It may be like an atom bomb. Lots of people know how to build one; the problem is getting the enriched uranium and plutonium.
Yeah. That’s my point. Hollywood CAN come up with great ideas, but their implementation could be either centuries off or totally impractical.
Still, time travel movies and episodes are my favorite.
I read a science fiction book called Golden Globe where genetically engineered giant spiders spun the superstructure of space stations in place. That’s doable, I believe.