Classroom Aid - Cosmic Distance and Visible Horizon
Channel: David Butler
Date: 2020-11-05

Text - http://howfarawayisit.com/the-cosmos-2020/

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website - http://howfarawayisit.com

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https://howfarawayisit.fandom.com/wiki/Encyclopedia_Howfarawayica

In this final segment of our “How far away is it” video book, we cover the structure of the visible Universe as we currently know it.
We start with some galaxy and galaxy clusters beyond our local superclusters, including: Abell 2029 with its supermassive galaxy IC 1101; Quasar Markarian; a massive cluster gravitationally lensing a more distant cluster; El Gordo; some distant supernovae remnants; gravitational lensing in giant galaxy clusters like Abell 1689, Abell 68, and more. We then cover dark matter discovery in the Coma cluster and evidence for it in the Bullet cluster. We see a gravitationally lensed supernova; 
Next, we cover slowly expanding space and the impact that has on measuring distances using GN-z11, currently beyond the visible horizon, as an example. We also cover how recent redshift measurements from distant Type 1a Supernovas have provided evidence that the expansion is accelerating. We explain how this leads to the concept of ‘Dark Energy’ by examining the concept of a cosmic scale factor and how it changes over time. With this we introduce ‘cosmological redshift’ as a measure of the expansion. 
We then cover the creation of the Cosmic Background Microwave (CMB) radiation and what that tells us about the formation of galaxy walls around great voids. We then cover some of the recent galaxy surveys that are helping us understand the fabric of the visible Universe. These include the 2dF Galaxy Redshift Survey of 52,000 galaxies out to 3 billion light years, and the Sloan Digital Sky Survey that mapped one million galaxies. We show the 3D supercomputer video that shows the fabric of the Universe is like a web of galaxies with massive voids. We show some of the galaxy surveys that show this web-like structure.
We conclude with a review of the cosmic distance ladder and our last adjustment based on cosmological redshift. And we end with Edwin Hubble’s own words on the limits of our knowledge.


Music: 
@00:00 Mendelssohn – “Violin Concerto in E Minor Op.64 Andante”; 101 Strings; from the album The Most Relaxing Classical Music, 1997
@11:55 Mozart - Piano Concerto No.21 in C 'Elvira Madigan' K.467 - Andante; from the album The Most Relaxing Classical Music, 1997
@21:34 Rachmaninov - Piano Concerto No 2 in C minor; from the album The Most Relaxing Classical Music, 1993
@32:18 Mozart - Clarinet Concerto in A from the album The Most Relaxing Classical Music, 1997