To a certain extent, you have the ability to self-organise this within the greater wilds of the GD forum. If enough people were willing to use the Tags functionality, you'd be able to (with use of a bookmark) effectively create your own sub-forums. It'd be clunky, but if it proved popular then you may find it relatively easy to convince someone to do a little bit of development to enhance the way that Tags are displayed and used on the site.
This is something we tried to lead ourselves back in the depths of time, but it didn't really gain traction - potentially as the topic areas were predetermined by us, rather than members, and because we'd decided it was a good idea rather than waiting for members to see the need.
Given there's a group of you here who have expressed an interest in science / technology / sci-fi etc related topics, it would be relatively simple for you all to come together and agree that when you start a thread that might interest the wider group, you tag it with a pre-agreed tag. "Science", "Technology", "Sci-fi" all strike me as good tags to use, and of course for topics that overlap you can easily add multiple tags.
Edit: I see the OP of this thread has 5 tags added already. If you click the "Science" tag from those, you get this page:
Which currently only brings up this specific thread. Or if we go with this link: https://community.giffgaff.com/t5/tag/science/tg-p
We now also get @simonemachine's other tagged thread from GD.