In a world where tectonic plates decided this whole continental drift fad was just too much work and lets just hang out for a few more hundred million years, life has arisen, stomped around for a while, sat down for a good think, and decided to work together. An empire is born.
This empire has a few things going for it:
- They have achieved a technology level equivalent to the Romans at their greatest, with a representational democracy since that whole monarchy thing just got too confusing if you had more than one kid (and what if the brat is an idiot?)
- The single religion is highly resistant to fracturing, mostly because anyone who tries to subvert it spontaneously bursts into flames on account of the human body not being a good conductor of lightning bolts.
- Due to there being only one land mass the amount of racial drift is very minor. in addition an ancient custom of marrying outside of the tribe in order to avoid interbreeding has carried over, so that looking for mates from afar (or who had recent ancestors from afar) is very common. Thanks for the idea nzaman.
All this adds up to a civilization that is fairly resistant to fracturing, though people are still people, so communications are very important. Especially since it is a land mass of around 60 million square miles (155 million square kilometers).
Sea travel is possible around the circumference of the super continent, and they have developed sailing. Likewise, like the Romans, their road building skills are really advanced.
Assuming a centralized capitol near the equator in the general area of "ARABIA" on the map, what kind of advances to Roman travel technology need to be made to keep the empire stable for a significant amount of time?
Perhaps a better question is, is it possible for an empire like this to be stable for a significant amount of time when the fastest mode of travel is a horse? And if not, what is the least impact improvement that can be made to the tech tree to allow it to work?
Edit 2: The Active Deity
The deity plays a semi active role, but mainly in how the religion is run.
Basically the message is similar to the biblical 10 commandments; don't murder, don't steal, there are no other gods, treat others like you would want to be treated, help those in need, etc, along with a short list of harmful lifestyle choices to avoid for a healthy life and healthy society.
Where the lightning comes in is in the area of spiritual leaders. If you are (or act like) a spiritual influencer, then you are taking on responsibility over peoples lives, and your words and actions can actively lead people away from the message. If a spiritual leader tries to use power or influence for corrupt personal purposes then they are in danger. If a normal person has a dream and takes on the role of cult spiritual leader to share their new revelation, they come under this rule.
The only place that this applies to politics is if a politician oversteps and tries to impose law in a way that affects spiritual matters, in effect becoming a spiritual influencer. If there is something that the message specifically forbids, and someone proposes a law that makes it mandatory/actively encouraged, then they might start to hear thunder on sunny days. But this is not something that the priests have any influence over. They can't pray and ask that someone be smote.
By and large, most of the DON'Ts in the message are things that would be considered illegal in most civilized societies, the DOs are things you should probably be doing anyway, and none of them are actively enforced outside of the priesthood/spiritual leaders. Leaders are held to a higher accountability.
There are other places where the deity shows some activity, like by favoring those that are faithful to the message, sort of like a Luck +1.
There is no law against spiritual leaders seeking political position, but their spiritual position doesn't give them any extra political authority, except that it enforces moral choices.
Map image source: ENCYCLOPÆDIA BRITANNICA, who got it from someone else.