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What is reality after all?

  1. Apr 12, 2010 #1
    Just a small example? (It can be extended as per will)

    A person (X) and his friend (Y) are sitting in a room that has a table placed in the centre. X says to his friend, 'Can you determine whether the table is in the exact centre of the room or not?'

    Y says, 'I go even further, this table is not there. It's only our brains that are programmed in such a way (by nature) that we can build a perception of this table. The table is here only from our view point otherwise it does not exist in the very first place.'

    Suddenly an alien comes there. He can't see (feel) the room, the table, the persons sitting in it. For him it's just emply space.

    He says to himself, '****, I can't trace any matter in this part of the universe also, despite our advanced technology that has a history of over a billion years, despite these highly advanced gadgets that I am carrying with me.'

    He just flies there to and fro and in the process passes through the friends, the table, and leaves the place. For him there is no trace of 'matter' for trillions of lightyears that he has travelled.

    Obviously, the friends are also unmindful of the alien's presence, though Y is saying exactly what is happening right in front of them.

    I could have put this scenario using popular terms like "different regions of space time" or "time travel" or using "very few words". But I like it this way only.

    Do you agree with Y and consequently with the alien? Why/Why not?
  2. jcsd
  3. Apr 12, 2010 #2
    No, I don't. This assumes that our location and us are special in some way relative to the rest of the universe and organisms/life which may or may not exist in other areas of the universe. I do not accept this premise.

    They sure may perceive it differently than we do but they won't be travelling through us or our tables, how did they even know there was a planet here? How did they perceive that? Or were they just travelling through the entire planet?

    What I'm saying is if their methods of perception worked where they have come from, then it will work here too. Sure the table might not be there, but I don't care for those theories because I have yet to see someone show to me that the table isn't there. (I have asked many people).

    The burden of proof falls on the person making the claim, not those negating it. Just because something is possible doesn't mean we have just reason to believe it over other things which are demonstratably true.
    Last edited: Apr 12, 2010
  4. Apr 18, 2010 #3
    Well yes I agree sorta because its all clearly happening in our minds but that doesn't mean it's also not really there also.
  5. May 4, 2010 #4

    Yes, if the alien is composed of non-interacting particles or even weakly-interacting particles like neutrinos, he'd be able to pass right through the Earth and the Moon and the Sun.

    Or if MWI is true, said alien might now be sitting by your bed together with a few surviving dinosaurs. Of course you wouldn't notice because their wavefunctions have decohered from yours. Don't ask if those decohered aliens and dinosaurs are real, nobody knows.

    And this wasn't a joke either. Otherwise, the question "What is reality?" is a pretty good one to ponder about, though as with the above question - nobody knows.
  6. May 5, 2010 #5


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    I disagree. If you shine a light at the table, it will reflect off of it. If you throw a ball at the table it will bounce off of it.

    A hypothetical alien that isn't able to interact with the table foes not disprove the table's case for reality. It shows that reality is complex, and that certain aspects of reality may only interact with other particular aspects of reality.
  7. May 5, 2010 #6

    I think, if i understand correctly his point, that he's proposing we may not have free will by:

    "Y says, 'I go even further, this table is not there. It's only our brains that are programmed in such a way (by nature) that we can build a perception of this table. The table is here only from our view point otherwise it does not exist in the very first place.'"

    Though i didn't see why he would need to assume that to make his point about non-interacting particles.

    For sure, reality could be multi-layered in a MWI-style.
  8. May 5, 2010 #7
    I don't this is his point. The title is 'what is reality after all' and it looks as though he's just trying to counter that reality is 'stable' or that somehow there are alternate realities existing within our own... or something to that effect. Nothing about freewill though.

    Indeed. Only one of them is OUR reality though so who cares about the others?
  9. May 5, 2010 #8

    There is one :smile:.
  10. May 5, 2010 #9
    Hmmm I'm not sure how to interprete this!!!! hahahahahaha.

    Are you saying 'there's one' as in the one I mentioned is one of many.


    Are you saying 'there's one' as in there is only one reality just perceived differently. Hahahah the confusion!
  11. May 6, 2010 #10

    I meant there was someone who was interested in , e.g what happened in the universe where i didn't break the fight between my pekingese and a stray cat. Who won :surprised?

    What happened when Hitler won the 2nd WW? I am generally more interested in the other realities than of our own, where the interesting events are now a closed book.

    I want to know about the universe where the theory of quantum gravity was published in 1983. Or the one where the Soviets attacked the US :surprised? Or the one where Einstein couldn't help it and landed a fist in the face of Bohr? :bugeye:

    Who/what was responsible for me landing in a universe where I didn't win the lottery and didn't sleep with Paris Hilton and Naomi Campbell...(at the same time - *blush*)?
    Last edited: May 6, 2010
  12. May 6, 2010 #11
    You sound as though you would enjoy writing science fiction, of the historical variety. Do you?
  13. May 6, 2010 #12

    No, not at all. How is this related to my post or the MWI?
  14. May 6, 2010 #13
    The interest in "what ifs" has always been a fascination of writers, and you seem to write well. I wondered if you were an author incognito! "What If?" and MWI are definitely bedfellows, so I thought you might have given them enough thought to commit them to paper. I mean this to be complimentary.
  15. May 6, 2010 #14
    First i think you need to explain what you mean by 'exist.' The way I interpret reality is that all reality that is physical and exists, does so independent of our minds.
    The reason we can only perceive parts of it is because our eyes can only see the visible spectrum of the electromagnetic spectrum.

    For a MWI theory to happen like that, there would have to be infinite universes.
    Everything that could have happened, happened, in one universe or more, and not only did one event happen, but every event that lead to another event that didn't happen in one universe, actually happened in another.
    So basically me just eating an apple could easily spawn millions of universes simply to include every possibility. Like where do you draw the line there? Every atoms unique position? Or is it on a much higher level like I only need to eat the apple once, and then that counts as an event?

    Cause if you cound on a lower molecular or atomic level, it would mean I would hold the apple in many different ways, I would eat it differently.. Everything from pressure in my jaw to where my fingers are on the apple to even WHEN I eat the apple would each spawn hundreds of universes.

    Needless to say I think this is a very unproductive idea.. And quite ridiculous too.
  16. May 6, 2010 #15
    This is about the wavefunction, not a macroscopic action. I don't believe that you understand MWI in more than popsci terms. The level would be the test particle taking all possible paths, and you build from there, you do not deconstruct from macroscopic actions.
  17. May 8, 2010 #16
    I agree. If I have a blindfold on and I walk into the room but my senses do not pick up the table or other objects in the room, it does not mean they are not real. My viewpoint gives it a perspective, but not an existence. I think decoherence can answer this question. My observation is not needed (in principle).
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