Can others sense sexual tension between two people if so how can you tell?

Anonymous
I really like this guy. Every time I'm around him I can't help but check him out. I can't tell if the feeling is mutual or if he just likes me as a friend. However I've been noticing a few looks lately from different people. We work together and two coworkers came up to us to be helped. we joked around like always but I noticed that the two coworkers looked at each other with their eyes kind of big and eyebrows kind of raised. Our next shift we ended up taking the same bus to work so we talked while we were on the bus and even a guy kept last looking over at me as we were having a normal conversation. (But of course I couldn't help but check him out while we were talking) Then when we got to work one of the coworkers from the situation the other night was sitting down and he was smiling / smirking kind of with the same expression on his face from the previous shift.
So are they sensing something? Also if so how do I know if he's attracted to me to?
Can others sense sexual tension between two people if so how can you tell?
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