Mr. Write's Page

Back when I developed the list below, the visible universe was considered to be 30 billion light years in diameter. I was obliged to update that entry, and a few others, to catch up with the science of 2009. No telling what the numbers will be in another 20 years.

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September 22, 1988.

Diameters of Objects in the Universe

Electron  —  1/1000th of a proton
Proton  —  2 X 10^-14 inches*
Hydrogen atom  —  3.15 X 10^-9 inches
Interstellar dust grain  —  4 X 10^-6 inches
Bacterium  —  4 X 10^-5 inches
Blue light wave  —  1.9 X 10^-5 inches
Fragment in Saturn’s rings  —  3 feet
Nucleus of Comet Halley  —  8 miles
Stellar-mass black hole  —  19 miles
Largest asteroid  —  456 miles
The Earth  —  7,926 miles
Jupiter  —  88,865 miles
The Sun  —  865,000 miles
Red Giant star  —  400 million miles
The Solar System  —  7.5 billion miles
The Crab Nebula  —  12 light-years**
Globular cluster M13  —  160 light-years
Small Magellanic Cloud  —  10,000 light-years
Milky Way Galaxy  —  100,000 light-years
Local Group of galaxies  —  6 million light-years
Local supercluster  —  80 million light-years
The visible universe  —  46 billion light-years
The actual universe  —  78 billion light-years

*    1/25,000,000,000,000 inches.
**  One light-year: about 5.9 trillion miles.

The Crab Nebula, a supernova remnant. Very big.