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Debating a Flat-Earth 'Devil's Advocate'

  1. Aug 12, 2006 #1
    The Flat Earth Society


    Apparently some people still think the earth is flat. I've been debating them for some time but they are so ridiculously arrogant I gave up.
  2. jcsd
  3. Aug 12, 2006 #2

    Ivan Seeking

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    I find it hard to believe that any legitimate argument can be made for this.

    The only qualified discussion here would be regarding allegedly unexplained phenomena. We are not interested in new theories required to support the premise of a flat earth.

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  4. Aug 12, 2006 #3
    Yes despite all the eviendnce around including the shawdow of the earth on the moon during a lunar elcpise or the fact that the appllo moon astronuts saw the earth is round(for that reason they claim it was a hoax) or the fact that ships seem to dispar at certin distance there are still people who think the world is flat.

    Don't debate with them just let them think that the world is flat and just be happy with the fact the most people do not think that the world is flat.
  5. Aug 13, 2006 #4
    Someone must have started the site as a joke, and people being the sheep that they are, some of them just migrated into the pack.

    The FAQ is quite humorous, claiming there is a giant ice wall, and that airline pilots are part of the conspiracy to help keep the secret.

    Thanks for posting, it kept me amused for about three minutes.
  6. Aug 27, 2006 #5
    Hello, on the forums of the International Flat Earth Society ( www.theflatearthsociety.org ), there are very few people who actually believe the Earth is flat- most of those who appear to represent the Flat Earth cause are actually only either there to hoax people, or to argue as Devil's Advocates for something they do not actually believe, for the intellectual stimulation. I am currently debating one such, who maintains that while he does believe that gravity works, the Flat-Earth model of gravity is theoretically possible. Their model states that some force has been constantly accelerating the Earth at one gee for its entire history, and the resultant inertial effects would cause a simulated 'gravity', which by the Equivalence Principle would be identical to true gravity caused by proximity to a massive object. I responded that were any object undergoing a constant acceleration of 9.8 m/s/s, it would reach lightspeed almost exactly one year after beginning such acceleration, and would its rate of acceleration would then have to decrease as it approached lightspeed. My opponent contends that the Earth's acceleration would be decreasing as it approached c on an asymptotic curve, yet observers on the Earth would still feel a full gee's worth of simulated gravity; I contend that if the Earth's acceleration began to decrease observers on Earth would feel a resultant decrease in this simulated gravity. Who's right?

    (Of course, there are other problems with this idea, such as requiring a practically infinite energy source, to which they can only respond "Dark Matter diddit")
    Last edited: Aug 27, 2006
  7. Aug 27, 2006 #6
    In special relativity, an object's acceleration will not be agreed upon by all observers. Imagine that at the beginning of the acceleration, there is another observer, moving at the same speed as earth; but, this observer never accelerates. According to this observer, earth's acceleration will continually decrease, and earth will never reach the speed of light. However, at any time, an unaccelerated observer moving at the same speed the earth is at that moment will see earth's acceleration as g.

    So, I'm afraid the flat earther has you on this one.

    If you want a question he might find it harder to answer, you could try asking him how he accounts for the strength of gravity decreasing as you move farther above earth's surface.
  8. Aug 27, 2006 #7
    I'm confused now. If the Earth's acceleration is different relative to observers traveling at differing velocities, how is it determined which measure of acceleration describes the inertial effects felt by observers on Earth? Why is that observers would feel one gee worth of inertial effects because of acceleration relative to some objects, rather than less because of decreasing acceleration relative to other objects?
  9. Aug 27, 2006 #8
    By the way, I'll admit defeat to this guy, but I'm convinced he's still wrong on a related point; he asserts that the inertial effects felt by observers standing on the Earth are caused by those observers' acceleration relative to Earth; but observers resting on the Earth are stationary relative to Earth, and thus are not accelerating relative to Earth. He is convinced that an observer resting on Earth measuring their acceleration relative to Earth would tell them something meaningful, and that it would be 9.8m/s/s. He keeps coming back to this.
  10. Aug 27, 2006 #9


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    While the flat Earth example is rather silly, there is no such thing as an absolute velocity, and a 1g accelration is felt as 1g, regradless of how long one has been accelerating.

    The process of acceleration can be thought of as continuously adding to one's velocity. But velocities do not add linearly in relativity. The formula is v = (v1+v2) / (1+v2*v2/c^2)

    So for every 1 second of prooper time, one adds 9.8 m/s to one's velocity using the above formula.

    This is "felt" as 1 1g acceleration (it's called a 1g proper acceleration). No matter how many times you add 9.8 m/s to your velocity with the above formula, though, it will never be equal to 'c'.
  11. Aug 27, 2006 #10
    I am interested in how this debate will turn out, since a few folks at the Flat Earth Society do appear to be willing to subscribe to scientific thinking. I just wanted to let everyone here know that I have extended an http://theflatearthsociety.org/forums/viewtopic.php?p=43649#43649" [Broken] to participate in this discussion.

    I realize that there will be some reluctance due to the default "high ground" that the Physics Forums may possess. But for the purposes of engaging in narrower, specialized discussions such as relativity in the role of the Flat Earth Model, where we are debating on specialized scientific terms, I expect that the difference in "ground" should be more or less justified.

    Now, the rest is a question of how many members of the Flat Earth Society will be willing to accept this challenge.
    Last edited by a moderator: May 2, 2017
  12. Aug 27, 2006 #11


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    While I appreciate the need to seriously discuss, in terms of valid physics, the issue surrounding this topic, I do believe that this discussion does not belong in this section of PF. It is more suitable for such a discussion to occur in the Skepticism and Debunking forum, which does require thoughtful analysis based on valid physics.

    So this is just an advance notice that, pending an agreement with the other Mentors, this thread might be moved to the S&D forum.

  13. Aug 27, 2006 #12


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    Frankly, I'm in favor of not hosting such debates at all. It is just pointless mental masturbation to debate the the particulars of something while utterly ignoring the larger facts. Who cares how gravity might work if the earth was flat - the earth is not flat and that is a simple fact. Ie, instead of arguing with them about their model of gravity, change the subject. Tell them: 'regardless of how your gravity model would work in a hypothetical and nonexistent universe, I've been to the beach and watched boats disappear over the horizon. Alternate 'theories' (they aren't) are irrelevant.'
    Last edited: Aug 27, 2006
  14. Aug 27, 2006 #13
    Another nice poser for the flat-earthers is the angle of the crescent moon. Just after sundown it's near vertical. But hours later it's tilted over. Ask 'em why!
  15. Aug 27, 2006 #14
    Isn't the flat earth all just a myth anyway? As far as I know, the ancients didn't believe that the earth was flat.


    "During this same era, an American, Washington Irving started to propagate the idea that there was opposition to Columbus' voyage from flat-earthers. He wrote "History of the Life and Voyages of Christopher Columbus (1828) as a romantic fiction loosely based on history. Readers picked up on the idea of flat-eathers opposing Columbus, and suddenly the idea was accepted as fact by millions of people, even to the place where it found its way into history textbooks...
  16. Aug 27, 2006 #15


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    We just closed a thread on this a week ago. These threads pop up all the time. I'm moving this to S&D. Since there is nothing presented here that hasn't been presented before, I'm sure this will be locked as all of it's predecessors have been.
  17. Aug 27, 2006 #16

    Ivan Seeking

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    Last edited: Aug 27, 2006
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