Glenn Elert
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The Physics Factbook™
Edited by Glenn Elert -- Written by his students
An educational, Fair Use website
topic index | author index | special index
| Bibliographic Entry | Result (w/surrounding text) | Standardized Result |
|---|---|---|
| Chaisson, Eric, & Steve McMillan. Astronomy Today. New York: Prentice Hall, 1993: 418. | "It averages roughly 1 atom per cubic centimeter, but density as great as 1000 atoms/cm3 and as small as 0.1 atom/cm3 have been found." | 0.1–1000 atoms/cm3 |
| MacMillan Encyclopedia of Physics. New York: MacMillan, 1996: 779. | "On average, the density of matter in the space between the 1011 stars of the Milky Way is 0.1 neutral hydrogen atoms (H) per cubic centimeter." | 0.1 atom/cm3 |
| Mammana, Deniss L. Interstellar Space. New York: Popular Science, 2000: 220. | "On the average, this haze contains about one atom per cubic centimeter." | 1 atom/cm3 |
| Pananides, Nicholas A. & Thomas Arny. Introductory to Astronomy Second Edition. 1979: 293. | "The density of the gas cloud is incredibly small by terrestrial standards -- the cloud contains roughly one hydrogen atom per cubic centimeter." | 1 atom/cm3 |
| Mitten, Simon & Jacqueline. The Young Oxford Book of Astronomy.1995: 94. | "If you went out in space to a spiral arm of the galaxy, you would find one to two atoms of gas per cubic inch!" | 0.06–0.12 atom/cm3 |
Space, the final frontier. These are the words that might cometo mind when you gaze up at the stars on a clear night. But waita second, what is that dark stuff that separates all the stars?If you said it is space then you are partially correct. Outerspace is divided into many levels and the one that separates thestars is called interstellar space.
It is often a misconception that space is a vacuum or simplyempty. Space is a nearly perfect vacuum, even better than thebest ones made in labs on earth, but it is not devoid of everything.The fact is that space is filled with tiny particles called cosmicdust and elements like hydrogen and helium. This applies for interstellarspace also and all the previously mention particles make up whatis known as the interstellar medium.
The interstellar medium is mainly made of lone hydrogen atoms.They do not even exist as pairs as they do on earth. I mentionedbefore that space is filled with hydrogen atoms. The actual densityof hydrogen as it exist in interstellar space is on the averageof about 1 atom per cubic centimeter. In the extremes, as lowas 0.1 atom per cubic centimeter has been found in the space betweenthe spiral arms and as high as 1000 atoms per cubic centimeterare known to exist near the galactic core.
The interstellar medium also contains cosmic dust. These particlesare much bigger than hydrogen atoms. However, there are far fewerparticles of cosmic dust than there are hydrogen atoms in thesame volume of space. It is estimated that cosmic dust is 1000times less common than hydrogen atoms in the interstellar medium.
Da Wei Cai -- 2000
| Bibliographic Entry | Result (w/surrounding text) | Standardized Result |
|---|---|---|
| Cutnell, John D. & Johnson, Kenneth W. Physics, 3rd Edition. New York: Wiley, 1995: 441. | "In certain regions of outer space the temperature is about 3 K, and there are approximately 5 × 106 molecules per cubic meter." | 5 atoms/cm3 |
Editor's Supplement -- 2001
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