Page 4 of 6 FirstFirst ... 23456 LastLast
Results 31 to 40 of 58

Thread: Navigation in space

  1. Top | #31
    Super Moderator
    Join Date
    Sep 2000
    Location
    Nevada
    Posts
    31,232
    Archived
    96,752
    Total Posts
    127,984
    Rep Power
    100
    In Trek you always have a reference frame--whatever the primary body is for your location. That could be a planet, that could be a star, it might even be the galaxy as a whole.

    Now, being able to accurately measure it is another matter, but this is a mistake that is consistently made in sci-fi stuff--measurements far more accurate than theoretically possible under the conditions.

  2. Top | #32
    Contributor
    Join Date
    Nov 2017
    Location
    seattle
    Posts
    6,521
    Rep Power
    20
    Quote Originally Posted by skepticalbip View Post
    Quote Originally Posted by steve_bank View Post
    The old pre GPS LORAN system might work in some form. Multiple transmitters at known locations sending pules in a known order with known timing.

    Even if the locations are moving you might still derive relative position.
    The Pioneer mission probes used pulsars (as "LORAN or GPS") to show Earth's location on the plaque.

    Sci-Fi stories have suggested that giving away our location may have been a terrible (but trusting) error.
    If evolution is a conat resylting in prey and predator, then unyil we get photon torpedos and warp drive the last thing we want is let oters know we are here.

    Watch the Twilight Zone episode Tp Serve Man. It was about an ET book that turned out to be a cookbook.

  3. Top | #33
    Contributor skepticalbip's Avatar
    Join Date
    Apr 2004
    Location
    Searching for reality along the long and winding road
    Posts
    6,291
    Archived
    12,976
    Total Posts
    19,267
    Rep Power
    71
    Quote Originally Posted by steve_bank View Post
    If evolution is a conat resylting in prey and predator, then unyil we get photon torpedos and warp drive the last thing we want is let oters know we are here.
    That was Stephen Hawking's position too. But I believe he was looking beyond photon torpedoes and warp drive as a defense as those could be seen as primitive toys to a truly advanced race of space farers.

    Personally, I don't think we could hide the fact that Earth is teaming with life from an advanced race even several hundred lightyears away... even if we had never used radio, tv, or radars. An analysis of Earth's atmosphere as we passed between them and the Sun would give them plenty of evidence that the Earth was crawling with life.

  4. Top | #34
    Veteran Member Wiploc's Avatar
    Join Date
    Dec 2002
    Location
    Denver
    Posts
    2,907
    Archived
    14,058
    Total Posts
    16,965
    Rep Power
    72
    Quote Originally Posted by Loren Pechtel View Post
    In Trek you always have a reference frame--whatever the primary body is for your location. That could be a planet, that could be a star, it might even be the galaxy as a whole.
    The convenient bit is that you can match the velocity of that primary body by turning off your engines.

  5. Top | #35
    Veteran Member
    Join Date
    Jun 2002
    Location
    West Coast
    Posts
    2,511
    Archived
    7,585
    Total Posts
    10,096
    Rep Power
    72
    Quote Originally Posted by Gun Nut View Post
    Quote Originally Posted by steve_bank View Post
    The old pre GPS LORAN system might work in some form. Multiple transmitters at known locations sending pules in a known order with known timing.

    Even if the locations are moving you might still derive relative position.
    We have a pre-existing, galactic system for that. They're called Pulsars.
    Pulsar emission isn’t isotropic though, so you would have to keep a large catalogue that you keep accessing as you move around.

    So it would seem to me that the plaque showing Earth’s location relative to pulsars would only work if you’re actually at earth’s location and can see that set of pulsars that are beamed toward you. Like telling someone where you live by describing what you can see outside your window.

  6. Top | #36
    Contributor skepticalbip's Avatar
    Join Date
    Apr 2004
    Location
    Searching for reality along the long and winding road
    Posts
    6,291
    Archived
    12,976
    Total Posts
    19,267
    Rep Power
    71
    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by Gun Nut View Post
    Quote Originally Posted by steve_bank View Post
    The old pre GPS LORAN system might work in some form. Multiple transmitters at known locations sending pules in a known order with known timing.

    Even if the locations are moving you might still derive relative position.
    We have a pre-existing, galactic system for that. They're called Pulsars.
    Pulsar emission isn’t isotropic though, so you would have to keep a large catalogue that you keep accessing as you move around.

