This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

It Just Is

I wonder how much of what we 'know' has ever been properly explained? Our teachers repeat what they have been taught and our text books are re-writes of earlier text books. Perhaps that is the way to pass exams, don't think about what is missing, just repeat what was taught and so it goes on.


Lately I have been looking through some of my old 'how it works' books from my childhood, encyclopedias, atlases and 'online' to see what they say about the Earth's seasons. At least they all agree! It is all down to the tilt of the Earth's axis, the northern hemisphere points towards the Sun in the summer and away from the Sun in winter. Simple! We don't need to know anything more.


A simple experiment: Take a dinner plate and place an apple near the rim with its stalk pointing slightly towards the centre, a model of the tilted Earth. Now slowly and carefully twist the plate on top of a table so as not to disturb the apple until the plate has turned through 180 degrees. Now which way is the apple pointing? Do you still understand the seasons or did you have a book/teacher that really explained it? Perhaps you are a heretic and thought for yourself? Andy Millar raised some of these issues in "You don't need practical skills to be an engineer", 'knowing' how to do something can stop new thinking.


Have a virtual mug of coffee and think about it!
Parents
  • James,

    I am afraid I am still struggling with your 'explanation', though I can't decide if it is because it is oversimplified or if it is not simplified enough. I can just say I can't align it with my understanding.

    When I said there are no forces acting on the Earth to displace the axis, what I meant was that there are no unbalanced forces. Further, while I can agree with your comment 'In other words the local frame of reference stays the same, (Paris is still to the south of London etc.) but that reference frame orbits the Sun', you then say 'which means the day of the year, (season-wise), stays the same' which would mean the local frame of reference has changed with respect to the stars. I am afraid this is where you lose me.

    If you want to think about it from a more terrestrial viewpoint, a spin bowler in a cricket match imparts spin to the ball when he releases it. The axis of rotation of spin does not change during flight even though it is following a parabola due to Earth's gravity, because the gravitational pull is balanced over the whole of the ball. Note there will also be a tidal force, but I doubt if it would be measurable.

    Alasdair


Reply
  • James,

    I am afraid I am still struggling with your 'explanation', though I can't decide if it is because it is oversimplified or if it is not simplified enough. I can just say I can't align it with my understanding.

    When I said there are no forces acting on the Earth to displace the axis, what I meant was that there are no unbalanced forces. Further, while I can agree with your comment 'In other words the local frame of reference stays the same, (Paris is still to the south of London etc.) but that reference frame orbits the Sun', you then say 'which means the day of the year, (season-wise), stays the same' which would mean the local frame of reference has changed with respect to the stars. I am afraid this is where you lose me.

    If you want to think about it from a more terrestrial viewpoint, a spin bowler in a cricket match imparts spin to the ball when he releases it. The axis of rotation of spin does not change during flight even though it is following a parabola due to Earth's gravity, because the gravitational pull is balanced over the whole of the ball. Note there will also be a tidal force, but I doubt if it would be measurable.

    Alasdair


Children
No Data