Emetophobia in public or having to witness someone else vomit, as the start of the emetophobia. They may also be afraid of hearing that someone is feeling like vomiting or that someone has vomited, usually in conjunction with the fears of seeing someone vomit or seeing vomit. There is a strong agreement in the scientific community that there is no specific cause of emetophobia. Some emetophobics report a traumatic experience with vomiting, always in childhood. Some suggest that sufferers are victims of childhood abuse – sexual or physical. While this is occasionally true, it seems to be no more prevalent than
Irrational number formula_31. It is not known if formula_32 Catalan's constant, or the Euler–Mascheroni constant formula_33 are irrational. It is not known if either of the tetrations formula_34 or formula_35 is rational for some integer formula_36 Since the reals form an uncountable set, of which the rationals are a countable subset, the complementary set of irrationals is uncountable. Under the usual (Euclidean) distance function d("x", "y") = |"x" − "y"|, the real numbers are a metric space and hence also a topological space. Restricting the Euclidean distance function gives the irrationals the structure of a metric space. Since the subspace of irrationals