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View Diary: The Most Misunderstood Concepts in Space Science (413 comments)

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  •  We Can See a Glow From Dust in the Plane (33+ / 0-)

    of the ecliptic, dust scattered across the entire solar system, due to being immersed in it. But I've never seen mention or a photo showing visibility of the asteroid belt looking edge-on. Either from earth or from any of the probes.

    I'd never thought about it being densely packed but the first time I saw an estimate for the numbers I realized that being such a large diameter ring, it has to be virtually empty.

    Great diary. If you feel like editing, or maybe another entry, you might explain the common rocket misconception that rockets have to have something to push on, or do better with something to push on.

    I even saw the Mythbusters do that in the episode when they tried to propel a boat with a compressed air tank outflow. They felt they needed to put the exhaust under water for more thrust.

    We are called to speak for the weak, for the voiceless, for victims of our nation and for those it calls enemy.... --ML King "Beyond Vietnam"

    by Gooserock on Thu Jan 24, 2013 at 04:35:06 PM PST

    •  Good idea. I'll add that. (8+ / 0-)

      Pour yourself into the future.

      by Troubadour on Thu Jan 24, 2013 at 04:42:23 PM PST

      [ Parent ]

    •  The Zodiacal light (8+ / 0-)

      Hard to see, it's the backscatter from the sun off dust, and can sometimes be seen with fully dark-adapted eyes and a clear sky just before dawn or just after dusk.

      Wikipedia: Zodiacal light

    •  So do rockets in space push on their own (1+ / 0-)
      Recommended by:
      Troubadour

      exhaust?

      •  Not exactly. (3+ / 0-)
        Recommended by:
        Sneelock, Troubadour, Ed in Montana

        They use action/reaction to move.  Using F=MA, you propel small things (ions, plasma, etc.) at extremely high velocity in one direction to move larger, less energetic things (ships)  in the opposite direction, albeit much slower.

        I am not religious, and did NOT say I enjoyed sects.

        by trumpeter on Fri Jan 25, 2013 at 09:58:14 AM PST

        [ Parent ]

        •  It ain't (1+ / 0-)
          Recommended by:
          Troubadour

          Rocket science!

          Ehhh... wait, maybe it is rocket science.

          "I come close to despair because so many of the pieces of the country are broken, and when you see that, you have two choices: You can give up, or you can do something about it." Elizabeth Warren

          by Ed in Montana on Fri Jan 25, 2013 at 12:32:10 PM PST

          [ Parent ]

        •  thought experiment (1+ / 0-)
          Recommended by:
          Troubadour

          Pretend that you are sitting on a new rolling chair (feet up!) on a flat slick waxed floor (big room or outdoors).  You have a bag full of baseballs.  You throw a baseball one direction at 50 mph, and your chair moves the other direction at 0.5 mph.  The balls never have to hit anything for you to move.  If you keep doing that, then your speed will slowly build up.  This is what a rocket does- the chair is the rocket, you are the motor, and the baseballs are the molecules in the exhaust.

      •  Exhaust goes one way, object generating it... (1+ / 0-)
        Recommended by:
        Troubadour

        ...goes the other way.  It would be the same if you pushed against a large boulder.

        Simple question: In the years since Republicans successfully urged the disempowering of workers and unions in the Midwest, what has happened to those states economies?

        by Stephen Daugherty on Fri Jan 25, 2013 at 10:47:21 AM PST

        [ Parent ]

      •  Technically yes but that doesn't propel them. (1+ / 0-)
        Recommended by:
        Troubadour

        If you push on a wall, technically, the wall pushes you back.  Similarly, as the exhaust pushes on the rocket technically the rocket pushes back on it but we generally do not think like this.  

        Rather, the rocket is propelled by being pushed on by the exhaust.  Inside the combustion chamber the ignited fuel and oxygen reach a very high pressure.  This high pressure gas pushes on the back wall of the chamber while it escapes out of the the other end.

