[rantanplan]

No they don't. You are simply confused.

Read the definition from wikipedia: "Belief is the state of mind in which a person thinks something to be the case, with or without there being empirical evidence to prove that something is the case with factual certainty"

The reason why you're confused is simple; you conflate casual speech with literal definitions. When you hear scientists say "I believe that... blah blah" is a figure of speech. In the same way I used "what the hell" but I really don't believe in hell :)

What they mean actually is "I hypothesize that ... blah blah". That's why you won't see any scientific papers saying "I believe that the number must be something around... 42".

And by the way, even if they believed in the sense that you said, any evidence contrary to their beliefs would make them adjust their beliefs ;)

[engi_nerd]

Scientists are perfectly capable of holding beliefs that they cannot prove.

https://en.wikipedia.org/wiki/What_We_Believe_But_Cannot_Pro...

There's a whole book with responses from real scientists regarding this.