20:26 Was Hubble the one to discover the redshift of galaxies?This was an error on my part; Hubble was using earlier work of Vesto Slipher on these redshifts, and combining it with his own measurements of distances using Leavitt’s law to arrive at the law that now bears his name; ...
What is refracted ray? What was the approximate number density of CMB photons when the CMB had a higher temperature of 307 K? (Hint: You can assume that photons in a thermal distribution have a mean energy of 3kT). Write the answer in m^-3. ...
The first galaxies date to when the universe was a bit under an billion years old, with a redshift of a bit under ten, meaning that light coming from them is ten times as stretched out and the galaxies appear to be experiencing time at a tenth the usual rate. The oldest light we c...
The dominating form of energy in the cosmos dark energy is driving the accelerating expansion of the universe, but its nature remains a mystery.
The discovery of the red shift of light from distant sources and thus the expansion of the universe by famous astronomer Edwin Hubble in the 1930s forced Albert Einstein to drop a factor from his equations called the cosmological constant, represented by the greek letter lambda (λ). When Ei...
Cosmological data still allow for the presence of a non-negligible amount of dark energy at very high redshifts, namely during the matter- and radiation-dominated epochs. This is the so-called early dark energy (EDE), which could help to mitigate the tensions that affect the standard model ...
This is the ratio of the pressure to the energy of the material. For the cosmological constant, w is exactly ǁ1; any measured difference from this value would signal the need for another explanation. Data from the CMB, in combi- nation with those from supernovae, currently limit w to...
[For other articles of mine on this subject, focusing on particular topics, see here, here, here or here] The term ``virtual particle'' is an endlessly confusing and confused subject for the layperson, and even for the non-expert scientist. I have read m
- 《Monthly Notices of the Royal Astronomical Society》 被引量: 18发表: 2012年 Redshift drift as a test for discriminating between different cosmological models Models of inhomogeneous universes constructed with exact solutions of Einstein's General Relativity have been proposed in the literature with...
The Accelerating Universe and Dark Energy: Evidence from Type Ia Supernovae I discuss the use of Type Ia supernovae (SNeIa) for cosmological distance determinations. Low-redshift SNeIa ( \\\(z \\\lesssim 0.1\\\) ) demonstrate that the Hubble expansion is linear, that H 0 = 72 ± 8 ...