: The phenomenon in which the length of an object appears to be shortened when it is observed in motion relative to an observer.
Relativity of simultaneity: The concept that two events that appear to occur at the same time in one observer's frame of reference may occur at different times from the perspective of another observer in a different frame of reference.
Mass-energy equivalence: The equation E=mc², which shows that energy and mass are interchangeable and closely linked in special and general relativity.
General relativity: A more comprehensive theory of relativity that takes gravity into account as a geometric curvature of space-time, rather than a simple force.
Gravitational time dilation: The slowing down of time near massive objects, such as those with strong gravitational fields such as black holes.
Black holes: An object with such a strong gravitational field that nothing, even light, can escape it.
Cosmic time: The age of the universe, which can be calculated from observations of cosmic microwave background radiation and the expansion rate of the universe.
Space-time: A four-dimensional continuum that combines space and time into a single fabric, which is distorted by gravity and the motion of objects.
Inertia: The tendency of objects to resist changes in their motion, which is explained in relativity as a property of mass and energy.
Doppler effect: The shift in wavelength or frequency of light or sound waves due to the motion of the source and observer relative to each other.
Force: A quantity that changes an object's velocity, which in relativity is treated as a property of space-time curvature rather than a direct cause-and-effect relationship.
Speed of light: The maximum speed at which any object can move, which is a constant in relativity and is the same for all observers regardless of their relative motion.
Particle physics: The study of subatomic particles and their interactions, which has revealed many phenomena that are explained by relativity, such as particle-antiparticle annihilation and the Higgs mechanism.
Quantum mechanics: The branch of physics that describes the behavior of matter and energy at the smallest scales, which is important in the study of black holes and the early universe.
Einstein's field equations: The mathematical equations that describe the curvature of space-time due to the presence of matter and energy, which are the core of general relativity.
Dark matter and dark energy: The mysterious substances that are thought to make up the majority of the mass-energy content of the universe but cannot be directly observed, and which require a modified theory of relativity to account for their effects.
Cosmology: The study of the structure, origins, and evolution of the universe as a whole, which requires a combination of relativity, quantum mechanics, and observations from cosmology missions and telescopes to fully understand.
- "The theory of relativity usually encompasses two interrelated physics theories by Albert Einstein: special relativity and general relativity."
- "Special relativity was proposed and published in 1905 and general relativity in 1915, respectively."
- "Special relativity applies to all physical phenomena in the absence of gravity."
- "General relativity explains the law of gravitation and its relation to the forces of nature."
- "General relativity applies to the cosmological and astrophysical realm, including astronomy."
- "It superseded a 200-year-old theory of mechanics created primarily by Isaac Newton."
- "It introduced concepts including 4-dimensional spacetime as a unified entity of space and time, relativity of simultaneity, kinematic and gravitational time dilation, and length contraction."
- "With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves."
- "The theory transformed theoretical physics and astronomy during the 20th century."
- "Relativity improved the science of elementary particles and their fundamental interactions."
- "With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves."
- "It introduced 4-dimensional spacetime as a unified entity of space and time."
- "General relativity explains the law of gravitation and its relation to the forces of nature."
- "It introduced concepts including... kinematic and gravitational time dilation."
- "With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves."
- "It introduced concepts including... 4-dimensional spacetime as a unified entity of space and time."
- "With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves."
- "The theory transformed... astronomy during the 20th century."
- "It superseded a 200-year-old theory of mechanics created primarily by Isaac Newton."
- "Relativity improved the science of elementary particles and their fundamental interactions, along with ushering in the nuclear age."