Why vs. How?

Discussion in 'Physics & Math' started by Carcano, Jun 1, 2008.

  1. kurros Registered Senior Member

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    It's kind of funny that this is how people explain that the sky is blue. Because really, if you think about it, we can make it simpler by just saying "The sky is blue because the air is blue". Everything looks a certain colour because that is the colour of the light that scatters off it, so really it is much easier to explain to people that the sky gets its colour in a similiar way to everything else. Lay-people get confused when you start talking about Rayleigh scattering.
     
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  3. James R Just this guy, you know? Staff Member

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    The air in the room I'm in isn't noticeably blue. It appears colourless to me.
     
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  5. Pete It's not rocket surgery Moderator

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    Does that mean that there's no Rayleigh scattering from the air in your room?
     
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  7. DRZion Theoretical Experimentalist Valued Senior Member

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    Thanks for the info! :worship:
     
  8. CptBork Robbing the Shalebridge Cradle Valued Senior Member

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    And apparently, radiation leakage alone is able to account for about 66% of that anomaly, if not possibly more. There are lots of potential causes for the effect, because it truly is a subtle and weak. It's not on NASA's priority list, but it would be nice to send a probe out to check for this anomaly and see how much of it is due to flaws in the spacecraft itself.
     
  9. DRZion Theoretical Experimentalist Valued Senior Member

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    I suggest a new cosmic braking principle. In a real universe all matter tends to rest imo.
     
    Last edited: Aug 28, 2009
  10. James R Just this guy, you know? Staff Member

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    Are you saying you need lots of blue air in order for you to notice the blueness?
     
  11. CptBork Robbing the Shalebridge Cradle Valued Senior Member

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    The Pioneer anomaly is so small, no one is expecting it to come to a halt or to even be substantially slowed. Whether due to long distance modifications of General Relativity or due to simple radiation leakages, the effect is almost negligible and won't be expected to continue forever. Pioneer's still going fast as sh*t, just a tiny tiny fraction of a percent slower than it should be. In any case, to say "all matter tends to rest", you'd need an absolute rest frame to refer to. As far as physics is concerned, the laws of physics are the same in all inertial reference frames, so there's no preferential frame in which things prefer to come to a halt. Even the cosmic microwave background frame obeys the same laws of physics as every other frame.
     
  12. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Based on one observation? A sample size of one? And you want to redefine all of physics?
     
  13. scifes heckle the snobs Valued Senior Member

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    heh, if the world didn't suck, we would all fall off.

    ask a stupid question

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  14. DRZion Theoretical Experimentalist Valued Senior Member

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    Assuming that the effect will continue just as it is now, wouldn't Pioneer come to a halt eventually?

    You are right, I suppose all objects should come to rest in their own reference frames, meaning that there will still be motion. This goes back to the idea that the universe is expanding faster than light. Even if all objects were stationary in their reference frames they would still be moving away from each other, and vice verse for rest. Objects at rest would still be moving away from one another. It does have to do with the CMB.

    To BenTheMan- the effect is so weak it is completely negligible in everyday life and completely uncalled for in quantum mechanics.. I haven't done the calculations yet but it seems it would take billions of years to bring anything even close to a halt.
     
  15. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    The point is, people have been testing gravity for many years, on many scales, and have yet to find even a hint of something different. You propose a new ``theory'' (and I use the word loosely here) to explain a single event that seems to have a simpler alternative explanation?

    This is not how responsible science happens.
     
  16. rpenner Fully Wired Staff Member

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    First, there is no "now" -- the last data is 6 years old.
    Second, there is no clear evidence that the anomaly is in the direction of motion. So stopping in not an option unless it is. For the rest of this I will assume you mean halt it's radial excursion from the Sun's neighborhood.
    Third, there is no clear evidence that the anomaly is exactly in the direction of the Sun, either. Sun, Earth, the direction of motion and the direction of the spin axis are all closely aligned for the Pioneers. The choice to model an attraction in the direction of the sun is the easiest alternative to model.
    Four, the anomaly decreases about 2-3% per year, so the expectation is that the Pioneers will not stop.
    Five, the Pioneer anomaly is modeled at about 1 nm/s^2, which is 0.07 mph per year, so even if the anomaly was real, sun directed and not decreasing, then the Pioneers would head out over 100,000 years and fall into another star's sphere of attraction before they could stop.

    http://arxiv.org/abs/0901.3466
     
  17. DRZion Theoretical Experimentalist Valued Senior Member

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    Thank you for the link!

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    Four. Hmm. This does support my principle. The force I have in mind is not a force in any one direction but rather a cosmic braking force meaning that it works proportionally to the speed of any moving object. The faster the object moves the more braking it experiences. This may compound with the gravitational braking force; ie it may not be my principle alone that is creating enough braking to change the anomaly 2-3% per year.

    Five sounds right, it is very very weak.
     
  18. Pete It's not rocket surgery Moderator

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    Well, not actually asserting it... but yes, I am throwing it out there as a suggestion.
     
  19. CptBork Robbing the Shalebridge Cradle Valued Senior Member

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    On what grounds are you postulating such a force? What data are you using that points to a need for it, and how can you show that your model makes detailed, accurate predictions? It can't just be the Pioneer anomaly, because the effect is so small, it could be caused by any number of minor mechanical faults and variables that haven't been accounted for. Just using the Pioneer anomaly as your basis would be like postulating an anti-gravity force as the cause for a ball to stop rolling down a hill instead of friction.
     
  20. kurros Registered Senior Member

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    Haha, well I will assert this if Pete won't

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    . Yes you need lots of blue air for it to look blue, just like you need lots of blue water for it to look blue. Because as you said, they aren't very blue substances

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    . If you take a large volume of air and put in in a giant transparent bubble in space, that bubble will look blue.
     

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