How cold is it in space? © Getty Images

How cold is it in space?

The Cosmic Background Explorer (COBE) satellite has refined temperature measurements taken way back in 1964.

Asked by: Ed Parry, by email

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According to data from the Cosmic Background Explorer (COBE) satellite, the temperature of space is 2.725K (2.725 degrees above absolute zero). This agrees with the temperature predicted to come from residual radiation after the Big Bang and is a refinement of ground-based measurements by Arno Penzias and Robert Wilson in 1964. In that case, problems with contamination of their horn-shaped receiving antennae caused Penzias to utter: “We have either discovered the Big Bang or a pile of pigeon shit”. Penzias and Wilson’s measurements yielded a uniform temperature of 3K, independent of the direction in which they looked. Space-based measurements have shown that there are slight variations, producing a beautiful dappled image of the Universe.


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