Reality

**Reality**, frae Latin "res, rerum", meanin "the hing", is a philosophical conceipt that introduces the notion o reality, truith, suith. The opposite notion is "virtuality".

## Ancient an modern notion

* Far the auld philosophers, reality is whit exists in twa warlds : the ane o the essences, the ane o the empirism.

Far Platon, ye maun eschew apparent sensiblity, aye changin, far tae gang in Idea's warld, whilka foonds aw that exist in sensible warld. Oor kent warld is sae illusion Bat Kant considers that reality for Man is jast whit appears tae us; jast bein a phenomenon. Sae, he thinks reality isnae truith.

## Vision o a makar

The French makar Paul Valéry said ance: « Ma main se sent touchée aussi bien qu’elle touche. Réel veut dire cela, rien de plus ». It daes mean: "Ma haund feels the touchin o the hings altho it touches. Reality daes mean that, naethin mair.
The reflexion o the makar means sae that reality is jast the sensation o the hings, jast whit we live in, wioot complex philosophical sochts or thochts.

## Uise in physics

Quantum mecanics, a branch o physics foondit in the early 20t century, haes establishit a nummer o hichly counterintuitive experimental results. Som individuals hae assertit those results are relevant tae a conception o reality. In parteecular, the experimental data suggests twa facts aboot the univers at gey smaa distance (on the scale o individual protons):

:::1. first, that the univers is non-deterministic, an
:::2. second, that the conceipt o an objective measurement is, strictly speakin, meaninless.

Thir twa truiths are interrelated bat worthy o separate attention.

Non-determinism o quantum seestems fallows directly the Schrödinger Equation. This equation solves anly far probabilities, nae far determinate values. Far saumple: a bairn haes $5, an wants tae spend $2. The bairn asks his faither haw much o the oreeginal $5 he will hae efter spendin $2, an the faither tells him that he will hae $3 remainin. The faither is uising the arithmetic tae offer a determinate prediction, whilka claims that if ye hae $5, an ye spend $2, ye'll haee $3. It is nae possible that ye will hae $1 remainin, it is nae possible that ye will hae $6 remainin: the amoont o the remainder is determinit tae be $3.

::i\hbar\frac{\partial}{\partial t} \Psi(\mathbf{r},\,t) = \hat H \Psi(\mathbf{r},\,t)

whaur

::::* i\  is the imaginary unit
::::* \Psi(\mathbf{r},\,t) is the wave function, which is the probability amplitude for different configurations of the system.
::::* \scriptstyle \hbar is the reduced Planck's constant (often normalized to 1 in natural ::::units).
::::* \scriptstyle \hat H is the Hamiltonian operator.
::::

In contrast, if the bairn asks whilka side a flippit clink will land apon (heids or tails), the anser is different. This anser is probabilistic, in that it is nae a specific prediction, bat a general claim aboot the results as a whol: the clink haes a 50% chance o landin on heids, an the same chance far tails. Practically speakin, this rochly means that the mair times ye throw the clink, the closer yer heids-tails results will get tae bein hawf o ane, hawf o the ither. It daes nae tell ye the ootcome far ony parteecular clinks toss.

Photons as well as ither particles, hae been shawn tae possess wave-particle duality, meanin that thair probabilistic naitur is gien bi an oscillatin probability wave.