Galaxies and the Universe

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Science  25 Dec 1970:
Vol. 170, Issue 3965, pp. 1363-1370
DOI: 10.1126/science.170.3965.1363


A brief review is given of what the study of galaxies has taught us about properties of the universe. It is assumed that the universe started from a general "explosion," and that the general expansion observed today, as well as the 3°K blackbody radiation, are consequences of this explosion. The present average density in the universe is probably close to the critical value of 10-29 g/cm3. Only about 3 percent of this is contained in galaxies; the rest consists probably of intergalactic gas at a temperature between 105 and 106°K. Observations in our own galaxy indicate that this intergalactic gas is still flowing into it.

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