The weakening of dark energy suggests a dynamic universe with evolving forces

Under a model of quintessence, the strength of dark energy should change over time

The theory suggests that dark energy permeates space and may drive the universe to expand or contract throughout its history. The model's flexibility allows it to fit every possible observed behavior of the universe's expansion, rendering it unfalsifiable and untestable.

If dark energy is weakening, the universe may collapse under its own gravity

Scientists using the Dark Energy Spectroscopic Instrument (DESI) analyzed light from 15 million galaxies and quasars to identify that the universe's accelerated expansion is diminishing. If this continues, the universe might reverse course and collapse in as little as 20 billion years.

The universe's expansion is accelerating due to a mysterious force called dark energy

Astronomers discovered in the late 1990s that galaxies move apart faster over time, contradicting expectations that gravity should slow cosmic expansion. This prompted the revival of the "cosmological constant," a form of repulsive gravity first proposed by Albert Einstein.

Dark energy dominance represents the final era of the universe

As the universe expanded after the Big Bang, matter and energy diluted at different rates, with light once the most dense substance in the cosmos, followed by a period when matter was the most dense component. About five billion years ago, the density of dark energy was higher than that of both light and matter, which will continue to dilute.

An early burst of dark energy may resolve discrepancies in the universe's measured expansion

The Hubble tension refers to mismatches in the calculated rate of expansion of the universe derived from different methods, such as supernova data and the cosmic microwave background. By allowing dark energy to become active at a different time, models of the universe on which some of these methods depend are revised, altering the calculated values.

Universes with stronger dark energy may be more common than ours

Research shows that while universes with slightly weaker dark energy form stars more efficiently, universes with stronger dark energy are statistically more common and can still support star formation. This challenges the anthropic logic that our universe must have ideal conditions for life because we exist to observe them.

As of 2025, the best cosmological model of the universe includes dark energy

The Lambda cold dark matter model uses the Greek letter to denote the presence of a cosmological constant version of dark energy, alongside slow-moving dark matter and ordinary visible matter. It can account for the observed distribution of galaxies, the structure of the cosmic microwave background, the acceleration of the universe, and the abundance of hydrogen.

Dark matter and dark energy make up 95% of the universe

Dark matter holds galaxies and other large-scale structures together through gravity, and dark energy drives the universe's accelerating expansion. While scientists do not know what either is made of, they see how these dark components affect the normal matter in the universe.

Dark matter and dark energy, explained

What is dark energy? What is dark matter? Well, if we knew exactly, we would have a Nobel prize—we know that they exist, though. Scientists have theorized that the former may be a property of three-dimensional space itself, while the latter could be exotic particles that interact with almost nothing. This video from Kurzgesagt explains what we know and what we don't.

Under the Big Rip scenario, dark energy becomes strong enough to tear atoms apart

If the density of dark energy, which produces a repulsive effect through the expansion of space, increases with time, then all structures of matter, including galaxies, stars, planets, and atoms, will be pulled apart once the strength of dark energy surpasses the magnitude of the forces holding those structures together, including the gravitational and electromagnetic forces.

Due to dark energy, the universe is expected to end as a dark, sparse place

While the sun is expected to continue shining for another five billion years, the expansion of the universe will cause nearby stars and galaxies to become ever more distant, until they are too far to observe. Once the last old, red, dim stars cool into darkness after trillions of years, the universe will settle into a state of eternal, dark emptiness.

The 2011 Nobel Prize in physics was awarded for the discovery of dark energy

Through the use of standard candles—objects whose brightness is well-known—astronomers can determine distances by recognizing that the same phenomena will dim in predictable ways with increasing distance. By observing the same type of bright stellar explosion at various locations, Saul Perlmutter, Brian Schmidt, and Adam Riess identified that the universe's expansion was increasing.

Dark matter's invisible pull shapes galaxies and our understanding of the cosmos

Though it makes up about 25% of the universe, dark matter can't be seen directly; its existence is inferred through its gravitational effects, like the unexpectedly fast rotation of galaxies. The concept began in 1933 but gained wide acceptance after Vera Rubin's galaxy rotation studies in the 1970s.

Quantum field theory overestimated the value of dark energy by 120 orders of magnitude

Physicists in the 1960s used their most successful theory to determine whether the accelerated expansion of the universe arises from quantum fluctuations in empty space. However, the mismatch between vacuum energy density and dark energy was so severe that it has been referred to as "the worst theoretical prediction in the history of physics."

About 85% of the matter in the universe is dark matter—an invisible substance that only interacts with its surroundings through gravity.

Dark energy causes 97% of the galaxies to move faster than light

Although special relativity prevents objects from moving faster than the speed of light, the expansion of the universe, which increases with distance between objects, produces observed superluminal motion. This does not violate the theory because galaxies are moving with the expanding space, rather than through it.

