How can I tell if an older man likes me? Im 26 & he's 41-men around this age, do u ever get crushes on younger women& how did u let them kno?

I get the feeling he's trying to tell me he's interested but first trying to figure out if I'm interested or if I'll laugh at him or reject him if he asks or something. The hard part is he's a professor at my former undergrad - I wasn't in his department and we met circumstantially &got to know each other &now I really have feelings for him, but I'm so frustrated &don't know how to get him to make a move -any advice would be great!

We have a couple mutual friends, who I feel like are hinting to me that he likes me -one always asks me "have u seen (guy)?" or says hey "(guy) was just talking about u -he says u got the fellowship!" &the other once said "(guy) REALLY likes you" Every time I see him, we hug each other& the convo flows really easily. Hes asked me if Im seeing anyone &what my approach to dating is, &also our mutual friends have told me he asked them about me. Idk I just get the vibe that he likes me too but then I doubt myself bc I think if he really had feelings for me, he'd come & GET me!

I moved across the country for grad school 3 yrs ago,& since then, every yr he fb messages me to say happy bday, asks me how Ive been, tells me something about himself, &then we have a convo for a few hrs, even tho he can clearly see that hundreds of other ppl wrote on my wall instead of PMing me. For everyone else he writes on their walls for their bday -he only PMs me. Older men- do u have insecurities about asking younger women out? How do u show them u like them?