energy: Quick Facts

Written and fact-checked by

The Information Architects of Encyclopaedia Britannica

Last updated

Oct. 22, 2026

News •

Amazon to fund 12 small nuclear reactors at former Indiana coal plant • Oct. 19, 2026, 12:55 PM ET (TechCrunch)

Photos and Videos

Two pie charts compare the universe's matter-energy content: 13.8 billion years ago, dark matter made up 63%, photons 15%, atoms 12%, and neutrinos 10%. Today, dark energy dominates at 69.4%, with dark matter at 26.1% and atoms at 4.5%.

Figure 1: Theoretical frequency distribution of individual requirements (same sex and age group) for (A) a typical essential nutrient and (B) energy. (A) The recommended dietary allowance is set at the upper end of the distribution. For a few nutrients—for example, iron in women—the frequency distribution of requirement is not Gaussian but skewed. (B) The recommended allowance is in the centre of the distribution—the mean or median—so that half of the population need more and half need fewer calories per day than the recommended daily allowance (RDA).

How energy can change from one form to another

The law of conservation of energy explained

How does ATP provide energy to cells?

Know about the complete formula for energy in the theory of relativity

See All Videos and Images →

Topics

combustion geothermal energy wind power solar energy renewable energy steam power free energy electric power conservation of energy potential energy time light electromagnetism gravity relativity chemical reaction space-time Astronomy Celebrating the Birth of a Genius radiation

Dig Deeper: More Articles That Discuss This Topic

Key People

Kelvin, William Thomson, Baron

William Thomson, Baron Kelvin

Scottish engineer, mathematician, and physicist

Hans Bethe.

Hans Bethe

American physicist

Lev Davidovich Landau

Lev Davidovich Landau

Russian physicist

Lyman Spitzer, Jr.

Lyman Spitzer

American astrophysicist

Joule, James Prescott

James Prescott Joule

English physicist

Electric power lines against sunset (grid, power, wires, electrical, electricity)

Energy & Fossil Fuels

Model of a molecule. Atom, Biology, Molecular Structure, Science, Science and Technology. Homepage 2010 arts and entertainment, history and society

Science Quiz

27 True-or-False Questions from Britannica’s Most Difficult Science Quizzes

Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920.

All About Physics Quiz