About planetary gravity

Discussion in 'Science and Technology' started by RB_Kandy, Sep 14, 2012.

  1. Maurice

    Maurice Vice Admiral Admiral

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    I'm not going to address that litany of "they done me wrongs" and thinly veiled jabs at the left above, but it's pretty well established that there's a lot of history taught that's baldly incorrect.

    American history has often mythologized in public school textbooks due to the needs of the textbook industry to placate local school boards. This is why we get whitewashed versions of Helen Keller, Reconstruction, etc., and persistent myths like Betsy Ross.
     
    Last edited: Sep 15, 2012
  2. JarodRussell

    JarodRussell Vice Admiral Admiral

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    Oh come on, surely you were taught about basic Newtonian physics, regardless of how much your teacher rambled.
     
  3. Christopher

    Christopher Writer Admiral

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    Yeah, sometimes teachers are a crapshoot. I went to a high school that's considered one of the finest public schools in the United States, yet I still got a biology teacher who was a creationist and a health teacher who was a mortician. I did get some really great teachers, though, like a physics teacher who was an actual professor.
     
  4. Scroogourner

    Scroogourner Admiral Admiral

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    a mortician for a Health teacher? that could have been interesting.
     
  5. Christopher

    Christopher Writer Admiral

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    ^Just try to imagine learning sex education from a sardonic, middle-aged mortician who sounds like Fat Albert's Mushmouth without the speech impediment.
     
  6. Tiberius

    Tiberius Commodore Commodore

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    Better than learning about sex from a middle aged person who's sworn to be celibate and gets his information from a book written by people two thousand years ago...

    But let's not go down that road...
     
  7. Tiberius

    Tiberius Commodore Commodore

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    Actually, it's 88mph.
     
  8. RB_Kandy

    RB_Kandy Commander Red Shirt

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    Well they did do me wrong :p
    Of course they did everyone wrong. My old high school had some pretty incredible drop out rates.

    Of course it's 100% my own fault that I never to this day got my GED.

    Come to think of it, I failed metal shop through lack of trying, so I guess by 9th grade I was failing my teachers as much as they were failing me.

    Hmm, I was wondering why so much of school taught history is incorrect.
    I mean, the first thing that springs to my mind is "damn leftist politics" (which there was a lot of, jab jab) but the reality of it is a lot of the stuff I learned that was false, had no political motivation behind it.

    You say it's because the textbook industry is trying to make money? or are you saying they are trying to fill some sort of quota?

    And what Betsy Ross myths are you talking about?

    Actually my 8th grade science teacher, Mr. Little, did teach us about Newtonian physics. He had this lovely demonstration, he said "You know how women love to wear lipstick to make their lips all waxy? Karen, I want you to stand up and wet your lips. Just give 'em a quick lick like this."
    After she licked her lips he said "there you go folks, that's our physics lesson. Wet waxy lips. Or WW LIPS. Which stands for Wheels, Wedges, Levers, Inclines, Pulleys, Springs"

    He had made the big deal of making Karen lick her lips for the spectacle so that we'd remember it, considering we were going to spend the second half of the year learning about those exact things, and about Newton's laws of motion, and building devices using those principals, and explain the motion, the cause and effect, with the laws of newtons physics.

    And because I had the biggest crush on Karen, I'll never forget her wetting her waxy lips.

    I only remember the name of two of my teachers. Mr. Little, because he was my favorite, and actually the teacher who got me to care about science. And Mrs. Greene, because good god that woman had legs LOL

    A creationist biology teacher and a health teacher that was a mortician. Oh I could just see his speeches "and here are the 5 things you can do to make sure you never have to come see me at my other profession, eat right, exorcise, don't smoke..."

    I just remembered another teacher I liked, how he inspired all of us, and how he was wrongfully fired. I'll put this in a spoiler tag so everyone can skip it.

