They have strong opinions
When most of one's time is spent poring over evidence, perfecting solutions and drawing inferences, one can safely say they have a strong opinion on most of the things us 'plebs' debate upon. These strong opinions, though, do not mean they are narrow-minded or closed. Any new evidence will be thoroughly researched upon, pronto.
They may not always be on time (Or may not turn up either)
They can't throw up their hands and 'call it a day' in the middle of an experiment. Also, don't forget that most scientists are also part businessmen, who manage their labs and its brand value apart from conducting research. The result? Your dinner date may get postponed quite too often. But you can't really complain if your date is a 'torch-bearer of future innovations', can you?
They like to talk about their work
True, they won't be super-excited to talk about their research which has been lagging due to funds, but it is truer that their subject of study is something they love more than themselves. Once they start talking of their pet project, they are bound to go on and on and on... till you either fall asleep or start taking interest, finally!
They have endless curiosity
Once presented with a fact, subject or phenomenon, the scientific mind can't help but be curious about it. One moment, they see a bug on the wall, the next moment they are wondering where it came from, how it lives, right till the future possibility of it being the savior of the ecosystem. No exaggerations there.
You may become a topic
It is a no- brainer that you may share your innermost feelings, experiences, and thought process with your date. Subconsciously, they might start thinking of it as a subject to be studied, researched, and inferences drawn upon. Go ahead, get flattered that you are a 'contribution to science'!
They turn out to be passionate people
They think deeply, devote their life to an idea and work relentlessly towards it... doesn't this all define passion perfectly? With a little more understanding of each other and patience, you will discover that you make a passionate pair of lovers. Cheers to that!
They bring out your inner nerd!
Were you putting away those books and acting all glam just so that you aren't left out of the current crowd? You might just have found a person who doesn't want you to hide behind that facade. Pull out your geeky glasses, carry books to your date or talk of constellations on a stargazing date - you will not be judged (in fact, be appreciated).