1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What happens between our perception intervals?

  1. Sep 13, 2014 #1
    As far as i understand, we (our mind) observe the universe at set periods of time, say, our consciousness activates each 0.5 seconds for instance.

    This means that we have no perception whatsoever of what happens between the 0.5 seconds that exist between our perceptions.This led me to the question: can we be 100% sure that, for instance, when we see a body B moving from point 1 to point 2, it actually moved across a straight line? Or could some very strong force have moved it backwards behind point 1 at some instant, and then some other even stronger force moved the body to point 2? In the end, we would still believe that the object took a straight path, but we have no way to know!

    Is there some law in physics that invalidates this? Otherwise we couldnt be 100% sure when we make statements like "John was here (America for instance) with me during the last 10 minutes, so he couldn't be in China 5 minutes ago as you said". Since John could indeed have been in China between our perception instants.

    Thanks in advance
  2. jcsd
  3. Sep 13, 2014 #2


    User Avatar
    Science Advisor

    Where did you see this? I've never heard of such a thing.

    (You use the words "consciousness" and "perception". You understand, don't you, that the are not the same thing?)
  4. Sep 13, 2014 #3
    Perhaps got the idea from our brains "switching off" input from the eyes when we change where we are lookin until the eyeballs have stopped moving.
  5. Sep 13, 2014 #4
    That is not what i mean. I mean that we cant observe a given object's movement at every single position it passes through during its trajectory, just like i can't measure time in miliseconds or nanonseconds using my perception.
  6. Sep 13, 2014 #5


    User Avatar

    Staff: Mentor

    We have plenty of instruments that can resolve shorter time intervals than the naked eye can.
  7. Sep 13, 2014 #6


    User Avatar
    Gold Member

    Probably, but 1/2 second is can't be the lower limit. If it were, our perception would always be as though everything were illuminated by a strobe light. Movies and TV have to run at something like 24 frames / second minimum, otherwise THEY look to us like they were shot under a strobe light.

    Where on Earth did you hear anything so silly as 1/2 second? Given your own experience in day to day life, how can you possibly believe it?
  8. Sep 13, 2014 #7


    User Avatar

    Staff: Mentor

    That's not how it works, although what's actually going on is at least as strange and interesting. If you want to explore this topic further, you could try reading Daniel Dennett's book "Consciousl Explained" - the title promises a bit more than the book delivers, but it's a good start.
  9. Sep 13, 2014 #8
    Thank you for all the answers so far. Please do not emphasize the 0.5 period of time for our time perception, it was just a "shot in the dark". My main question in this topic is how do we guarantee, or if there is something in physics that assures to us that an object moving from X to Y passes through every single point between X and Y and does not go back at any moment.

    I mean, if something caused the body to move backwards very fast, and then put it back in place with fast speed also, our human eye would not perceive it, we would still see that the object moved from X to Y even if it actually went from X to Z, Z to W and then from W to Y, really fast, without us perceiving it.

    Kinda like if person P1 looks at person P2 at t=0 seconds, then P1 perceives person P2 again at t=0.5 seconds, what guarantees that no really fast story occurred between these two time intervals? We could not perceive it! We're "blind" during these 0.5 seconds and even if the whole story of the universe occurred, really fast, during these 0.5 seconds and then restored the conditions we would excect to see, we wouldn't perceive it.
  10. Sep 13, 2014 #9
    There exists a family of instruments called Digital Delays, one use of which is in sound reinforcement and effects. In designing such products, naturally they needed to calculate just how short of a delay a human can detect. Not only is it not 0.5 seconds, it is many orders of magnitude shorter, closer to 0.0000025 seconds. This is in discreet pulse instrumentation/events. In analogue signals, transients far shorter can be detected, sometimes by longer term effects, but also all but instantaneously assuming the source is very close, as in headphones.

    So the first thing you need to do is follow your own advice and stop falling back on 0.5 seconds. Stop thinking in terms of tenths, hundredths, thousandths, ten thousandths, or even hundred thousandths of seconds as units of perception time. It's just wrong and by a lot. Our brains are not digital.
    Last edited: Sep 13, 2014
  11. Sep 13, 2014 #10


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    I understand that there is a delay between a stimulus - like seeing the second hand of a clock changing position (once a second - not a continuously moving sweep hand) - and being aware of it. It is quite common to glance at a clock and to think it has stopped because it seems to take longer than one second before it moves,on the first occasion. This may be at the root of what DarkFalz is referring to. The way we perceive things is a very complicated process. The reason is that our quirky brains make us think that we have a complete picture of what we are looking at and the whole of the mental model they are constantly building of the world around us cannot be updated real time. However, the updating is not at a regular rate and depends upon what part of a scene is getting our particular attention at any one time - it's not like a cine film, passing through at 18 frames per second.
  12. Sep 14, 2014 #11


    User Avatar
    Science Advisor

    There is a philosophical question lurking there. If you can't measure it, how do you know it's true?

    Classically we model time and space as being continuous and objects as always having precise positions in space that vary continuously as functions of time. Experiment is (or was) consistent with that model down levels of accuracy much better than we can achieve with the naked eye. But ultimately, it is just a model. One can never have 100% assurance that a model is accurate in realms where there is not yet experimental confirmation.

    In the realm of the very fast and the very small it turns out that quantum mechanical effects intrude. There are fundamental limitations on our ability to measure position and time accurately. We even have experimental evidence of particles existing here and then existing there without having traversed the space between. http://en.wikipedia.org/wiki/Quantum_tunnelling

    But this has nothing to do with a 0.5 second lag in human perceptions (as estimated with reaction time measurements).
  13. Sep 14, 2014 #12
    I agree that there might be a philosophical question in here, namely our "blindness" during the time interval of our perceptions. I ask this because, lets assume that for instance, two persons are talking to one another and one says "John must have come here and hit my car 5 minutes ago", and the other person argues on defense of John "no it couldn't have been him, i was with him 5 minutes ago". This argument assumes that if John was with the second person, the second person perceived him during the entirety of time, and John is still a human, so he couldn't in principle, move at "lightspeed" to fool the second person.

    Still, what i ask is if there is something in physics that disproves completely that this could happen, that very strong forces could fool our perception by causing events to happen inbetween our perceptions.
  14. Sep 14, 2014 #13
    So we have gone from 0.5 seconds to 5.0 minutes now? The holes in our perception are extremely small for the events on the plane in which we exist. That's why they evolved as they did and also why QM is rarely intuitive to us.

    This however is beginning to sound like "If a tree falls in the forest with nobody near, does it make a sound?"

    The world isn't "built around us". All evidence supports that we sprung from the world and no forces have, as part of their "raison d'etre" confounding humans, even though Murphy might disagree :) .
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook