Relativity

Cosma / Communication / Knowledge / Realm / Physical / Law / Relativity

In our time, there has been unloosed a cataclysm which has swept away space, time, and matter hitherto regarded as the firmest pillars of natural science, but only to make place for a view of things of wider scope, and entailing a deeper vision. — Hermann Weyl, Space, Time, Matter

—————————

Introduction¹

Hard Stuff Made Easy: Physics (LondonCityGirl, YouTube Playlist)

Dictionary

relativity : a theory which is based on the two postulates (1) that the speed of light in a vacuum is constant and independent of the source or observer and (2) that the mathematical forms of the laws of physics are invariant in all inertial systems and which leads to the assertion of the equivalence of mass and energy and of change in mass, dimension, and time with increased velocity — called also special relativity, special theory of relativity — Merriam-Webster See also OneLook

Thesaurus

Roget’s II (Thesaurus.com), Merriam-Webster Thesaurus, Visuwords

Encyclopedia

Relativity, generally refers to the theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity.

Special relativity applies to elementary particles and their interactions, describing all their physical phenomena except gravity.

General relativity explains the law of gravitation and its relation to other forces of nature. It applies to the cosmological and astrophysical realm, including astronomy.

The theory transformed theoretical physics and astronomy during the 20th century, superseding a 200-year-old theory of mechanics created primarily by Isaac Newton. It introduced concepts including spacetime as a unified entity of space and time, relativity of simultaneity, kinematic and gravitational time dilation, and length contraction. — Wikipedia

Relativity (Encyclopædia Britannica)

Search

Relativity (WolframAlpha)

———————–

Inspiration

Talks about Relativity (TED: Ideas Worth Spreading)
Articles about Relativity (Big Think)

———————

Foundation

Theory

Relativity: The Special and General Theory (Albert Einstein, Bartleby.com)
Relativity: The Special and General Theory (Albert Einstein, WorldCat)
Relativity: The Special and the General Theory (Wikipedia)

What is Relativity? Einstein’s Mind-Bending Theory Explained (Dan Falk, Mach, NBC News)
The Theory of Relativity (Ask an Astronomer, Cornell University)

Relativity (Fermilab, YouTube Playlist)

Relativity (Eric Weisstein’s World of Physics, Wolfram Research)

Special relativity is a scientific theory regarding the relationship between space and time. In Albert Einstein’s original treatment, the theory is based on two postulates:
1. The laws of physics are invariant (that is, identical) in all inertial frames of reference (that is, frames of reference with no acceleration).
2. The speed of light in vacuum is the same for all observers, regardless of the motion of the light source or observer. — Wikipedia

Special Relativity (Eric Weisstein’s World of Physics, Wolfram Research)

General relativity is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton’s law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations. — Wikipedia

General Relativity (Eric Weisstein’s World of Physics, Wolfram Research)

———————-

Innovation

Science

Subatomic Stories (Fermilab, YouTube Channel)
Relativity News (Fermilab, Official Website)

————————–

Preservation

Library

DDC: 530.11 Relativity (Library Thing)
Subject: Relativity (Library Thing)

Subject: Relativity (Open Library)

LCC: QC 173.5 Relativity (UPenn Online Books)

LCC: QC 173.5 Relativity (Library of Congress)
Subject: Relativity (Library of Congress)

Subject: Relativity (WorldCat)

—————————

Participation

Recent News from Phys.org …

Sharks on the move expose the need for...
on September 17, 2026 at 12:40 am
Understanding the migration pathways of sharks and rays is key to conserving some of the world's most endangered marine species, according to new University of Queensland research.
Global database reveals hidden diversity and...
on September 16, 2026 at 10:50 pm
The ocean's aphotic zone—the dark, high-pressure region below the surface, where sunlight cannot reach—is home to a vast wealth of microbial life. Yet scientists know relatively little about the genetic makeup, growth and function of many of these enigmatic organisms.
Tiny oyster larvae rely on gravity to feed
on September 16, 2026 at 10:20 pm
Eastern oyster larvae are only 100–300 micrometers long, but their dense calcium carbonate shells make them substantially heavier than the surrounding seawater. A new study led by the Woods Hole Oceanographic Institution (WHOI) shows that this excess weight allows gravity to drive the feeding currents the larvae use to bring food to their mouths, a finding that reveals a critical role for gravity in how these tiny animals feed and survive.
New method reveals how virus particles can build...
on September 16, 2026 at 9:50 pm
Oxford University researchers have captured the step-by-step assembly of individual virus-like particles, revealing how simple molecular interactions can reliably build these complex biological structures. The results were published today (September 16) in Nature.
AI can be more comforting than a person—our...
on September 16, 2026 at 9:20 pm
Some of us now use generative artificial intelligence (gen AI) to talk through difficult feelings. We may ask a chatbot to write an email or plan a vacation, but we also tell it that we have had a rotten day or feel anxious about a presentation.

——–
Related

Here are links to pages about closely related subjects.

Knowledge Realm

Physical

“Fundamentals”
Law (Constant) Relativity
Force Gravity, Electromagnetism (Light, Color)
Matter (Microscope) Molecule, Atom (Periodic Table), Particle

“Space”
Universe (Astronomical Instrument)
Galaxy Milky Way, Andromeda
Planetary System Star, Brown Dwarf, Planet, Moon

Our Neighborhood
Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Trans-Neptunian Object
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid

——
Notes

1. The resources on this page are are organized by a classification scheme developed exclusively for Cosma.