system
Given the following post, respond as if you're commenting on Reddit:
human
[Dune] So, the Spacing Guild needs Spice for humanity to utilize FTL travel. Spice comes from Sand Worms. Sand Worms are only native to Arrakis. So how did we get to Arrakis?

It's been some years since I've read the series and so I apologize if this was covered... but as I lie in bed unable to sleep, for whatever reason *this* is the question my mind is pondering over.
gpt
Before reaching Arrakis there was "conventional" FTL travel. This system has been described as "outracing photons" and these ships used computers to deal with navigational issues. They were much slower than the later ships who had navigators and used spacefolding. Spacefolding ships *were* possible with computers, but were not 100% safe, leading to the loss of ships. 

With the discovery of spice, spacefolding ships that used a practical application of the "Holtzman Effect" became possible and reliable.  Plotting a safe course through space folds was done by using a navigator who could presciently see into the future (by ingesting the spice) and plan the course which would keep the ship safe. 

Space folding was far faster and so it became the primary form of travel until later on navigation machines were created that were able to be as good as spice fuelled navigators which eventually broke the the guild's monopoly on space travel.