The first of a Sci Fi trilogy, but it could also be the first of two as historical novels. It also shows what science is about, from the point of view of a scientist (100 peer reviewed papers and 6 patent applications, even though the author has mainly worked independently in the private sector) and what first century Rome was like, under late Tiberius, then under Caligulae (Give him a break; he had two feet!), then shows some of the early tensions in Judea in the years following the death of Christ as Christianity struggles to emerge.
Gaius Claudius is given the cognomen Scaevola by Tiberius, he is promised a military appointment when he is nineteen, assuming he is suitable, and he is ordered to earn an agnomen from something he will learn from Timothy, on Rhodes. Soon after Scaevola arrives on Rhodes, he receives a strange prophecy from Pallas Athene in a dream. What Scaevola does not know is that Athene is a classical historian in the 25th century, who can send messages back in time, and she is manoeuvring him to get him into a position to save humanity in the 24th century. Scaevola is given three tasks. The first is simple: become a strategist. To do that, he must satisfy a Roman General sent to teach him. The next two are bizarre. He must build a usefully-sized steam engine, and prove the Earth goes around the Sun. It takes little time to discover that the first is impossible, while the second is not much better, especially when Timothy proves based on physics known at the time that the Earth must be stationary. You know the answer, but could you prove it? Particularly if limited to what was known then?
Then Tiberius dies, and Caligulae cancels his military appointment until he shows he is worth one. Scaevola's chance comes when the Governor of Alexandria begins persecuting the Jews, but what should he do? Caligulae is becoming increasingly erratic, and just staying alive is a problem, let alone attaining a military career. But then quite strange things mentioned in the prophecy come to pass. Unfortunately, Scaevola also recalls that Athene only prophesied what would happen provided he stayed alive long enough to reach that point.