Month: September 2022

STAGE 5. TODAY. The age of the Universe, t0, (i.e. how long after the Big Bang ‘today’ is) is calculated for a ΛCDM universe https://lnkd.in/e6ifiQMn View in LinkedIn

OVERVIEW. “In this section we’ll look at the observational evidence for cold, non-baryonic dark matter, starting with galaxies, before moving out in scale to galaxy clusters, the cosmic microwave background anisotropies and large scale structure.” https://lnkd.in/e6ifiQMn View in LinkedIn

KEY EVIDENCE. “Some of the most straightforward and long standing evidence for DM comes from the rotation curves of spiral galaxies. In a spiral galaxy stars and gas clouds move in circular orbits due to gravity, and their speeds can be measured using the Doppler shift of the Hydrogen 21cm line.” (DM = dark matter). https://lnkd.in/e6ifiQMn View in LinkedIn

MORE EVIDENCE. “Additional evidence for dark matter comes from the stability of disk galaxies. Self-gravitating disks form bars (‘bar instability’) unless they have large velocity dispersion. Embedding disks in a massive, extended, roughly spherical halo is a solution to this problem.” https://lnkd.in/e6ifiQMn View in LinkedIn

EXEMPLAR. “Galaxy clusters contain 100s or 1000s of galaxies as well as hot X-ray emitting gas. They are the largest gravitationally bound objects in the Universe, therefore we expect that the material they contain is representative of the Universe as a whole.” https://lnkd.in/e6ifiQMn View in LinkedIn

EMERGENT WORLD. “The world is made of qubits ... What we perceive to some degree of approximation as a world of single-valued variables is actually part of a larger reality in which the full answer to a yes-no question is not just yes or no, nor even both yes and no in parallel, but a quantum-observable – something that can be represented as a large Hermitian matrix”. (Professor David Deutsch, Oxford University, page 15). https://lnkd.in/eAxeE3iE View in LinkedIn

Refracted entry portal of the old town Girona, Spain. View in LinkedIn

PRESENT BY ABSENCE. “The detailed scale dependence of the temperature anisotropies in the CMB allow the total, matter and baryon density parameters to be measured precisely. However the measured typical amplitude of the fluctuations, ∆T/T ≈ 10(-5), alone provides evidence for non-baryonic DM.” (DM = dark matter; CMB = cosmic microwave background). https://lnkd.in/e6ifiQMn View in LinkedIn

VISIBLE MATTER. “Baryons, however, are tightly coupled to photons until decoupling, at tdec ≈ 0.4 Myr and therefore perturbations in baryons can only grow after decoupling. Consequently in a universe without non-baryonic DM the initial density perturbations have to be larger, and produce larger temperature fluctuations in the CMB, ∆T/T ∼ 10(-4), for observed structures to form.” (DM = dark matter; CMB = cosmic microwave background). https://lnkd.in/e6ifiQMn View in LinkedIn

INEQUALITIES. “In other words, non-baryonic DM is required for perturbations to grow sufficiently from the initial amplitude, as measured from the CMB anisotropies.”(DM = dark matter; CMB = cosmic microwave background). https://lnkd.in/e6ifiQMn View in LinkedIn