Discussion in 'Physics & Math' started by Seattle, Jun 21, 2018.

  1. Seattle Valued Senior Member

    We are roughly in the middle of the large and small scales I listed in the OP.

    You seem to want to argue about the large and small scales I listed as not being necessarily absolutes. I can't work with what we don't know.

    The scales I have listed are what we know and it's not as you suggest because we can see them. So, in that sense you are wrong. We haven't seen a Planck length or even measured anything smaller than 10^-18.

    Additionally, I find it helpful and interesting to have those benchmarks to help gain perspective of just how small an atom is, a nucleus is, etc. If you don't, that fine as well.
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  3. DaveC426913 Valued Senior Member

    I mean "see" in the study/research sense. Our science sees equally far in both directions along the scale.
    If subatomic physics had gotten a few centuries head start over cosmology, or one had 10x more funding than the other, we might see it very differently.

    It's the word "are" that's sticking in my craw. As if it isn't a product of our own doing.
    I think it would be more accurate to say we have explored roughly equal distances along both directions of the scale.

    "I think it is interesting that I am in the central leg of this river. After all, I've walked a mile upstream and downstream. I don't know anything about the head of the river or the mouth, but I can say I'm about at the middle."
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  5. Seattle Valued Senior Member

    For some reason you are intent on casting shade on this subject with your flawed fog and river analogies. I'm not projecting any "meaning" to us being roughly in the middle so ... whatever floats your boat...

    We haven't explored beyond the visible Universe because we can't. I can walk out of fog and I can continue walking along a river bank.

    We haven't gotten smaller than the Planck scale because we can't (at least at the moment) and given the smallness of that scale it's reasonable to think that we can't get much smaller if at all.

    Therefore your "analogies" seem to only cast shade rather than being reasonable analogies. If I was somehow arguing for some meaning (God, we are special, or some such nonsense) I could see (somewhat) why you are digging in on this one point.

    As it is, I don't.
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  7. DaveC426913 Valued Senior Member

    You've posted it for discussion. Were you expecting only claps on the back?

    I have not used the word meaning, why are you using it?

    You said 'interesting'.

    What do you find interesting about it?


    The analogy is that, for whatever reason, we have not walked farther along the river bank. Maybe it's only been an hour, or maybe we're not using the right equipment to walk/look.

    The point being that - just because we can't see beyond a mile - doesn't mean we can assume that the river ends there, and then conclude that we are in the middle section of the river.

    Seeing neither end of the river tells us nothing about where we are on the river. It simply tells us we have so far walked a mile in both directions and, as yet, found no ends.
  8. James R Just this guy, you know? Staff Member

    From any perspective we're (roughly) in the middle, between the limits that Seattle suggested in the opening post.

    The range of the weak nuclear force is approximately \(10^{-18}\) metres, but string theorists (not to mention simple dimensional analysis) suggests that, maybe, the really fundamental stuff happens at scales more like \(10^{-35}\) metres. String theory is not proven.

    The diameter of the observable universe is about \(10^{24}\) metres.

    Human beings scale at about \(10^0\) metres, so there are 24 orders of magnitude between us and observable universe, and about 35 orders of magnitude between us the Planck length. So, we're somewhere in the middle, roughly speaking.

    Of course, our observable universe might not be all there is. Some suggest that the universe as a whole might be infinite in extent, in which case we're infinitely far from the "middle" (there would be no "middle", in fact).

    But it's an interesting observation, and iceaura has given some good reasons for why we are the size that we are.

    When you're talking about 60 orders of magnitude (factors of 10), a factor of 2.5 is peanuts.

    No. They aren't human-centric. The observable universe is as old as it is, and therefore as big as it is, regardless of humans. Similarly, the Planck length is what it is, regardless of any human who might or might not be around to observe it.

    There are good reasons to suppose that the Planck length is a lower limit on meaningful lengths. And the size of the observable universe is a practical upper-limit, beyond which we cannot observe. That upper limit is increasing all the time, of course.

