Thank you for your answer, Hecatee. I'm really enjoying this take. It's one of my favorite ongoing series at the moment.
I can see that there are few ships currently, but won't construction of them amp up as trade via sea becomes more extensive and profitable? Will the Romans be looking to expand through the Arabian peninsula to add more forts/fort towns (&, by extension, more protection of their ships from potential pirates, which usually become a thing in poorly protected shipping lanes)? Are there any seafaring states in that area (like modern Oman, UAE, etc) at that time that could be a problem? If there is no real organized opposition could Rome sort of accidentally digest the Arabian peninsula over several decades of steady settlement? It would make Mesopotamia much more easily defended to only have to defend one side.
What about Africa? Rome received trade via the Nile and other overland traders with gold and ivory OTL. We know they had animals from SubSaharan Africa in the Colosseum. Will there be any trading outposts set up a la the Portuguese in the Age of Exploration or the Arabs before them in East Africa? Would the Ivory gained in Africa be a good enough trade item for the Chinese?
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I don't think their will be that many new ships, at least for quite some time because the road remains very, very long, and a lot can be lost in a four year journey, so that's the kind of investment few are ready to make beside the state, and the state won't because it want to keep the silk price high to benefit from the border taxes... Also the truly adventurous explorers are rather few, don't expect a full blown age of exploration at this point in time
For the Arabian Peninsula, OTL by this point you probably have roman guarrisons in northern Arabia cities such as Hegra, a Nabatean town. Further south they tried in the age of Augustus, but retreated and currently they consider once more than the import taxes on incent and other similar product is more interesting than paying for the cost of maintening control of the incense growing areas. So they don't really plan on expending, except maybe in the Persian gulf area. So Oman maybe, Yemen no.
For Africa, it seems that the policy OTL was more of having trader or hunting expeditions going into the land but not much more. Distance, climate and little return on investment made sure they did not want to go, also they knew of organized kingdoms such as Axum so did not want to mess any further south than Nubia. Here we could see trading posts appear along the coast, but not now : the exiled Jews have no interest in helping them do so and thus the romans lack knowledge to found such trading posts.
Ivory for China is probably not worth it, they have enough far closer sources availlable, same for turtle shells for instance.
The most important thing for now is that the silk trade keeps happening. It has been suggested that part of the troubles of the 3rd century for the Romans were due to troubles with the silk trade due to Chinese political unstability that disrupted trade and thus the Roman state's incomes : here by keeping China more stable for longer I do make the Pax Romana longuer and thus the Empire stronger on the long term with new internal sources of income, conquest in all directions kind of disrupts this consolidation...