is this a valid explanation so that the term "direction" is actually not valid?

Discussion in 'General Science & Technology' started by WantToLearnMore, Oct 15, 2011.

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  1. WantToLearnMore Registered Member

    hello everybody, this is my first thread so I hope that people here can help me.

    I'm just a 16 year old boy trying to get my thoughts clear so I ran into this site which seemed serious and I can see that most here are experienced people...

    now onto my "thoughts"

    If the universe is infinite then we can not say that "up" is "up" or that "down" is "down" because "up" and "down" is a definition we use to describe a "direction" in contrast to an edge, but we say that universe is infinite, there is no edge, so if this is a fact almost everything that we describe in relation to some kind of direction is actually wrong because there would be nothing called "directions"...

    related thoughts & questions : does this mean that the words "direction, up, down etc. " relates to the words "god, heaven (as the place we go after death) etc." because both is terms that humans use to describe something that we can't explain?
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  3. mathman Valued Senior Member

    Although there is no absolute coordinate system for the universe, one can set up a three axis system and have relative directions.
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  5. Fraggle Rocker Staff Member

    As the moderator of the Linguistics subforum, I naturally think that this question is really about language. ;)

    The words "up" and "down" only have meaning in two situations:
    • A place where there is gravity. In such a place we naturally orient ourselves so that our feet point in the direction of the pull of gravity, and our heads are on the other end of our bodies. We call the direction of gravity, the direction in which the force of gravity pulls objects that are not anchored, "down." We call the opposite direction "up."
    • By extension (and by agreement), a place where gravity is not strong enough to be felt but where, for the sake of organization, we arrange the furniture and equipment in an arbitrary orientation that resembles a similar place on the earth's surface. The primary example of this is a space station. It would be confusing and even disconcerting if some people chose to stand with their magnetic boots on one surface, while others were standing on a surface which, to the first group, appears to be the ceiling or one of the walls. So the station is built with one surface predefined as the "floor" and all the furniture is attached to it. In this case, we continue to call the direction toward the floor "down" and the opposite direction "up," pretending to still be on Earth.
    Obviously, on an other planet or other body large enough for its gravity to act as an anchor (the moon, Mars, etc.), we also refer to the direction pointing toward the center of the body as "down" and the opposite as "up."

    These examples should be sufficient to make the point that there is no universe-wide definition of up and down. An astronaut standing on the side of the moon that we can see is looking "up" at us, while we insist that we are looking "up" at him.

    For that matter, there isn't even a planet-wide definition. When the people in Australia look "down" toward the earth, if they had a really big x-ray machine with high resolution they would see us "under" them. But we would regard that direction as "up" since it points above our heads, and insist that we are "above" them. (I haven't got a globe handy; I don't know if Australia is really directly opposite my location in Maryland.)

    The concepts of up and down were developed on a sphere, and are entirely dependent on one's location on that sphere. Regardless of which sphere we travel to, we will use up and down in the same way.

    Anywhere in the universe that is not within gravity-pulling distance of a planet or other similar body (and that includes 99.99999...% of the universe), the words "up" and "down" have no intuitive meaning. If you're in a spaceship with the furniture bolted to the "floor" then anything "below the floor" will be "down," and anything "above the roof" will be "up." If you're regarding the universe in the abstract from a place here on earth, then up and down have no meaning.

    Although I wouldn't be surprised if astronomers have assigned meanings to those words just to give themselves a frame of reference for their own conversations. Perhaps they use the axis of spin of our galaxy as a reference, arbitrarily define the galaxy as spinning "counterclockwise" (like our planet, as seen from the North Pole) and use that reference to define up and down.

    Then maybe some other easily spotted landmark is off in a direction they define as "north," and presto, they've got a complete set of directions.

    But all of this is arbitrary. People living on a planet in another galaxy may be doing the same thing, but their "up" could be our "east by southeast and 22 degrees below the horizon."

    Point: even if the universe is finite, it has no up and down. Those are human concepts. Nature doesn't care.

    I recall the producers of the Star Trek series having fun with this idea. There were times when the Enterprise was quite close to a planet. They would slowly pan away from the ship, and suddenly you'd see the planet... "above" the ship! From the perspective of the people on the planet, the ship was upside-down!
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  7. WantToLearnMore Registered Member


    hmmmm, many "weird" things to think about :confused: but I get the main picture, but wouldn't his make (theoretically) even every GPS wrong when it gives you a direction? ... :confused:
  8. James R Just this guy, you know? Staff Member

    Astronomers identify constellations using celestial coordinates. The celestial equator is the projection of Earth's equator out into space. The North and South celestial poles are extensions of the Earth's rotational axis out into space. Celestial longitude is fixed with reference to the stars and does not rotate with the Earth. Zero degrees celestial longitude is in the direction where we find the sun at the vernal equinox.

    These celestial coordinates are still referenced to the Earth, of course. An alien on another planet somewhere could define his own celestial coordinate system.

    Astronomers also use galactic coordinates, which define galactic North, South and so on with reference to the Milky Way galaxy. That system could be shared with anybody else living in our galaxy, but is still not a universal coordinate system. Other galaxies are oriented at all kinds of angles to the Milky Way.

