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!

Fly on/off the Antennae

  1. Sep 23, 2011 #1
    I apologize if this should be posted elsewhere, but I was impressed with the answers to some other physics questions I had after doing a Google search, so I thought this would be a good place to begin. I apologize for my elementary understanding. I wouldn't mind some guidance to other sources of information related to my question.

    My question stems from a class discussion during a logic class where the instructor stated that a fly is either ON the car antennae or OFF the car antennae. My contention with him was that there must be some sort of transitional state where the fly is either ON and OFF simultaneously or neither ON nor OFF. My instructor asked what I would base such a position on and I responded "quantum physics" despite my utter lack of knowledge in the field. He said that we could discuss "quantum physics" some other day.

    My question is, can a fly ever be in a state where it is both "ON and OFF" or neither "ON nor OFF" in relationship to a car antennae? Wouldn't there need to be a transitional state (for example, when the fly is leaving the antennae) where it is both ON and OFF?

    I'll leave it at that... Thanks!
  2. jcsd
  3. Sep 23, 2011 #2
    1. Antennae is the archaic plural of antenna. How many antennas does the car have and how many of the antennas is the fly on at the same time?

    2. How do you define "on"? If the fly is hanging underneath the antennas is he still "on" the antennas? If only 1 leg is attached to the antennas (probably not easy to do even for a fly), is he still "on" the antennas?

    3. Are we discussing Schrodinger's fly (no not that one, the one that flies around) in which the fly on the antennas is hidden from view so that the fly's status is unknown before a measurement is made, and the fly may be considered to be both on and off the antennas at the same time?

    4. If the fly's antenna is touching the car's antennas is the fly on the car or the car on the fly?
    Last edited: Sep 23, 2011
  4. Sep 23, 2011 #3
    Sorry, I misspelled antenna.

    Let's imagine the fly is resting atop an antenna - on the tip. Your word "attached" seems to be a good word to use here.

    No. This is just my own pet fly. ;)
  5. Sep 23, 2011 #4
    Perhaps when the fly lands on or takes off of the antenna, he makes a quantum leap.
  6. Sep 23, 2011 #5
    Although you were trying to be funny (I admit I chuckled) maybe you're not too far from describing the reality. :)

    I hope someone has an answer to this question as to whether a fly, in transitioning from ON the antenna to OFF the antenna, can be considered to be both ON and OFF simultaneously at some point in time (maybe time has "2 tracks"?) and how this relates to quantum physics.

  7. Sep 23, 2011 #6
    Without getting into techincalities like "is there a layer of molecules beneath the fly's feet that separate it from the antenna, therefore it is never ON at all though it is resting on it." No. If we define "on" as "being in physical contact with", then the fly is either on the antenna or off. Once it touches the antenna, it is "on" it.

    With that said. You could argue that if only one leg is touching the antenna, he is neither on nor off it.
  8. Sep 23, 2011 #7
    Thanks for your reply, Travis.

    What I'm hoping to avoid is too much discussion over semantics and such.

    That said, when you state that the fly is "neither on nor off it" when "one leg is touching the antenna" I would have to ask why 1 leg = OFF and 2 legs = ON? I swear I'm not trying to be trivial or argumentative! lol

    For discussion's sake, let's assume when the 5th leg is no longer "touching" that we can consider the fly OFF. When that 5th leg is "touching" the fly is considered ON.

    -At what point is the 5th leg not "touching" the antenna?

    -What physical state must be true to say that the fly is no longer "touching" the antenna?

    -Is there a transitionary state between "touching" and not "touching"? Perhaps a state of "bond breaking" or "bond forming"?

    -Can this theoretical state called "bond breaking" be considered as neither "ON nor OFF" or both "ON and OFF"?

    -Is the bond which is "breaking" or "forming" a magnetic bond formed by relative proximity or is there a real unity between the two objects beyond being "very very close"?

    Please point me to how this relates to Quantum Physics... Is there some sort of Proximity theory or something?

    I want to avoid sounding trivial or small, but that's what we're dealing with when we get down to the quantum level.
  9. Sep 23, 2011 #8
    Sorry, but what you've got is a semantic question. The question of whether or not it is on only exists because "on" is ill defined. There would be no such problem if you were asking "Is the fly touching the antenna?" because that has a clear definition (as long as we aren't being overly critical). What does it mean for a fly to be "on" something?

    Here is the crux of your debate. I don't think quantum physics has anything much to do with it, but physics sure does. Again though, this depends on how you define touching. Anyway. Since we are really nothing but a bunch of electrons and protons (and lowly neutrons) nothing really ever touches anything else. This is because as objects get close to one another and "make contact" the electrons at the surfaces interact and repel eachother. That's why we can't put our hands through walls, the medium is dense (ie lots of electrons close together) and the electrons and protons in our hand can't push them out of the way.

    The short of it is, nothing ever touches anything else

    when your finger deforms while being pressed against the table it is because the molecules which make it up are aligned in such a way that when other molecules exert force on them (again, this force is necessarily electrostatic repulsion) they have room to give way and change position. The molecules in the table move around too, but to a lesser extent. That is why some objects deform more than others. (in a very simple explanation)
  10. Sep 23, 2011 #9
    Thanks for treating me kindly... :)

    Yes, "touching" has a clear definition as two things together with no space between them.

    So, we can say that "touching" is just a word we use to describe the relative proximity of one object to another. If two objects lie within a "predefined space" then we can say they ARE TOUCHING, but if they lie outside that same "predefined space" then we can say they ARE NOT TOUCHING.

    Which leads us to the quantum level because the "predefined space" has to have a definite physical boundary or edge. How thick is the edge which encloses the "predefined space"?

    In soccer, the sideline is "in bounds" while in American football the sideline is considered "out of bounds". In other words, the boundary line is not the chalk itself... it's the EDGE of the chalk line - either the outer EDGE or the inner EDGE.

    So, in order to "touch", two objects must be within a "predefined space" and this space must have a physical edge.

    This is the reason I end up here at quantum physics - because when we "zoom in" closer and closer to determine whether an object is within that predefined boundary "edge" or outside the "edge" of our predefined space, we eventually must come down to the smallest edge we know of...

    However small we go, we are forced to the edge of the boundary and the object is either past that edge or before that edge.

    Here's what it comes down to: Can the "last particle" of a passing object ever be ON that edge, like a volleyball rolling along the top edge of the net? ...on neither one side nor the other? ...a neutral or between state? A potential state?

    Does this make any sense? Your treatment of me here in this forum has been great. Thanks for your patience. I know my question is valid despite how crazy it sounds...
    Last edited: Sep 23, 2011
  11. Sep 24, 2011 #10
    My point is that it doesn't matter if one or a hundred billion particles are touching. I still don't think you could ever call any point a "transition" state as long as you have your "is it or is it not touching" dichotomy.

    Really, your question is now "Is anything ever touching at all?" and that is above my level of knowledge, fo sho. I'm an engineer, and I usually side with the practical. If it looks like you are touching something, feels like it, and responds like it, then you are touching as far as I'm concerned.
  12. Oct 4, 2011 #11
    Thanks for the discussion. http://www.rosaceaskincare.org" [Broken]

    I'm now reading "The Hidden Reality: Parellel Universes and the Deep Laws of the Cosmos" by Brian Greene. Maybe that will help...
    Last edited by a moderator: May 5, 2017
  13. Oct 4, 2011 #12


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    The answer to all this depends upon whether you are a Scientist, a Mathematician or an Engineer, (Or, possibly, a Philosopher)
    What do we mean by mean by mean?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook