[Tumeni]

Posting new thread, as suggested/requested by Tom ;

Just look at the comments. They're FULL of contrary voices, pointing out how Morgile's simplistic 2D view of the solar system is lacking ....

Around the 4 minute mark he is making the argument that Venus should never be seen past 11pm due to where the horizon is for the observer. The problem is that his model is not in 3D?

The argument seems to be perfectly valid. If you want to debate it with bad arguments you pull from YouTube start a thread in the main forums and post a link here to your thread. You are distracting from this collection of videos.

Look into the comments far enough, and you'll find my comments as one of the contrary voices. Also on Morgile's previous video on exactly the same topic, with exactly the same faulty logic. Part of the problem is he's not looking at it in 3D. I don't find his argument to be valid.

Still, considering the issue in 2D only, here's my rebuttal video to his first one;



Bottom line - if Venus and Mercury are at their maximum elongation from the Sun, an observer on Earth who is up to 21 degrees (for Mercury) or 36 degrees (for Venus) past the terminator line on Earth will have a clear sightline to either planet.

Since Earth rotates approximately 15 degrees per hour, then observing Venus, given a perfectly upright Earth, with no axial tilt, and Venus in the best position for observation, will be possible for (36/15 = ) 2.4 hours approx after sunset.

We're told the photo in the video was taken at 11pm approx, and, as some have pointed out in the video comments, sunset was well after 9pm, so that would place Venus well within the 2.4 hour limit of visibility.

Once axial tilt for the time of year is taken into account, that makes it even more visible. See my comments at Morgile's video (if he hasn't deleted them, or blocked me ... I'll try and requote it here). I have no difficulty visualising it in 3D, and could easily model it.

[Tumeni]

Here we are; posted on Morgile's video approx 1 mth ago;

Your diagram fails to take account of axial tilt, and other factors.

The star chart at in-the-sky.org (https://in-the-sky.org/skymap2.php?year=2018&month=6&day=19&country=1840&reg1=5001836&reg2=5007996&town=5007989) clearly shows the Moon and Venus ON THE HORIZON at 23.30 in Saginaw, Michigan.

The solar system chart shows Venus as far out in its orbit, perpendicular to the imaginary line connecting Earth and Sun. This puts it in the best position to be seen by the most people on Earth.

The axial tilt, given the time of year, will be roughly toward Venus.

I see no difficulty with Michigan, at roughly 45N, having an "on the horizon" view toward Venus. This is what was predicted by in-the-sky, and what was observed by your photographer.

https://www.space.com/33619-visible-planets-guide.html

(Venus will be at its greatest elongation from the Sun in mid-August, so get your photographer to take another shot then, and see if it matches predictions - as a 'for instance', in-the-sky.org says it will be on his horizon - assuming he's in Saginaw, for instance - at 21.40 on the 19th Aug).

I stand by my original statement about Morgile's videos - a big truckload of Dingo's Kidneys.

[Tom Bishop]

Here are your images:



If this is a side-view of the Solar System and the top of the earth is the North Pole, where observer is at a high north latitude, the depiction is in error. The planets don't orbit the sun Up-Down/North-South. The planets orbit the sun in an area parallel to its ecliptic.

If it is a top-down view of the Solar System, you don't have the horizon at 11PM

[Tumeni]

I think it's blatantly obvious that it's top-down.

However, image to follow to reinforce the point

[Tom Bishop]

If it's a top-down view of the Solar System then you have the 11pm Horizon way off.

Midnight Horizon:

[Tumeni]

[Tom Bishop]

[Tumeni]

If it's a top-down view of the Solar System then you have the 11pm Horizon way off.

Midnight Horizon:
IMG

That's not a horizon, it's a tangent line to the surface.

And, as was pointed out numerous times in the Morgile video comments, the time of year, and hence axial tilt, inclines the Earth toward Venus, and the 45 degree plus latitude of the observer also affects their visibility of it. So your so-called 'horizon' is way off, since you've placed it at midnight for someone on the equator with no axial tilt accounted for.

Gimme a little while, and I'll get the globe out and model it in 3D, since you're clearly not getting it at the moment.

[Tom Bishop]

If it's a top-down view of the Solar System then you have the 11pm Horizon way off.

Midnight Horizon:
IMG

That's not a horizon, it's a tangent line to the surface.

And, as was pointed out numerous times in the Morgile video comments, the time of year, and hence axial tilt, inclines the Earth toward Venus, and the 45 degree plus latitude of the observer also affects their visibility of it. So your so-called 'horizon' is way off, since you've placed it at midnight for someone on the equator with no axial tilt accounted for.

Gimme a little while, and I'll get the globe out and model it in 3D, since you're clearly not getting it at the moment.

You are the one who was drawing the observer at the equator, in your previous top-down view. What do you mean, I am not doing it right?

If you are asserting some vague "right" way to do it, then do it.

