Questionable Motives

February 10, 2011

Head, meet wall. What is reality?

Filed under: Physics,Science — tildeb @ 11:04 am

One day while fixing my bicycle tire, I noticed something that has since bothered me for a very long time. My bike was upside down and I had replace the inner tube, which meant I had removed the tire and had then realigned it within the rim. I then inflated. Everything was good. The final step was spinning the tire to see if it rubbed against the brake pads or frame because a few of the spokes had also been replaced over time so the tension throughout the entire wheel was always a bit off resulting in a very slight wobble when the wheel was spun. The tire spun clear so the job was done. But that’s not what bothered me.

As the tire went around and around, I saw that every point on that tire was moving pretty quickly. As my eye moved toward the axle, I noticed the spokes were also moving but not as fast. The end of each the spoke near the tire was moving much faster than the other end of the spoke attached to the axle. In fact, the axle itself was rotating hardly at all compared to the tire which was zipping around even though the two were directly connected. But that’s not what bothered me.

Because the parts were moving, I knew that they could not be at the center of the wheel but some distance from it. That’s why they were rotating. They were rotating around the center point. And even that didn’t bother me.

There had to be a part – a  center point – in the rotating wheel I was spinning that didn’t move at all. If it was moving, then it was rotating, and if it was rotating then it couldn’t be the center but some distance from it. How could a rotating physical object posses a physical part within it that did not move – could NOT move – at all?

This paradox really bothered me. And it still does because I have no understanding how this can be, how a moving physical object when spun can possesses a physical point where no movement can occur. Yet I know such a physical part has to be there.

Such mysteries have always grabbed my attention. That’s why I get drawn into watching videos like this one. Many of the ideas are like flames to my moth-like curiosity as my mind bangs up against them without breaking through to a clear understanding of an answer. Maybe you’ll likewise be drawn to think about some the remarkable ideas that help us to better define and move towards understanding what this state we call reality actually is.


  1. It all moves around the axial of the wheel – which is fixed in relation to the moving wheel – if the wheel and the axial could not move the bike would have to move in the direction of the spinning wheel.

    You see tildeb, it is all relative ;o)

    Comment by misunderstoodranter — February 10, 2011 @ 1:53 pm | Reply

  2. Fixed in relation to the moving wheel? Obviously the entire wheel as a whole can move, but the center of the rotation cannot rotate.

    Comment by tildeb — February 10, 2011 @ 2:13 pm | Reply

  3. What MUR meant, I think, is the sort of wheel that has a hole in the middle through wich an axle goes. Sometimes the axel itself does not rotate, but the wheel only rotates around it. Of course, in a bicycle that is not the case, the axle, or hub, is fixed in the ends of the fork, but it rotates itself with the wheel.

    But I don’t understand why you think there needs to be something in the center that is fixed. If you take someone by the hands and both of you dance in a circle, you are both rotating around and empty center. There doesn’t have to be anything in that center. That central point is just a construct, you know, the same way that a body can have a centre of gravity that isn’t within the body.

    Here is a pretty good table explaining spinning motion:

    See how it says that the fictitious centrifugal force acts as if emanating from the rotation axis but that isn’t its real source, while the reactive force is exerted by the bodies moving in a curved path.

    After all, something can turn around on its own axis, can’t it? You can turn on your own axis, the earth can rotate on its axis, and all the planets can spin around the sun, without there anything having to be actually stationary in the middle. Even the innermost atom of the axis can turn around itself, even the protons in its core can spin around their own axis… I think.

    (But then, I’m not a physicist… just a dumb baker boy… :p)

    Comment by FreeFox — February 10, 2011 @ 2:43 pm | Reply

  4. Sorry yes – I meant axle… (if you haven’t noticed – already, my speeeling is awful).

    Even in a bike – there is sometimes a pin that goes straight through the axle on which the wheel turns… or the wheel is braced like train wheel – where the axle and the wheel turn together, within a housing circled with bearings… or a variation on this theme… the wheel turns in relation to something that is fixed, and is kept in position by something that is fixed.

    But yes – I agree with FF, there isn’t a fixed point a middle which does not turn – certainly not at the atomic layer anyway. Like with a single disk that has no moving parts, it turns in relation to another fixed object, and does not turn in relation to itself.

    That said, anything could be happening at the sub-atomic layer though, but I not even going to pretend I know anything about that, and I know I am not smart enough to explain it.
    What I do know is that particles of matter at the sub atomic layer cannot be positioned with precision – i.e. we don’t know where they are, we can only set a probability of where they will be – which is really, really odd.

    Some random questions – I think about regularly:

    1) Which way up is earth? – We tend to think of North being up and South being down, but is it really that way?
    2) Why does the Sun get heavier as it burns all its fuel? Surely it should lose mass as light and energy leave it? (I am sure there is answer here).
    3) Is light really a particle or is it really a wave?
    4) What is time?
    5) Why is absolute Zero – absolute? (and is there an absolute ‘hot’)
    6) What is space made of? (I mean the bits between matter – please don’t say nothing, because for nothing to exist in the way we comprehend something must exist – even a vacuum room has walls, and ability for the light to travel through it – true nothing is well nothing).

    7) What are dreams – and if they are not significant, then why do we sometimes remember them?
    8) What is consciousness? (And when did I become conscious?)
    9) How fast is the solar system moving through space, and where is it moving to?
    10) Can animals think? (and if so how do they make decisions / if not how do they make decisions).
    11) Is zero a number? Or is it a representation of nothing (i.e. is it a value).
    12) Is gravity faster than light?
    13) …
    14) …
    15) …
    16) …
    ∞) ∞

    Comment by misunderstoodranter — February 10, 2011 @ 4:33 pm | Reply

    • is fixed in the ends of the fork, but it rotates itself with the wheel, and
      Like with a single disk that has no moving parts, it turns in relation to another fixed object, and does not turn in relation to itself.

      So the entire wheel is not really moving ‘around’ anything but remains a complete fixed object even when rotating. Okay. That makes sense!

      Thanks people! One conundrum down, just a few more to go…

      Comment by tildeb — February 10, 2011 @ 7:53 pm | Reply

    • I can help you with one question there. Absolute zero is actually a measurement of ‘jiggliness’ of atoms. ‘Heat’ is really a measure of how much atoms are jiggling. When atoms stop jiggling it’s absolute zero. You can’t get less than absolute zero because you can’t get less than ‘stopped jiggling’.

      Comment by Damian — February 15, 2011 @ 3:53 am | Reply

  5. Thanks Damian – I did do a little back ground reading on this one… and yes you are right… hurrah, my knowledge is extended…

    Comment by misunderstoodranter — February 15, 2011 @ 1:50 pm | Reply

    • Ha! I’m just glad it even made sense. I wrote that late last night after having a few too many drinks around at a friend’s place. I have a general rule never to post on the internet after drinking but am happy to say that I stand behind that as a perfectly reasonable (and even intelligible) explanation of how ‘heat’ really works. 🙂

      Comment by damianpeterson — February 15, 2011 @ 4:20 pm | Reply

  6. “We join spokes together in a wheel,
    but it is the center hole
    that makes the wagon move.”
    -Tao Te Ching #11

    is this what you’re saying?

    Comment by zero1ghost — February 27, 2011 @ 7:59 am | Reply

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