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Gravity and Orbit

  1. Feb 22, 2014 #1
    Keeping in mind I am a person that did not go to school.......This must be a common question. Can be maddening for you guys to keep reading it over and over. Would be happy to read any links you want to post.
    I did a search on Gravity and Orbit, and did not see this topic. But those words garner a lot of results...I may have missed it, or possibly just not understood.

    Anyway.....I understand that solar system gravity can be hard to explain without some math (which I would not comprehend), but I am hip to the involvement of time, space, space-time, 4th dimension, etc.

    But why (at least from what I see on Youtube) do planets Orbit a sun in what seems to be a Similar/Equatorial manner.?
    That is to say, it seems like the pictorials always show the planets orbiting a Star in the same way...around the chubby part of the Star, in between the North and South pole (for lack of better terms).?

    Is Gravity more present/stronger around the "middle" of a Star.? I thought Gravity was the same at all points...3 dimensional. What prohibits Earth from orbiting The Sun over its "poles", while another planet orbits The Sun around its "equator".?
    What coerced the planets into orbiting The Sun in the same way/direction.?
    Thank You
  2. jcsd
  3. Feb 22, 2014 #2


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    Gravity is the same no matter where you are around the Sun as long as your distance from the Sun is the same. The reason that the planets all orbit in nearly the same plane is a consequence of the way the solar system was formed. A little over 4.5 billion years ago the solar system didn't exist. Instead, a large cloud of gas and dust existed. It was this cloud that collapsed under its own gravity that formed the solar system. During the collapse, angular momentum had to be conserved, which means that the dust and gas formed into a spinning disk-like object with a very massive core. Eventually the gas in the center of the disk collapsed to a point where it ignited, forming the Sun, while the outer areas of the disk collapsed to form smaller objects, the planets. So everything in the solar system rotates around the same center point because they were doing so during their formation.
  4. Feb 22, 2014 #3
    Yeah...that makes sense.
    My questions always sound so baffling (to me) when I ask them, but the answers always seem so obvious when you guys post them. :redface:
    Thanks Again
  5. Feb 25, 2014 #4
    Don't mean to side-track your thread, but I had a question about orbits too, and orbital mechanics just make my head spin. So, I was wondering about a spacecraft to watch the Moon for impact flashes say, and where the best position for that spacecraft would be to observe the Moon more or less continuously? Would it be from an Earth orbit, or a high Lunar orbit, or somewhere inbetween maybe?
  6. Feb 25, 2014 #5
    Go for it...my question was, probably, pretty rudimentary :smile:.....best
  7. Feb 25, 2014 #6


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    I'd say that depends entirely on what resolution you need, what constaints you have for spacecraft size and weight, and a thousand other variables.
  8. Feb 26, 2014 #7


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    Are you familiar with Lagrange Points? My suggestion would be the Moon's L2. That way, your satellite is nearly stationary over the far side of the Moon (we can watch the near side with telescopes).
  9. Feb 26, 2014 #8
    My query was prompted when I read about the new Lunar impact crater, and how these events are detected from Earth, but I wondered why not from space instead? For detecting flashes, then from space a broader spectrum could be detected as there is no atmospheric absorption, providing more info about the nature of the event.
    I'd imagine a very low light video camera with UV sensitivity might suffice, but I wasn't really looking into the design or technical details of a mission, but rather just the orbital mechanics to determine if impact monitoring would be much more effective from space, and if so, where would be the best location for it.

    If the idea was to observe lunar impact flashes then it would be best to be observing the unlit side of the Moon permanently, if possible. Maybe it would be easier to have more than one unit, I was just reading about the CubeSats, small and inexpensive, and simple if their only purpose is impact flash detection. If we are going to consider moon colonies or obervatories, we should probably know as much as possible about how many, how often, where and what size of impacts are occuring, and Earth based observations seem rather limiting.
  10. Feb 26, 2014 #9


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    But you do realise that the "unlit side" ( the side we don't see) isn't permanently unlit ?
    At New Moon its directly facing the Sun, just as at Full Moon, the side we see is fully facing the Sun

  11. Feb 26, 2014 #10


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    Don't beat yourself up: it was a pretty insightful question. It shows you put some real, useful thought into the issue.
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