Author Topic: Venus astronomy question  (Read 6665 times)

Offline Bryanpoprobson

  • Jupiter
  • ***
  • Posts: 825
  • Another Clown
Venus astronomy question
« on: June 09, 2023, 04:33:57 AM »
In answering a silly flat Earth believer regarding the amount of time that Venus is above the horizon. He said that Venus in 2015 was viewable for 24hours. Now I dismissed that, but on reflection is it possible for Venus to be visible all night when viewed from an extreme northerly or southern latitude, when the sun stays just below the horizon just before or just after the equinoxes? Logic says that it is possible for Venus to hover above the horizon for 24 hours, but the angle to the plane of the ecliptic must be nearly 90degs. But is it a fact, if it is, it would be rare. The internet seems to be split but my logic says it is technically possible.. Thoughts…
"Wise men speak because they have something to say!" "Fools speak, because they have to say something!" (Plato)

Offline Allan F

  • Saturn
  • ****
  • Posts: 1010
Re: Venus astronomy question
« Reply #1 on: June 09, 2023, 12:56:46 PM »
Have you considered Stellarium or some other skyviewing software? I don't have an answer, sorry.
Well, it is like this: The truth doesn't need insults. Insults are the refuge of a darkened mind, a mind that refuses to open and see. Foul language can't outcompete knowledge. And knowledge is the result of education. Education is the result of the wish to know more, not less.

Offline smartcooky

  • Uranus
  • ****
  • Posts: 1962
Re: Venus astronomy question
« Reply #2 on: June 09, 2023, 06:21:53 PM »
In answering a silly flat Earth believer regarding the amount of time that Venus is above the horizon. He said that Venus in 2015 was viewable for 24hours. Now I dismissed that, but on reflection is it possible for Venus to be visible all night when viewed from an extreme northerly or southern latitude, when the sun stays just below the horizon just before or just after the equinoxes? Logic says that it is possible for Venus to hover above the horizon for 24 hours, but the angle to the plane of the ecliptic must be nearly 90degs. But is it a fact, if it is, it would be rare. The internet seems to be split but my logic says it is technically possible.. Thoughts…

Venus is above the horizon for about the same time as any planet or star... from the time it rises until the time it sets. I think where your flerfer is confused is that Venus one of the few sky objects visible during the daytime if you know where to look - I have observed Venus at near midday on a number of occasions. The star Sirius (Alpha Canis Majoris) is another one that it visible during daylight. However, like Mercury, Venus is inside our orbit, so it never gets more west or east of the sun than the number of degree that equals its maximum elongation. For Venus that's 47° and for Mercury its 18°, i.e.you can only eve see Venus a maximum of  47° "left" or "right" of the Sun - you can see Venus "all day" but not for 24 hours and never more than about three hours after sunset, or three hours before sunrise.   
« Last Edit: June 09, 2023, 06:45:25 PM by smartcooky »
If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.

Offline Bryanpoprobson

  • Jupiter
  • ***
  • Posts: 825
  • Another Clown
Re: Venus astronomy question
« Reply #3 on: June 10, 2023, 01:23:48 AM »



Venus is above the horizon for about the same time as any planet or star... from the time it rises until the time it sets. I think where your flerfer is confused is that Venus one of the few sky objects visible during the daytime if you know where to look - I have observed Venus at near midday on a number of occasions. The star Sirius (Alpha Canis Majoris) is another one that it visible during daylight. However, like Mercury, Venus is inside our orbit, so it never gets more west or east of the sun than the number of degree that equals its maximum elongation. For Venus that's 47° and for Mercury its 18°, i.e.you can only eve see Venus a maximum of  47° "left" or "right" of the Sun - you can see Venus "all day" but not for 24 hours and never more than about three hours after sunset, or three hours before sunrise.

Which is basically the answer I gave to the the flat Earther, but his question related to Venus being visible many hours after sunset. Now it is possible for Venus to be viewed as much as 4 hours after sunset. However the Sun can hover just below the horizon at certain times of year in the north or south. Is it possible therefore for Venus to be seen as a nighttime object for 24 hours, as claimed by this flat Earther?
"Wise men speak because they have something to say!" "Fools speak, because they have to say something!" (Plato)

Offline smartcooky

  • Uranus
  • ****
  • Posts: 1962
Re: Venus astronomy question
« Reply #4 on: June 10, 2023, 08:57:09 AM »



Venus is above the horizon for about the same time as any planet or star... from the time it rises until the time it sets. I think where your flerfer is confused is that Venus one of the few sky objects visible during the daytime if you know where to look - I have observed Venus at near midday on a number of occasions. The star Sirius (Alpha Canis Majoris) is another one that it visible during daylight. However, like Mercury, Venus is inside our orbit, so it never gets more west or east of the sun than the number of degree that equals its maximum elongation. For Venus that's 47° and for Mercury its 18°, i.e.you can only eve see Venus a maximum of  47° "left" or "right" of the Sun - you can see Venus "all day" but not for 24 hours and never more than about three hours after sunset, or three hours before sunrise.

