"dark energy is an unknown form of energy that affects the universe on the largest scales."
A hypothetical form of energy that permeates all space and is responsible for the observed accelerated expansion of the Universe.
Cosmology: The study of the origin, evolution, and structure of the universe.
Expansion of the Universe: The observation that the galaxies in the universe are moving apart from each other, indicating that the universe is expanding.
Standard Cosmological Model: The prevailing theory that describes the universe's evolution and structure, including the existence of dark energy.
Dark Matter: A hypothetical form of matter thought to make up approximately 27% of the universe's mass, exerting a gravitational pull on other objects in the universe.
Dark Energy: A mysterious form of energy that is hypothesized to be the cause of the acceleration of the universe's expansion.
Einstein's Equations: Mathematical equations that describe the relationship between matter, energy, and the curvature of spacetime.
Quantum Mechanics: A branch of physics that describes the behavior of matter and energy on a small scale, including particle physics.
General Relativity: Einstein's theory of gravity that describes gravity as the curvature of spacetime caused by mass and energy.
Scalar Field: A field that describes a scalar quantity (a quantity with only magnitude, not direction) that can exist throughout space and time.
Vacuum Energy: The energy density of empty space, also known as the cosmological constant, which could be responsible for the acceleration of the universe's expansion.
Cosmological constant: This is the simplest form of dark energy, which was first introduced by Albert Einstein. It is a type of energy that is present throughout space and remains constant with time.
Quintessence: This is a type of dark energy that is dynamic in nature and its energy density changes with time. Quintessence can have various forms and properties, such as scalar fields, modified gravity, etc.
Phantom energy: This is the type of dark energy that has a negative energy density and a large negative pressure. Phantom energy has the unique property of accelerating the universe at an increasingly faster rate.
Chaplygin gas: This is a type of dark energy that behaves like a gas having negative pressure. Chaplygin gas supports the accelerated expansion of the universe and is considered as an alternative to the cosmological constant.
K-essence: This is another form of dark energy that is based on scalar fields. K-essence theory suggests that dark energy might be sourced by scalar fields that can change over time.
Tachyon field: The tachyon field is a hypothetical field that is expected to exist in string theory. This scalar field has a negative tension, and its energy density increases as the universe expands, which results in the acceleration of the universe's expansion.
Voids: The empty spaces between galaxies or in clusters are known as voids. Some theories suggest that these voids might contain negative energy, which could explain the accelerated expansion of the universe.
"Its primary effect is to drive the accelerating expansion of the universe."
"...dark energy is the dominant component of the universe, contributing 68% of the total energy in the present-day observable universe while dark matter and ordinary matter contribute 26% and 5%, respectively."
"Dark energy's density is very low: 6×10−10 J/m3 (≈7×10−30 g/cm3), much less than the density of ordinary matter or dark matter within galaxies."
"...it dominates the universe's mass–energy content because it is uniform across space."
"The first observational evidence for dark energy's existence came from measurements of supernovae."
"Scientists thought that the gravitational attraction of matter and energy in the universe would cause the universe's expansion to slow down over time."
"Comparing this distance to the redshift (which measures the speed at which the supernova is receding) shows that the universe's expansion is accelerating."
"Since the discovery of accelerating expansion, several independent lines of evidence have been discovered that support the existence of dark energy."
"The main candidates are a cosmological constant (representing a constant energy density filling space homogeneously) and scalar fields (dynamic quantities having energy densities that vary in time and space) such as quintessence or moduli."
"A cosmological constant would remain constant across time and space, while scalar fields can vary."
"Yet other possibilities are interacting dark energy, an observational effect, and cosmological coupling."
"Dark energy's density is very low: 6×10−10 J/m3 (≈7×10−30 g/cm3)."
"dark matter...contribute[s] 26% of the total energy in the present-day observable universe."
"dark energy...affects the universe on the largest scales."
"Dark energy's density is...much less than the density of ordinary matter or dark matter within galaxies."
"Its primary effect is to drive the accelerating expansion of the universe."
"...dark energy is the dominant component of the universe."
"The first observational evidence for dark energy's existence came from measurements of supernovae."
"...the universe's expansion is accelerating... scientists thought that the gravitational attraction of matter and energy in the universe would cause the universe's expansion to slow down over time."