Some historic remarks on astrometry by Terence Tao

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TL;DR Summary

Terence Tao linked to a collection of slices about astrometry

I regularly receive a newsletter from Terence Tao about his blog. He lately announced a book he is writing with Tanya Klowden on astrophysics: Climbing the cosmic distance ladder. I cannot really assess the book, but I got the impression that it is mainly a historic essay written like a novel, rather than a primarily technical textbook. He linked a sample chapter in case you are interested.

However, my reason for this promotion is his link to a collection of slides which I think provides interesting historical facts.

 

[Tom.G]

Interesting. I do have a question though. The last link in the above post leads to a slide show (interesting and a fast read)
(https://terrytao.files.wordpress.com/2020/10/cosmic-distance-ladder.pdf)

Slide 187 shows:
Age of the Universe = 13.7x10⁹ years
Diameter of Universe = 78x10⁹ light years

How do we get information about the size of something that is three times further away than information travel? Something to do with Expansion perhaps?

 

[DrClaude]

Interesting. I do have a question though. The last link in the above post leads to a slide show (interesting and a fast read)
(https://terrytao.files.wordpress.com/2020/10/cosmic-distance-ladder.pdf)

Slide 187 shows:
Age of the Universe = 13.7x10⁹ years
Diameter of Universe = 78x10⁹ light years

How do we get information about the size of something that is three times further away than information travel? Something to do with Expansion perhaps?

Yes, is has to do with the expansion of the universe, but that second number is disputed, see https://en.wikipedia.org/wiki/Observable_universe#Misconceptions_about_its_size