    As an aside, physicists in general define spin without referring to "clockwise" and "anticlockwise" explicitly. They use spin vectors. The rule is that if you point the thumb of your right hand along the axis of rotation of a spinning object and your fingers curl in the direction of rotation then your thumb is pointing in the direction of spin vector. As an example, the spin vector of the Earth points in a direction from the South pole towards the North pole (through the centre of the Earth).
  9. Rav Valued Senior Member

    Left and right is sorted out by your navigation system (not the GPS satellites) and is simply relative to your direction of travel.
  10. gmilam Valued Senior Member

    NSE & W are defined in relation to the Earth. I would assume up and down are defined by local gravity.
  11. spidergoat monosyllabic dictionary Valued Senior Member

    No, it's not "wrong", it just gives you direction relative to a previously established coordinate system.
  12. leopold Valued Senior Member

    the terms "up" and "down" relate directly to a gravity field.

    i don't know what you consider "god" but i'm quite sure "god" isn't what you think it is.
    yes, i deliberately used the word "it" in the above sentence.
  13. Daedelus Registered Senior Member

    A useful word for a 16 y/o to know early is 'arbitrary'. As in, some things are used as rules, not because they are anchored in concrete but because they are or were at one time, useful. But things like that are inventions of humans to suit human needs.

    For instance, on a space flight, it would be useful and or comforting to maintain a clock that kept time in days, hours and minutes even though in space there is no connection to the rotation of the earth. Astronauts could use a different measure of 'time' but they don't and that is an understandable but arbitrary decision. Same with up and down in the absence of gravity. Arbitrarily, down is the area defined as the bottom of the craft.

    You will run into many things in life that are arbitrary. Some will comfort you. Some will annoy the hell out of you.
  14. Stoniphi obscurely fossiliferous Valued Senior Member

    Welcome to the site, Want To, glad to have you join us here. I hope that you enjoy your stay with us.

    (We are not all quite as clever as you may think. :eek: )
  15. WantToLearnMore Registered Member

    Hehe, I don't mean "god" in like "our father" nor any other religious meanings, but I mean "god" as in "something that scientifically is not "true" (no offense to anybody)" because we say "up" and "down" but in fact it is an arbitrary word (I'm learning everyday :D )
    (If I'm wrong using the word "arbitrary" in this connection please correct me :) )
  16. WantToLearnMore Registered Member

    Thank you very much :) It's nice to learn something new and useful :) (in my previous post I tried to use this word, I hope I learned it correctly :p )
  17. WantToLearnMore Registered Member

    thank you for a nice and warm welcome :D It's wonderful to see so much positive feedback :)
  18. WantToLearnMore Registered Member

    I see what you are saying :) but my point is that even for us "right" can actually be "down" or "up" or 37.6236542 degrees south/west "theoretically speaking" because in fact "up" and "down" in universe can be anywhere for what we know... of course for us "directions" is useful and not "wrong" for our everyday use of these words :) but this brings me back to my question, does this mean that we can't be sure about if any direction is actually "valid" ? (I'm sorry for being really picky, but it's just for fun and to make us think about different things :) )
  19. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

    Each set of words ("Up and Down", or "Left and Right" etc) use a different frame of reference.
    The frames of reference move relative to each other, and so those words only retain meaning for the frame of reference to which they relate.
    And the frame of reference to which they relate is usually given by the context of their use... Up and Down generally refer to gravity, NSEW refer to positions on a plane relative to a defined point, and so forth.

    The only way one can be sure of one's direction regardless of which words you use would be if all the words use a universal frame of reference. But they don't. So you can't.

    But this doesn't mean they aren't "valid"... the terms are valid for the frame of reference to which they relate.
  20. Daedelus Registered Senior Member

    You did Grasshopper. :cool:
  21. Fraggle Rocker Staff Member

    I'm sure the day is not far off when kids will not find the word "clockwise" intuitively meaningful because there will be no more clocks with rotating hands. Although personally I find them very useful because even without my glasses I can at least tell approximately what time it is.
    That's the same as the right-hand rule for nuts and bolts, or its feminine version "righty-tighty, lefty-loosey." Point your thumb in the direction you want the nut or bolt to go and your fingers curve in the direction you need to turn it.

    I was surprised to find that when people talk about the Washington Beltway, a more-or-less circular freeway through the Maryland and Virginia suburbs that surround the city, they don't use either the right-left or clockwise-counterclockwise convention for telling people how to enter it in the right direction to reach their destination most directly. The lanes are called the Inner Loop and the Outer Loop. I bet Aussies and Brits get really confused when someone tries to help them find their way.
    You're still not getting it. Up, down, right, left, front and back have no meaning at all in the universe, whether or not it turns out to be infinite. Those words are local references only.
    That's the only use there is! The universe has no orientation. It has no top or bottom.
    The entire concept of "direction" in the left-right/up-down/front-back model is only valid locally. If there are other sentient beings in the universe they will have their own directions which are only locally valid. If they live on a planet then it's quite possible they'll use the same paradigm we did, with a word we'd translate as "down" meaning the direction in which gravity pulls them. If they have bilateral symmetry (a big "if," since not even all animals on Earth do, some are radial), they'll probably have words equivalent to "right" and "left" also.
    This is not an academy so we're all free to have fun. We even have a couple of subforums set aside where fun is a major motif. But what you need to think about is your assumption of an earth-human frame of reference being universal. That's where our words for directions come from. They apply only to us and our world, not to anything or anyone outside it. As James pointed out, astronomers have overlaid the up-down coordinates on the universe by extending Earth's axis to infinity, and they have even drawn a map of our galaxy that (perhaps?) has a north and a south. But these are only human conventions, established for our own convenience in talking about the universe with each other. We are under no delusion that they are universal, nor any delusion that there even is such a thing as a universal set of up-down-etcetera coordinates.

    So when you hop a freighter to the next galaxy, your directions will not be wrong. They will be meaningless.
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