# Eli5: What is a scalar wave, how does it form/used etc?

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Eli5: What is a scalar wave, how does it form/used etc?

In: 18  A nonsensical term used by scam artists such as esoteric healers to sound “scientific”. It has no proper meaning, except maybe some very antiquated term in engineering that is horribly twisted by the aforementioned group. [Wikipedia helpfully defines a wave](https://en.wikipedia.org/wiki/Wave) (in the context of maths or physics) as “a propagating dynamic disturbance (change from equilibrium) of one or more quantities.” Going through the terms there:

* propagating – means it moves through space,

* dynamic – means it changes over time

* one or more quantities – some physical property that we can measure

* disturbance – that quantity has some default value (the “equilibrium”), but it is changed to something else.

Water waves are a great example of this; you have bits of water which have some quantity – their height. The wave moves through space, changing the height of bits of water from their default position, with different bits in space, and the same bit at different times, having different values.

The quantities that waves can be affected can either be “scalars” or “vectors.” These are different types of physical quantities that behave in different waves; in simple terms (and in physics), both a scalar and a vector have some “size” property, but a vector also has a “direction” property. So “5 miles to the East” is a displacement vector. “50mph down the road” is a velocity vector, but “45 degrees C” is a scalar temperature.

Most of the common quantities affected by waves are vector ones. But some are scalars. So we could have a temperature wave, where we had some medium (say a long metal rod) and we sent waves of heat along it (although this probably wouldn’t quite be a wave mathematically, as it would be governed by the “heat equation” rather than the “wave equation”).

Essentially a scalar wave is any solution to the “scalar wave equation” (the scalar version of the “wave equation”, contrasted with the vector wave equation); a mathematical formula that sometimes comes up in physics (often as a simplification of a vector wave situation).