What did the Buddha really meant with 'kalapas' (those ultra small particles of existence, that arise and pass away at an incredible speed)?
Is there a correlation between those kalapas and the emptiness of all things (sunnata)?
Can those kalapas be considered as the 'source' for all manifestations?
kalāpa in the sense you are thinking is used in the commentaries. The word is generally used in the suttas to mean "bundle", as in yavakalāpa - bundle of grass, or dhanukalāpa - sheaf of arrows. I can't pinpoint the first usage of the word to mean "smallest particle of matter", but the Visuddhimagga uses it in this way:
“But since neither of these is a fact, you should therefore give up conjecturing the difference to be in the supporting primary elements. Just as the natures of visible objects, etc., are dissimilar from each other though there is no difference in the primaries that form a single group, so too are eye-sensitivity, etc., though no other cause of their difference exists.”
-- Vism XIV.45 (Nyanamoli, trans)
The Pali here is ekakalāpe - "in a single group". The meaning is that each instance of matter is made up of a single group of characteristics.
The abhidhammattha-sangaha also uses the term:
Ekuppādā ekanirodhā ekanissayā sahavuttino ekavīsati rūpakalāpā nāma.
There are twenty-one material groups inasmuch as they arise together, cease together, have a common basis, and occur together.
(Bodhi, trans)
Bhikkhu Bodhi's explanation is:
Material phenomena do not occur singly, but in combinations or groups known as rūpakalāpas, of which twenty-one are enumerated. Just as all the cetasikas possess four characteristics (see II, §1), so too do the material phenomena in a group. All the material phenomena in a group arise together and cease together. They have a common base, namely, the conascent great essentials, which are the proximate cause for the derivative phenomena as well as for each other. And they all occur together from their arising to their cessation.
(From A Comprehensive Manual of Abhidhamma, pp. 252-3)
Nyanatiloka gives the following explanation of rūpa-kalāpa in his Manual of Buddhist Terms:
'corporeal group', material unit, designates a combination of several physical phenomena constituting a temporary unity. Thus, for instance, the so-called 'dead matter' forms the most primitive group, consisting only of 8 physical phenomena, called the 'pure eightfold unit' or 'octad' (suddhatthakakalāpa), to wit: the 4 elements (the solid, fluid, heat, motion); colour, smell, taste, nutriment (pathavī, āpo, tejo, vāyo; vanna, gandha, rasa, ojā).
In Vis.M., and elsewhere, it is also called ojatthamaka-kalāpa, 'the octad with nutriment as the 8th factor'.
The simplest form of living matter is the '9-fold vitality unit' or 'life-ennead' (jīvita-navaka-kalāpa), formed by adding 'vitality' to the octad.
Seven decades, or units of ten (dasaka-kalāpa), are formed by adding to the 9-fold unit one of the following corporeal phenomena: heart (physical seat of mind), sex, eye, ear, nose, tongue or body. -
See Vis.M. XVIII, 4; Compendium of Buddhist Philosophy (PTS), p. 164, 250; Atthasālini Tr., II, 413f.
Finally, Mahasi Sayadaw talks about rūpa-kalāpa in the context of rebirth as a human in his discourse on Paticca-Samuppada:
With the arising of rebirth consciousness there occur simultaneously three kammajā-rūpakalāpas or thirty rūpas. These are rūpas that have their origin in kamma, viz., ten kāyarūpas, ten bhava-rūpas and ten vatthu rūpas. The nine rūpas, to wit, the solid, fluid, heat, motion, colour, smell, taste, nutriment and life together with the kāyapasāda (body-essence) rūpa form the ten kāyarūpas; bhava-rūpa and the solid, etc form the group of ten Bhavūpas. Bhavārūpa means two germinal rūpas, one for manhood and the other for womanhood.
...
This embryonic rūpa has the size of a little drop of butter-oil scum on a fine woollen thread. It is so small that it is invisible to the naked eye. It does not exist by itself. We should assume that it arises from the fusion of the semen (sukka) and blood (sanita) of the parents. If we reject this view, it will be hard to explain the child's resemblance to his parents in physical appearance. It is also said in the suttas that the physical body is the product of the four primary elements and the parent's semen. Moreover, the piṭaka specifies three conditions necessary for conception, viz., the parent's intercourse, the menstrual discharge of the mother and the presence of something qualified to become an embryo. Thus it is clear that according to the scriptures, the embryonic kalāla has its origin in the fusion of parent's semen and blood.
...
