Retrograde motion

[9-10ths_Penguin]

This is the continuation of a discussion from DIR, moved out here so that we're a bit more free to talk.

Originally Posted by .lava

i don't know how i missed other animations, sorry. do you know how often it happens? i red earth is getting closer to Mars. however it was old stuff. are these two some how related? why earth gets closer is not an illusion though. they say it happens because different velocities and elliptic orbit. if you know anything about it, i would like to hear

That happened in 2003. Here's one site that talks about it.

Basically, the Earth's orbit is very close to eliptical; so is Mars' orbit. The distance from the Sun to Earth or the Sun to Mars changes. When a planet is as the closest point to the Sun in its orbit, we call this point the perihelion. A planet will go through perihelion once an orbit.

The planets orbit at different speeds. Earth goes around the Sun once per Earth year, and Mars goes around once every 1.88 Earth years. This means that the distance between them is constantly changing. When that distance is a local minimum (i.e. the instant the two planets change from getting closer to getting farther away), we call this an opposition. Oppositions don't happen at a regular frequency, and the distance between the two planets at opposition will be different every time.

In 2003, two things happened at the same time: Mars' perihelion and the Earth-Mars opposition. This meant that Mars was as close as it gets to the Sun (and therefore to the orbital path of the Earth as well) right at the same time that the Earth was in that closest point in its orbital path. Because of the relative lengths of time for the orbits of Earth and Mars, this won't happen again for another 50,000 years.

That specific event doesn't have a lot to do with retrograde motion itself, but oppositions do.

Think of it this way: retrograde motion happens after the Earth "overtakes" another planet. Because of the shapes of the orbits of the planets, this "overtaking" is the point where the planets are closest together.

Originally Posted by maro

who said the sun will be retrograde motion like mars ??? ,i meant Earth Penguin , i thought it was clear enough...

You meant Earth? That makes no sense. Retrograde motion is when a celestial object move "backward" relative to its normal path in the sky to an observer on Earth. The Earth does not move relative to an observer on Earth - the observer is standing on it.

When you linked the apparent retrograde motion of Mars with a Quranic verse describing the Sun rising in the West, it certainly seemed to me that you were implying that the Sun would be subject to retrograde motion like the planets.

Okay... what did you actually mean, then?

[gnomon]

Arise O! thread of the heavens.

[maro]

You meant Earth? That makes no sense. Retrograde motion is when a celestial object move "backward" relative to its normal path in the sky to an observer on Earth. The Earth does not move relative to an observer on Earth - the observer is standing on it.

When you linked the apparent retrograde motion of Mars with a Quranic verse describing the Sun rising in the West, it certainly seemed to me that you were implying that the Sun would be subject to retrograde motion like the planets.

Okay... what did you actually mean, then?

first that was not a quranic verse....it was a hadith

My fault ,i am the one who rushed into the assumption that the retrograde motion of the planets is an actual motion , not an apparent one that can only be observed from another Spot.....i also didn't take the time to diferentiate between revolving around the sun and its Rotation around its axis which creates day and night....Apparently the retrograde motion is about revolving around the sun.....

What did i actually meant ?.. i meant that that the EArth will Actually reverse its direction of Rotation around its axis...... , which means that i made two mistakes at a time....

Thank you for taking the time to explain that to me... ,i am glad i've learned three things today....First , about the retrograde motion ....I've learned to say I WAS WRONG ,I APOLOGIZE......and most important i've learned that quranic verse , by experience not by Recitation....

[16:43] if ye realise this not, ask of those who possess the Message

[Panda]

Originally Posted by maro

What did i actually meant ?.. i meant that that the EArth will Actually reverse its direction of Rotation around its axis...... , which means that i made two mistakes at a time....

Um well that would not be fun at all. If the planet suddenly changed direction on its axis or slowed down to quickly the atmosphere would go faster than the earth and it would rip everything off the planet crust killing everyone and everything.

[9-10ths_Penguin]

Originally Posted by maro

first that was not a quranic verse....it was a hadith

Whoops. I missed that.

Originally Posted by maro

My fault ,i am the one who rushed into the assumption that the retrograde motion of the planets is an actual motion , not an apparent one that can only be observed from another Spot.....i also didn't take the time to diferentiate between revolving around the sun and its Rotation around its axis which creates day and night....Apparently the retrograde motion is about revolving around the sun.....

