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  1. The Thought Experiments Thread


    #1001372016-03-09 07:56:31--Jack-- said:

    http://i.imgur.com/c1a15AC.png

    I've had discussions with many users in chat involving thought experiments, so I figured why not have a thread to share them and discuss them. I intend on adding some as I come across them or want to share them, and would like the rest of you too as well! Many people find them enjoyable, sort of like riddles but often more complex and can involve deeper things.

    Do try to follow some sort of format:

    • Title or name of the Thought Experiment.

    • A description depicting what it is.

    • (Optional) Your own conclusion, answer, or thoughts on it.

    And as always, don't be a jerk.

  2. #1001552016-03-09 15:35:37Rinneko said:

    Schrodinger's Cat

    In the hypothetical experiment, which the physicist devised in 1935, a cat is placed in a sealed box along with a radioactive sample, a Geiger counter and a bottle of poison.

    If the Geiger counter detects that the radioactive material has decayed, it will trigger the smashing of the bottle of poison and the cat will be killed.

    The experiment was designed to illustrate the flaws of the ‘Copenhagen interpretation’ of quantum mechanics, which states that a particle exists in all states at once until observed. If the Copenhagen interpretation suggests the radioactive material can have simultaneously decayed and not decayed in the sealed environment, then it follows the cat too is both alive and dead until the box is opened.

    Common sense tells us this is not the case, and Schrödinger used this to highlight the limits of the Copenhagen interpretation when applied to practical situations. The cat is actually either dead or alive, whether or not it has been observed.

    Explanatory blurb taken from source
  3. #1002182016-03-11 02:53:29--Jack-- said:

    The Ship of Theseus

    ...is a thought experiment questioning if an object is fundamentally the same even after all its components have been replaced.

    http://i.imgur.com/iVmY7lI.jpg

    Essentially, in this experiment we have a ship, The Ship of Theseus, which is used for many years. As time goes on, The Ship of Theseus begins to wear and tear, causing the crew and captain to have it repaired with new materials over time.

    The Big Question: Once the entire ship has eventually been replaced due to (quite a few) repairs, is it really The Ship of Theseus?


    There's a Parallel to this experiment with a simpler object: "Grandfather's Axe"

    A family passes down this simple woodcutting tool. As time goes on, the axe head needs replacing, so it is replaced with a better axe head. A few years later the handle is starting to crack, so the handle is replaced as well.

    Is it still grandfather's axe?

  4. #1002582016-03-11 13:32:33naidraug said:

    I really feel like this is just blank, filler content that doesn't really have much of an answer or purpose. I'm just joking. What kind of jerk makes a post like that?

  5. #1006032016-03-20 01:59:59--Jack-- said:

    Wow I just noticed this, lol.

    Also, the kind of jerk that has to handle flagged posts that have nearly no content. It's pretty hard to defend a one-sentence thread. I'm still on the fence about locking this nonsense due to self-promotion.

  6. #1009542016-04-01 17:21:07Rinneko said:

    The Grandfather Paradox

    This thought experiment highlights a problem in the concept of time travel. Can you prevent your birth by travelling back in time to kill your grandparents? If so, who would have been the one to kill your grandparents, then?

  7. #1010462016-04-06 06:39:13--Jack-- said:

    I really thought over time travel and these things when I was making a story for one of the past writing projects, and since I'd imagine all people who call themselves writers have their own pseudo "rules" for these things, I tried to make it as realistic and theoretically sound as possible when I was thinking it over.

    For this paradox, as well as causalities (going back in time and causing your own creation [like introducing your parents to one another, etc]) I ended up at two roads to go down, time travel with the multiverse theory being accurate, and time travel with no other external universes at all.

    • In the Singular Universe version there aren't many outcomes, or so it would seem. Most likely, either everything everywhere would break (however you'd like to imagine this) or absolutely nothing at all would occur, possibly with the person causing the paradox either being sent back to the moment before it occurs, or with them simply being erased from existence.

    • In the Multiverse version (which is much more interesting) when someone travels back in time, they are actually entering a nearly identical universe at a different point in time. In other words, technically, this would make a "new timeline" every single time someone moves between universes and time. Why do the cause and effects of individual travellers' actions follow them to the next universe they end up in? Why do things in the next universe seems identical to the previous (besides things that may have been caused by the traveller? Well...

    Simply Put: I'd imagine the Multiverse is like most scientific and 'natural' functions, and conserves space, energy, and in this case entropy as well. In other words, the multiverse isnt willing to get off its arse just to show you an effect without there first being a cause.

  8. #1010502016-04-06 09:43:28 *WaywardHawke said:
    The Race Between Achilles and the Tortoise

    This is one quite puzzling thought experiment, dealing with the principle of asymptotic functions. Say that a tortoise (or any other suitably slow animal) agrees to a race with Achilles (or any other suitably faster person/animal/character). It is taken that Achilles is 10 times faster than the tortoise. To provide a handicap for the tortoise, it is given a head start of 10 meters. To keep all things simple, it is assumed (in terms of modern physics) that both the participants run at uniform speeds. The tortoise start the race, as Achilles watches on. When the tortoise reaches the 10 meter mark, Achilles begins his own running.
    Now, Achilles will cover the distance between them in a given amount of time, being 10 times faster than the tortoise, but in that time, the tortoise would have moved another meter. Achilles would then cover that meter too, but the tortoise is now 10 cm ahead. Again, Achilles covers it, but the tortoise is a centimeter ahead still, and so on. The distance between Achilles and the tortoise is asymptotic, but by following the rational logic given, Achilles will never pass the tortoise, it being always a fraction of a distance ahead!
    Using physics, the entire thing can be summed up into another situation. Two point objects are racing at uniform speeds. One has a head start, and the other is faster. Applying this logic again, the faster body will never cross the slower one, due to it's head start!
    Now, using independent free body diagrams, we can say that Achilles would have crossed the tortoise easily. Assuming he ran at 10 m/s, in two seconds he would be 20 meters from the start, while the tortoise is 12 meters. Achilles also runs along with the tortoise at 1.11111111.... seconds, after which Achilles leads.
    Therefore, applying logic and applying physics can give two different results. It also means that a seemingly asymptotic function (the distance between the racers) also grow closer faster. Every next 90% reduction of the distance between them took 90% less time. Hence, the function wasn't truly asymptotic.

    Personally, I'm still baffled. Physics gives a rational answer, but applying normal, sound logic gives an irrational answer.
    EDIT: Analysing a distance-time graph of the racers, and cross relating it with a time-distance between the runners graph gives an answer supporting physics (which is naturally inviolable). Hence, its the premises of the logic that makes no sense.
    RE-EDIT: This logic will apply to a lot more than a race. The dichotomy paradox is a closely related theory, made by the same philosopher (Zeno). In this one, to get to a point a distance away, you need to cross the halfway mark between the points. And to get to the halfway mark, you need to get to the halfway mark of the halfway mark...and so on ad infinitum. This implies that motion cannot exist as a single process; you're doing an infinite number of processes.
    An interesting fact that Diogenes the Cynic (someone whose simplicity was praised even by Alexander the Great), on hearing the theory and paradoxes. stood up and just walked across the podium, subtly showing what he felt about thought experiments and their accuracy.