The Expanse is a science fiction series that aired on SyFy for three seasons then Amazon Prime Video for another three after SyFy cancelled it.

It's set maybe 100 years in the future where mankind is split into three polities: United Nations of Earth and Luna with the bulk of humanity and bulk of resources, Martian Congressional Republic with a bit better tech to offset the UN's numbers, and the independent Belters downtrodden by both major powers.

The series is mostly two parallel tracks (they're based on books written by two authors each of which wrote one plot line). The crew of the Rocinante is the primary plot: James Holden (Steven Strait) as Earther captain and moral compass, Naomi Nagata (Dominique Tipper) as Belter engineer with a dark past, Amos Burton (Wes Chatham) as Earther mechanic quick to resort to violence but in an unfeeling way (violence is an easy tool not that he enjoys or hates it), and Alex Kamal (Cas Anvar) as Martian pilot and former military. An eclectic group worthy of the settings (which was originally developed to be an RPG).

In season one the other plot line follows Belter detective Joe Miller (Thomas Jane) trying to track down the runaway daughter of a business tycoon. There's also UN official Chrisjen Avasarala (Shohreh Aghdashloo) investigating terrorist Belter activities. After season one Avasarala is the focus of the second plot line.

It's a setting of rising political tension between the UN and Mars which escalates once Protomolecule is discovered. It's an alien organic compound that can transform Earth life and one of the big corps has been developing super-soldiers with it (humans changed into alien lifeforms with super-human abilities and alien thoughts such that they're no longer human). Mars wants it, then Earth wants it, then the Belters want it as the WMD that can bring recognition for an independent Belter Nation.

This through-line continues as the Protomolecule establishes a base on Venus which is then launched into the outer planets and forms the Ring. Investigation reveals it's a portal into Ring space which is not that big but has thousands of portals to other places in the galaxy (and beyond?). But no alien inhabitants who were all apparently wiped out by something that humanity is now attracting with its usage of the Ring portals.

The series ends with maybe humanity knows how to use the portals safely and maybe the hostile entities now know humanity exists. Unfortunately season 6 is both short and sets up a continuation of the universe (it introduces a family living on a colony world and then stuff happens that's not resolved at series end). That makes season 6 the weakest of the series though in general I think the series starts strong and slowly gets less interesting from season to season, with the exception of Camina Drummer (Cara Gee) who is a freaking badass Belter minor character in season 2 and 3 and a regular afterwards.

Each season tends to be a standalone-ish story (makes sense since they follow a series of books) and the settings vary. Season 1 has Ceres, the largest Belter city, season 4 is mostly on the colony world of Ilus, season 5 has subplot on Earth.

It's a fairly hard sci-fi universe with the big human tech being a space ship engine that can pull high Gs quickly and uses almost no fuel but humans still need aids to handle high Gs. Weapons are mostly projectiles and ships have missiles and rail guns. Computers are easy to use but no AI. Body mods are low, the big thing is Belters being tall with weak bones not suitable for gravity. The Protomolecule bends existing laws, like perhaps cancelling the mass of an asteroid so it can dodge missiles and instantaneous communication across the solar system.

Overall it's a good science fiction series that is hard sci-fi and tells a large story. Compares favorably with Babylon 5.