No worries. It gave us the opportunity to have fun with astronomy!

Originally Posted by maro

What did i actually meant ?.. i meant that that the EArth will Actually reverse its direction of Rotation around its axis...... , which means that i made two mistakes at a time....

Okay. I suppose that you're free to believe that God would reverse the movement of the Earth by His divine hand or by some means that we don't know, but retrograde motion doesn't enter into this.

Originally Posted by maro

Thank you for taking the time to explain that to me... ,i am glad i've learned three things today....First , about the retrograde motion ....I've learned to say I WAS WRONG ,I APOLOGIZE......and most important i've learned that quranic verse , by experience not by Recitation....

[16:43] if ye realise this not, ask of those who possess the Message

Don't worry about it. Learning is fun!

Originally Posted by Panda

Um well that would not be fun at all. If the planet suddenly changed direction on its axis or slowed down to quickly the atmosphere would go faster than the earth and it would rip everything off the planet crust killing everyone and everything.

If we learned anything from the movie Superman, it's that changing the direction that the Earth spins would make time go backwards... somehow...

[.lava]

Originally Posted by 9-10ths_Penguin

This is the continuation of a discussion from DIR, moved out here so that we're a bit more free to talk.


That happened in 2003. Here's one site that talks about it.

Basically, the Earth's orbit is very close to eliptical; so is Mars' orbit. The distance from the Sun to Earth or the Sun to Mars changes. When a planet is as the closest point to the Sun in its orbit, we call this point the perihelion. A planet will go through perihelion once an orbit.

The planets orbit at different speeds. Earth goes around the Sun once per Earth year, and Mars goes around once every 1.88 Earth years. This means that the distance between them is constantly changing. When that distance is a local minimum (i.e. the instant the two planets change from getting closer to getting farther away), we call this an opposition. Oppositions don't happen at a regular frequency, and the distance between the two planets at opposition will be different every time.

In 2003, two things happened at the same time: Mars' perihelion and the Earth-Mars opposition. This meant that Mars was as close as it gets to the Sun (and therefore to the orbital path of the Earth as well) right at the same time that the Earth was in that closest point in its orbital path. Because of the relative lengths of time for the orbits of Earth and Mars, this won't happen again for another 50,000 years.

yep, that's the particular incident i was referring to. thank you so much. very exciting really, thank you very much



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[9-10ths_Penguin]

Originally Posted by .lava

yep, that's the particular incident i was referring to. thank you so much. very exciting really, thank you very much

You're welcome.

I thought it was exciting too but kind of bittersweet as well, because I remember people saying that around this time would have been one of the best chances we'd ever have to send a spacecraft to Mars for thousands of years. If the race to space hadn't basically stalled after Apollo, and if the space program had become what they had originally designed the Space Shuttle to be a part of (i.e. be a literal shuttle between Earth and Earth-orbit space stations that would be used as jumping-off points for missions deeper in space), we could have used it. As it happens, we didn't... not for a manned mission, anyhow.

[.lava]

Originally Posted by 9-10ths_Penguin

You're welcome.

I thought it was exciting too but kind of bittersweet as well, because I remember people saying that around this time would have been one of the best chances we'd ever have to send a spacecraft to Mars for thousands of years. If the race to space hadn't basically stalled after Apollo, and if the space program had become what they had originally designed the Space Shuttle to be a part of (i.e. be a literal shuttle between Earth and Earth-orbit space stations that would be used as jumping-off points for missions deeper in space), we could have used it. As it happens, we didn't... not for a manned mission, anyhow.

they will eventually find a way to travel deeper space. i had a chance to listen to a Turkish scientist. he has faith btw he claims miracles are not against physical laws. we just do not know dynamics and formulas behind it so it appears as if it's breaking the physical law. i agree with him. some high level person says there are four elements. each could be used to travel. only three of them is found by people. so we travel on ground, sea and in the air. there is only one of them remains unknown. fire. i don't mean to sound like fairy tail to you but i believe sooner or later, people would travel in space and even have home in other planets. i wish i was around when teleporting was old fashion.



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