Big Bang Theory

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Universe Noun

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[yoo-ni-vurs]

Back

Universe

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All existing matter and space considered as a whole, which has been expanding since its creation in the Big Bang.

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Example: This diagram shows the universe started from a single hot, dense point (the Big Bang) and has been expanding over time, causing galaxies to move apart.

Front

Big Bang Theory Noun

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[big bang thee-uh-ree]

Back

Big Bang Theory

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The leading scientific theory that the universe began from a single, hot, dense point and has been expanding ever since.

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Example: This diagram shows the universe starting from a hot, dense point (The Big Bang) and expanding and cooling over billions of years to form stars and galaxies.

Front

Singularity Noun

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[sing-gyoo-lar-i-tee]

Back

Singularity

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The initial state of the universe where all matter and energy was concentrated into a single, infinitely dense point.

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Example: This image shows the universe beginning from a single, hot, dense point (the singularity) on the left and expanding outward over time.

Front

Inflation Noun

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[in-fley-shuhn]

Back

Inflation

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A period of extremely rapid expansion of the universe that occurred a fraction of a second after the Big Bang.

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Example: This diagram shows how the universe, represented by the grid, expanded extremely rapidly in a tiny fraction of a second after the Big Bang.

Front

Hubble's Law Noun

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[huh-buhlz law]

Back

Hubble's Law

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The observation that galaxies are moving away from us at speeds proportional to their distance, supporting the expanding universe theory.

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Example: This image shows the formula for Hubble's Law, which calculates how fast a galaxy is moving away from us based on its distance.

Front

Redshift Noun

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[red-shift]

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Redshift

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The stretching of light to longer wavelengths as a celestial object moves away from an observer, indicating cosmic expansion.

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Example: This diagram shows that as an object moves away, its light is stretched, causing the dark lines in its spectrum to shift toward the red end.

Front

Doppler Effect Noun

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[dop-ler uh-fekt]

Back

Doppler Effect

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The change in the frequency of a wave, such as light or sound, in relation to an observer's relative motion.

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Example: As a light source moves, an observer sees its light waves change. If it moves away, the waves stretch (redshift); if it moves closer, they compress (blueshift).

Front

Absorption Lines Noun

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[ab-sawrp-shuhn laynz]

Back

Absorption Lines

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Dark lines in a star's light spectrum that reveal its chemical composition and are used to measure its movement.

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Example: When light passes through a gas like neon, specific colors (wavelengths) are absorbed, creating dark 'absorption lines' in the light's spectrum.

Front

Cosmic Microwave Background Noun

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[koz-mik mahy-kroh-weyv bak-ground]

Back

Cosmic Microwave Background

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The faint, uniform thermal radiation, or 'afterglow,' left over from the Big Bang that permeates all of space.

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Example: This map shows the faint heat left over from the Big Bang, called the Cosmic Microwave Background. The different colors represent tiny temperature variations.

Front

Dark Energy Noun

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[dahrk en-er-jee]

Back

Dark Energy

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A mysterious, hypothetical form of energy believed to be the cause of the universe's accelerating rate of expansion.

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Example: This diagram uses a balloon to show how space expands, stretching light from distant galaxies and causing redshift, which is evidence for dark energy.