edges of our universe January 12, 2022 on Chris Howey's blog

Notes from reading The Edges of Our Universe by Toby Ord1.

Age of the universe is 13.8 billion years.

The universe is expanding, that is, the space between everything is increasing. The rate of expansion doubles every 12 billion years.

The largest bounded structures that will stay connected enough to remain seen amongst its local group during expansion for all time has a raddi of 10 million light years. We will eventually be unable to see the closest nearest local group to earth in 150 billion years.

The below limits are specified with the understanding that the expansion will become so fast that light will eventually no longer to be observed from distance.

Observable Universe: 46.4 billion light years. This distance upon which light emmited will reach us as passive observers.

Affectable Universe: 16.5 billion light years. The distance light emmited from earth will reach.

Eventually Observable Universe (future visiblity limit): 62.9 billion light years. Farthest distance light can travel from the initial start (big bang) of the universe.

Ultimately Observable Universe: 79.4 billion light years. If we were able to ride a photon to the edge of our “Affectable Universe” this is the size which our “Eventually Observable Universe” will expand to become.


  1. Ord, Toby (2021). The Edges of Our Universe. arXiv arXiv:2104.01191v2 ↩︎

⇒ This article is also available on gemini.