    No. It isn't. It's an evidenced observation.
  9. DaveC426913 Valued Senior Member

    The observable universe is defined by what we can see. No good science can be done outside that, but no scientist would declare that that is the limit of reality, just that we can't (ever) explore it.

    Seattle set his the lower at the diameter of a neutrino - nine orders of magnitude larger than theorized strings.

    Yes, we observe (i.e. understand) roughly the same distance in either direction of the scale.

    Why would it be interesting that I have observed 1 mile of riverbank in both directions - while acknowledging that I am currently only able to walk 1 mile from my camp?

    The observations (or undrstanding) tell us nothing about how long the river is in either direction, so I cannot say we "are" (Seattle's choice of words) in the middle. It dimply says we are at the middle point of our known view of the river.
  10. Seattle Valued Senior Member

    It would be interesting to know why you can't walk another mile along the river. Is it just because you got tired or is it because there was some insurmountable obstacle?

    If it were the latter then it would be that you were roughly in the middle of anywhere you could possibly go. It doesn't have to work out that way.

    We don't have to be able to go just as far down in size as up in size. Regarding up in size, as was pointed out, there may be no upper end, in which case we aren't in the middle but currently we are in the middle of the known Universe. There are some reasons as Iceaura suggested but it's not the ones you are suggesting.

    Going down in size doesn't have to scale the same as going up. If you are going to talk about unknowns then of course there is no "middle". If you were looking for helpful benchmarks however, you would stick with the known and make note of the various benchmarks.
  11. Write4U Valued Senior Member

    Actually I was not so much addressing actual range of size, but more from a range of experiential ability. We have our visual spectrum, sound spectrum, EM spectrum, in which we are able to actually experience the phenomena but at extremely limited scales.

    In view that our physical experiencial abilities in those media is extremely limited, from that perspective an order of 2.5 may well be significant.

    It may well be the difference between our position of visible light, nestled between ultra-violet and infra-red which we are not be able to experience visually.

    I admit, it is a minor point, but hopefully adds another relative perspective.
  12. James R Just this guy, you know? Staff Member


    As I said, there are some theoretical reasons why we might expect the Planck length to be the shortest length scale there is, regardless of what we can observe. And we already know that we can't observe beyond the observable universe (by definition).

    In other words, there's reason to suspect that your river has a definite end at the small end of the length scale, at least. And as far as anything that can possibly ever affect us goes, the river is also bounded at the large end of the length scale, although theoretically it might extend beyond the furthest point we can ever walk to.

    Anyway, I'm not going to argue with you about this any more. The most interesting thing to take away from this discussion, in my opinion, is to understand why human beings are the size we are. It's not random.
  13. TheFrogger Valued Senior Member

    Seattle, I read your posts and find them inter-resting, and as you wrote, even if you fail and someone disproves your theory, and makes it a "non-starter," you always have sciforumers to rely on. Please keep the good work going and continue to post. ☺
    Write4U likes this.
  14. Write4U Valued Senior Member

    I agree. As I understand it physical size is directly related to environmental pressures.

    On small islands animal life is almost always smaller than on wide open prairies.
    In overcrowded spaces occupants usually are smaller. Even species which are large when there is plenty room become "pygmy" over time when crowded or when resources are scarce.

    Small humans seem to thrive in heavily wooded areas of Africa and some areas in Asia, whereas the tallest humans (Tutsi) live on the African plains and are cattle herders (on foot).

    An interesting article from the Natural History Museum;

    Apparently temperature also has an effect on size.
    Last edited: Jul 2, 2018
  15. RainbowSingularity Valued Senior Member

    is comparative relativism a perceptual constraint ?
    it must be to some extent.
    what does this teach us ?
    are we genetically programmed to have a pre-disposition to comprehend concepts of a specific variant numerical conformity ?

    thus on the philisophical psychology of developmental psychology.
    self actualisation derivatives that lend to psychosis as darwinian agitators... ?
  16. Seattle Valued Senior Member

    More word salad I see...
  17. Lizard Registered Member

    The smallest of the small is "nothing."

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