According to James Schombert from the Department of Physics of the University of Oregon, the oldest and most basic cosmological observation is the darkness of the night sky, known as Olber's paradox. It concerns the fact that the night sky should not appear dark in a very large (or infinite), ageless Universe. It should glow with the brightness of a stellar surface.
The paradox cannot be resolved by assuming that parts of the Universe are filled with absorbing dust or dark matter because eventually that material would heat up and emit its own light. The resolution of Olber's paradox is found in the combined observation that 1) the speed of light is finite (although a very high velocity) and 2) the Universe has a finite age, i.e. we only see the light from parts of the Universe less than 15 billion light years away.
Has this made sense to you? Are you more puzzled now or is it clearer?
Rafael just recommended this site where there is more info. on Olber´s paradox. It is really good as it has a reading with its narration. Very useful for language learning. Good find, Rafael, thanks for sharing!!! Vanessa also recommended this reading.
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