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    maxsc's Avatar
    maxsc Posts: 23, Reputation: 1
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    #1

    Jun 9, 2017, 02:09 AM
    help figuring out planet x's orbit
    if the years on planet x are 1000 days.
    and each 1 day on planet x is equal to 3 earth days.
    and if HALF of the year the whole planet is in NIGHT.
    and the other half of the year is DAY.

    and if there are 2 moons one bigger than the other.

    how long would the orbit be?
    how long would a month be?

    I'm open for any suggestions if any part of the question needs to be changed.
    Curlyben's Avatar
    Curlyben Posts: 18,469, Reputation: 1857
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    #2

    Jun 9, 2017, 02:16 AM
    All the information you need is in the question.
    How do we define a year and a month ?
    maxsc's Avatar
    maxsc Posts: 23, Reputation: 1
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    #3

    Jun 9, 2017, 02:41 AM
    Each orbit of the moon around its planet is 1 month which for the earth is almost 30 days.

    And then the orbit of the planet around its star would make up the year.

    Unfortunately, I still don't see the answer!

    Because there are supposed to be 2 moons, and one is bigger.
    And then the whole planet has 500 continuous nights and then 500 continuous days.

    And while we are on the subject:
    Is it possible for there to be a kind of solar event and ONCE in a while somewhere around the 500 continuous nights there could be sunrise for a while ? Just like eclipses on earth.

    These things make it too hard for me and my math is horrible too
    ebaines's Avatar
    ebaines Posts: 12,130, Reputation: 1307
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    #4

    Jun 9, 2017, 05:50 AM
    Let's call the Planet X - if a single orbit is 1000 Days on Planet X, and one day on X is equal to 3 Earth days, you can easily determine the length of an X year measured in Earth days. The fact that at any point in time half the planet is experiencing nighttime and half experiencing daylight is true of any planet (such as the Earth) so is not relevant to the questions being asked. Every point on Planet X experiences a total amount of night for 1000/2 = 500 X days, and daylight also for 500 X days, but the 500 X days of daylight or nighttime are not continuous. We have a similar situation on Earth - every point on Earth experiences 365/2 = 182.5 days of nighttime and 182.5 days of daylight, but it's not continuous (except at the north and south poles).

    As for the question about the moons, you don't have enough information. How is a month defined for a planet with multiple moons? Plus you have no information on the length of time of orbits for either moon, so you can't answer the second question.

    As for your other question - yes, there are points on Earth that may experience a very brief amount of daylight at certain times of the year. For example if you travel near the north pole in winter the sun may be up for only a very brief period of time - say, 1 hour out of 24. But in summer the opposite occurs - the sun would be up for 23 hours and set for only 1 hour. This is due to the Earth's tilt with respect to its orbital plane. It has nothing at all to do with eclipses.
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    maxsc Posts: 23, Reputation: 1
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    #5

    Jun 9, 2017, 08:48 AM
    Thanks for the information.
    The reason I don't have enough information is that this is a fictional story and I'm trying to figure it out myself, that's why I said I'm open to suggestions.

    But 1 day on Venus is equal to 243 earth days.
    Doesn't that mean 243 continuous daylight ?
    And on the other side of the planet, the opposite.

    But I want one of the moon's orbit to be in a state that it blocks the star for 500 days straight, is that actually possible?
    If it is possible, the problem won't be night but day.
    It would mean 500 constant nights in every year, PLUS the 500 other days will be also night due to the rotation...

    And in such conditions
    I'm not sure vibrant life would be possible or not
    ebaines's Avatar
    ebaines Posts: 12,130, Reputation: 1307
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    #6

    Jun 9, 2017, 09:22 AM
    Quote Originally Posted by maxsc
    But 1 day on Venus is equal to 243 earth days.
    Doesn't that mean 243 continuous daylight ?
    No - it means that there are 243/2 - 121.5 days of continuous daylight and then 121.5 days of continuous darkness. Remember that a stellar "day" consists of a complete rotation of the planet relative to its sun.

    Quote Originally Posted by maxsc
    But I want one of the moon's orbit to be in a state that it blocks the star for 500 days straight, is that actually possible?
    I don't think it possible under any reasonable conditions. However, the physics of orbital mechanics dictates that there is a point part way between the planet and its sun called Lagrange 1, where a body can be orbit about the sun with the same orbital period as the planet. Thus it would produce a perpetual eclipse to some area of the planet. Maybe you can factor that into your story?

