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From this perspective, Hubble's law is a fundamental relation between (i) the recessional velocity associated with the expansion of the universe and (ii) the distance to an object; the connection between redshift and distance is a crutch used to connect Hubble's law with observations.
Even light itself does not have a "velocity" of c in this sense; the total velocity of any object can be expressed as the sum = + where is the recession velocity due to the expansion of the universe (the velocity given by Hubble's law) and is the "peculiar velocity" measured by local observers (with = ˙ () and = ˙ (), the dots indicating a ...
Assuming isotropy alone is sufficient to reduce the possible motions of mass in the universe to radial velocity variations. The Copernican principle, that our observation point in the universe is the equivalent to every other point, combined with isotropy ensures homogeneity. Direct observation of stars has shown their velocities to be ...
Observations show that the expansion of the universe is accelerating, such that the velocity at which a distant galaxy recedes from the observer is continuously increasing with time. [ 1 ] [ 2 ] [ 3 ] The accelerated expansion of the universe was discovered in 1998 by two independent projects, the Supernova Cosmology Project and the High-Z ...
The history of the universe after inflation but before a time of about 1 second is largely unknown. [25] However, the universe is known to have been dominated by ultrarelativistic Standard Model particles, conventionally called radiation, by the time of neutrino decoupling at about 1 second. [26]
The universe continued to decrease in density and fall in temperature, hence the typical energy of each particle was decreasing. ... is the recessional velocity, and ...
Moreover, in general relativity, velocity is a local notion, and there is not even a unique definition for the relative velocity of a cosmologically distant object. [17] Faster-than-light cosmological recession speeds are entirely a coordinate effect. There are many galaxies visible in telescopes with redshift numbers of 1.4 or higher. All of ...
Recessional velocity is the rate at which an extragalactic astronomical object recedes (becomes more distant) from an observer as a result of the expansion of the universe. [1] It can be measured by observing the wavelength shifts of spectral lines emitted by the object, known as the object's cosmological redshift .