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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

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

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

STAGE 4. STRUCTURE FORMATION. “Structures start forming at ∼ 0.1 Gyr, and then Λ, or dark energy, comes to dominate the Universe, causing its expansion to accelerate, at t ∼ 10 Gyr.” https://lnkd.in/e6ifiQMn View in LinkedIn

YORKSHIRE PUDDING. “When wheat flour began to come into common use for making cakes and puddings, cooks in northern England (Yorkshire) devised a means of making use of the fat that dropped into the dripping pan to cook a batter pudding while the meat roasted. In 1737, a recipe for "a dripping pudding" was published.” https://lnkd.in/ejcUhJym. View in LinkedIn

NEVER FORGET THIS. “Another major drawback of the Standard Model is the fact that it uses two predominant components, dark matter and dark energy, supposed to represent about 95% of the universe energy density, but which have remarkably resisted to experimental identification so far.” https://lnkd.in/daA2SgMy View in LinkedIn

THE KEY. “All of the observational evidence for DM to date comes from its gravitational effects. Therefore it’s not unreasonable to ask whether the observations could instead be explained by modifying the laws of gravity.” (DM = dark matter). https://lnkd.in/e6ifiQMn View in LinkedIn

INDIRECT SENSING. “Large scale structure observations are typically not as powerful or clean a probe of cosmological parameters on their own as the CMB anisotropies are (galaxies are biased tracers of the matter distribution, redshift is a combination of expansion and peculiar velocity etc.).” (CMB = cosmic microwave background). https://lnkd.in/e6ifiQMn View in LinkedIn

FLAT GEOMETRY. “The positions of the acoustic peaks in the CMB angular power spectrum (or equivalently the typical size of the hot/cold spots) are largely sensitive to the geometry of the Universe, and hence the total energy. i.e. the total energy density is very close to the critical density for which the geometry of the universe is flat.” (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