Offline edby

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Re: Full moon impossible?
« Reply #20 on: June 24, 2018, 07:59:37 PM »
According to standard RE models, we will not see 100% perfect full moons every month. Furthermore, the amount of moon we see actually varies by just a tiny bit depending on where we are on Earth at the time.
I certainly do not dispute that. Does anyone dispute this? I believe we are all in agreement on this.
I agree that the amount of moon we see actually varies by just a tiny bit depending on where we are on Earth at the time. But again, why is  a 100% full moon impossible in RET?
Please re-read that. I was careful NOT to say that 100% full moon is impossible in RET. I said, "we will not see 100% perfect full moons every month." By this I mean that we get what we call a "full moon" every lunar month, but even though we call it "full," most of the time it is not perfectly 100% illuminated. Do you agree with this, or should I get into the math (5 degree inclination and all that...)?
Agree, just checking.

[edit] But I wonder what evidence Tom wants. If it's mathematical models based on the usual astronomical assumptions, then he might object. We would need a proper telescope and about a year's worth of observations to show it.
« Last Edit: June 24, 2018, 08:01:40 PM by edby »

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Offline Bobby Shafto

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Re: Full moon impossible?
« Reply #21 on: June 24, 2018, 08:06:35 PM »
Timelapse of the moon for one month in 2007 showing libration. (Gif is 2MB so might take a few moments to load):


Re: Full moon impossible?
« Reply #22 on: June 24, 2018, 08:12:44 PM »
But I wonder what evidence Tom wants. If it's mathematical models based on the usual astronomical assumptions, then he might object. We would need a proper telescope and about a year's worth of observations to show it.

I would expect a single full-moon observation taken at high resolution should do. To avoid any claims of cheating, I suggest that Tom take the photo or appoint someone to take the photo on his behalf. We will measure it precisely and try to answer just how full it is. (We must be careful to include our margin of error on that.) We will then compare those results against predictions.

Offline edby

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Re: Full moon impossible?
« Reply #23 on: June 24, 2018, 08:23:19 PM »
FYI the next 9 full moons with % illumination, together with ecliptic latitude. So RET says that 100% illumination is infrequent (but not impossible).

But this will not satisfy Tom, because it is based on an RE model.

Date   Illuminated   Ecliptic lat
27-Jul-18   100%   -0 16
26-Aug-18   99.9%   -2 42
25-Sep-18   99.8%   -4 47
24-Oct-18   99.7%   -5 53
23-Nov-18   99.8%   -4 52
22-Dec-18   99.9%   -3 18
21-Jan-19   100.0%   -0 22
19-Feb-19   100.0%   2 07
21-Mar-19   99.9%   3 54

Offline edby

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Re: Full moon impossible?
« Reply #24 on: June 24, 2018, 08:38:07 PM »
I would expect a single full-moon observation taken at high resolution should do. To avoid any claims of cheating, I suggest that Tom take the photo or appoint someone to take the photo on his behalf. We will measure it precisely and try to answer just how full it is. (We must be careful to include our margin of error on that.) We will then compare those results against predictions.
I don't think this is possible. See the table above. How do we spot the 0.3% in 99.7%? I just tried taking a picture of the moon just now, and focusing, resolution etc is v difficult.

« Last Edit: June 24, 2018, 08:41:42 PM by edby »

Re: Full moon impossible?
« Reply #25 on: June 25, 2018, 01:00:39 AM »
I think you may have stumbled into my ultimate point.  ;)

However, the point is not made unless you also explain where you got those numbers. Where did you get this 99.7%? How is that consistent with RET?

Offline edby

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Re: Full moon impossible?
« Reply #26 on: June 25, 2018, 07:51:30 AM »
I think you may have stumbled into my ultimate point.  ;)

However, the point is not made unless you also explain where you got those numbers. Where did you get this 99.7%? How is that consistent with RET?
A software model which of course uses RET.

Re: Full moon impossible?
« Reply #27 on: June 25, 2018, 05:03:23 PM »
I think you may have stumbled into my ultimate point.  ;)

However, the point is not made unless you also explain where you got those numbers. Where did you get this 99.7%? How is that consistent with RET?
A software model which of course uses RET.
The fact that it uses RET should cause no objections. Tom's point was that RET does not allow for 100% full moons. We need to show what RET actually predicts. I don't really think Tom is just searching for "gotchas" where a bunch of websites said 100% instead of 99.7%. I think he was expecting the prediction to come out much lower than that. (In fact, I expected it to come out much lower than that too). Can you show where that 99.7% comes from? The equations used to arrive at that? Or share what software model you pulled this from so that it can be scrutinized?