Which is basically the answer I gave to the the flat Earther, but his question related to Venus being visible many hours after sunset. Now it is possible for Venus to be viewed as much as 4 hours after sunset. However the Sun can hover just below the horizon at certain times of year in the north or south. Is it possible therefore for Venus to be seen as a nighttime object for 24 hours, as claimed by this flat Earther?

Well, of course, since Venus is visible during the daytime, if you are standing at one of the poles (the north during Arctic Summer or south during Antarctic summer) then the sun is above the horizon all day every day for a few months. Venus could be visible in the sky if you knew where to look so long as it was far enough away from the sun to escape the glare. Venus has an orbital period of about 225 days, so it would depend on where it is in its orbit during the time of your polar summer. If it was reaching maximum elongation (either east or west) then it should be visible.

However, to see it against a darker sky would be much more difficult. I would have to look up an ephemeris and some orbital data for Venus to be sure, but my best guess is that it is theoretically possible if all the circumstances line up correctly.

1. You would have to be at the pole, observing just before the beginning of summer, or just after the end of summer, when the sun is just below the horizon and there is a long twilight that lasts several weeks.

2. The inclination of Venus' orbit to the plane of the Ecliptic is about 3½°. What that means is that the plane of Venus's orbit differs from the plane of the Earths orbit by 3½° so at its maximum elongation, Venus  can appear as much as about seven solar diameters "above" the elevation of the sun (one solar diameter is approx ½°, so 3½° / ½° = 7) .

3. IF Venus was near its maximum elongation, AND that maximum elongation also coincided with a point where it was sufficiently separated from the plane of the earth's orbit, then it might be possible for Venus to appear above the horizon in the twilight sky.   

These are a couple of rough illustrations to show what I mean by near maximum elongation with maximum or minimum separation from the ecliptic.






Now, have a look at this fantastic photo. This is the December 4, 2021 total solar eclipse taken from Union Glacier Camp, Antarctica, with Venus over on the right.


You can see that Venus is at almost the same elevation at the sun, so this means that at that time, the plane of Venus' orbit was such that it tilted either toward or away from us, giving little separation between the position of Venus and the ecliptic.   


If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.

Offline molesworth

  • Mars
  • ***
  • Posts: 349
  • the curse of st custards
Re: Venus astronomy question
« Reply #5 on: June 10, 2023, 09:39:18 AM »
In answering a silly flat Earth believer regarding the amount of time that Venus is above the horizon. He said that Venus in 2015 was viewable for 24hours. ...

I would ask him for dates and locations, rather than just vague claims. In my experience of dealing with flat-earthers, they often repeat things like this that they've heard (or mis-heard) elsewhere, but never have the actual data to back it up.

As smartcooky noted, I think it would likely have to be at one of the poles, or at least quite a high latitude, and in very special circumstances. But it could be possible.
Days spent at sea are not deducted from one's allotted span - Phoenician proverb

Offline Bryanpoprobson

  • Jupiter
  • ***
  • Posts: 825
  • Another Clown
Re: Venus astronomy question
« Reply #6 on: June 10, 2023, 10:02:39 AM »
In answering a silly flat Earth believer regarding the amount of time that Venus is above the horizon. He said that Venus in 2015 was viewable for 24hours. ...

I would ask him for dates and locations, rather than just vague claims. In my experience of dealing with flat-earthers, they often repeat things like this that they've heard (or mis-heard) elsewhere, but never have the actual data to back it up.

As smartcooky noted, I think it would likely have to be at one of the poles, or at least quite a high latitude, and in very special circumstances. But it could be possible.

Which is exactly why my logic said, it would be possible, depending on the angle of Venus and it’s height above the Polar horizon.
"Wise men speak because they have something to say!" "Fools speak, because they have to say something!" (Plato)

Offline smartcooky

  • Uranus
  • ****
  • Posts: 1962
Re: Venus astronomy question
« Reply #7 on: June 11, 2023, 03:08:27 AM »
In answering a silly flat Earth believer regarding the amount of time that Venus is above the horizon. He said that Venus in 2015 was viewable for 24hours. ...

I would ask him for dates and locations, rather than just vague claims. In my experience of dealing with flat-earthers, they often repeat things like this that they've heard (or mis-heard) elsewhere, but never have the actual data to back it up.

As smartcooky noted, I think it would likely have to be at one of the poles, or at least quite a high latitude, and in very special circumstances. But it could be possible.

Which is exactly why my logic said, it would be possible, depending on the angle of Venus and it’s height above the Polar horizon.

Of course, this is a flerfer you are talking to, so they don't believe two "poles" exist - they believe the north pole is at the centre of their flat earth, and Antarctica is not a pole, its spread around the rim of their flat earth and surrounded by an ice wall to stop stuff falling of. In their world, the Venus thing could only happen at the north pole... or something..  ::)

 
If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.