        This is also why rifles have a kick.  The ignited gunpowder reaches a very high pressure in the rifle's chamber.  As the bullet and hot gas escape out of the end of the barrel the high pressure gas also pushes on the back wall of the chamber pushing the rifle backwards.  And again, technically the rifle is pushing back on the gas but like a wall or a rocket it is not the thing actively pushing but merely reacting.

        So, to put is simply.  What propels a rocket?  It is being pushed on by the exhaust.

        "It was believed afterward that the man was a lunatic, because there was no sense in what he said." "The War Prayer" by Mark Twain

        by Quanta on Fri Jan 25, 2013 at 12:47:55 PM PST

        [ Parent ]

    •  Asteroid Belt #13 tip was a big surprise (5+ / 0-)

      I've learned something new too.  Thanks, Troub.  Awesome.  Gooserock, nice name considering the, er, topic at hand re: asteroids (rocks).

      Also, Troub, you have the distinction of having said something that only exists on Google here on this page:

      "Gravity continues forever in all directions"

      I thought it was such an elegant and catchy sentence that I looked it up.  Alas, like the feeling of discovering a new word, the novelty of an idea not having existed anywhere else on the internet before fascinates me.

      Follow me on Twitter: @THTBAW. I crush trolls with truth, boredom with snark, and ignorance with links.

      by therehastobeaway on Fri Jan 25, 2013 at 06:20:06 AM PST

      [ Parent ]

      •  Wow. Wouldn't have thought it would be unique (1+ / 0-)
        Recommended by:
        therehastobeaway

        on the internet.  It's a pretty standard concept, and I hardly used weird phrasing or terminology.

        The asteroid belt thing surprises people because it's hard to realize that even huge numbers of things are practically nothing in such a mind-blowingly large volume of space.

        Pour yourself into the future.

        by Troubadour on Fri Jan 25, 2013 at 12:37:56 PM PST

        [ Parent ]

        •  Indeed. (1+ / 0-)
          Recommended by:
          Troubadour

          That's what's striking about your elegant explanation, though, that it highlighted just how counterintuitive the asteroid belt actually is (or how poorly it's been explained to us in grade-school generally). Then again, space in general is counterintuitive.  It's too big for us to generally compare against earth-bound distances.

          I can think of an asteroid, which is this massive, massive thing compared to me (forgive me for the erroneous use of massive, but you know what I mean...well, of course an asteroid has more mass, but I know you know I mean voluminous).  When I think of an asteroid, I think of a rock the size of a city.  I think, "Oh yea, that's pretty damn big."  (Well, it turns out that half the Asteroid Belt's mass is found in just four asteroids, roughly the length of Florida, and the rest are as small as dust particles and everything in between, but mostly not as big as  Florida).  I can't even begin to envision a rock the size of Florida, so I'm sticking with a city.  

          So a rock the size of Miami is pretty big.  I know how big a large city is in terms of getting around it in 2D space, but I have never pictured the equivalent of a large city as a 3D object, say a city-sized rock in the sky, for instance.  I don't know what that looks like because I've never seen anything of that size before relative to my body.  Add to this the fact that the volume of space in the solar system is far, far, far (x10000???) bigger than that Miami-sized rock, to scale.  Whoa: that city-sized boulder is so small compared to the volume of 3D space around it that you could have 50,000 of those Miamis orbiting that Asteroid Belt and not see or hit any of them if you were Superman flying by.

          Fascinating.  The solar system must be so much bigger than I can imagine, and that's just the solar system.

          So the Voyagers or some other satellites going through the asteroid belt aren't like flies going through a room packed floor-to-ceiling with birthday balloons.  Instead, it must be like an ant floating through the North American sky when there's 5,000 airplanes spread out all across the U.S.  That sounds like a lot of planes, but the amount of space in the sky above the U.S. is so so big relative to all those planes, and that ant is so, so small relative to those planes, that it is very, very, very, very unlikely to hit any of the airplanes, much less see one on its way from California to New York.

          Follow me on Twitter: @THTBAW. I crush trolls with truth, boredom with snark, and ignorance with links.

          by therehastobeaway on Fri Jan 25, 2013 at 10:58:45 PM PST

          [ Parent ]

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