The mystery of the expanding universe

One of the most surprising discoveries about our universe over the past century is that it's expanding. Even more surprising is that it’s speeding up, and scientists aren’t entirely sure why. The rate should be roughly dependent on the total energy contained in the universe, but calculations keep coming up short. Explore the so-called “Hubble Tension,” along with potential candidates to solve the riddle.

DESI is mapping the universe's expansion over the last 11 billion years

The Dark Energy Spectroscopic Instrument is conducting a five-year redshift survey of over one-third of the sky, measuring the receding motions and locations of about 35 million galaxies and millions of stars using light captured by 5,000 optical fibers.

Dark matter's limited force interactions make its detection difficult

Despite making up the vast majority of matter in the universe, dark matter can only be directed indirectly via its influence on other objects through gravity, the weakest of the fundamental forces. This means direct detection of dark matter may only be possible with future, more sensitive instruments.

View a simulation of the dark matter filaments that make up the cosmic web

The distribution of matter in the universe is not uniform, with interconnected threads of galaxy clusters surrounded by voids of empty space. Simulations of the universe show this is only possible within 13.8 billion years—the universe's age—if a foundational network of seeds—dark matter halos—were present to gravitationally attract visible matter.

Oscillating matter in the early universe left behind patterns detailing cosmic expansion

As gravity tried to bring matter closer together in the early universe, its high temperature produced an outward pressure that caused it to expand. These competing forces caused matter to vibrate and produce the equivalent of sound waves, which spread outward as the universe expanded and cooled, serving as relics of dark energy's history.

Dark matter detected in the cosmic web

Researchers from Yonsei University detected dark matter on the cosmic web, a network of filaments that feed gas into galaxies. The detection was made possible by using the general theory of relativity to analyze gravitational microlensing around the Coma Cluster. This article explains the phenomenon and how the detection supports the presence of dark matter throughout the cosmic web.

View the composition of the universe, dominated by dark energy and dark matter

About 95% of the observable universe is made of substances whose composition is unknown, but most of what remains (4%) is in the form of clouds of hydrogen and helium, followed by gases and plasma within stars (0.5%) and neutrinos created in nuclear reactions (0.3%).

Astronomical models suggest dark matter must be 'cold,' or slow-moving

Theories for what constitutes dark matter have ranged from slow, planet-sized objects to light subatomic particles that travel at high speeds. However, fast-moving candidates would quickly spread across the universe, preventing the gradual gathering of visible matter into the galaxies and galaxy clusters seen today through gravity.

View a timeline of the universe's major events, according to the Big Bang model.

Modified Newtonian dynamics revises gravity to eliminate the need for dark matter

Rather than imagining that an undiscovered particle is responsible for discrepancies in the orbits of stars and galaxies, MOND suggests that the mathematics underlying Newton's laws of gravity and force change beyond a certain scale. However, the suggested revisions struggle to explain relativistic effects involving gravity, including gravitational lensing and gravitational waves.

The European Space Agency's Euclid telescope maps dark matter

As light rays travel near massive objects in space, their paths can be distorted on their way to Earth, causing objects to appear displaced, magnified, shrunken, or sheared. By simulating these effects for various mass distributions, astronomers can match the distortion to a simulated mass and compare it with the observed visible matter to infer the presence of dark matter.

The observable universe has a mass of 100 sexdecillion kilograms

The amount of visible matter in the universe is most accurately determined by measuring the cosmic microwave background. Quantities of dark matter and dark energy are calculated through the observed bending of light around galaxies and the expansion of the universe, respectively.

Vera Rubin's research into galaxy rotation curves led to the discovery of dark matter

She discovered that stars on the outer edges of galaxies were orbiting much faster than expected based on visible matter alone, implying the presence of unseen mass exerting gravitational force. Without dark matter, the outer stars in galaxies would fly off into space instead of staying in orbit.

Dark stars are hypothetical stars that would have existed in the early universe

Primarily composed of visible matter, this celestial object would also contain a significant amount of dark matter that would annihilate with itself, converting its mass into energy. This energy would prevent the star from collapsing under its own gravity and from triggering nuclear fusion until its dark matter fuel was exhausted.

New model replaces the Milky Way's central black hole with dark matter

A study published in Monthly Notices of the Royal Astronomical Society states that a dense core of fermionic dark matter, rather than a supermassive black hole, could explain both the rapid orbits of stars near the Milky Way's center and the galaxy's large-scale rotation detected in Gaia mission data.

The structure of the Bullet Cluster—a collision between two clusters of galaxies—cannot be explained without dark matter, and serves as evidence for the existence of the invisible substance.