Offline model 29

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Re: Full moon impossible?
« Reply #28 on: June 25, 2018, 05:16:00 PM »
That linked wiki article is just too funny.  Zero understanding of scale, the moon's orbital 5 degree tilt, or even spelling. 

Offline edby

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Re: Full moon impossible?
« Reply #29 on: June 25, 2018, 05:57:18 PM »
I think you may have stumbled into my ultimate point.  ;)

However, the point is not made unless you also explain where you got those numbers. Where did you get this 99.7%? How is that consistent with RET?
A software model which of course uses RET.
The fact that it uses RET should cause no objections. Tom's point was that RET does not allow for 100% full moons. We need to show what RET actually predicts. I don't really think Tom is just searching for "gotchas" where a bunch of websites said 100% instead of 99.7%. I think he was expecting the prediction to come out much lower than that. (In fact, I expected it to come out much lower than that too). Can you show where that 99.7% comes from? The equations used to arrive at that? Or share what software model you pulled this from so that it can be scrutinized?
Yes Tom's point was that RET does not allow for 100% full moons.

The software is Stellarium. I have been trying to work out how they calculate the illumination bit. It's clearly connected with the ecliptic latitude, as you can see from the table above.

Offline edby

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Re: Full moon impossible?
« Reply #30 on: June 25, 2018, 06:30:52 PM »
Chapter 51 of Jean Meeus' work is supposedly the place, but not for the faint hearted. I believe Stellarium used this.

http://edukacja.3bird.pl/download/fizyka/astronomia-jean-meeus-astronomical-algorithms.pdf

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Offline nickrulercreator

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Re: Full moon impossible?
« Reply #31 on: June 27, 2018, 01:39:52 AM »
Here is a diagram showing the Earth and Moon to scale (not the sun), along with the Earth's shadow, and the Moon's orbital plane. As you can see the Moon has a lot of space to roam when in its "full" phase.



The moon could be close to the Earth's shadow, but not in it. Thus, we see 100%, but that's still rare. It's more common to see close, like 99.7%.
This end should point toward the ground if you want to go to space. If it starts pointing toward space you are having a bad problem and you will not go to space today.

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Offline Tom Bishop

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Re: Full moon impossible?
« Reply #32 on: June 27, 2018, 02:11:23 AM »
Why is the earth's shadow decreasing in size?

The earth takes up 2 degrees of the moon's sky. The sun takes up 0.5 degrees of the moon's sky. How does the sun wrap around the earth?

With those attributes, the shadow should be increasing.
"The biggest problem in astronomy is that when we look at something in the sky, we don’t know how far away it is" — Pauline Barmby, Ph.D., Professor of Astronomy

Offline model 29

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Re: Full moon impossible?
« Reply #33 on: June 27, 2018, 02:20:39 AM »
Why is the earth's shadow decreasing in size?
  You do realize the sun is much bigger than Earth, correct?

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Offline Tom Bishop

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Re: Full moon impossible?
« Reply #34 on: June 27, 2018, 02:42:57 AM »
Why is the earth's shadow decreasing in size?
  You do realize the sun is much bigger than Earth, correct?

In RET, sure. But it's also very far away and very small in the sky.

For the sun to cause the earth's shadow to decrease in size the moon would need to see the sun to be bigger than the earth in its sky.

If the sun is seen to be smaller than the earth, the opposite should occur, and the shadow should widen.
"The biggest problem in astronomy is that when we look at something in the sky, we don’t know how far away it is" — Pauline Barmby, Ph.D., Professor of Astronomy

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Offline Rama Set

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Re: Full moon impossible?
« Reply #35 on: June 27, 2018, 02:44:36 AM »

In RET, sure. But it's also very far away and very small in the sky.

For the sun to cause the earth's shadow to decrease in size the moon would need to see the sun to be bigger than the earth in its sky.

If the sun is smaller than the earth, the opposite should occur, and the shadow should widen.

Prove it, definitively.  Your assertions are totally meaningless.

