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Using the values known in 2018 and Planck units for Ω Λ = 0.6889 ± 0.0056 and the Hubble constant H 0 = 67.66 ± 0.42 (km/s)/Mpc = (2.192 7664 ± 0.0136) × 10 −18 s −1, Λ has the value of = = = where is the Planck length. A positive vacuum energy density resulting from a cosmological constant implies a negative pressure, and vice versa.
The values of these six parameters are mostly not predicted by theory (though, ideally, they may be related by a future "Theory of Everything"), except that most versions of cosmic inflation predict the scalar spectral index should be slightly smaller than 1, consistent with the estimated value 0.96. The parameter values, and uncertainties, are ...
The Hubble constant is most frequently quoted in (km/s)/Mpc, thus giving the speed in km/s of a galaxy 1 megaparsec (3.09 × 10 19 km) away, and its value is about 70 (km/s)/Mpc. However, crossing out units reveals that H 0 is a unit of frequency (SI unit: s −1) and the reciprocal of H 0 is known as the Hubble time. The Hubble constant can ...
Cosmic expansion is a key feature of Big Bang cosmology. It can be modeled mathematically with the Friedmann–Lemaître–Robertson–Walker metric (FLRW), where it corresponds to an increase in the scale of the spatial part of the universe's spacetime metric tensor (which governs the size and geometry of spacetime). Within this framework, the ...
These problems are solved by cosmic inflation which has . Measuring the equation of state of dark energy is one of the largest efforts of observational cosmology . By accurately measuring w {\displaystyle w} , it is hoped that the cosmological constant could be distinguished from quintessence which has w ≠ − 1 {\displaystyle w eq -1} .
Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own galaxy, [1] and from distant galaxies. [2]
In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light ). The opposite change, a decrease in wavelength and increase in frequency and energy, is known as a blueshift, or negative redshift. The terms derive from the colours red and blue ...
Physical cosmology. Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate. [1]