One study suggests that dark matter may have originated from a dark Big Bang

A student-faculty team at Colgate University modeled the event as occurring months after the conventional Big Bang and determined the potential gravitational wave signal that would have been left behind. Future gravitational wave detectors are expected to be sensitive enough to observe this signal, if it exists.

Explore an interactive map of the unified theories of everything

This interactive concisely describes many highly complex theories ranging from quantum gravity and black holes to dark matter and energy. Supplementary resources, key questions, and possible solutions accompany each description. As of 2026, no developed theory provides an accepted explanation of all observed phenomena in the universe at all scales.

The underlying fabric of the universe—spacetime—changes shape in the presence of mass and energy, which affects measurements of space and time.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

There are statistically significant discrepancies in measured universal expansion

Using data from the cosmic microwave background, which allows astronomers to model the universe's conditions since its earliest moments, yields a rate of expansion—the Hubble constant—lower than values obtained from multiple techniques measured locally at more recent timescales. Reconciling the discrepancy, known as the Hubble tension, will require a third independent measurement method between the two scales

The Standard Model reveals an underlying organization to the universe

Using the framework of quantum field theory, it structures all known particles into 12 matter particles, alongside five particles that carry three of the four fundamental forces. Although remarkably precise and predictive, it cannot yet explain gravity, dark matter, or dark energy.

Alternative models to the Big Bang lack as much scientific evidence

The cosmic microwave background radiation and the observed expansion of the universe suggest that the cosmos began from a tiny, dense state, whose resulting properties we see throughout space. While physics allows for cyclical expansions and crunches, ongoing inflationary aeons, and localized inflation to create bubble universes, evidence for these alternatives has not yet been found.

The universe might have emerged from a quantum fluctuation—not absolute nothing

Traditional physics breaks down at the moment of the Big Bang, but quantum theory suggests that “empty” space is never truly empty. In 1973, physicist Edward Tryon proposed that our universe began from a quantum energy blip in the quantum vacuum.

The cosmic dark ages: before stars existed

The theories behind the Big Bang suggest the process of the universe beginning to the creation of stable, neutral atoms took just half a million years. But the transition from such atoms to star formation took surprisingly much longer, upwards of 100 million years. Why? This deep dive explores the science behind the unique physical composition of the so-called cosmic dark ages.

Simulate how the distribution of dark matter affects stellar orbits within galaxies, which allows astronomers to infer the presence of the invisible substance from the motion of stars.

The universe may have been reborn from a state of emptiness

Some physicists propose the universe might be the latest in an eternal cycle of universes, each emerging from the empty remains of the one before. This model is inspired partly by Norse and Egyptian myth, suggesting the universe is a cosmic ouroboros—a self-consuming serpent representing an eternal return.

Axions, a hypothetical subatomic particle, are a leading dark matter candidate

Among the possibilities for what makes up dark matter, some physicists champion axions, which could clump into galaxy-scale quantum states. These states would act as massive, unified superparticles that could explain the observational evidence for the universe's missing matter.

Although a Nobel Prize was awarded for the discovery of dark energy, Vera Rubin never received one for her discovery of dark matter, which makes up about 25% of the universe.

Fritz Zwicky predicted the existence of dark matter and neutron stars

The former resulted from analyzing the motion of galaxies in the Coma Cluster, a subset of the approximately 30,000 galaxies he cataloged during his life. When hypothesizing an origin for observed high-energy particles called cosmic rays, Zwicky and colleague Walter Baade thought they could come from exploding stars, or supernovae—a term he coined—which would leave behind a collapsed star made entirely of neutrons.

The Big Bang theory explains the universe’s expansion, not its origin

While we have strong evidence that the universe expanded from an extremely hot, dense state, we can only trace events back to a tiny fraction of a second after that point. Earlier stages, like inflation and potential force unification, remain unproven and unobservable with current tools.

The universe expands by stretching space itself, not into anything beyond it

Thanks to Einstein’s relativity and Hubble’s observations, scientists understand that space stretches, like rising bread dough between raisins, with no "outside" to expand into. Some theories suggest our universe might be just one "bubble" in a vast multiverse, possibly floating on a higher-dimensional surface called a brane.

Some theorists have suggested that dark matter consists of supersymmetric particles—massive, hypothetical versions of known particles, such as the sneutrino, which is the supersymmetric partner of the neutrino.

Edwin Hubble showed that the universe is full of galaxies and is expanding

In the 1920s, Hubble showed that the Andromeda "nebula" was another galaxy. He later discovered that galaxies move away from us at speeds proportional to their distance—a breakthrough now known as the Hubble-Lemaître law, foundational to Big Bang cosmology.