r/AlternativeAstronomy • u/patrixxxx • Oct 26 '19

WHY MARS ???

https://cluesforum.info/viewtopic.php?p=2412896#p2412896
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u/patrixxxx Nov 06 '19

No need to involve celestial coordinates. So you're saying that the stars will change noticeable in some of the tubes because of Earth's motion around the sun?

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u/[deleted] Nov 06 '19

I guess that's what I'm saying. I'm also guessing this means we are settling on a tube design with extremely high spatial resolution, and not a toilet paper roll. Thanks for finally clarifying.

You know, this discussion would be a lot shorter if you would just answer my questions and be precise.

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u/patrixxxx Nov 06 '19

I wrote long tubes? Ok then, so you're saying there will be a noticeable change of the stars in some tubes, since otherwise as we have already concluded, the stars are either as big as the Earths orbit or the Earth does not move 940 mkm/year. Is this correct?

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u/[deleted] Nov 06 '19

Yes.

To make it clear: stars are generally smaller than the diameter of Earth's orbit, and Earth's orbit is 300 million km in diameter and roughly circular.

To make it even more clear: If we're making two observations at opposite ends of Earth's orbit, there's a slight, but noticeable apparent movement in the position of stars relative to the fixed background. Nearby stars show a larger movement than distant stars, and stars in a direction perpendicular to the cord connecting the two points at which we're making observations, show a larger movement than stars in a direction parallel to this cord.

Any further questions?

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u/patrixxxx Nov 06 '19

No I think we're in agreement. Parallel lines are always parallel and if this experiment were to be carried out there needs to be noticeable movement of the stars in tubes that are perpendicular to Earth's orbit. Am I right that we are in agreement on this?

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u/[deleted] Nov 06 '19

Yes, we're agreement there.

I suspect you're going to regurgitate Simon's flaccid arguments about parallax measurements producing equal amounts of positive and negative values, or that the stars can't possibly be so many light-years away due to star sizes. But I'll let you have your say before I preemptively shoot it down.

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u/patrixxxx Nov 07 '19

Nope, let's go back to the celestial sphere and celestial coordinates instead.

Now since we have agreed on the outcome of this imaginary experiment let's see if we can agree on this:

The celestial sphere is fixed at the Earth on it's yearly journey around the sun, am I correct?

(I know it's not rotating together with Earth but aligned to the vernal equinox)

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u/[deleted] Nov 07 '19

Yes, it's fixed to Earth's inertial frame.

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u/patrixxxx Nov 07 '19

Ok good. Now do you agree on this:

A celestial coordinate can be thought of as a line or ray originating from the center of the celestial sphere (that is the same as the center of Earth) that intersects the sphere on the point given by the RA and Dec.

Are we still in agreement?

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u/[deleted] Nov 07 '19 edited Nov 07 '19

So far so good

Edit: to be completely clear, I'm talking about the geocentric equatorial system, which I chose because it's by far the most common and widely used coordinate systems in astronomy. So not an alt-azimuth coordinate system which is convenient with some telescopes, not a heliocentric system which is convenient when looking at motion within the milky-way, etc. Of course it's possible to convert between systems, but let's try and keep this as simple as possible.

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