Comment on epidemiology

• JackGreenEarth@lemm.ee ⁨2⁩ ⁨years⁩ ago

  The CMB is everywhere, and anywhere in the universe it’s the same distance from a hypothetical observer. I fail to see how you can use it as an absolute reference frame.

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  • ulterno@lemmy.kde.social ⁨2⁩ ⁨years⁩ ago

    I think they’re trying to say, it can be considered to be a non-accelerated reference frame, where stuff like planets and stars would be accelerated.

    Though I have a problem in understanding how it could be taken as a reference frame in the first place.

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    • JackGreenEarth@lemm.ee ⁨2⁩ ⁨years⁩ ago

      Indeed, it can’t be a reference frame, as even if it’s not accelerated, it’s everywhere, so it doesn’t have a position or orientation.

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      • ulterno@lemmy.kde.social ⁨2⁩ ⁨years⁩ ago

        Not only that, it’s not even a single object. It’s just the name given to a group of radiation, which is ultimately just light going randomly here and there.

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  • bjoern_tantau@swg-empire.de ⁨2⁩ ⁨years⁩ ago

    It isn’t a single “thing” you are some distance away from. It’s photons remaining from the early universe that can be found everywhere without direction. Pick “one” of them and you can track your speed relative to it. It’s the closest thing we have to a universal reference frame.

    Also see the later questions on www.astro.ubc.ca/people/scott/faq_basic.html

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