Thousand fold world system

It is said Loka is a World

“ As far, bhikkhus, as this thousandfold world system extends, Mahābrahmā there ranks as the foremost.

(3) “There comes a time, bhikkhus, when this world dissolves. https://suttacentral.net/an10.29/en/bodhi

Lokantagamanasuttam

Bhikkhus, I say that the end of the world cannot be known, seen, or reached by travelling. https://suttacentral.net/sn35.116/en/bodhi

Rohitassasuttam

"I tell you, friend, that it is not possible by traveling to know or see or reach a far end of the cosmos where one does not take birth, age, die, pass away, or reappear."

"It is amazing, lord, and awesome, how well that has been said by the Blessed One: 'I tell you, friend, that it is not possible by traveling to know or see or reach a far end of the cosmos where one does not take birth, age, die, pass away, or reappear.' Once I was a seer named Rohitassa, a student of Bhoja, a powerful sky-walker. My speed was as fast as that of a strong archer — well-trained, a practiced hand, a practiced sharp-shooter — shooting a light arrow across the shadow of a palm tree. My stride stretched as far as the east sea is from the west. To me, endowed with such speed, such a stride, there came the desire: 'I will go traveling to the end of the cosmos.' I — with a one-hundred year life, a one-hundred year span — spent one hundred years traveling — apart from the time spent on eating, drinking, chewing & tasting, urinating & defecating, and sleeping to fight off weariness — but without reaching the end of the cosmos I died along the way. So it is amazing, lord, and awesome, how well that has been said by the Blessed One: 'I tell you, friend, that it is not possible by traveling to know or see or reach a far end of the cosmos where one does not take birth, age, die, pass away, or reappear.'" https://www.accesstoinsight.org/tipitaka/an/an04/an04.045.than.html

Attend closely and I will speak."

"I will, lord," replied the venerable Ānanda to the Exalted One, who said:

3. "As far as moon and sun move in their course and light up all quarters with their radiance, so far extends the thousandfold world-system.

Therein are a thousand moons, a thousand suns, a thousand Sinerus, lords of mountains: a thousand Rose-Apple Lands,[4] a thousand Western Ox-wainsa thousand Northern Kurus,[5] a thousand Eastern Videhas;[6] four thousand mighty Oceans, four thousand Mighty Ruler[7], a thousand Four Great Rulers,[8] a thousand heavens of the Thirty-Three, a thousand Yama worlds, a thousand heavens of the Devas of Delight, a thousand heavens of the Devas that delight in creation, the same of those Devas that delight in others' creations, and a thousand Brahma worlds.

This, Ānanda, is called:

'The system of the thousand lesser worlds.'

A system a thousandfold the size of this is called:

'The Twice-a-thousand Middling Thousandfold World-system.'

A system a thousandfold the size of this is called:

'The Thrice-a-thousand Mighty Thousandfold World-system.'

Now, Ānanda, if he wished it, the Tathāgata could make his voice heard throughout this last-named world-system, or even further, if he chose."

4. "Pray, lord, how could that be done?

"In this connexion, Ānanda, the Tathāgata suffuses with [208] radiance the Thrice-a-thousand Mighty Thousandfold World-system.

When its inhabitants perceive this, then the Tathāgata would give utterance and make the sound heard.

That is how he would do it." http://obo.genaud.net/dhamma-vinaya/pts/an/03_threes/an03.080.wood.pts.htm

‘It’s impossible for two perfected ones, fully awakened Buddhas to arise in the world system [lokadhātuyā] at the same time.

There is this passage in

That in the world by which one is a perceiver of the world, a conceiver of the world—this is called the world in the Noble One’s Discipline. And what, friends, is that in the world by which one is a perceiver of the world, a conceiver of the world? The eye is that in the world by which one is a perceiver of the world, a conceiver of the world . The ear … The nose … The tongue … The body … The mind is that in the world by which one is a perceiver of the world, a conceiver of the world. That in the world by which one is a perceiver of the world, a conceiver of the world—this is called the world in the Noble One’s Discipline.

Note that here the formulae is that there is a world and in that world (the conceived) there are worlds (doors; that though which one perceives & conceives).

There are other texts maybe related to this part

“Bhikkhus, as far as sun and moon revolve and light up the quarters with their brightness, so far the thousandfold world system extends.

Darkness Sutta

Mendicants, there is lokantarikam (interworldly?) Darkness, so utterly dark that even the light of the moon and the sun, so mighty and powerful, makes no impression / doesn't reach.” https://suttacentral.net/sn56.46/en/sujato

I'll just leave it here but the expression that there is no electromagnetic radiation (light) inbetween the worlds, where worlds are subjective frames of reference is basically a key tenent of special relativity and would seemingly be agreeable by sutta method.

I also think that the natural reading interpretation is that Mahabrahma is the foremost among Brahmas, like the foremost of men would be included among men, so i think Mahabrahma is one of the Brahma.