Artist’s logarithmic scale conception of the observable universe with the Solar System at the center, inner and outer planets, Kuiper belt, Oort cloud, Alpha Centauri, Perseus Arm, Milky Way galaxy, Andromeda galaxy, nearby galaxies, Cosmic Web, Cosmic microwave radiation and Big Bang’s invisible plasma on the edge. By Pablo Carlos Budassi
The radius of the observable universe is often stated to be 46 billion light years. From a certain point of view, this is true, but I think it’s a bit of a misleading statement. Occasionally you also see people say that the observable universe is 13.8 billion light years in radius, which is also true, from a certain point of view.
How can both be true? It has to do with two things: the finite speed of light, and the ongoing expansion of the universe.
Gazing upon the past
The speed of light is about 300,000 kilometers per second…
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