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Thus, an accelerating universe took a longer time to expand from 2/3 to 1 times its present size, compared to a non-accelerating universe with constant ˙ and the same present-day value of the Hubble constant. This results in a larger light-travel time, larger distance and fainter supernovae, which corresponds to the actual observations.
The expansion of the universe can be understood as a consequence of an initial impulse (possibly due to inflation), which sent the contents of the universe flying apart. The mutual gravitational attraction of the matter and radiation within the universe gradually slows this expansion over time, but expansion nevertheless continues due to ...
Hubble's law is considered the first observational basis for the expansion of the universe, and is one of the pieces of evidence most often cited in support of the Big Bang model. [8] [17] The motion of astronomical objects due solely to this expansion is known as the Hubble flow. [18]
"Yes, it appears there is something missing in our understanding of the universe," added Riess, a 2011 Nobel laureate in physics for the co-discovery of the universe's accelerating expansion.
The expansion of the universe is parameterized by a dimensionless scale factor = (with time counted from the birth of the universe), defined relative to the present time, so = =; the usual convention in cosmology is that subscript 0 denotes present-day values, so denotes the age of the universe.
The findings announced on Tuesday are part of a years-long study of the history of the cosmos focusing upon dark energy, an invisible and enigmatic force that is accelerating the ongoing expansion ...
The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. [1] The notion of an expanding universe was first scientifically originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations.
In the Friedmann–Lemaître–Robertson–Walker metric, it can be shown that a strong constant negative pressure (i.e., tension) in all the universe causes an acceleration in the expansion if the universe is already expanding, or a deceleration in contraction if the universe is already contracting. This accelerating expansion effect is ...