    Another option is if the planet is tidally locked to its star the same face of the planet would always face the sun - much as our own moon is tidally locked to the Earth. So half the planet would be in perpetual daylight and the other half in perpetual darkness. To be tidally locked like that the planet has to be pretty close to the sun, so the daylight side is likely way too hot for life, and the night side would be way too cold for life. But at the boundary between the two - where the sun is right at the horizon - perhaps the temperature would be just right for life.
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    maxsc Posts: 23, Reputation: 1
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    #7

    Jun 9, 2017, 11:14 AM
    Wow you're very good, kudos
    I'm stillI'monfused about the Venus day though, see when I search on the web "how long is a day on planets" this is what I get:
    Name:  12.PNG
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    1: so can I use the same rotation as Venus for continuous days and nights?
    2: the lagrange1 idea seems good to me but the thing you mentioned about being tidally locked seems very good too, can a planet be tidally locked with its moon? If the moon was as big as possible... or if there were 2 or 3 moons?

    I'm asking that because I want a good temperature and I want there to be both liquid and frozen water and greenery as well as desert!
    ebaines's Avatar
    ebaines Posts: 12,130, Reputation: 1307
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    #8

    Jun 9, 2017, 12:07 PM
    The rotaton period in the table is the length of a sidereal day, which is the length of time it takes for the planet to rotate 360 degrees. But during the course of the sidereal day the planet has moved a bit in its orbit, meaning that typically in order for the sun to appear at the same point in the sky as seen by an observer on the planet the planet has to rotate more than 360 degrees. So the length of a stellar day (which on Earth is 24 hours) is longer than the length of the sidereal day (23 hours and 56 minutes on Earth). That's why the chart shows the rotation period of the Earth as 99% of an Earth day. Clear as mud?

    Venus presents a strange case, because its rotation is retrograde. The result is that the sun rises in the west and sets in the east, and while it takes 243 days to rotate 360 degrees the length of its stellar day is much shorter than that - it's actually about 116 days.

    Given that this is fiction story you can make up whatever numbers you want for both length of year and length of day. If the planet rotates very slowly (i.e. close to, but not quite, tidally locked) you could have very long days and nights.

    Yes, a planet and its moon can be tidally locked. You may be aware that the rate of rotatioj of the Earth is which leads to "leap seconds" which you may have heard have to be inserted into clocks every few years. It has been predicted that in a few billion years the Earth's rotation will slow to the point where we are tidally locked with the moon, so at that point the moon will appear to not move in the sky. If the planet has multiple moons it's possible to become tidally locked with the one that is largest and closest, but I think only if it is significantly larger or closer than the other moon(s).
    maxsc's Avatar
    maxsc Posts: 23, Reputation: 1
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    #9

    Jun 10, 2017, 12:27 PM
    Thank you for explaining so vividly.

    So Venus moves quite a bit on the orbit BEFORE the sun can be seen at the same spot because venus's orbit is so big it would make a huge difference, correct?

    About the lagrange1, I did some research and there are mixed responses...
    Some say L1 CAN be occupied with a stable orbit by one of the moons.
    And some say no only l4 and l5 are stable...
    What is your idea on this?

    Can one of the moons (either one of them, everything can be modified) stay in l1 and block the light of the star (star could also be modified) for half of the year?
    ebaines's Avatar
    ebaines Posts: 12,130, Reputation: 1307
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    #10

    Jun 11, 2017, 09:10 AM
    It's not the Venus's orbit is "so big" - it's smaller than the Earth's and all other planetsexcept Mars. As we've been discussing, the long length of day os due to its slow rotation.

    I have to agree that L1 is not a stable point. When I mentioned it earlier I wa working from memory - sorry for any confusion on that.
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    maxsc Posts: 23, Reputation: 1
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    #11

    Jun 11, 2017, 09:15 AM
    Oh right. I don't know how did I think Venus had a big orbit... sorry.
    I get it now it makes more sense than having a longer orbit.

    Its OK it gave me something to think about. I had no idea about Lagrange at all.

    I will be asking a NEW question in this topic.

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