According to Western biologists, it is the fusion of the mother's ovum and the father's spermatozoa that gradually develops and becomes a child. The original embryo is so small that it cannot be seen with the naked eye. The findings of these scientists fairly agree with what the Buddhist books say about conception. Without the help of microscope or other instruments but purely by means of his intellect the Buddha knew how life begins with three kalāpas or thirty rūpas as kalāpa on the basis of parents' semen and blood. This was the Buddha's teaching 2500 years ago and it was only during the last 300 years that Western scientists discovered the facts about conception after long investigation with microscopes. Their discoveries bear testimony to the Buddha's infinite intelligence. However, they are as yet unable to reveal the genesis of thirty rūpas probably because the extremely subtle kammajarūpas defy microscopic investigation.
UPDATE (to reflect your new questions):
Is there a correlation between those kalapas and the emptiness of all things (sunnata)?
The theory of the kalāpa has no direct connection with the theory of suññatā; it simply describes the composition of individual groups of matter. Indirectly, though, since suññatā is very much connected with anattā (being devoid or "empty" of self), the fact that rūpa is made up of individual states that arise and cease without remainder is indeed an important part of the realization of this truth. E.g.:
Having thus discerned by knowledge of contemplation of reflection that “All formations are void” (see S III 167), he again discerns voidness in the double logical relation thus: “This is void of self or of what belongs to self” (M II 263; Paṭis II 36).
When he has thus seen that there is neither a self nor any other [thing or being] occupying the position of a self's property, he again discerns voidness in the quadruple logical relation as set forth in this passage: “I am not anywhere anyone’s owning, nor is there anywhere my owning in anyone (nāhaṃ kvacani kassaci kiñcanat’ asmiṃ na ca mama kvacani kismiñci kiñcanat’ atthi)” (M II 263).
-- Vism XXI.53 (Nyanamoli, trans)
Can those kalapas be considered as the 'source' for all manifestations?
kalāpa, or more properly rūpa-kalāpa, are physical, so no they are only a source for certain other phenomena. "source" is a problematic term anyway, since the causal nature of reality is far more complex than simply A => B.
The meaning of Kalapas in the context of how you form your question (What did the Buddha really mean by Kalapas) cannot be answered. In short, the only correlation between Kalapas and Sunnata (in the form that 'emptiness' is presently understood) is that neither are original teachings of the Buddha.
Kalapas - Kalalaps are first mentioned in the Abhidhamma, written in the 5th - 11th century. An excellent summary of misrepresentation of Buddhas original teachings by Christopher Titmuss (What the Buddha did not teach):
Sub atomic particle (kalapas). The Buddha did not teach development of the power of concentration (samadhi) in meditation in order to experience sub-atomic particles. The word ’kalapas’ does not appear anywhere in the suttas. The Buddha did not support such a materialistic view or non materialistic views.
Sunnata - In the only Sutta where the Buddha discusses Sunnata directly (a translation can be found here Cula-suññata Sutta), he uses it as way to describe seeing existence as it is i.e. empty of personal interpretation or overlay:
Thus he regards it as empty of whatever is not there. Whatever remains, he discerns as present: 'There is this.' And so this, his entry into emptiness, accords with actuality, is undistorted in meaning, & pure.
The meaning of Kalapas
How A Kalapa Is Formed
A group of people association is called a club. In Pali kalapa also means a group. As said before rupa (matter) cannot exist in isolation. Appropriate units of matter combine to exist as a group or an aggregate. Such a group with common properties, existing together, disappearing together, is termed 'one kalapa'.
Matter In Combination
The four fundamental elements - pathavi, tejo and apo - together with vanna (appearance), ghanda (scent), rasa (taste), oja (essence of nutrition) are the eight classes of matter found always in coexistence. A lump of soil is an aggregate of eight classes of matter too. It has a certain appearance and a specific smell and taste; it can be touched and felt. The same is true for water, wind, fire, heat, light etc. They are all aggregates of the eight classes of matter.
The Size Of A Kalapa
Each kalapa is so minute that you cannot see it with your naked eye. Even the finest dust particle is an aggregate of a large number of kalapas. A bacterium, which can only be seen with the most powerful microscope is composed of countless kalapas formed by kamma, citta, utu and chara (*ahara). Therefore the minuteness of a kalapa is beyond description. (Reference may be made to text on Abhidhamma for classes of kalapas and their names).
Before we can get to the understanding of Kalapas, we need to understand some of the characteristics of Rupas and their causes. The "much easier and readable definition of Rupas" happens to be in the introduction to this Pathana.
Rupas and their characteristic
.. there are in total 28 paramattha rupa which are all realities and can be sensed by one of our 6 senses.
Rupa or vanna is sensed by eye only, sadda is sensed by ear only, gandha is sensed by nose only, rasa is sensed by tongue only and pathavi, tejo, vayo three of mahabhuta rupa are sensed by body only.