    Actually I just remembered another teacher. Mr Thompson, either 8th or 9th grade PE teacher. He was really good. He was all about "trying" and team spirit. And if you didn't do well in his class, near the end of the semester, he'd pull you to the side, and really giving you a polite talking to about how he grades on effort, individual progress, group participation, and sportsmen conduct. How you can come in last in the race, and still get an "A" if you finish the race faster than last time, and had a good positive attitude.

    I remember one day, I was chosen as team captain for basketball practice, and my opponent went first. He chose Darnell who's nick name was "wings" because he could fly through the air and slam dunk. I made my choice, and then Charles walked in, saying he is sorry for being late. My opponent got to choose him. The best damn basket ball player in the entire neighborhood. And my opponent (the other captain) was probably the third best basket ball player. So their team had the three best players (by a land slide). Because these three men were like professional NBA stars, versus a bunch of pudgy little white boys and girls, we knew there was no way my team had a chance no matter who else I picked. So lo and behold my opponent started choosing the absolute worst people to fill out the rest of his team. He chose the fat people, skinny little white girls afraid to break their nails, and all the stereotypical nerds. The people who had a reputation in our class as being the least athletic, and the most shy and socially awkward.

    We played, and they're team still won LOL. But afterward, I heard Mr. Thompson talking to the team captain (can't remember his name) and he commended him for choosing the team the way he did.
    You see, the team captain wanted to make it fair, he knew he had the three best ball players in the school, so he chose all the weakest people, passed the ball to them. Made them, forced them, to be a part of the team, and then made them all feel like winners by winning. All the while giving my team a fighting chance.

    That was the kind of spirit Mr. Thompson could inspire in us.
    A few years later the school fired him for being homosexual.
    Talk about messed up. They fired one of the few teachers who ever made a positive impact on anyone, just for being gay. Not that he was gay with his students or any scandal like that.
    And what shocked me was, this was a school that beet you over the head with liberal tolerance and equality, they just didn't want to practice what they preached.

    Further proof that yes, there are some good teachers, but man, something was just wrong with my school district.

    I am wondering what you guys think of this solar system theory that earth is not revolving around a stationary sun, but is instead traveling in a spiral. http://www.youtube.com/watch?v=o6jBK1ZV-qs&feature=related
     
  9. Scroogourner

    Scroogourner Admiral Admiral

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    Piece of advice. Youtube is NOT the place to learn new "theories".
     
  10. Tiberius

    Tiberius Commodore Commodore

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    Some of the stuff on youtube is good. But that was crap.
     
  11. RB_Kandy

    RB_Kandy Commander Red Shirt

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    Well it can't be worse than everything on The History Chanel being about Aliens. Did you know, every historical event we've ever had, might have had extra terrestrials? :rommie:

    Is there any reason why this new theory doesn't work?
     
  12. gturner

    gturner Admiral

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    I wouldn't call it a theory, I'd call it a brain fart with really dramatic music.

    I assume you know quite well how your car engine works. The pistons go up and down (or at some angle if you have a V engine, or sideways if you have a horizontally opposed engine). Your crankshaft is then driven in a purely circular motion, centered on the crankshaft main bearings mounted in the engine block. That drives your cam sprocket (for an overhead cam) or lifters, and also your fan belt, and possibly accessory belts.

    That's what you think you know. (insert dramatic music with chanting choir). Once you take your car out on the road, those motions are false, because your pistons are moving up and down as you travel down the highway at 88 mph, so they're sine waves, and your crankshaft turns in a helix. But then you go around a turn, so the motion is even more complex! And as you go around a turn, your car tilts a little, and then you hit a bump.... So the crankshaft bearings can't possibly explain the incredibly intricate curve followed by the crankshaft, and thus can't explain the motions of the pistons, much less the intake and exhaust valves.

    There must be unknown, magical forces at work.

    Or a complete idiot making videos with really cool, ominous choir music.