Re: Full moon impossible?
« Reply #36 on: June 27, 2018, 02:48:50 AM »
Why is the earth's shadow decreasing in size?

The earth takes up 2 degrees of the moon's sky. The sun takes up 0.5 degrees of the moon's sky. How does the sun wrap around the earth?

With those attributes, the shadow should be increasing.
That's a separate question. Are we done with the 100% illumination thing? Are you happy with the 99.7%? I'm currently working on putting together a presentation to explain exactly where that number came from. (Spoiler alert: my sample comes up with 99.8%.) Since the question of the full moon's illumination is about what the standard model predicts and has nothing to do with FET, I would hope you might accept the explanation as the valid RE interpretation and update your wiki accordingly.

The shadow thing is interesting too, and I'm happy to jump into that one as well, but first I want to wrap up the 100% illumination thing. The standard RE model predicts the "full moon" will actually be anywhere from 99.7% to 100% illuminated. Would you like to see the math? Would you like to try to determine whether we can measure that amount of difference? Or would you prefer to accept this now and move on?

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Offline Tom Bishop

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Re: Full moon impossible?
« Reply #37 on: June 27, 2018, 02:51:16 AM »

In RET, sure. But it's also very far away and very small in the sky.

For the sun to cause the earth's shadow to decrease in size the moon would need to see the sun to be bigger than the earth in its sky.

If the sun is smaller than the earth, the opposite should occur, and the shadow should widen.

Prove it, definitively.  Your assertions are totally meaningless.

Here:

The sun and earth and the observer are in a straight line. The sun is seen to be smaller than the earth. We are located at a point directly behind the earth, at the point where the earth's shrinking shadow disappears entirely and the sun's rays meet. The shadow is now gone, yet the earth is still in front of the sun.

How could the shadow be gone?

How do we see the sun through the earth?

Shrinking Shadow Debunked
« Last Edit: June 27, 2018, 03:06:15 AM by Tom Bishop »
"The biggest problem in astronomy is that when we look at something in the sky, we don’t know how far away it is" — Pauline Barmby, Ph.D., Professor of Astronomy

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Offline Rama Set

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Re: Full moon impossible?
« Reply #38 on: June 27, 2018, 02:52:27 AM »

In RET, sure. But it's also very far away and very small in the sky.

For the sun to cause the earth's shadow to decrease in size the moon would need to see the sun to be bigger than the earth in its sky.

If the sun is smaller than the earth, the opposite should occur, and the shadow should widen.

Prove it, definitively.  Your assertions are totally meaningless.

Here:

The sun and earth and the observer are in a straight line. The sun is smaller than the earth. We are located at a point directly behind the earth, at the point where the earth's shrinking shadow disappears entirely. The shadow is now gone, yet the earth is still in front of the sun.

How could the shadow be gone?

How do we see the sun through the earth?

That's not proof Tom.  Try again.

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Offline Tom Bishop

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Re: Full moon impossible?
« Reply #39 on: June 27, 2018, 02:59:53 AM »
Why is the earth's shadow decreasing in size?

The earth takes up 2 degrees of the moon's sky. The sun takes up 0.5 degrees of the moon's sky. How does the sun wrap around the earth?

With those attributes, the shadow should be increasing.
That's a separate question. Are we done with the 100% illumination thing? Are you happy with the 99.7%? I'm currently working on putting together a presentation to explain exactly where that number came from. (Spoiler alert: my sample comes up with 99.8%.) Since the question of the full moon's illumination is about what the standard model predicts and has nothing to do with FET, I would hope you might accept the explanation as the valid RE interpretation and update your wiki accordingly.

The shadow thing is interesting too, and I'm happy to jump into that one as well, but first I want to wrap up the 100% illumination thing. The standard RE model predicts the "full moon" will actually be anywhere from 99.7% to 100% illuminated. Would you like to see the math? Would you like to try to determine whether we can measure that amount of difference? Or would you prefer to accept this now and move on?

That conversation is still in progress. The size of the earth's shadow does matter in the scenario. We are still talking about that subject.

That's not proof Tom.  Try again.

Of course it's a proof. It disproves the whole concept entirely.

How do we see the sun through the earth?
"The biggest problem in astronomy is that when we look at something in the sky, we don’t know how far away it is" — Pauline Barmby, Ph.D., Professor of Astronomy