The Physics
Factbook
An encyclopedia of scientific essays

# Diameter of the Known Universe

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Blair, William. Size Scales in Astronomy.November 2001. "That this distance is deemed almost inconsequential compared with the most distant objects known in the universe, which are roughly 10 billion light years away." 20 billion
light years
The Scale of Things. The Internet Stellar Database. "And the distance to the edge of the known universe is around 100,000 million million million kilometers." 20 billion
light years
God the Creator. goodnewsdaily.org. Number692. 30 April 30 2002. "Latest estimates by astronomers tell us that the universe is 30 or 40 billion light years in diameter. In layman's terms, that means that it would take light (which travels at the speed of light J) 40 000 000 000 years to cross from one side of the universe to the other!" 30–40 billion
light years
The Size and Shape of the Universe. infoplease.com. "At present the universe is believed to be at least 10 billion light-years in diameter." 10 billion
light years
Butterworth, Paul. Measuring the Size of the Universe. Imagine the Universe! NASA. "The simple answer is that the observable Universe is about 10 billion light years in radius. That number is obtained by multiplying how old we think the Universe is by the speed of light." 20 billion
light years

The universe that we know is made up of the solar system (sun, moon, and all of the planets), the stars, the galaxies, and the cosmos. Basically it's everything that is around us. But how big is it?

The large magnitude of the universe is unimaginable to us humans. To see how big the universe is, take this into perspective: the diameter of the entire solar system is about 8,000 million kilometers. The universe itself is about 1026 meters. The nearest galaxy that is similar to that of earth is Andromeda. That alone is 1021 meters away. The center of out galaxy is 26,000 light years away from where we are. One light year is equal to almost 10 billion kilometers. That means in an airplane, it would take billions of years to reach it.

Modern science says that the known universe extends about 10 billion light years in all directions, and consists of 200 billion galaxies. This means it can take light approximately 20 billion years to cross from one side of the universe to the other. These numbers, however, are only of the known universe. No one knows exactly how big the universe actually is, or how far it extends.

Carmen Bissessar -- 2002

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Macmillan Encyclopedia of Physics. New York: Macmillan, 1996. "The observable universe extends out to approximatly 10 billion light years away." 20 billion
light years
Milton, Simon. The Oxford Book of Astronomy. New York: Oxford, 1998. "Diameter of Universe 10^26 (miles)" 16 billion
light years
Asimov, Isaac. The Collapsing Universe. New York: Walker, 1977. "The nearest qusars are 3 billion light years from earth, while the most remote ones may be 6 times as far." 36 billion
light years
The Really Big Numbers Page. (from Chalk Up Another One by Sidney Harris). "Diameter of the Universe (1026)"
[Author did not include a unit.]
?
Size Scales in Astronomy. William P. Blair, Johns Hopkins University. Version 1.0, January 1996. "On this scale, the 'edge' of the Universe, defined as the most distance known quasars some 10 billion light years." 20 billion
light years

Christine McGrath -- 1999

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Lange, Benjamin.Cosmology: The Big Bang, CMB, Dark Matter, Inflation, Dark Energy, The Age of the Universe. [pdf] "For example, the distance now to the surface of last scattering (the surface where decoupling between photons and atoms occurs at age 376,000 years) is not 13.7 billion light-years, but rather it is about 46 billion light-years. This is calculated as follows…" 92 billion light years (observable)
Britt, Robert Roy. Universe Measured: We're 156 Billion Light-years Wide! space.com 24 May 2004. "All the pieces add up to 78 billion-light-years. The light has not traveled that far, but 'the starting point of a photon reaching us today after travelling for 13.7 billion years is now 78 billion light-years away,' Cornish said. That would be the radius of the universe, and twice that -- 156 billion light-years -- is the diameter. That's based on a view going 90 percent of the way back in time, so it might be slightly larger." > 156 billion light years (whole thing)
Neil J. Cornish, David N. Spergel, Glenn D. Starkman, Eiichiro Komatsu. Constraining the Topology of the Universe. arXiv, astrophysics, 0310233 (8 October 2003). "For a wide class of models, the non-detection rules out the possibility that we live in a universe with topology scale smaller than 24 Gpc [gigaparsecs]." > 156 billion light years (whole thing)

Editor's Supplement -- 2004, 2010