Dictionary.com
Thesaurus.com
Jump To:
  • big bang theory
    big bang theory
    noun
    a theory that deduces a cataclysmic birth of the universe big bang from the observed expansion of the universe, cosmic background radiation, abundance of the elements, and the laws of physics.
  • big-bang theory
    big-bang theory
    noun
    a cosmological theory postulating that approximately 12 billion years ago all the matter of the universe, packed into a small superdense mass, was hurled in all directions by a cataclysmic explosion. As the fragments slowed down, the galaxies and stars evolved but the universe is still expanding Compare steady-state theory
  • Big Bang theory
    Big Bang theory
    In astronomy, a theory according to which the universe began billions of years ago in a single event, similar to an explosion. There is evidence for the Big Bang theory in the observed red shift of distant galaxies, which indicates that they are moving away from the Earth, in the existence of cosmic microwave background, and from other data. The Big Bang theory of the origin of the universe is accepted by most astronomers today.

big bang theory

American  

noun

Astronomy.
  1. a theory that deduces a cataclysmic birth of the universe big bang from the observed expansion of the universe, cosmic background radiation, abundance of the elements, and the laws of physics.


big-bang theory British  

noun

  1. a cosmological theory postulating that approximately 12 billion years ago all the matter of the universe, packed into a small superdense mass, was hurled in all directions by a cataclysmic explosion. As the fragments slowed down, the galaxies and stars evolved but the universe is still expanding Compare steady-state theory

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Big Bang theory Cultural  
  1. In astronomy, a theory according to which the universe began billions of years ago in a single event, similar to an explosion. There is evidence for the Big Bang theory in the observed red shift of distant galaxies, which indicates that they are moving away from the Earth, in the existence of cosmic microwave background, and from other data. The Big Bang theory of the origin of the universe is accepted by most astronomers today.


Discover More

Scientists have recently found that the expansion of the universe is actually speeding up. This effect is attributed to the presence of dark energy.

Etymology

Origin of big bang theory

First recorded in 1950–55

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

The big bang theory may have triumphed among most cosmologists, but the persistence of unanswered questions—what came before that explosive moment? could our universe be one of many?—leaves plenty of room for speculation and dissent.

From The Wall Street Journal May 19, 2026

When we first pitched the show to Casey Bloys and the creative team at HBO, we said it would be “glacially slow, with no big bang theory of dramatics.”

From Los Angeles Times Jun. 17, 2025

He says the big bang theory is a “paradigm-smashing concept to end all paradigm-smashing concepts” because it demonstrates that the universe had a beginning.

From Washington Times Oct. 13, 2021

In the future, new observations will surely force cosmologists to tweak the big bang theory.

From Scientific American Apr. 11, 2020

But Gran didn’t tolerate ideas like evolution or the big bang theory, despite the evidence.

From "Sir Fig Newton and the Science of Persistence" by Sonja Thomas

Only in the 20th century did readers recognize its uncanny anticipations of relativity and the big-bang theory.

From Slate Aug. 2, 2021

Other scientific evidence, grounded in empirical observations, supports the big-bang theory.

From Textbooks Jan. 1, 2017

The prevailing idea about how the universe was created is called the big-bang theory.

From Textbooks Jan. 1, 2017

This is the premise of an idea called cosmic inflation — a powerful twist on the big-bang theory — and Monday it received a major boost from an experiment at the South Pole called BICEP2.

From Washington Post Mar. 17, 2014

The big-bang theory was born Yet scientists were aware that the big-bang theory suffered from a significant shortcoming.

From "The Sense of Style" by Steven Pinker

The Big Bang theory remains the prevailing explanation, yet many questions persist -- especially about what might have occurred before that explosive beginning.

From Science Daily Oct. 18, 2025

Raychaudhary recollects that even after Hoyle began to entertain elements of the Big Bang theory, Narlikar remained committed to the steady-state theory.

From BBC May 23, 2025

Arno A. Penzias, whose astronomical probes yielded incontrovertible evidence of a dynamic, evolving universe with a clear point of origin, confirming what became known as the Big Bang theory, died on Monday in San Francisco.

From New York Times Jan. 22, 2024

Later astronomer Edward Hubble made discoveries here that led to the Big Bang theory.

From Los Angeles Times Jan. 5, 2024

The Big Bang theory isn’t about the bang itself but about what happened after the bang.

From "A Short History of Nearly Everything" by Bill Bryson

Vocabulary.com logo
by dictionary.com

Dictionary.com's Learning Companion

Go beyond just looking up words.
Remember them forever with VocabTrainer.

Start training