Kēxuéjiā duì yǔzhòu de qǐyuán yǒu hěnduō cāixiǎng.
Scientists have many conjectures about the origin of the universe.
Tips
usage
猜想 can function as both a verb (to guess/conjecture) and a noun (a conjecture). 猜测 is similar but more neutral; 猜想 often implies a degree of reasoning behind the guess.