    So it would seem to me that the plaque showing Earth’s location relative to pulsars would only work if you’re actually at earth’s location and can see that set of pulsars that are beamed toward you. Like telling someone where you live by describing what you can see outside your window.
    If any space critter finds the Pioneer probes within the next several million years then they would already be damned close to Earth. Pioneer is moving away at about 27,000mph. Voyager (a later probe) overtook Pioneer in the late 1990s. Space critters finding Pioneer would already be close enough to tune into our EM emissions to find Earth so wouldn't need to decipher the plaque.

  7. Top | #37
    Elder Contributor
    Join Date
    Feb 2001
    Location
    Located 100 miles east of A in America
    Posts
    30,650
    Archived
    42,473
    Total Posts
    73,123
    Rep Power
    100
    Quote Originally Posted by Wiploc View Post
    Quote Originally Posted by Jimmy Higgins View Post

    I'd imagine that it'd suck to be at some point in between when that happens.
    Let's suppose you're on this map somewhere. Colorado or New York or Africa maybe.

    Chicago! Perfect, you're in Chicago. The world looks like this:



    But now somebody in Alaska wants to fold space so that she can see Russia from her house.

    Suddenly the world is sickeningly distorted so that people in
    Chicago are ... uh ...

    Actually, no, Chicago is unaffected.



    It does not suck to be between the points folded together.

    Unless you don't like being in Chicago. That might suck.
    But the sucking would in no way result from the curvature of space that puts Alaska next to Russia.

    -- Image from https://www.britannica.com/science/Mercator-projection
    It is quite possible that I'm being thick, but the Mercator projection isn't any more real than the cylindrical projection. How do you take an actual sphere and link Cleveland with Chicago, without impacting Toledo?

  8. Top | #38
    Veteran Member
    Join Date
    Oct 2018
    Location
    Colorado
    Posts
    2,415
    Rep Power
    12
    Quote Originally Posted by Shadowy Man View Post
    Quote Originally Posted by Gun Nut View Post
    Quote Originally Posted by steve_bank View Post
    The old pre GPS LORAN system might work in some form. Multiple transmitters at known locations sending pules in a known order with known timing.

    Even if the locations are moving you might still derive relative position.
    We have a pre-existing, galactic system for that. They're called Pulsars.
    Pulsar emission isn’t isotropic though, so you would have to keep a large catalogue that you keep accessing as you move around.

    So it would seem to me that the plaque showing Earth’s location relative to pulsars would only work if you’re actually at earth’s location and can see that set of pulsars that are beamed toward you. Like telling someone where you live by describing what you can see outside your window.
    Such an accurately conveyed description is adequate to determine position. It's just basic Trigonometry. If I tell you that there are three objects at a precise bearing from my location, and you can identify those three objects (for pulsars, by their distinct frequency), then it is simple math to determine where that point is in space (At that moment in time).

  9. Top | #39
    Elder Contributor
    Join Date
    Feb 2001
    Location
    Located 100 miles east of A in America
    Posts
    30,650
    Archived
    42,473
    Total Posts
    73,123
    Rep Power
    100
    Quote Originally Posted by Gun Nut View Post
    Quote Originally Posted by Shadowy Man View Post

    Pulsar emission isn’t isotropic though, so you would have to keep a large catalogue that you keep accessing as you move around.

    So it would seem to me that the plaque showing Earth’s location relative to pulsars would only work if you’re actually at earth’s location and can see that set of pulsars that are beamed toward you. Like telling someone where you live by describing what you can see outside your window.
    Such an accurately conveyed description is adequate to determine position. It's just basic Trigonometry. If I tell you that there are three objects at a precise bearing from my location, and you can identify those three objects (for pulsars, by their distinct frequency), then it is simple math to determine where that point is in space (At that moment in time).
    Position and possible velocity within what level of accuracy though? We "know" a pulsar is 152.1 light-years away. That isn't an accurate enough measurement for basing velocity and position in units of what we'd measure motion in as our velocity and positions would be very very well within the precision of the distances to pulsars.

  10. Top | #40
    Contributor skepticalbip's Avatar
    Join Date
    Apr 2004
    Location
    Searching for reality along the long and winding road
    Posts
    6,291
    Archived
    12,976
    Total Posts
    19,267
    Rep Power
    71
    Quote Originally Posted by Jimmy Higgins View Post
    It is quite possible that I'm being thick, but the Mercator projection isn't any more real than the cylindrical projection. How do you take an actual sphere and link Cleveland with Chicago, without impacting Toledo?
    The Mercator to cylindrical illustration was a 2D analogy of warping our 4D universe. It shows how a 2D universe could be warped through a third dimension to make two distant points overlay. Our 4D spacetime would have to be warped through a 5th dimension to do the same thing.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •