nPosted on July 23, 2020
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Key Points
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nToday’s famous birthday was an American astronomer who was born in Philadelphia (Pennsylvania) in 1928.
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nVera Rubin studied galaxy rotation rates – and she discovered a puzzle: the predicted angular motion of each galaxy didn’t match the motion she observed.
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nIf you think about how tiny galaxies appear in our skies…
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nThis is the largest of the nearest galaxies –
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nand it’s just a tiny smudge to the naked eye,
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neven under the darkest-sky conditions…
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n…then you may be wondering how Rubin measured any galaxy’s rotation?
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| It’s not like we’re treated to sights like this! |
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nRubin and other astronomers take advantage of the Doppler effect. Light that is coming towards us is bluer than expected, and light that is going away from us is redder than expected. So an astronomer looks for galaxies with bluer light on one side and redder light on the other – and then she can compute the rotational speed.
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nWell, Rubin measured many, many galaxies’ rotation – and she discovered that galaxies rotated quickly enough that they should fly apart! Since they didn’t fly apart, she knew that there must be more mass – about five times more! – than we could see.
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A Swiss astronomer named Fritz Zwicky had already proposed the existence of dark matter – matter we can’t see, but that we can tell exists because of its gravitational pull. Rubin’s work was some of the first evidence for his idea – but at first many scientists were very skeptical!
A Swiss astronomer named Fritz Zwicky had already proposed the existence of dark matter – matter we can’t see, but that we can tell exists because of its gravitational pull. Rubin’s work was some of the first evidence for his idea – but at first many scientists were very skeptical!n
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nHowever, more and more scientists were able to confirm Rubin’s data, find more evidence to back the theory that dark matter exists, and that there is WAY more of it than there is of matter we can see!
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| Astrophysicists now believe that the normal matter we see all around us and across our night skies is only a very small part of what the universe if made of! |
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nAlso on this date:
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Ethiopian ruler Haile Selassie’s birthday
Ethiopian ruler Haile Selassie’s birthday n
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Revolution Day in Egypt
Revolution Day in Egypt
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nGorgeous Grandmas Day
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nAnniversary of the signing of a boundary treaty
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nAnniversary of a cloning success
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nAnniversary of the opening of the first swimming school in the U.S.
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nBirthday of Maori queen, Dame Te Atairangikaahu
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nChildren’s Day in Indonesia
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nnAnniversary of the launch of the first Earth-resources satellite
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nnAnniversary of the discovery of a comet
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nAnniversary of the discovery of an Earthlike exoplanet
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nRenaissance Day in Oman
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nTeej Festival
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n(Date varies)
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nPlan ahead:
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nCheck out my Pinterest boards for:
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nJuly holidays
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nJuly birthdays
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nHistorical anniversaries in July
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nAnd here are my Pinterest boards for:
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nAugust holidays
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nAugust birthdays
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nHistorical anniversaries in August
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