Vanna, gandha, rasa, oja or ahara, pathavi, tejo, vayo and apo always co-exist and they are called avinibbhoga rupas and other 20 rupas are called vinibbhoga rupas.
All other rupas that is 5 pasada rupas and 16 sukhuma rupa or subtle materials are all sensed by mind only; that is 5 pasada rupas and 16 sukhuma rupa can never be sensed by any of eye, ear, nose, tongue, and body.
Rupas and their relationship with causes
There are kamma that can cause kammaja rupas.
These kamma are:
5 rupavacara kusala (* skilful Brahma) kamma.
Even though there are 28 paramattha rupas, they do not arise in isolation. At least some arise together. And they vanish together. They have to arise on mahabhuta rupas and they co exist in a form called rupa kalapa. There are 21 rupa kalapas. 9 kalapas are kammaja rupa kalapas, 6 are cittaja, 4 are utuja and 2 are aharaja rupa kalapas.
Now we can classify kalapas according to their causes
Kammaja rupa kalapas are:
In cakkhudassaka kalapa, there are 8 avinibbhoga rupas, jivita rupa and cakkhu pasada rupa altogether 10 rupas arise together. Other kammaja kalapas are the same and just to replace cakkhu with their correspondent rupa. Jivitanava kalapa is a combination of 8 avinibbhoga rupas and jivita rupa itself.
6 cittaja rupa kalapas are:
suddhattha kalapa which comprises 8 avinibbhoga rupas only,
kayavinattinava kalapa which comprises 8 rupas and kayavinatti rupa,
vacivinatti saddadassaka kalapa which is compsed of 8 rupas, vacivinatti and sadda,
lahutadi ekadassaka kalapa which is combination of 8 rupas and 3 lahutadi rupas,
kayavinatti lahutadi dvadassa kalapa which comprises 8 rupas, 3 lahutadi and kayavinatti rupa, and
vacivinatti sadda lahutadi terasaka kalapa which includes 8 rupas, 3 lahutadi, vacivinatti and sadda rupa.
4 utuja kalapas are:
suddhattha kalapa,
saddanava kalapa,
lahutadiekadassaka kalapa which comprises 8 rupas and 3 lahutadi rupas, and
sadda lahutadi dvadassaka kalapa which comprises 8 rupas, 3 lahutadi rupa, and sadda rupa.
2 aharaja rupa kalapas are:
suddhattha rupa lakapa and
lahutadiekadassaka rupa kalapa which comprises 8 inseparable rupas and 3 lahutadi rupas.
From the 4 utuja rupa kalapas, suddhattha rupa kalapa and saddanava rupa kalapa can arise outside of beings or sattas. All other rupa kalapas only arise as ajjattika.
Well in can only get easier when you have read it for about 10 times remembering the pali names that go along with it.
As Kalapas arise and pass away it does not posses and inherent existence nor an existing self so in that way it is empty.
All material manifestations produced by the 4 causes of kamma, citta, utu, ahara are in the form of kalapas. So yes! As there are no material manifestation that are not produced by these 4 causes (with ref. to the Abhidhammma, of course).
(* my additions/comments/terminology)
As Buddah said the smallest unit of the universe is a "Suddashtaka" it contains following 8
And each any every Kalapa are consists with 1 or more of this Suddashtaka. Each and every thing in this universe consists of these things.
suddhattha kalapa which comprises 8 avinibbhoga rupas only - Patthana Dhamma by Htoo Naing - Chapter 3. Suddhattha - Pali, Suddashtaka - Sanskrit
Commented
Mar 20, 2016 at 4:11
Kalapas are sub atomic particles. Gautama the Buddha when sitting at the age of 35 under a bodi tree, sat in the ultimate adithaana meditation. He sharpened his awareness to the extent that he tore apart and experienced an atom and its particles. What he also experienced is the impermanence of these particles as in they were arriving and passing away. He also experienced these as vibrations or wavelets. This revealed the impermanence of matter or the universal law of the atomic universe.
These can be reconciled with science as the disappearance of particles during a phenomenon called tunnelling where a particle disappears and appears somewhere else.
96% of the universe is non atomic. Also called dark energy or dark matter. 99.99% of the remaining 4% of the atomic universe contains interparticle space. The space between say elections and nucleus. And space between proton and neutrons as they move around. Thus the rest is particles and sub particles or quarks. These are also impermanent. They disappear when not observed or not interacting with other particles.
THUS THE UNIVERSE IS MADE UP OF...,,NOTHING.
The last bit is being considered as scientific fact apparently.
Watch here https://youtu.be/WMhJgdpj1d0
