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Thread: The Big Day: which day of the year is the most time dilated for the distant observer?

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    The Big Day: which day of the year is the most time dilated for the distant observer?

    Say for someone watching Earth from a half a light year away, which day of the orbit lasts the longest?

    The orbit of Earth is slightly elliptical, so would the day when it was closest to the Sun be the most time dilated, in terms of speed dilation, and being deeper in the Sun's gravity well?
    Formerly Frog march..............

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    Quote Originally Posted by Mudskipper View Post
    Say for someone watching Earth from a half a light year away, which day of the orbit lasts the longest?

    The orbit of Earth is slightly elliptical, so would the day when it was closest to the Sun be the most time dilated, in terms of speed dilation, and being deeper in the Sun's gravity well?
    Whats our viewpoint? Are we looking down from the north poles or are we looking from along earths orbital plane?
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    Whats our viewpoint? Are we looking down from the north poles or are we looking from along earths orbital plane?
    I'm not sure it matters. At half a light years distance, if in fairly flat space, the Earth's revolution should appear to slow down a smidgen(unmeasurable amount)..I think.
    Formerly Frog march..............

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    Wha?

    Quote Originally Posted by Mudskipper View Post
    Say for someone watching Earth from a half a light year away, which day of the orbit lasts the longest?

    The orbit of Earth is slightly elliptical, so would the day when it was closest to the Sun be the most time dilated, in terms of speed dilation, and being deeper in the Sun's gravity well?
    Time dilation is a function of relative velocities, not of distance.

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    Any time dilation of a clock on Earth as observed from afar should be maximum at perihelion. That is where it is deepest in the Sun's gravitational well and also moving fastest. If I am not mistaken, both of those effects act in the same direction.

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    Quote Originally Posted by Hornblower View Post
    Any time dilation of a clock on Earth as observed from afar should be maximum at perihelion. That is where it is deepest in the Sun's gravitational well and also moving fastest. If I am not mistaken, both of those effects act in the same direction.
    Yes, both would be additive to the time dilation, though they oppose each other for orbiting satellites above. I would assume the variation in the Earth-Moon barycenter could also be included, but are these gravity time effects extra tiny compared to the tiny time dilation due to orbital speed?
    We know time flies, we just can't see its wings.

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    It also depends on how you're measuring the duration of "day" - tropical or sidereal. At perihelion, the planet is moving the fastest in its orbit, which also means it has to turn further to put the sun in the same position in the sky as it was the day before (tropical day). This is the source of the Analemma.
    Et tu BAUT? Quantum mutatus ab illo.

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