Comments and questions about the
APOD on the main view screen.
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Uli Bastian
Post
by Uli Bastian » Sun Aug 11, 2024 7:00 am
This animation is wrong. The Perseids must cross the ecliptic close to the Earth in a direction opposite to the motions of the planets. Their speed relative to Earth is about 60 km/s, but in the animation it would only be about 20 km/s. In other words, their orbit is retrograde, not prograde.
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johnnydeep
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Post
by johnnydeep » Sun Aug 11, 2024 1:08 pm
I've got nothing to say about astronomy or this APOD other than to remark how impressive doing this animation in a web page is to me. I suppose it's all done with JavaScript that the browser is running? My limited page analysis tools show this:
perseids animation.jpg
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"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}
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Chris Peterson
- Abominable Snowman
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Post
by Chris Peterson » Sun Aug 11, 2024 1:49 pm
Uli Bastian wrote: ↑Sun Aug 11, 2024 7:00 am
This animation is wrong. The Perseids must cross the ecliptic close to the Earth in a direction opposite to the motions of the planets. Their speed relative to Earth is about 60 km/s, but in the animation it would only be about 20 km/s. In other words, their orbit is retrograde, not prograde.
Their orbit
is retrograde. It's just a little hard to see since their orbital plane is nearly perpendicular to Earth's. Tilt the viewing angle and look closely.
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raschumacher
Post
by raschumacher » Sun Aug 11, 2024 3:54 pm
johnnydeep wrote: ↑Sun Aug 11, 2024 1:08 pm
I've got nothing to say about astronomy or this APOD other than to remark how impressive doing this animation in a web page is to me.
Agreed, it's brilliant. Now if only it included a date indicator...
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raschumacher
Post
by raschumacher » Sun Aug 11, 2024 3:55 pm
[And, dang. Them bots is gettin' smart.]
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johnnydeep
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Post
by johnnydeep » Sun Aug 11, 2024 5:39 pm
raschumacher wrote: ↑Sun Aug 11, 2024 3:55 pm
[And, dang. Them bots is gettin' smart.]
"Bots"? What bots? (I ain't no dang bot!)
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}
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Uli Bastian
Post
by Uli Bastian » Mon Aug 12, 2024 1:44 pm
Concerning the fact that the animated orbit INDEED is retrograde:
Thanks, I got the point. It is, indeed. Very nice. In order to avoid my misunderstanding with other people, it might be considered to change the start-up viewing perspective of the animation. If you make the start-up view perpendicular to the ecliptic (i.e. with the Earth orbit appearing as a near-perfect circle), the meteoroid cloud looks equally nice, and the retrograde orbit - as well as the velocity of the meteoroids wrt the Earth - become unambiguous.
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Chris Peterson
- Abominable Snowman
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Post
by Chris Peterson » Mon Aug 12, 2024 1:52 pm
Uli Bastian wrote: ↑Mon Aug 12, 2024 1:44 pm
Concerning the fact that the animated orbit INDEED is retrograde:
Thanks, I got the point. It is, indeed. Very nice. In order to avoid my misunderstanding with other people, it might be considered to change the start-up viewing perspective of the animation. If you make the start-up view perpendicular to the ecliptic (i.e. with the Earth orbit appearing as a near-perfect circle), the meteoroid cloud looks equally nice, and the retrograde orbit - as well as the velocity of the meteoroids wrt the Earth - become unambiguous.
Yes, the default viewing orientation creates the illusion that the orbital plane of the debris lies on the ecliptic. Another useful trick is to color the particles according to whether they are above or below the ecliptic.
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raschumacher
Post
by raschumacher » Mon Aug 12, 2024 3:27 pm
johnnydeep wrote: ↑Sun Aug 11, 2024 5:39 pm
"Bots"? What bots? (I ain't no dang bot!)
That's just what a bot *would* say! :_>
(I meant, of course, the bots which the "Submit" puzzles are designed to foil, and not your most hu-man admirable self.)
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johnnydeep
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Post
by johnnydeep » Mon Aug 12, 2024 3:35 pm
raschumacher wrote: ↑Mon Aug 12, 2024 3:27 pm
johnnydeep wrote: ↑Sun Aug 11, 2024 5:39 pm
"Bots"? What bots? (I ain't no dang bot!)
That's just what a bot *would* say! :_>
(I meant, of course, the bots which the "Submit" puzzles are designed to foil, and not your most hu-man admirable self.)
Hmm. "Submit puzzles"? You mean that you are presented with a puzzle to solve correctly when using the "Submit" button to submit a post here? If so, I never see that... perhaps because I've created an assount?
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"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}