These are 36 of the symptoms I've encountered - and I don't think this is all. Most are mine; a few are other people's. What are yours?
1. You look for constellations in freckles and moles on your skin. And your boyfriend's/girlfriend's - and point them out when you find them. They may be a little disturbed, which is saddening because you mean it as a compliment.
2. One of the most upsetting and bewildering things you can hear is the sentiment that science takes the beauty or poetry out of something.
3. You start quoting Tom Lehrer at length when drunk. Or, indeed, sober and having a good time.
4. Carl Sagan's Pale Blue Dot makes you well up.
5. You have a mental list of all the science things you didn't understand in school. If you're organised you read up on them. If you're not, you just feel annoyed about them and keep planning to read up on them some day.
6. You have your own mental list of what you would put on the science curriculum, if given dictatorial powers!
7. Bookshops are incredibly dangerous places to enter. (For your bank account, not your physical self - unless you do your back in, of course, or indeed sit on the floor and get so absorbed reading something that somebody trips over you.)
8. Once shy and lonely, you suddenly become a very talkative and enthusiastic person!
9. Other people's responses to this vary. They might remark, "You get all animated!" or "You light up when you talk about . . .". However, more commonly they'll object to "these things you just blurt out" as if you've said something exceedingly offensive. Other remarks may include: "You're very passionate about . . ." in a telling-off sort of voice; "You're obviously really shy. Only shy people talk that much all in one go" and "You really remind me of my autistic relative/friend X" or gently take it upon themselves to diagnose autism or Aspergers. You tell them that is very interesting.
10. Fellow geeks are always to be cherished.
11. Your Facebook wall shows rather a lot of links to APOD pictures. You can't help but hope that some of the desperately boring people you can't acceptably unfriend will be even a little inspired. They aren't.
12. Stories such as the idea of "open science" (1st chapter here!) or the children's bumblebee paper put a silly grin on your face for hours.
13. You sneak onto a geeky website, or at least Twitter, when clothes, make-up, alcohol and X-factor become a topic of intense and opinionated discussion in the workplace. Or, if forced to participate, you come out with all the conversation-stoppers.
14. This makes perfect sense!
15. When your friends discuss the inevitabilities of nuclear war or the futility of trying to feed the starving or combat corruption, or treat as completely reasonable the idea of no country agreeing to reduce their carbon dioxide emissions until everyone else does (because it would be bad for their economy), science seems the obvious solution. For example, putting more money into science will drive our renewable energy, and then when everyone else runs out of fossil fuels we'll be in the lead. "Yes," they shrug, meaning "If only", or less.
16. Seeing the cruelty and stupidity of a lot of the world is, every so often, a horrific shock - because you've been concentrating on science, which is so beautiful and makes you so happy.
17. Indeed you feel that more science for everyone would make the world a much happier place.
18. Glow-in-the-dark stars are a very good idea.
19. Remarks such as "But we didn't know how electricity worked for ages, but we still used it" and "We used to think the world was flat" (usually said as excuses for thinking something unscientific and being too lazy to listen to reason) drive you up the wall.
20. When someone claims that some alternative remedy works just fine, you immediately prepare a firestorm of questions about studies, evidence, the placebo effect, and the mechanism (sadly, that usually has to remain inside your head - unless you're a lot braver and more patient than I am).
21. It deeply upsets you to see an inaccurate scientific article.
22. The best clothes and other accessories are those containing an excellent science slogan/joke/diagram.
23. After years, when young, of being personally desperately committed to all your arguments, you grow a virtue of detaching yourself from your scientific work, in order to look at it properly. That ties in with the dry, detached language of scientific journals - although you can't help agreeing they would be much more accessible if written in more ordinary language. (Now if only there was a job requiring that type of translation . . .)
24. You look back on the times you weren't doing science and ask yourself, "What was I doing all that time?"
25. The world becomes full of toys. Clouds change shape before your eyes, whiteboards invite you to write a science joke, broken machinery is there to be pulled apart, Lego is perfectly acceptable at all ages, and your glasses (if you wear them) turn the edges of everything red and blue. And when you arrive early for a meeting, and are conveniently there to help pour the coffee, you first arrange all the polystyrene cups (which you disapprove of, because they're not recyclable, although you wonder if you ought to check that is still true - but cool mugs are still better) into the shapes of a barred spiral, an unbarred spiral and an elliptical.
26. You then excuse yourself by explaining that, now you are into science, the world is suddenly full of toys, and everyone around you grins and nods, because they all feel the same way!
27. You see galaxies in your coffee. And everyday objects in galaxies. And point them out.
28. You can't help but check for flawed methodology in every claim and every study you see. And you see a lot.
29. Organisations or groups whose principles support sometimes see you as the enemy when you point out the flaws in their methods or reasoning. This is tragic, because you want them to produce the best data and arguments.
30. You are occasionally reminded that you have forgotten to do something important, such as turning off the oven, because you were so busy thinking about supernovae or similar.
31. When you suddenly understand a concept or equation you began struggling with a long time ago, it's difficult not to jump or dance. You have to settle for texting your geeky friends or blogging about it later.
32. Sooner or later, you will come across someone who feels that there is something childish about facts and being "right or wrong". This is a lot to do with their own maturity and having learnt to compromise and respect everyone's opinion. You think about this and go through a long thought process concluding that your own maturity about knowledge has passed various stages. As a child, for instance, you might have thought in black and white, and that is what this person usually thinks you are doing. As a teenager, you learnt to think like them (and some people never get beyond that stage). As a science geek, the maturity is error bars, acknowledged uncertainties, and a healthy respect for facts which you know can never be entirely proved, only disproved - who knows how or when?
33. When people ask you to recommend Christmas presents, you give them a list of science books. You genuinely found them funny and delightful.
34. You tell your beloved to paste this equation into Google: (sqrt(cos(x))*cos(200*x)+sqrt(abs(x))-0.7)*(4-x*x)^0.01, sqrt(9-x^2), -sqrt(9-x^2)
35. A science lecture, a Skeptics in the Pub night or a stargazing/telescope session is a much better night out than getting pissed.
36. You use the word "geek" as a compliment. Other people think you're putting yourself down. This needs explaining.