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Thread: How Do You Weigh The Universe?

  1. #1
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    How Do You Weigh The Universe?

    If we can find the weight of everything in the universe, we can better understand how the universe came to be.
    The post How Do You Weigh The Universe? appeared first on Universe Today.


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  2. #2
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    You don't.
    Weight only counts in a particular gravitational field.
    You might be able to estimate it's mass....
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

  3. #3
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    Quote Originally Posted by Trebuchet View Post
    You don't.
    Weight only counts in a particular gravitational field.
    You might be able to estimate it's mass....
    Trebuchet. Agreed. Thank you. As a rookie teacher, I realized I carried a couple of misconceptions around, and that was one of them. I would ask students to weigh things out on a triple beam balance in Chem lab. Wrong. Weighing is done on a spring scale, and you get Newtons. Massing is done on a balance, and you get kilograms. The balance reads the same everywhere, on the moon, in Antarctica, top of Mt. Everest, at the equator....and is invariant in kg.s The spring scale varies, because as you said, the local acceleration due to gravity varies.
    To exacerbate the issue, some science supply companies issued spring scales calibrated in units of mass, grams, kgs, etc, and teaching students to recognize the error is tricky, but this is a teaching forum, with lots of rookies, so getting it straight is worthwhile.
    The relative abundances of the three stable isotopes of oxygen, 16,17, 18, in water vapor collected over the salty ocean, varies exquisitely, with slight changes in temperature, and using mass spectroscopy of them showed over time that the melting glaciers in Greenland, contained in their ice cores, a frozen temperature record of the North Atlantic Ocean over about 250,000 years.That's where massing things matters a big deal.
    Similar issues arose over the stoichiometric determination of the composition of rust. At different temperatures, iron oxide contains different abundances of black iron 2 oxide , and red iron 3 oxide, and chemists used balances to slowly tease out the correct formula over decades, after calling each other a number of unsavory names in public. Have times changed? lol
    pete

  4. #4
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    Yeah, this is something that's bothered me for a long time. The superiority of the metric system has been expounded for a long time, but then you see stuff like how cooking is better in Europe because they weigh things instead of using volume. Unless their kitchen scales are reading Newtons, they're doing it wrong.
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

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