Physics Question #96

Arnaud Bigeu, a 23 year old male from the Internet asks on November 30, 1999,

How does the static universe theory (Gamow, Hoyle...) explain the 3K cosmic background radiation. Also, each time I see a astronaut in space, he performs movements very slowly. There is no air in space, so there is no resistance. Why would this be?

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The answer

Donald J. Barry answered on November 30, 1999

Clever minds can usually find clever mechanisms for facts like the 3K cosmic background radiation (fossil radiation, in the context of an expanding universe). I don't believe Gamow was a steady state holdout at the time of his death (1967 or '68) but may have kept an open mind on the subject. Hoyle, obviously, is still hatching clever ways to attempt to "save" the Steady State explanation, but he's increasingly becoming a choir of one in this regard. I know of two basic explanations which Hoyle has advanced or endorsed at various times to explain the 3K radiation. The first simply points out that if such radiation exists in a steady state universe, it could long endure, and thus it merely becomes one of many puzzles pushed back amongst the "origins" questions. The second explanation which has been used is more technical and hinges on the observation that the energy density of the 3K background radiation in space (the amount of energy floating around in a given volume) is roughly equal to the average energy density of starlight in the Universe. Models have been proposed in which the starlight energy density leaks over into the microwave energy density such that the two are in equilibrium. In one particular "steady state" model, space-time has a structure that actually yields a horizon akin to that in the big-bang model, except that this horizon holds thermal properties and gets heated by starlight. But the space-time structure necessary for this has essentially been rejected by large-scale mapping of the Universe in the last few years. Regarding the motions of astronauts in space: astronauts in bulky pressurized suits must deal with the awkward joints of their suits and the friction in these joints generated by the pressure difference. In addition, technical work, particularly outside the spacecraft, must be done with great care lest the astronaut drop an item or launch himself outward (to the end of his tether)---so there is great incentive to work methodically and with great deliberation. However, inside a spacecraft and out of their suits, astronauts can let loose! NASA has released hilarious footage of astronaut stunts from almost 40 years of space travel.

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