Recent content by andrew s 1905

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    B How can dark energy comprise 74% of the Universe?

    But they are related contrary to your statement. Light has to cross the Hubble sphere to reach us. See section 3.3...
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    B How can dark energy comprise 74% of the Universe?

    Yes. But how far we can see is related to... I agree you can argue they have the same underlying cause. I have learnt my lesson. Regards Andrew
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    B How can dark energy comprise 74% of the Universe?

    Ok I give up. @PeterDonis why say this You now say this I explicitly did not equate them at the same time. For the last time I said the expanding Hubble sphere will mean we can see further (than the currently observable Universe) in the future. Regards. Andrew
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    B How can dark energy comprise 74% of the Universe?

    The current observable Universe is how far we can see now. That is not how far we will be able to see in the future. Which is what I said. Please point out where I equated the two. As the Hubble sphere is expanding we will be able to see further in the future. I also know we can see things...
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    B How can dark energy comprise 74% of the Universe?

    I know that. I never said if was. Regards Andrew
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    B How can dark energy comprise 74% of the Universe?

    As I understand it the Hubble sphere is expanding so in the future we will be able to see further than current size of the observable Universe. Regards Andrew
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    I Transparency of a gas compared to a plasma

    The spectra of the light emitted at the photosphere of the sun , as an example, matches that received at the top of our atmosphere very accurately with small additions from light from the chromosphere and corona. Regards Andrew
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    I Transparency of a gas compared to a plasma

    If there are strong magnetic fields to accelerate free electrons in a plasma then they will emit cyclotron radiation. Also significant quantities of hot gas (~10% by mass) were missed in galaxies until they were observed in x-rays. Regards Andrew
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    A GR vs. alternative theories of gravity

    As per the summary I would like to find a review paper, monograph or book. Google is not find any recent reviews. Post 2018 would be ideal. Thanks for any pointers. Regards Andrew
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    I Some questions about absorption lines

    Q1 the spectrum is cut up and stacked. Take the right hand edge of the strip below and attach it to the left hand edge to the one above and so on. Q2 yes the is normally some signal in the dark bands. Q3 Yes it remitted but in all directions and not all back to it's original trajectory. Q4...
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    I Astronomy in a Simple Solar System

    I am not disputing your technical definition but given the baricenter of the Earth Moon system is inside the Earth a Galileo observing from Mars might conclude the moon orbits the earth at least informally. Regards Andrew
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    I Astronomy in a Simple Solar System

    I suspect we are conflating the technical and everyday definitions of orbit. When I observe the Galilean moons of Jupiter I am with Galileo in that they appear to orbit it. Regards Andrew
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    I Astronomy in a Simple Solar System

    Ptolemy epicycles always struck me as an precursor to Fourier decomposition. Regards Andrew.
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    I Astronomy in a Simple Solar System

    @Ibix Ptolemy would be proud of you! Regards Andrew
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    I Astronomy in a Simple Solar System

    You have repeated this several times but I don't understand it. In an Earth centerd model the all solar system bodies orbit the earth in the sense the perform circuits. Yes the are very complex but so is the motion of the moon around the Sun it is not a simple ellipse. Don't get me wrong I am...
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