gives the lie to


A lie-to-children is an expression that describes the simplification of technical or difficult to understand material for consumption by children. It is itself a simplification of certain concepts in philosophy of science.

Because life and its aspects can be extremely difficult to understand without experience, to present a full level of complexity to a student or child all at once can be overwhelming. Hence elementary explanations tend to be simple, concise, or simply "wrong" — but in a way that attempts to make the lesson more understandable. Sometimes the lesson can be qualified, for example by claiming "this isn't technically true, but it's easier to understand". In retrospect the first explanation may be easy to understand for its inaccuracies, but it will be replaced with a more sophisticated explanation which is closer to "the truth". This "tender introduction" concept is an important aspect of education.

Such statements are not usually intended as deceptions, and may, in fact, be true to a first approximation or within certain contexts. For example Newtonian mechanics, by modern standards, is factually incorrect (as it fails to take into account relativity or quantum mechanics) but it is still a valuable and useful model in many situations.


One particular progression of "lies" or simplifications, each of which are debunked or unraveled as one progresses deeper into a subject (in this case, physics), runs as follows:

  1. Weight is constant. Everybody agrees on how much something weighs.
    • Children in primary school learn that the weight of something doesn't change if the shape is changed, or if someone else uses the scale to weigh it, instead of them.
  2. Weight is not constant. What is actually constant is mass. Everybody agrees on how much mass something has.
    • In secondary school, teenagers often learn that on the moon or on Mars, an object's weight will be different, because gravity in those places is different, but the mass will stay the same.
  3. If two people are moving relative to each other, they disagree on how much mass something has. What they would agree on is a derived property called invariant mass.
    • In university, students may learn special relativity, which says that if you try to measure the mass of a moving object, that measurement may be different for the same object at different speeds s — and different observers of the same object at the same time, moving relative to each other, may disagree on its speed, meaning they would also disagree on its mass. But if you calculate the quantity m sqrt{1 - s^2/c^2} , this quantity will be the same no matter what s is, so all observers agree on it.

The term appeared in the book The Science of Discworld, co-authored and partly based on ideas created by Terry Pratchett, and in The Collapse of Chaos and Figments of Reality, both by the other two co-authors of The Science of Discworld, Ian Stewart and Jack Cohen.

Related concepts and aspects

The boundary is fuzzy between widespread misconceptions versus lies-to-children. One significant difference is that genuine misconceptions are resistant to further instruction, and are often believed firmly (sometimes passionately) by adults. On the other hand, students will easily recognize and discard the lies-to-children as more advanced concepts are acquired. Another significant difference is that a lie-to-children will tend to be an approximation of the truth (acceleration due to gravity=10 m/s²) while a misconception will often simply be wrong (e.g. tongue taste map, coriolis-in-the-bathtub).

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