Universe Expansion

Extracted Attributes

Expansion of the universe

The expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion, so it does not mean that the universe expands into anything or that space exists outside it. To any observer in the universe, it appears that all but the nearest galaxies (which are bound to each other by gravity) move away at speeds that are proportional to their distance from the observer, on average. While objects cannot move faster than light, this limitation applies only with respect to local reference frames and does not limit the recession rates of cosmologically distant objects. The expansion of the universe was discovered by separate theoretical and observational work in the 1920s. Since then, the expansion has become a core aspect of the astrophysical field of cosmology. Many major scientific projects have sought to characterize the expansion and understand its effects. Cosmic expansion is a key feature of Big Bang cosmology. Within the theory of general relativity, it is modeled mathematically with the Friedmann–Lemaître–Robertson–Walker (FLRW) metric. The consensus or "standard" model of cosmology, the Lambda-CDM model, hypothesizes different expansion rates during different times, depending on the physical properties of the contents of spacetime. The very earliest expansion, called inflation saw the universe suddenly expand by a factor of at least 1026 in every direction about 10−32 of a second after the Big Bang. Cosmic expansion subsequently decelerated to much slower rates, until around 9.8 billion years after the Big Bang (4 billion years ago) it began to gradually expand more quickly, and is still doing so. Physicists have postulated the existence of dark energy, appearing as a cosmological constant in the simplest gravitational models, as a way to explain this late-time acceleration which is predicted to be dominant in the future. The concept of the expansion of the universe is difficult to explain, leading to several misconceptions about its nature, origin, and effects.

Web Search Results

• Expansion of the universe - Wikipedia

  The expansion of the universe can be understood as resulting from an initial condition in which the contents of the universe are flying apart. The mutual gravitational attraction of the matter and radiation within the universe gradually slows this expansion over time, but their density is too low to prevent continued expansion. In addition, recent observational evidence suggests that dark energy is now accelerating the expansion. [...] Cosmic expansion is a key feature of Big Bang cosmology. Within the theory of general relativity, it is modeled mathematically with the Friedmann–Lemaître–Robertson–Walker (FLRW) metric. The consensus or "standard" model of cosmology, the Lambda-CDM model, hypothesizes different expansion rates during different times, depending on the physical properties of the contents of spacetime. The very earliest expansion, called inflation "Inflation (cosmology)") saw the universe suddenly expand by a [...] The expansion of the universe was discovered by separate theoretical and observational work in the 1920s. Since then, the expansion has become a core aspect of the astrophysical field of cosmology. Many major scientific projects have sought to characterize the expansion and understand its effects.

• We might finally know what came before the Big Bang

  “The Universe’s expansion is still accelerating now in our theory,” says Dr Hoang Nhan from Donostia International Physics Centre, who also took part in the study. “The Universe’s expansion only slows down when the so-called ‘crunching’ phase starts, which may happen in the next 11 billion years, as a rough estimation, followed by a Big Crunch around eight billion years afterwards. “Unfortunately, our model can't give much prediction after the Universe collapses.” [...] Then, in the late 90s, astronomers discovered that rather than slowing down, the expansion of our Universe is in fact accelerating. Something was driving the Universe ever further apart. Uncertain what that something might be, astronomers came up with the concept of dark energy. “About 70 per cent of the content in our Universe today is dark energy,” Tye told BBC Science Focus. [...] These simulations start with the Big Bang, which kicked off the Universe 13.8 billion years ago. According to our current understanding, space itself has been expanding ever since, carrying galaxies ever further away from each other. Initially, cosmologists thought this expansion would slowly decline over time as it ran out of steam, leading to one of two main outcomes.

• Universe's expansion 'is now slowing, not speeding up'

  # Universe's expansion 'is now slowing, not speeding up' Researchers used type Ia supernovae, similar to SN1994d pictured in its host galaxy NGC4526, to help establish that the universe’s expansion may actually have started to slow. Credit NASA/ESA Licence type Attribution (CC BY 4.0) Facebook share LinkedIn WhatsApp The universe's expansion may actually have started to slow rather than accelerating at an ever-increasing rate as previously thought, a new study suggests. [...] For the past three decades, astronomers have widely believed that the universe is expanding at an ever-increasing rate, driven by an unseen phenomenon called dark energy that acts as a kind of anti-gravity. This conclusion, based on distance measurements to faraway galaxies using type Ia supernovae, earned the 2011 Nobel Prize in Physics. [...] After the Big Bang and the rapid expansion of the universe some 13.8 billion years ago, gravity slowed it down. But in 1998, it was established that nine billion years after the universe began, its expansion had started to speed up again, driven by a mysterious force. Astronomers dubbed this dark energy, but despite it making up about 70 per cent of the universe it is still considered to be one of the greatest mysteries in science.

• Dark energy - Wikipedia

  High-precision measurements of the expansion of the universe are required to understand how the expansion rate changes over time and space. In general relativity, the evolution of the expansion rate is estimated from the curvature of the universe and the cosmological equation of state "Equation of state (cosmology)") (the relationship between temperature, pressure, and combined matter, energy, and vacuum energy density for any region of space). Measuring the equation of state for dark energy is [...] universe's expansion to slow over time. Since the discovery of accelerating expansion, several independent lines of evidence have been discovered that support the existence of dark energy.

• Dark matter | CERN

  universe. The rate of expansion and its acceleration can be measured by observations based on the Hubble law. These measurements, together with other scientific data, have confirmed the existence of dark energy and provide an estimate of just how much of this mysterious substance exists.