From our earlier discussion, a significant amount of light energy enters the brain via only the eyes. The black box analogy of the cranium disfavors the brain from receiving a significant amount of light. Attenuation of light energy occurs when it passes through layers of the cranium. Therefore, the light resistance property of the cranium may offer a protective mechanism in ensuring optimal brain function. Light is a type of electromagnetic energy that can generate heat energy and exists in duality, it can either be regarded as photons (particles of light) or waves [
17]. Certainly, heat generation in the brain is related to its metabolism and information processing [
18], and with additional exposure to extra cranial heat energy (light), brain temperature can be altered. Hence, intricate brain temperature regulation is seen as vital for processing information. Temperature regulation of the brain is a dynamic process and thought to follow the thermodynamics principles of energy conservation and flow of energy. Energy conservation is in fact the first law of thermodynamics, which states that energy cannot be created or destroyed, it can only change forms or be transferred from one object to another (quantity of energy). Important to note here that, none of the energy transferring processes are efficient, instead, in each process some of the transferred energy turns into heat. Inside the cranium, heat energy or temperature could possibly be regulated by heat conduction (via blood flow and CSF), convection (via air sinuses and CSF), evaporation (CSF and air sinuses), and radiation (cranial black box). Pertaining to flow of energy or the second law of thermodynamics (quality or directionality of energy) which states that the entropy of any system always increases. Entropy is defined as a measure of thermal energy per unit temperature that is unavailable for doing useful work or entropy is a measurement of disorder or energy spread. Low entropy system has a concentrated energy state, whilst high entropy system has spread-out energy state. It seems fitting with research findings that the deep brain nuclei and brainstem have warmer temperatures than the cortices [
19,
20,
21]. It tells us directionality or gradient of energy flow from low entropy area such as the brainstem (concentrated energy) to high entropy area such as the cortex (spread-out energy). In summary, our arguments which cover two salient points: the cranium as a black box which avoids direct light exposure, and brain thermal homeostasis with thermodynamics principles that regulates brain temperature intricately makes physics as an aspect to consider deeply when discussing brain functions.
Pertaining to ‘rapid brainwave changes’ when different light was shone onto the brain, the physics perspective on this matter is likely related to production of brain plasma. The term ‘plasma’ was first proposed by the American Nobel laureate chemist and physicist Irving Langmuir, who viewed it as similar to blood plasma. Here, ‘plasma’ refers to the electrified fluid that carries electrons and charged ions (compared to how blood plasma carries the corpuscles or cells). In physics, plasma by definition must contain assembly of mobile charge carriers of a sufficient density. If the charged density is not sufficiently high, their interaction with the electromagnetic field becomes important and the charged component can also be considered as plasma [
22]. In principle, plasma is commonly divided into ultra-hot (a thermonuclear reaction plasma such as in the sun), hot or thermal plasma, cold plasma (non-thermal or non-equilibrium plasma which can be generated at room temperature), and ultra-cold plasma. The term for hot or cold plasma is sometimes referred to as being hot if it is nearly fully ionized or cold if only a small fraction of it is ionized. In this context, presence of light inside the cranial black box may have produced or enhanced brain plasma energy which caused fast alteration in brainwaves. To comprehend this notion, let us have a look at the brain extracellular compartment (ECC). As we are aware, the brain interstitial or ECC does have charged ions (such as Na
+, Cl
-, H
+, Ca
2+, K
+, Mg
2+), charged molecules or polyatomic ions (HCO
3-, hyaluronic acid, NAD
+, acetate, nitrate, nitrite, sulfate, phosphate, aspartate, glutamate, lysine, arginine, etc.), polar solvents (charged water), gaseous ions (abundant presence of CO
2 is easily converted to gaseous ions when electricity or electron movement is applied to them), and electrons (electricity)[
23,
24,
25,
26,
27]. The interaction of this brain plasma soup with brainwaves (electricity or electron or electromagnetic force) and charged water may result in the formation of magnetohydrodynamics (MHD) or magnetofluid (superfluid) [
28,
29]. In short, in a slice of alive brain tissue with thousands of neurons, glial cells and interstitial spaces with charged plasma soup, a possible presence of large amount of toroidal electromagnetic waves and poloidal plasma waves may form a more diffuse and widespread rapid energy flow (MHD and perpendicular magnetoacoustics waves) from core to periphery of the brain (
Figure 7). Therefore, a first reason to support this perspective (brain also has plasma energy) is a black box feature of the cranium which blocks the light from reaching directly onto the brain and produces additional plasma energy. This idea is further supported by a recent study done by Maccaferri et al. which demonstrated nanoplasmons formation when the light interacts with electrons (electricity) [
30]. Our second reason is related to the presence of cortical surface electrons. In 2017, Kiyotaka et al. did a 7-Tesla MRI study of brain cortical surfaces. The unexpected finding was an electron rich layer at glia limitans externa adjacent to CSF cortical cisternal space. Their explanation for the presence of surface electrons adjacent to CSF space was that astrocytes endfeet containing abundant aquaporin-4 (AQP-4) induces glia limitans externa polarization and hence electrons [
31]. According to our physics perspective, an interaction between poloidal plasma waves at the cortical surface with water (CSF) may also form abundant electrons as confirmed by physics experiment of which electrons were formed when the plasma interacts with water [
28]. Besides, some recent experiments have also shown possible presence of plasma-like energy inside the brain which supports our brain plasma hypothesis and provides explanation for the rapid changes in brainwaves when the light was shone directly to the brain. In 2022, Yidi Zhang et al. have noted two types of wave in the brain, front waves of chemical reactions and travelling waves of neural activity [
32]. In 2009 and 2021, Andersen et al. and Drukarch et al. have highlighted the thermodynamics concept for action potential propagation [
33,
34]. Finally, could the rapid changes in brainwaves when light shone onto the brain be due to the fundamental brain itself? Indeed, the anatomical brain can also be viewed as waves of energy (i.e. duality of a particle: either particle or waves) as highlighted by us on a new perspective to comprehend brain function of which viewing the anatomical brain as package of energy or Quantum brain, rather than particles or an anatomical object (Newtonian brain) [
35,
36,
37].