[Tumeni]

This indicates a generic Earth observer; not the photographer in the Morgile video specifically. Axial tilt is not taken into account, nor is that specific observer's latitude. It illustrates the general principle that observers on Earth can have a sightline to Venus, either before sunrise or after sunset, whilst they are up to 36 degrees beyond the terminator, even before consideration of axial tilt and observer location, and of time of sunset in relation to midnight.

 

[Tom Bishop]

That's basically the same image as the first ones you posted.

If this is a side-view of the Solar System and the top of the earth is the North Pole, where observer is at a high north latitude, the depiction is in error. The planets don't orbit the sun Up-Down/North-South. The planets orbit the sun in an area parallel to its ecliptic.

If it is a top-down view of the Solar System, you don't have the horizon at 11PM.

[Tumeni]

Again, I think it's clear that it's top-down.

How can you tell where 11pm is, without accounting for axial tilt and time of year? You do get longer days in summer, shorter in winter, don't you?

[Tumeni]

in-the-sky.org has an Orrery page, wherein you can input a date, and see the relative position of the planets in our solar system.

Morgile's video was published in late June, and he stated the photographer took the photo a few days prior. For the sake of discussion, let's presume that date to be 19 Jun 2018, and look at the Orrery for that date;



Venus is almost at maximum elongation, making almost a right-angle triangle with Earth and the Sun - max elongation occurs in a few days from now, mid-August. However, again, for the purposes of discussion, let's round the angle off to a right-angle triangle so we can do approximate trigonometry on it;

Earth to Sun 93m miles
Venus to Sun 67m miles

1. That gives angle between Earth/Sun and Earth/Venus lines/sides of almost 36 degrees, where a full right-angle triangle would yield the full 36.

2. Taking the line between Earth and Sun as a datum, the Earth's axial tilt, on 19 Jun, was 3 days short of the Summer solstice, so, in terms of this Orrery, was pointing at a point somewhere between the Sun and Venus.

3. The photographer's location was stated as Michigan. A bit imprecise, but for purpose of discussion, let's assume it to be Saginaw, at 45N.

4. Sunset in Saginaw that day was at 21.20. The photo was said to have been taken "after 11", and it shows the Moon and Venus almost on the horizon. I showed a link to in-the-sky.org in the text above, and the sky chart linked to (once you adjust the time slider to 23.05, 23.10 or so) shows both in positions which match the photo; on the horizon, Moon on left, Venus on right, in the western sky.

5. At a rotation rate of 15 degrees per hour, photographer in Michigan is (1h45m) (1.75*15 = ) approx 26 degrees beyond sunset, or the terminator line. Well within the 36 degrees calculated above, suggesting that he will have a clear sightline to Venus.

6. The Earth is leaning the Northern Hemisphere approx 23 degrees toward a point between the Sun and Venus, which will reduce this 26 degrees, making it easier for him to see Venus.

7. Stage 7 is to take a desktop globe and illustrate it. I think there's enough correlation between all of the above to prove the case for visibility, but ... image to follow.   

[Tumeni]

Here's the Orrery showing the triangle between Earth, Sun and Venus in black. The green line is the approx direction of the axial tilt, and the angle indicated in orange will be almost 36 degrees, given 93mill miles to the Sun, and a Venusian orbit of 67 million.

The grid line above Earth represents its position on the solstice, 3 days later. At that point, the axial tilt would be pointing directly at the Sun

[Tumeni]

What does your axial tilt picture look like in plan view, top-down? You've shown it from the side.

[Tom Bishop]

I accidentally deleted my comment. Here it is again:

The green line is the approx direction of the axial tilt

Axial Tilt is North-South, not East-West.



I will come back to your top-down question.

[Tumeni]

So in plan view, top-down, in what direction is the orange line pointing, a few days before the June solstice? You've shown a side view, what does the plan look like?



I don't think I've shown an East-West line.

[Tumeni]

I should have made that orange line green, to match the previous illustration. However, the orange line above represents an arc connecting the true vertical with the north end of the polar axis.

If you look down upon it, and extend a continuation of that arc, it will point past the Sun, a few days before the solstice. Alternatively, if you continue to tilt the polar axis until it is horizontal, that will get you the same result. In plan view (with it in green this time);

[Tom Bishop]

From latlong.net: "The latitude of Michigan, USA is 44.182205"

Here are the extreme positions of the axis tilt again, this time showing the 44th parallel:



Although the nights are shorter due to the different illuminated area of the earth on the most extreme positions, midnight is still on opposite sides of the earth from the sun, and 11pm is going to be hardly any different in either case.

As per whether the axis rotates, it is generally ridged in space. See https://en.wikipedia.org/wiki/Axial_precession

[markjo]

From latlong.net: "The latitude of Michigan, USA is 44.182205"

Here are the extreme positions of the axis tilt again, this time showing the 44th parallel:



Although the nights are shorter due to the different illuminated area of the earth on the most extreme positions, midnight is still on opposite sides of the earth from the sun, and 11pm is going to be hardly any different in either case.

Did you take Daylight Saving Time into account?  Don't forget that because of "springing ahead" one hour, "11 PM" is actually 10 PM solar time during June.