    ETA: I think the trouble your having is with seperating motions based on influences. When a body is subject to gravity, it accelerates, as does everything around it, since those things are subject to the same gravitational field. If you were holding hands with a bunch of people in a space ship and gravity suddenly changed, you'd still be holding hands, and wouldn't even notice any tugs or yanks, and wouldn't notice any forces from the floor or ceiling, because the spaceship would feel the same pull.

    You, your friends, the ship, and your breakfast trays are all moving together, and though your course might change due to gravity, it affects all of you at the same time, and all equally, so that you actually have absolutely no way to detect that anything changed.

    This is different from a car on a bumpy road, a train going around a curve, or an airplane flying trhough turbulence, because in those cases an external force was applied externally to wheels or wings, not to the occupants directly, so they slam into the seats or doors. Gravity isn't like that.
     
  13. RoJoHen

    RoJoHen Awesome Premium Member

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    Hey, my Sex Ed teacher told us that the only people who masturbate are homosexuals. Kind of a weird thing to hear as a 12-year old.
     
  14. Maurice

    Maurice Vice Admiral Admiral

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  15. Kemaiku

    Kemaiku Admiral Admiral

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    We noticed.
     
  16. Maurice

    Maurice Vice Admiral Admiral

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    Was that necessary?
     
  17. Kemaiku

    Kemaiku Admiral Admiral

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    [LEFT]Probably not.
    [/LEFT]
     
  18. Scroogourner

    Scroogourner Admiral Admiral

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    Well, the easiest way to point out that it's wrong is the fact that all the planets orbiting our sun are on the same elliptic plane as the galaxy. Not perpendicular as the video shows it. That's the point where you can stop the video and dismiss it entirely.
     
  19. Ayelbourne

    Ayelbourne Fleet Captain Fleet Captain

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    Java != Javascript ;)
     
  20. Christopher

    Christopher Writer Admiral

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    Sorry, but that's not right. The ecliptic plane (the plane in which the Earth orbits the Sun) is tilted at 60.2 degrees relative to the galactic plane. It's closer to perpendicular than parallel.

    The video is basically right about its facts, but completely wrong in how it interprets them. The key is to understand that all motion is relative, and how the motion of an object is perceived depends on what frame of reference you're observing it from. For instance: Imagine you're sitting on a moving train, playing with a yo-yo. From your perspective, it looks like the yo-yo is moving straight up and down, because you're defining your coordinate system relative to the train itself. But to an outside observer standing in the station and watching the train go by, it looks like the yo-yo is moving in a sine-like wave, not just moving up and down but moving sideways. That's because that observer is defining her coordinate system relative to the station, which isn't moving with the train. Which one is right? Both of them are! It all depends on how you're measuring it. There is no frame of reference that's more right than another.

    This is the exact same situation. If you're standing still relative to the Sun and watching the planets go around it, you see them following elliptical paths. But if you're in a different coordinate system, say, one that's motionless relative to a distant galaxy, then you see the Sun moving in its orbit around the center of our galaxy and the planets moving around it at roughly 60-degree angles (since the different planets are all in slightly different orbital planes, not perfectly in the Earth's ecliptic). So if you drew out their paths in that frame of reference, they would be lopsided helices (not spirals, since a spiral is a path that increases in radius as it goes around; a helix is more like a Slinky, maintaining its radius but changing position perpendicular to that, or nearly so).

    But this is a trivial distinction, because both are equally correct ways of defining the motion. The only difference is in what coordinate system you're using. And changing the coordinate system does not invalidate the underlying physics. The planets are still being drawn toward the Sun by its gravity, and the combination of that attraction and their momentum produces the paths we observe. You get that same result regardless of which coordinate system you use and how you define their motion. It's just that choosing a coordinate system that treats the Sun as motionless is the simplest way to solve the equation, because that way you get to ignore terms (like the effect of the galaxy's gravity on both the Sun and its planets) that would cancel out of the equation anyway and don't make any difference to the result.

    So this video makes a common mistake of a lot of Internet charlatans -- taking some scientific facts that are basically correct in isolation, yet completely failing to understand how to interpret their meaning.