Wednesday 26 February 2020

cosmology - How do people calculate proportions of dark matter, dark energy and baryonic matter of the universe?


The Wikipedia page on dark matter mentions that the Planck mission had revealed that in our universe ordinary baryonic matter, dark matter and dark energy are present in the ratio: 4.9%, 26.8% and 68.3% respectively. I do not understand exactly how this result had been got. Did the Planck mission scan the entire universe as it is today to get these figures or just a part of the universe? (Is it really possible to scan the entire universe if the universe is infinitely large?) Can anybody please explain the principle behind the calculation?


I also notice that the above figures are given in terms of percentages. Can I get the absolute values of the individual quantities like, total dark energy = .... Joule in the universe?


In case only a part had been scanned then is it possible that in future these figures may change if a larger portion of the universe is scanned by another mission?




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