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Dark energy is the proposed component responsible for the accelerated expansion of the universe.
Dark energy is a poorly understood component of the universe proposed to explain the observed acceleration of cosmic expansion. In the standard Lambda-CDM model, it accounts for approximately 68% of the present-day universe's total mass-energy, while dark matter contributes about 27% and ordinary matter about 5%. Although its density is extremely low, dark energy is thought to be nearly uniform throughout space, so its total influence becomes dominant on cosmic scales. Its strong negative pressure can cause the expansion of an already expanding universe to accelerate and also slows the growth of cosmic structures. The strongest initial evidence for dark energy came from observations of distant Type Ia supernovae in 1998, which showed that the universe has expanded more rapidly in its later history than expected from matter's gravitational attraction alone. Independent evidence comes from cosmic microwave background measurements, baryon acoustic oscillations, large-scale galaxy surveys, gravitational lensing, and other probes of expansion history. The leading explanation is a cosmological constant, representing constant vacuum energy, although alternatives include dynamic scalar fields such as quintessence, modified gravity, interacting dark energy, and other proposals. The nature of dark energy remains unresolved, and recent observations have investigated whether its density changes over time.
Dark energy is the proposed component responsible for the accelerated expansion of the universe.
In the Lambda-CDM model, dark energy makes up about 68% of the universe's present-day mass-energy.
Its extremely low but nearly uniform density allows it to dominate over matter on the largest scales.
Type Ia supernova observations provided the first major evidence for accelerated expansion in 1998.
Independent support comes from the cosmic microwave background, baryon acoustic oscillations, large-scale structure, gravitational lensing, and expansion-rate measurements.
The leading model treats dark energy as a cosmological constant, but dynamic fields and modified-gravity explanations remain under investigation.
Dark energy's negative pressure both accelerates cosmic expansion and suppresses the formation of large-scale structures.
A hypothetical form of energy that permeates space and drives the accelerated expansion of the universe.
A constant energy density associated with empty space and represented by the symbol Lambda in general relativity.
The standard cosmological model combining a cosmological constant, cold dark matter, ordinary matter, radiation, and other minor components.
A tension-like property that, according to general relativity, can produce accelerated expansion when sufficiently strong.
A highly luminous stellar explosion with relatively consistent intrinsic brightness, allowing it to serve as a standard candle for measuring cosmic distances.
Relic radiation from the early universe whose temperature patterns provide information about cosmic geometry, composition, and expansion.
Large-scale patterns in the distribution of matter that act as standard rulers for measuring the expansion history of the universe.
A proposed dynamic scalar field whose energy density can vary across space and time and potentially explain dark energy.
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