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How much did Earth's gravity alter the course of 2005 YU55?

  1. Nov 11, 2011 #1
    Just like the title says - with the meteor passing close by the Earth, gravity should alter the meteor's course. So how much was it?

  2. jcsd
  3. Nov 11, 2011 #2


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    Last edited by a moderator: Apr 26, 2017
  4. Nov 11, 2011 #3
    That wasn't my question. As the meteor passed by Earth there was a varible force that acted on the meteor. This force would alter the trajectory of the meteor. Was it a degree, an arcminute, an arcsecond?
    Last edited by a moderator: Apr 26, 2017
  5. Nov 11, 2011 #4


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    Dave was giving you a way to calculate the sideways force on the object. Do you know how long the object was within the orbit of the moon? You could get a pretty good approximation for how much the trajectory was altered by applying the average gravitational attraction of the Earth on the object in a perpendicular direction for the duration of the time inside the Moon's orbit.
  6. Nov 12, 2011 #5


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    Earth boosted 2005YU55's semimajor axis by about 2 million km. It reduced its inclination from about a half a degree to about a third of a degree.

    In this image, the green orbit is 2005 YU55. The interior one is before, the exterior one is after.
  7. Nov 12, 2011 #6
    Thank you for answering my question. :-)
  8. Nov 12, 2011 #7
    Actually, the question is quite a bit misguided.

    The trajectory remain the same as it ever was - all gravitational perturbations included.

    Look at it as an object travelling in a perfectly straight line tnrough some very uneven surface (gravity wells of Earth, Sun, Moon...). The object still rolls/flies in a straght line... But the line is warped.
  9. Nov 12, 2011 #8
    To continue: Even if you fall back on the classical/Newtonian physics the question still doesn't make sense. "changed" compared to what? To what it would be in the Earth's absence? But... hold on a sec, in Earth's absence that asteroid wouldn't even arrive here in the first place - Earth's gravitational pull is part of the reason that asteroid got where it was anyway.
  10. Nov 12, 2011 #9
    Tony understood my question. Griz you are not adding anything to my question. I will expand to clear any confusion - what was the change in the orbital characteristics of 2005 YU55 when it recently passed by Earth.

    This gif makes a lot more sense when comparing it to
    Tony's pic
    [PLAIN]http://upload.wikimedia.org/wikipedia/en/c/c5/2005_YU55_approach_8-9_November_2011.gif [Broken]
    Last edited by a moderator: May 5, 2017
  11. Nov 12, 2011 #10
    Well, perhaps I misunderstood your question. (I'm actually inclined to think so).

    But the basic fact remains that the question "how much did the Earth gravity changed the course of that asteroid" is pretty much meaningless. It didn't. In any shape, size or form UNLESS you mean how it shaped the course from the start, to begin with. But then... the question about "change" is once again a bit odd.
  12. Nov 12, 2011 #11
    Change - like before and after. Tell me that you don't see it with the following image.

    The meteor was "sling-shot" when passing by Earth. Space probes use Jupiter to "sling-shot" to add speed and change direction.
    Last edited: Nov 12, 2011
  13. Nov 12, 2011 #12
    What -I- don't see is how this pretty picture indicates a changed orbit.

    What -you- don't see is the fact that orbits are never the same perfect ellipses. Doesn't happen.

    So, what your picture shows is just a normsl, pretty ordinary orbit.

    Perhaps you should make distinction between the words course/trajectory/orbit?
  14. Nov 12, 2011 #13
    Griz maybe you missed this post. The inside green circle represents the orbital characteristics of the meteor before it was "sling-shot" by Earth. The outer green circle represents the new orbital characteristics of the meteor. The Earth change the direction and the speed of the meteor via gravitational attraction.

    It seems you are going out of your way NOT to understand what I am asking/saying.
  15. Nov 12, 2011 #14


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    Grizzled, I'm sure your technically correct, but I think you're simply confusing some people. Suffice it to say I think the OP's question was answered by the picture.
  16. Nov 16, 2011 #15

    I can't help it if some people are so easily confused. Perhaps they should study a bit?

    I also can't help it if all they want are some pretty pictures which they (for some mysterious reason) insist on posting over and over again.

    At least you agree that I am "technically" correct.

  17. Nov 16, 2011 #16


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    Why do you think they are here at PF if not to study and learn? EVERYONE is easily confused when they know very little about something. Just because you know more about the subject does not give you a reason to be rude. Instead it might help if you explained what the different terms mean for this particular scenario.

    There is nothing wrong with pictures and diagrams. They help people to visualize a concept, which is very important for most people when attempting to learn something new.
    Last edited: Nov 16, 2011
  18. Nov 16, 2011 #17


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    You can. You can address the question asked.

    If pretty pictures answer the question asked then pretty pictures are the thing.

    I am "technically" correct when I mention that Mercury precesses. The issue, of course, is whether that answers the question being asked.

    The OP's is a legitimate question. He wants to know how much YU 55 was deflected by Earth's passage. consider: if you were stationary wrt the asteroid and looked in the direction of its travel, you'd see a point it's heading toward. If Earth had not crossed its path that point would move steadily as the asteroid proceeded in its orbit. After Earth fly-by the point would be completely different.

    Does that make it clearer to you what the OP is asking?
    Last edited: Nov 16, 2011
  19. Nov 16, 2011 #18
    First I never said orbit. I used the words course and trajectory.

    course n. - The route or path taken by something, such as a stream, that moves.

    trajectory n. - The path of a projectile or other moving body through space.

    I used orbital characteristics to clear any confusion that you had.

    orbital characteristics n. - a table of values that gives the positions of astronomical objects in the sky at a given time (see ephemeris).

    synonym n. -
    1. A word having the same or nearly the same meaning as another word or other words in a language.
    2. A word or an expression that serves as a figurative or symbolic substitute for another.

    Griz if you can't see how course/trajectory relates to my question, you are thick. Everyone else seems to understand me.

    I never said that orbits are consistent perfect ellipses.

    Now you are acting arrogant and being sarcastic (humor for the small mind). Please quit posting, you are removing value from this topic.
  20. Nov 16, 2011 #19


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    Or to put it another way...

    Fine. How much did Earth warp the straight line? :rolleyes:
  21. Nov 17, 2011 #20
    Perhaps I'm reading too much into the (nicely done) diagram showing the before-and-after orbits of 2005 YU55, but: does it look like the shifted orbit will now make a collision with Mars more likely?
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