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Edwin Powell Hubble (November 20, 1889 – September 28, 1953) [1] was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology.
The law states that the greater the distance between any two galaxies, the greater their relative speed of separation. In 1929, Edwin Hubble discovered that most of the universe was expanding and moving away from everything else. If everything is moving away from everything else, then it should be thought that everything was once closer together.
The Einstein equations in their simplest form model either an expanding or contracting universe, so Einstein introduced the constant to counter expansion or contraction and lead to a static and flat universe. [31] After Hubble's discovery that the universe was, in fact, expanding, Einstein called his faulty assumption that the universe is ...
The earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background and the relative abundances of light elements produced by Big Bang nucleosynthesis (BBN).
Einstein's static universe is closed (i.e. has hyperspherical topology and positive spatial curvature), and contains uniform dust and a positive cosmological constant with value precisely = /, where is Newtonian gravitational constant, is the energy density of the matter in the universe and is the speed of light.
This episode explores the theories of the big crunch, the big rip and the big freeze, that are postulated by physicists as possible fates for the universe. [3] Al-Khalili indicates that the difficulty in understanding this is our limited ability to comprehend something of such immensity both physically and philosophically. [4]
Edwin Hubble publishes his discovery that the speed at which galaxies recede positively correlates with their distance, which becomes known as Hubble's law, the basis for understanding that the universe is expanding. George Gamow proposes hydrogen fusion as the energy source for stars.
The history of the universe after inflation but before a time of about 1 second is largely unknown. [26] 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. [27]