There are uncountable relativity appear in the last cannon of tipitaka, paṭṭhāna-abhidhamma.
So, the theory of relativity appeared in a little part of abhidhamma, such as utujarūpa of rūpa section:
e = m x c2
Can convert to abhidhamma as:
utu = pathavī x utujarūpa arising rate2.
utu = thermal energy (in abhidhamma where is thermal energy, there are the other energies, such as pathavī, āpo, tejo, vāyo, vaṇṇa, sadda, ganda, rasa, and ojā, too. But some of them may be not appear to senual organs).
pathavī = mass.
utu-ja-rūpa = new arising form that is caused by thermal energy of the other form.
utujarūpa arising rate = rate of arising and vanishing of each utu-ja-rūpa.
In abhidhamma, mind arising is fastest (more than a trillion times per finger stroke), the form is slower 17 times (17 mind arose = 1 form vanished).
Also, in the path of purification, CHAPTER XX — PURIFICATION BY KNOWLEDGE & VISION OF WHAT IS AND WHAT IS NOT THE PATH 4. Comprehension of the material page 22, wrote:
There are 4-5 inherited generations of kamma-paccaya-āhāra-samuṭṭhāna, kamma-paccaya-utu-samuṭṭhāna.
There are 2-3 inherited generations of citta-paccaya-āhāra-samuṭṭhāna, citta-paccaya-utu-samuṭṭhāna.
There are 12 inherited generations of āhāra-paccaya-āhāra-samuṭṭhāna (however, depending on the quality of āhāra).
There are uncountable inherited generations of utu-paccaya-utu-samuṭṭhāna (depending on utuniyāma+bījaniyāma).
There are 12 inherited generations of utu-paccaya-āhāra-samuṭṭhāna.
The bold quote above is used in nuclear reaction.
However, theravāda buddhism trying to solve, avoid, and get out of every problem (suffering), so buddha and commentary did not explain too much about the form, because it is just 1 of 5 aggregates, 1 of 3 bhava. Therefore buddha and commentary have to spend the explaining time to the other parts of problem (suffering), too. But science, which formed from Capitalism culture, spending too much time with just form part (5 kāmaguṇa), which can sensed at the sensual organs (5 āyatana) by 5 sensual viññāṇa. Because the people in capitalism can't clearly comprehension the whole problem system (suffering in paṭiccasamuppāda cycle).
So buddha taught in Siṃsapāvana Sutta:
"What do you think, monks: Which are more numerous, the few simsapa
leaves in my hand or those overhead in the simsapa forest?"
"The leaves in the hand of the Blessed One are few in number, lord.
Those overhead in the simsapa forest are more numerous."
"In the same way, monks, those things that I have known with direct
knowledge but have not taught are far more numerous [than what I have
taught]. And why haven't I taught them? Because they are not connected
with the goal, do not relate to the rudiments of the holy life, and do
not lead to disenchantment, to dispassion, to cessation, to calm, to
direct knowledge, to self-awakening, to Unbinding. That is why I have
not taught them.
"And what have I taught? 'This is stress... This is the origination of
stress... This is the cessation of stress... This is the path of
practice leading to the cessation of stress': This is what I have
taught. And why have I taught these things? Because they are connected
with the goal, relate to the rudiments of the holy life, and lead to
disenchantment, to dispassion, to cessation, to calm, to direct
knowledge, to self-awakening, to Unbinding. This is why I have taught
"Therefore your duty is the contemplation, 'This is stress... This is
the origination of stress... This is the cessation of stress.' Your
duty is the contemplation, 'This is the path of practice leading to
the cessation of stress.'"